UC-NRLF 
 
 SB 
 
* 
 
 REESE LIBRARY 
 
 OF THE 
 
 UNIVERSITY OF CALIFORNIA 
 
 Received . . : ^**"-*^ , if!8 "g 
 
 Accessions No.*36>f 9 Shelf No.. 
 
Cfie Scientific Kloll 
 
 A 
 
 BIBLIOGRAPHY, GUIDE AND INDEX 
 
 TO 
 
 CLIMATE. 
 
 BY 
 
 ALEXANDER RAMSAY, 
 
 F.G.S., F.R.G.S., F.R. MET. Soc., F. SCOT. M.S., ETC. 
 
 HonHon : 
 
 W. SWAN SONNENSCHEIN AND CO., 
 PATERNOSTER SQUARE. 
 
 1884. 
 

 THE SCIENTIFIC BOLL 
 
 INTKODUCTION 
 
 1. CAPTAIN CUTTLE'S recommendation to make 
 a note of a fact, when once it has been found, has 
 long since passed into a familiar and well-ap- 
 proved-of by-word. The full advantage of the 
 operation, however, is not obtained until the 
 note made has been put where it can be easily 
 referred to again whenever wanted. 
 
 2. Scientific literature has long since become 
 an immense storehouse of facts, the contents of 
 which are so arranged that in many cases it is 
 very difficult indeed to find the individual state- 
 ment wished for. Every year the difficulty in- 
 creases, and efforts are made from time to time 
 to meet it by means of records, annuals, classified 
 catalogues, digests and indexes. These works 
 are unquestionably useful, and all honour is due 
 to those who have conceived and executed them ; 
 but the principles upon which they are based do 
 not seem calculated to supply the great deside- 
 ratum, viz. a simple, uniformly arranged key to, 
 and summary of, science. 
 
 3. A plan for effecting this is here proposed. 
 It is to thoroughly search each paper or volume 
 and arrange its contents under specified headings 
 classified according to a definite order. In this 
 way the information supplied by that particular 
 paper or volume is placed within easy reach of 
 everyone. By extending this process to other 
 papers and volumes, fresh facts are obtained and 
 classified. The larger the area of literature the 
 process is applied to, the more useful becomes 
 the collection of systematised notes. When a 
 large number of books have been thus treated, 
 the analyser finds that owing to repetition each 
 additional work which is examined contains com- 
 paratively little that has not already been entered 
 in the notes. The systematisation of notes, 
 hence, necessarily results in the most compen- 
 dious condensation and concentration possible 
 of all that is wanted in scientific literature, so 
 arranged that, generally, any particular foot 
 would be far more accessible in its new position 
 than where it was originally placed. 
 
 4. The ' SCIENTIFIC KOLL ' will endeavour to 
 develope this idea. It would be impossible to 
 complete the task without a great deal of 
 organised co-operation. Still it is hoped that 
 the beginning here offered will be found suffi- 
 ciently useful to lead to the plan being carried 
 out on a larger and more efficient scale. When 
 it is considered that there are upwards of six 
 thousand distinct scientific serials it will be mani- 
 fest that the ' SCIENTIFIC ROLL ' does not claim 
 to make any approach to completeness, except in 
 so far as relates to the books or articles which 
 are marked as having been read. 
 
 5. Notes thus collected may have a somewhat 
 disconnected appearance so far as the want of 
 
 PART I. 
 
 fluency of language is concerned, but the con- 
 tiguous statements usually have such a close 
 connection with each other that the flow of 
 ideas is unexpectedly even, so that not only are 
 lines of thought suggested, but facilities are 
 offered for following them O'it, which books as 
 a rule do not afford. 
 
 6. An opportunity will be taken at a later 
 period for giving a full explanation of the system 
 developed in the following pages. Here, how- 
 ever, it may be mentioned that although passages 
 are often taken verbatim, quotation marks are 
 not given. In all cases the endeavour is to give 
 the substantial meaning as briefly as possible ; 
 so that when it happens that to follow the actual 
 words of the author would be useless verbosity, 
 the passage L summarised. No attempt is 
 made at altering the sense, or correcting mis- 
 takes of fact or spelling, or modifying anything 
 which bears upon the subject of the heading 
 Everything unconnected with the subject under 
 consideration for the time is omitted. Hence it 
 will be clear that for purposes of quotation the 
 original work must be consulted. Correction 
 of errors, comments and explanatory remarks 
 by the Conductor or his coadjutors, will invariably 
 be placed in footnotes. 
 
 7. Considerable he'p has been afforded by the 
 Royal Society's Catalogue of Scientific Papers, 
 Nature, and many other useful repertories. Full 
 acknowledgments of this kind will be made at 
 the close of each section of the work. The 
 matter is mentioned here because in the case of 
 titles, and such like data, it would be inconve- 
 nient and unusual to cite the work whose 
 authority is relied on for them. Many of the 
 titles have been independently verified. 
 
 8. Explanations of the contractions used will 
 be given in due course. One or two, however, 
 require elucidation now. Every item, whether 
 it be a paper, or a volume, or a series which ha," 
 been examined and the facts afforded by it placed 
 in the notes, is marked ra if the article only 
 has been read; rv if the volume has been 
 analysed ; and rs if the series has been searched ; 
 but when such item has been read too late for 
 the insertion of the facts in their proper place 
 in a previously published part of the magazine, 
 it will be marked rp. 
 
 9. Authors desirous of securing a notice of 
 their publications will be conferring a favour 
 by sending a copy of them to the Conductor, 
 which will be returned to them, if desired, as soon 
 as they have been analysed. Publishers and 
 authors are respectfully asked to send early notice 
 of all publications bearing upon meteorology, as 
 by so doing they will enable the Conductor to 
 incorporate the most recently published works. 
 
ESSAY I. 
 
 ON THE DIURNAL PERIODICITY. 
 
 1. THE local weather changes are often and 
 in many places so frequent and so abrupt 
 that many nations have regarded the observed 
 succession of cold and heat ; of rain, snow, hail, 
 storms of wind, and of fine weather ; of electrical 
 disturbance and of electrical calm, as almost 
 matters of chance. Indeed the changes of the 
 weather are commonly referred to as typical of 
 fickleness. In other cases, where a number of 
 laws have worked together for the production 
 of a single event, individuals are prone to say 
 that chance, not law, has brought it about. 
 The knocking-down of a person by a vehicle in 
 the crowded streets of a city ; the so-called 
 trifling events which accompany the perpetra- 
 tion of a crime or the achievement of a national 
 blessing; the arrangement of the stones on a 
 pebble beach or of the stars in the heavens ; the 
 collocation of two or three individual particles in 
 this or that particular muscle or other orga- 
 nised structure ; the event of two black balls 
 being drawn from a heap of a 1000 balls, 500 
 of which are black, and 500 white all these, 
 and countless other examples which the reader 
 can easily supply, are said to be (to a greater or 
 less degree) dependent upon chance. But when 
 each individual case is followed out in detail 
 and the cases of the like kind are grouped 
 together, then the larger the number of ex- 
 amples forming each group the more evidently 
 are the laws which governed its occurrence 
 made manifest. Thus with reference to the 
 persons who are knocked down by vehicles in 
 the streets of London, the active concomitants 
 are so regular that it is possible to say before- 
 hand, with a near apprcach to accuracy, how 
 many persons will be run over in the ensuing 
 week, and what proportion the fatal injuries 
 will bear to those which are not fatal. The 
 degree of accuracy of the prediction will depend 
 upon the fulness of the knowledge possessed of 
 the concurrent circumstances which produce 
 such accidents. And so it is with the other 
 illustrative instances mentioned. The arrange- 
 ment of the pebbles upon a beach is undoubtedly 
 the result of the action of many definite laws, 
 and so also, scientific faith compels us to believe, 
 are the mazy arrangements of the starry hosts 
 of heaven and of the countless molecules of 
 matter. 
 
 2. As then the rational grouping of like 
 circumstantialities enables the statistician to 
 discern law where chance is ordinarily supposed 
 to prevail, so the methodical grouping of facts 
 will allow of the deduction of conclusions which 
 would not have been revealed bv the scattered 
 
 facts. Scientific faith constrains us to admit 
 that law, not chance, reigns over the succession 
 of the least, as well as of the most, striking of the 
 weather phenomena. In proportion as know- 
 ledge increases so will faith change into a 
 firmer and firmer conviction that law prevails 
 in these phenomena ; and doubtless with perfect 
 knowledge there would be absolute conviction 
 that there is no such thing as chance. Then, 
 indeed, it would be felt that only two positions 
 can be consistently maintained the one is that 
 everything is a matter of chance, the other that 
 everything is a matter of law ; or, in other 
 words, that the universe is under the rule of 
 nothing (which is tantamount to saying it is 
 under no rule at all), or the rule of God. There 
 is no middle position, so that when anything 
 is said to happen by chance, the meaning must 
 be understood to be that it happens according 
 to certain laws, but owing to ignorance of those 
 laws, the how and the why such a thing has 
 happened is beyond the present condition of our 
 understanding. 
 
 3. Of late years weather knowledge has made 
 such important advances, that the perusal of a 
 few pages will probably leave an impression 
 on the mind of the reader that there are weather 
 laws, and that meteorological science will 
 become as definite as many of the more advanced 
 sciences. 
 
 4. In the present essay the purpose is simply 
 to allude to some facts which indicate the 
 existence of a diurnal periodicity, that is, of a 
 complete succession of climatic events which 
 runs its course within a period of twenty-four 
 hours. The variations which this periodicity 
 may present according to place, and the 
 causes which actually and apparently bring 
 about these variations, will be left for further 
 consideration. 
 
 5. The sun is, or appears to be, the great 
 factor in climate; and the relative positions 
 and movements of the earth and sun seem to be 
 most intimately connected with the most pro- 
 minent climatic periodicities. But there are 
 also periodicities dependent upon other causes, 
 which causes probably are the movements and 
 positions of the moon and planets relatively t( 
 each other as well as to the earth, the sun an< 
 space, and the changes which are slowlj 
 worked out from age to age in the physical 
 geography of the earth itself. But further 
 allusion to these is unnecessary, as the move- 
 ment of the earth with respect to the sun is, 
 to all appearance, the chief, if not the only, 
 operating cause of the diurnal periodicity. 
 
ESSAY I. 
 
 ON THE DIUENAL PEKIODICITY. 
 
 6. In consequence of the earth's rotation on 
 its axis the sun appears on the eastern horizon 
 in the lower latitudes, gradually ascends to its 
 highest point in the heavens, then descends to 
 its setting on the western horizon, and remains 
 invisible for a time until it has completed its 
 circuit by reappearing on the eastern horizon. 
 This circuit is effected in twenty-four hours. 
 On and near the equator the days and nights are 
 of equal length all the year round, but as we 
 advance towards the poles the apparent motion 
 of the sun in the sky declines from the vertical 
 plane so that the relative lengths of the day 
 and night fluctuate about the two poles of 
 equality at the spring and autumn equinoxes; 
 the days wax longer from the spring equinox 
 till midsummer, and then wane to the autumn 
 equinox. Then the nights become longer than 
 the days, increasing in length till midwinter ; 
 after which they shorten again till the spring 
 equinox. The degree of maximum inequality 
 between daylight and darkness increases as we 
 proceed pole-wards. Beyond the polar circles 
 the duration of the presence or absence of the 
 sun extends over more than twenty-four hours, 
 so that the diurnal period vanishes for a portion 
 of the year. The proportion of the year during 
 which this diurnal movement is non-apparent 
 increases until at and near the poles the ap- 
 parent solar motion has become horizontal, and 
 the periods of sun-presence and sun-absence 
 are six months in length. In the north hemis- 
 phere the diurnal movement is from the left to 
 
 been restricted to the supra-horizontal presence 
 of the sun, but the remarks are so manifestly 
 applicable to light that no observations with 
 instruments are required to convince us that 
 light, as a climatal element, has a periodicity of 
 the same kind ; and that the occasional oc- 
 currence of dark days in consequence of fogs, 
 showers of volcanic ashes, flights of insects, 
 and other circumstances, does not obscure the 
 evidence. 
 
 8. As light and heat are close companions it 
 might be presumed that temperature is subject 
 to similar alternations ; but in this case instru- 
 mental observations have been made in abundance, 
 and the mind feels the need of other evidence 
 than what is afforded by general scrutiny. The 
 theoretical alternations in the intensity of light 
 may be inferred from the movements of the sun, 
 but practically the actual periodicity differs 
 somewhat from the theoretical owing to the 
 refractive power of the atmosphere and to 
 various local circumstances. The theoretical 
 annual mean would occur at the equinoxes and 
 would be represented by a curve with arms of 
 equal gradient and with six hours above and sii 
 hours below the mean. The gi-aphic representa- 
 tion, then, of a semi-diurnal periodicity of 
 twelve hours consists of a single hump with 
 slopes of equal gradient, as in Fig. 1. As the 
 duration of light each day increases, the hump 
 will broaden and its height lessen in proportion 
 to the lessened maximum intensity of the light, 
 until with a diurnal periodicity of almost 
 
 MEAN 
 
 6 7a.m. 8 9 10 11 12 1 2 3 456 p.m. 7 
 Fig. l. Theoretical semi-diurnal line. 
 
 the right of the observer, while in the south 
 
 hemisphere the direction is from right to left. 
 
 Thus although the earth rotates on its axis 
 
 mce in twenty-four hours, the oblique position 
 
 f that axis, relatively to the position of the 
 
 un's axis in space, causes the length of the 
 
 ongest day to increase from twelve hours to 
 
 ix months during one half of the year, and to 
 
 'ecrease from twelve hours to zero during the 
 
 ther half. The two hemispheres stand in 
 
 oposite relations to each other as regards 
 
 lylight, so that if we select two antipodal 
 
 .laces the mean time during which the sun is 
 
 bove the horizon is twelve hours on every day 
 
 n the year. So again, if we take the mean 
 
 duration of sun-presence on two days six months 
 
 apart, it will be found to be twelve hours all the 
 
 year round. 
 
 7. In the preceding paragraph attention has 
 
 twenty-four hours the curve would be repre- 
 sented graphically by a broad hump with 
 gradients less than those shown on the equinoxial 
 curve ; while in this flatter curve about twelve 
 hours would be above, and twelve below, the 
 mean, as shown in Fig. 2. In this case the 
 means would be at 6 A.M. and 6 P.M. If the 
 increment and^ decrement were equal for equal 
 portions of time, the lines would be straight ; but 
 as the changes are modified in rate by the 
 thickness of air through which the rays pass, 
 the lines assume a curved form. 
 
 9. The heat which is supplied by the sun 
 during the day is absorbed by the ground and 
 by the air resting upon it, and is retained by 
 them after the sun has set. There is usually 
 a loss of a portion of this absorbed heat during 
 the night, butf in most instances such loss is 
 gradual, so that the accession of heat daring 
 
 B 2 
 
ON THE DIURNAL PERIODICITY. 
 
 ESSAY I. 
 
 the day has a greater and more prolonged 
 influence on the nocturnal temperature than 
 the daylight has upon the succeeding period of 
 darkness. Hence the increase and decrease of 
 heat normally extends over the whole twenty- 
 four hours, thus giving rise to a diurnal periodi- 
 city. In the construction of diurnal curves it 
 is important to bear in mind that the observa- 
 tions should be such as have been taken at 
 times equal-distanced apart over the whole 
 
 tion as to the hours ; but as he records the 
 highest and lowest temperatures observed, these 
 help to supply the deficiency in Erskine's figure*. 
 The mean of the maximum temperatures is 77 
 and of the minimum not above 40. In a subse- 
 quent journey through the Limpopo basin, 
 where his former explorations were, Erskine 
 notices that from March 6, the mornings became 
 so cold that the blankets which had been dis- 
 carded since September were again brought 
 
 012345 
 
 7 8 9 10 11 12 1 2 3 4 5 6 
 Fig. 2. Theoretical diurnal line. 
 
 8 9 10 11 12p.m 
 
 twenty-four hours, and that those times should 
 embrace the epochs of maximum and minimum 
 range. This matter is not of material impor- 
 tance when the object is simply to trace the 
 existence of a diurnal periodicity ; but it is 
 essential when the rate of increase and decrease 
 at different localities has to be determined. 
 The point is mentioned here because it has been 
 desirable to utilise observations which suffice for 
 drawing a portion of the diurnal curve in the 
 
 into use. From these scattered materials we 
 are able to infer that the mean night minimum 
 temperature in July in certain parts of the 
 Limpopo basin is not above 40. Assuming 
 this to be so, and that the moment of minimum 
 cold is shortly before sunrise, the following 
 diurnal curve may be drawn. It is not to be 
 imagined that such a curve is more than a rough 
 approximation to the truth ; but these par- 
 ticulars are given to show how scattered isolated 
 
 4 5 b 7 8 9 10 11 12 1 2 3 45 6 1 89 10 11 12 1 2 3 4p.m. 
 Fig. 3. Hypothetical diurnal curve for July 1878, in the Limpopo river basin. 
 
 formation of a complete curve. For instance, 
 Erskine made some observations in July 1868, 
 on the line of the southern tropic in Africa 
 which gave a mean of 73 Fahr. at 9 A.M. ; of 79 
 at noon ; and of 88 at 3 P.M. These figures 
 taken by themselves are of little or no value for 
 the present purpose. They indicate a rise from 
 9 A.M. to 3 P.M. without giving any clue to the 
 times or degrees of the maximum and minimum 
 temperatures. From 9 A.M. to noon the rate of 
 increase is 2 per hour, and from noon to 3 P.M. 
 it is 3. So far as it goes the evidence would 
 induce us to infer there was a continuous rise 
 up to 3 P.M., and possibly beyond that hour. 
 Incidental mention is made that the temperature 
 of the water is 64 ; but the hour of observation 
 is not stated, and a guess has to be hazarded 
 that the water is river water. The minimum, 
 then, would presumably be below 64. In 
 July 1869, Baines collected some thermometrical 
 data in about the same district, the value of 
 which is diminished owing to want of informa- 
 
 notes may have their value enhanced by being 
 placed side by side. The reason why these 
 special figures were taken is because wishing to 
 show proof of the existence of a diurnal periodi- 
 city of temperature on the line of the southern 
 tropic of Africa, no better evidence was readily 
 to be found, and these had been collected and 
 systematised. All were found in less than 
 half an hour. Facts, however, are not wanting 
 which will suffice to show that there is un- 
 questionably a diurnal periodicity of temperature 
 in the inter-tropical region of Africa. Watson 
 made observations at Rigaf in December 1874. 
 This locality is in 4 44' 32" N. lat. The mean 
 temperature at 9 A.M. was 82 8 ; at 3 P.M. 94 ; 
 and at 6 P.M. 82; the mean maximum in the 
 day was 95, and the mean minimum at night 
 69 5. The maximum was clearly not at 3 P.M. ; 
 but judging from analogy and the probabilities 
 of the case it was before rather than after that 
 hour. The increase and decrease of temperature 
 was markedly regular. The range during the 
 
ESSAY I. 
 
 ON THE DIURNAL PERIODICITY. 
 
 twenty-four hours varied from 30 to 39, but 
 at the specified hours it never exceeded 9. 
 According to Skertchley the average daily 
 temperature in Wassaw, a territory on the 
 Gold Coast which lies between 5 and 6 N. 
 lat., is 75 Fahr., and that of the night 65. On 
 the Victoria river in Australia, at 15 30' S. lat., 
 Wilson found that the minimum temperature 
 occurred about an hour before sunrise ; and 
 that the records for nine months gave an 
 average of 72-8 at 6 A.M.; 92 "3 at 1 P.M.; 
 and 85 5 at 6 P.M. On the lower Amazon, as 
 at Para, which lies close to the equator, the 
 temperature is remarkably equable, the mean 
 daily temperature according to Orton's observa- 
 tions being 80 '2. The maximum is reached at 
 2 P.M. and the nights are invariably cool. At 
 Quito, where Orton stayed for a time and 
 registered the thermometric readings, the tem- 
 perature is very equable. Like Para it is 
 situated close to the equator, but the heat is 
 much moderated owing to its great elevation 
 above the sea. The range in the twenty-four 
 hours is about 10; the coldest hour is at 
 6 A.M., and the warmest between 2 and 3 P.M. 
 At Paca-yacu, in Ecuador, Spruce observed the 
 minimum temperature to occur at 6.30 A.M., 
 when it was generally 68 ; the maximum was 
 reached at from 2 to 3 P.M., when the tempera- 
 ture usually rose to 81. At Trevandrum, in 
 S. India, between 8 and 9 N. lat., the mean 
 annual daily temperature rises from a minimum 
 of 74 between 5 and 6 A.M., ascends to 85 at 
 1 P.M., and then sinks to 76 at midnight. In 
 New Guinea, a little south of the equator, the 
 temperature during the northern summer 
 changes little during the day, but the nights 
 are cold. In June the temperature on the 
 Octanata river, as recorded by Dr. S. MiilJer in 
 1828, was 77 in the morning just before 
 sunrise, 84 at noon, and about 78 '4 towards 
 evening. These illustrations from tropical 
 localities, and were it necessary many others 
 could be cited, all showing the same general 
 feature, plainly manifest a diurnal thermic 
 periodicity. No exceptions whatever are known. 
 There are differences in the rate and extent of 
 the increase and decrease of the temperature 
 according to locality, but such differences do not 
 in any way obscure the evidence. As a general 
 rule the daily maximum in equatorial regions 
 exceeds the minimum by about 5 on the land, 
 but not more than 2 or 3 on the sea. On the 
 land the maximum is reached between two and 
 three in the afternoon ; but at sea, at or soon 
 after midday ; while both on land and at sea 
 the minimum occurs a short time before the 
 sun rises. Recurring then to the observations 
 made by Erskine, it may reasonably be con- 
 jectured that the 3 P.M. data should be placed 
 not on the rising curve, but on the downward 
 slope just beyond the turn. In other words, the 
 maximum was probably 89 or 90 soon after 
 2 P.M. 
 
 10. In the regions between the tropics and 
 the circumpolar circles the available observa- 
 tions are more numerous, precise, and reliable. 
 A few selected instances need only be given 
 
 lere. Riippell made observations at Gondar, in 
 Abyssinia, during the winter of 1832-3. The 
 means were 57-5 at 5.40 A.M. ; 68-5 at 9.6 A.M ; 
 75-8 at 12.30 P.M.; and 74-3 at 3.33 P.M. 
 [n all probability the maximum was before 
 
 3 P.M., but is not shown here ; the temperatures 
 at 9 P.M. and midnight are also required to be 
 known for the ascertainment of the true diurnal 
 progression of temperature. At Plymouth the 
 mean annual daily temperature starts from a 
 minimum of 47 Fahr. between 4 and 5 A.M., rises 
 to the maximum of 55 between 1 and 2 P.M., 
 and, declining to 47 at midnight, slowly sinks 
 to the minimum. At the Stoiiyhurst observatory, 
 Blackburn, in Lancashire, the hour of daily 
 maximum ranges from noon in December to 
 
 4 P.M. in June and July, and, indeed, at most 
 places the hour of maximum varies more or less 
 with the length of the day. At Paris the 
 average annual daily" temperature is at its maxi- 
 mum at 2 P.M., being 58 Fahr. ; the minimum 
 
 s 44-8 at 4 A.M.; and the mean, 51-3, occurs at 
 8.20 A.M. and 8.20 P.M. The observations made 
 by Hayward in January 1869, at Yarkand, in 
 Tibet, gave the following averages : 
 
 Sunrise 13 Fahr. 
 
 9 A.M 21 
 
 Noon 29 
 
 3 P.M. 31 
 
 6 P.M 27 
 
 9 P.M 23 
 
 The time of the minimum, as well as of the 
 maximum, varies according to the length of the 
 day in the middle latitudes ; the minimum 
 occurring earlier in proportion as the days 
 lengthen, while the maximum gradually becomes 
 later as the evening light is extended. 
 
 11. The evidence harmonises well with what 
 has been stated with respect to the duration of 
 light. All the facts tend to show that the rise 
 and fall of daily temperature is so far dependent 
 upon the presence and position of the sun, and 
 the rotation of the earth upon its axis, that a 
 marked diurnal periodicity is plainly discernible 
 wherever night and day follow each other during 
 each rotation of the earth. In the Polar regions 
 there is a periodicity of the same kind, although 
 it is not so decided as in the lower latitudes. 
 This is shown by the observations made on board 
 the Erebus and Terror while cruising in the 
 Southern summers of 1841, 1842, and 1843, 
 between 60 and 78 S. lat. The figures are 
 those given by Moseley. 
 
 4 A.M . . . . . 28-795 
 
 8 A.M 30-065 
 
 Noon 31-540 
 
 4 P.M 31-594 
 
 8 P.M 28-956 
 
 Midn 28-892 
 
 The hours selected were not likely to show the 
 maximum ; this probably occurred between noon 
 and 4 P.M., and if anything nearer 4 than noon. 
 
 12. The foregoing results are based upon the 
 facts afforded by thermometers placed a short 
 distance above the ground, and therefore must be 
 accepted as applying to that level only ; because 
 
 5 
 
ON THE DIURNAL PERIODICITY. 
 
 ESSAY I. 
 
 from the investigations of Dines, Hamberg, and 
 Glaisher, as well as from certain casual observa- 
 tions made by meteorologists and others on the 
 appearance and disappearance of clouds, there is 
 known to be a diurnal periodicity in the vertical 
 distribution of temperature, the maxima and 
 minima of which occur at different hours from 
 those already noticed. Nevertheless the evidence 
 is conformable and consistent. The temperature 
 varies with elevation above the ground, and 
 passes through acomplete succession of variations 
 in the course of each twenty-four hours. The 
 observations made render it probable, it might 
 be said almost certain, that during the hotter 
 hours of the day the temperature decreases with 
 elevation above the ground, while it increases 
 with elevation during the cooler hours of the 
 night. The rate of increase seems to bear some 
 proportion to the radiation of heat from the 
 ground, while the decrease bears a similar rela- 
 tion to the radiant power of the sun on the 
 ground. According to Dr. Hamberg the lowest 
 strata of the air are the coolest from two to three 
 hours before sunset to at least two or three hours 
 after sunrise. Glaisher infers from observations 
 made by him at different levels from 22 feet above 
 the ground and less that the higher strata are the 
 warmer at night throughout the year in Eng- 
 land ; that this phenomenon extends to the 
 afternoon hours in March, September, and 
 October, and to all the hours of the day in 
 January, February, November, and December. 
 Burton and other travellers have remarked that 
 the natives of Africa and other countries 
 habitually encamp on slightly elevated spots 
 for the purpose of avoiding the cold of the lower 
 situations, and gardeners have frequently noticed 
 with surprise that, during severe frosts, the 
 plants above a certain height have escaped in- 
 jury thereby, owing to this law of increase of 
 temperature with elevation under particular 
 circumstances. But the phenomenon evidently 
 extends to greater heights, as is manifested by 
 the frequent gradual increase of clouds from 
 sunrise to 3 P.M., followed by their gradual dis- 
 appearance until all have vanished, leaving the 
 sky clear at and about sunset. 
 
 13. The connection between heat and evapo- 
 ration is so close that the facts about to be men- 
 tioned in illustration of the diurnal periodicity 
 connected with aqueous vapour, would in many 
 instances serve equally well as illustrations of the 
 above indicated diurnal periodicity in the change 
 of rate of alteration of temperature with height 
 above ground. This part of the subject is more 
 complicated and less easy to comprehend owing 
 in part to a paucity of suitable observations, 
 and in part to some of the evidence apparently, 
 but only apparently, pointing to a different con- 
 clusion from the remainder. However, as this 
 question of the nature and causes of local dif- 
 ferences will be considered when the variations 
 from the general rule are discussed, it need not 
 be further alluded to here. Suffice it to say 
 that the facts confirming or pointing to the 
 existence of a twenty-four hourly period in con- 
 nection with aqueous vapour are convincing 
 enough, when taken in conjunction with the 
 
 evidence relative to the other elements, to 
 warrant the belief that the daily periodicities 
 of increase and decrease of humidity, increase 
 and decrease of vapour tension, and of the 
 vertical distribution of the dew point (or 
 rather of the place of maximum humidity), are 
 harmonisable and correlated with those pre- 
 sented by light and heat. 
 
 14. The subject of aqueous vapour as an element 
 of climate presents several aspects, each of which 
 should be kept distinct from the others. One 
 is the rate at which the vapour is supplied or, in 
 other words, alternations in the intensity of eva- 
 poration ; another is the variation in the absolute 
 amount of aqueous vapour in the air ; and a 
 third is the changing ratio which this absolute 
 amount may bear to the quantity which would 
 suffice for perfect saturation. It would occupy 
 too long to treat all these, and therefore the dis'- 
 tribution of the dew point and of maximum 
 humidity will be selected on account of its 
 affording the most striking exemplification of 
 periodicity. But in order to connect this part 
 of the evidence with that which has gone be- 
 fore, a few lines may be devoted to the data 
 respecting the amount of aqueous vapour in the 
 air. This amount depends upon the temperature, 
 and its variations coincide in the main with 
 those of temperature. The greatest quantity 
 prevails during the hottest hours of the day 
 (provided there is a source of supply of vapour 
 within a moderate distance), while the smallest 
 quantity is found during the coldest hours. 
 The diurnal curve, then, of the amount of 
 aqueous vapour usually agrees with that of tem- 
 perature. It frequently happens that there is 
 only a moderate source of supply, and then the 
 quantity seems to diminish during the hotter 
 hours. This is owing to the upward diffusion of 
 the vapour and the consequent lessened amount 
 of it in a given bulk of air. 
 
 15. The dew point and zone of maximum 
 humidity occur in the coldest section of the 
 vertical column of air. As a rule it is situated 
 on the ground, especially on clear nights, and 
 about sunrise it gradually ascends in the air 
 until it has reached the zone where clouds are 
 usually formed. As the time of maximum 
 cloud occurs some hours after that of maximum 
 dew, the probability is that this zone of maxi- 
 mum humidity gradually ascends from the time 
 of sunrise until it reaches the cloud zone. 
 Towards evening it again descends, reaching the 
 ground when the dew forms, shortly before or 
 shortly after sunset. If this view be correct 
 then analogy would induce us to infer that from 
 this zone of maximum humidity there is an in- 
 crease of temperature downwards towards the 
 ground and upwards as far, perhaps, as the 
 normal position of the cloud zone. By way of 
 illustration take the following observations made 
 by Flammarion during balloon voya ges from Paris, 
 and other places in France. On June 10, 1867, 
 he started from the ground at sunrise, at a time 
 when the horizon was misty, and the fields 
 covered with a fog which gave them the appear- 
 ance of lakes. The humidity was 93 on the 
 ground, and it increased to its maximum of 98 
 
ESSAY I, 
 
 ON THE DIURNAL PEEI01 
 
 ^ 
 
 at the height of 492 feet. Above that it gra- 
 dually diminished to 93 at 919 feet, 92 at 984 
 feet, 86 at 2461 feet and 61 at 4101 feet. On 
 April 18, 1868, an ascent was made from Paris 
 at 3.15 in the afternoon. The humidity on the 
 ground was 73, and increased to 74 at 2546 feet, 
 75 at 2950 feet, 76 at 3412 feet, and 77 at 3773 
 feet. This was the maximum, and above this 
 there was a gradual decline to about 30 at the 
 height of 9843 feet. From the observations made 
 during his numerous balloon trips, he concluded 
 that the zone of maximum damp varies in eleva- 
 tion according to the time of the day, season of 
 the year, and other circumstances ; and that 
 occasionally it occurs near the surface of the 
 ground, especially at dawn. At Greenwich the 
 result of several years of investigation was that 
 (calling a cloudless sky 0, and one entirely over- 
 cast 10), the daily mean was 6 '04 at 9.20 P.M., 
 from which time there was a progressive in- 
 crease as follows : 
 
 11.20 P.M 6-14 
 
 1.20 A.M. 6-41 
 
 3.20 
 
 5.20 
 
 7.20 
 
 9.20 
 
 11.20 
 
 6-76 
 6-84 
 6-89 
 7-10 
 7-14 
 
 From this time there was a gradual decrease : 
 
 thus, 
 
 1.20 P.M 7-11 
 
 3.20 7-00 
 
 5.20 6-61 
 
 7.20 6-23 
 
 At Rome the period of maximum cloudiness 
 is from noon to 5 P.M. In the tropics during 
 the rainy season the weather is so uniform that 
 almost every day is characterised by the clear- 
 ness of the sky at sunrise, the appearance of 
 clouds at 10 A.M., their rapid increase till noon 
 when the rain pours for a few hours, generally 
 ceasing about 4, and then the clouds rapidly 
 disperse, allowing the sun to set in unclouded 
 glory. At Lucknow, as Bonavia observed in 
 October, 1877, the clouds appeared day after 
 day in the late morning hours and increased to 
 a considerable extent before 3 P.M. After that 
 hour they dispersed again, but did not quite dis- 
 appear till about two hours after sunset. In 
 Natal, as Dr. Mann infoi*ms us, it is usual for 
 the sky in summer to get cloudy soon after noon, 
 and to be overcast to a late hour at night, when 
 the sky again clears. He also indicates that on 
 the ground the condition of things is the reverse 
 of that in the cloud zone, as the mean humidity 
 at Maritzburg at 9 A.M. for a period of eight 
 years was 71-2; at 3 P.M. it was 60'1, and at 
 9 P.M. it was 83-4. In the Sahara desert the 
 minimum humidity near the ground occurs at 
 about 2 P.M. Under certain conditions, more 
 especially in localities near large lakes the order 
 of things seems to be different, although a diurnal 
 periodicity is still evident. Thus near lake 
 Tanganyika, Burton states that sunrise is seldom 
 clear, and that, if it is so, clouds gather in the 
 forenoon with the rising wind, but disappear 
 
 again between noVai^ /PrftM- ^wingy^in his 
 opinion, to their being melted by the fervent heat 
 of the sun ; but as he also alludes to a marked 
 fall in the wind, this circumstance may have 
 some influence in the matter. Thick mists 
 collect about sunset, and, as a rule, the skies at 
 night are more or less clouded. At Geneva, 
 again, where Plantamour has made observations 
 for upwards of fifty years, the least amount of 
 vapour occurs at sunrise, and the greatest about 
 2 P.M. during the winter months; whereas, 
 during the summer, there are semi-diurnal perio- 
 dicities. The morning minimum is shortly 
 before sunrise and the maximum between 8 and 
 11 ; the afternoon minimum occurs between 2 
 and 4 P.M., and the subsequent maximum from 
 6 to 10 P.M. The precise hour varies according 
 to the season. In the case of the clouds the 
 winter daily maximum is at sunrise and the 
 minimum at sunset. In the summer there is a 
 double periodicity in the twenty-four hours. 
 The morning maximum is shortly after sunrise, 
 and the minimum from 9 to 11 A.M. ; in the 
 afternoon the maximum is at about 6 P.M., and 
 the following minimum soon after midnight. 
 Whatever may be the explanation of these 
 curious phenomena, there is still apparent a daily 
 march and an antithetical relationship between 
 the increase and decrease of the humidity at the 
 higher and lower levels. 
 
 16. There is a striking coincidence between 
 the cloud changes at Geneva, and the two semi- 
 diurnal barometric periods which are so con- 
 spicuously developed in the tropical day. Under 
 the equator the maximum height of the mercury 
 occurs at 9 o'clock, or a few minutes after, and 
 the minimum with equal punctuality at 4 P.M. 
 From this it rises, reaching its second maximum 
 height soon after 10.30 P.M., and its second 
 minimum at 4 A.M. This extreme regularity of 
 barometric movement prevails for several degrees 
 on either side of the equator. This double 
 oscillation is due to the combination of two 
 distinct diurnal periodicities. The one arises 
 from the action of heat and cold in increasing 
 and decreasing the amount of vapour in the air. 
 It follows the same period as the temperature 
 near the ground. Its maximum corresponds 
 with the hottest hours, and causes a maximum 
 of pressure, while its minimum corresponds to a 
 minimum of pressure. On the other hand the 
 air is so acted upon by this same alternation of 
 heat and cold that its maximum of pressure 
 occurs during the coldest hours when the air is 
 densest, and its minimum at the warmest period. 
 The one is the reverse of the other ; and there is 
 here a repetition of the antagonistic relationship 
 observable in the diurnal curves of maximum 
 humidity. The two actions give rise to a double 
 barometric oscillation, in which the maxima 
 occur when the two separate pressures are at 
 their mean, and when, therefore, both co-operate 
 in producing pressure, whereas the afternoon 
 minimum barometric pressure is co-tempo- 
 raneous with the highest vapour tension, while 
 the morning minimum bears the same relation 
 to the highest atmospheric pressure. In accord- 
 ance with this, it is found that in proportion as 
 
 7 
 
ON THE DIURNAL PERIODICITY. 
 
 ESSAY I. 
 
 the absolute amount of aqueous vapour in the 
 air diminishes, or in other words as the vapour 
 tension decreases, so do the amplitudes of the 
 barometric oscillation lessen. Thus there is a 
 gradual diminution in the amplitude from the 
 tropics towards the poles, and from the localities 
 which have the greatest amount of aqueous 
 vapour in the air towards those which have the 
 least. The decrease in the amount of aqueous 
 vapour may arise from two causes, as before 
 mentioned, viz. a diminution of temperature 
 and a diminished rate of supply owing to dis- 
 tance from the ocean and other large bodies of 
 water. Hence the oscillations diminish from 
 summer to winter, from the sea towards the 
 interior of continents, and from the ground up- 
 wards. As with temperature and with aqueous 
 vapour, an inverse relationship is noticeable 
 between the fluctuations on the ground and at a 
 definite, but considerable, height above it. From 
 these statements it will be seen how closely in- 
 terwoven are numerous meteorological subjects, 
 and how a community of causes Avill account for 
 the variations connected, not only with the 
 period of day, but also with the latitude, the 
 season, and the distance from as well as altitude 
 above the sea. Other explanations have been 
 offered as to the cause of the diurnal baro- 
 metric oscillations ; but the purpose in view 
 here is not to discuss these explanations, or to 
 point out the influences which produce the 
 oscillations; but simply to adduce the best 
 evidence available in favour of the barometric 
 changes being due to a diurnal periodicity. The 
 curve of daily barometric change is so totally 
 different from that of temperature, that no 
 relation seems possible; but a little attention 
 shows that it may really conform with the 
 daily thermic changes, directly in one way and 
 indirectly in another. One or two local in- 
 stances may represent many examples which 
 could be cited to the same effect, did space per- 
 mit. At Habaua, in Cuba, the precise times of 
 the maxima and minima vary with the seasons ; 
 the minima occur at 2.4 A.M., and at 3.4 P.M., 
 and the maxima at 9 to 10 A.M., and at 10 P.M. 
 Ellis says of the diurnal variation at Greenwich, 
 that the morning minimum and the forenoon 
 maximum are latest in summer ; and that the 
 changes in the time vary much in the same way 
 as the times of sunrise and sunset vary ; so that 
 as the day lengthens, the interval between the 
 forenoon maximum and afternoon minimum in- 
 creases. The length of the night bears a similar 
 relation to the interval between the even- 
 ing maximum and morning minimum. At Ox- 
 ford the mean daily time of the oscillations in 
 May, deduced from observations extending over 
 16 years, are 3.55 for the first minimum, 7.55 
 for the first maximum, 4.25 for the second 
 minimum, and 10.45 for the second maximum 
 (Rundell). At Valentia the results for December 
 1877 were these : 
 
 29-245 in at 7 A.M. 
 
 9Q-9'-i 1 1 
 
 29-263 
 29-238 
 29-273 
 
 11,, 
 3 P.M. 
 10,, 
 
 Min. 
 Max. 
 Min. 
 Max. 
 
 At Leh there is a maximum at 9 A.M., and a 
 minimum at about 5 P.M. There is but one 
 diurnal oscillation here, a feature characteristic 
 of places having a dry atmosphere. And as 
 may be noticed the minimum occurs in the 
 afternoon, the period when the atmospheric 
 pressure by itself is presumably least. 
 
 17. If then the barometric changes silently de- 
 clare that they are mainly under the governance of 
 a diurnal period, the winds, which are admittedly 
 dependent, in a great degree, upon the relative 
 distribution of atmospheric pressure, should 
 furnish examples to the same effect. Indeed, as 
 the winds afford a clue to the general state of 
 the atmospheric pressure over large areas, it 
 frequently happens that casual notes on local 
 winds are of material help in deducing conclu- 
 sions respecting the diurnal barometric period. 
 At maritime places in tropical regions there is 
 a marked uniformity in the order of change of 
 the winds, as has been noticed in other climatal 
 elements. The day breeze commences soon 
 after sunrise, increases in velocity as the heat 
 increases, and ceases about four or five in the 
 afternoon. The lull continues till about sunset, 
 when a light breeze from the opposite quarter 
 sets in, and continues through the night. This 
 phenomenon has been found to exist at a great 
 many sea-side places within and without the 
 tropics. Winds present a second very remark- 
 able periodicity. It has been pointed out by 
 F. Chambers at Bombay. This periodicity 
 presents two minima in the twenty-four hours, 
 and consists of a rotation of the wind direction ; 
 which follows, or rather accompanies, the 
 barometric changes. The southerly winds reach 
 their maximum value at the time of the most 
 rapid rise of the barometric curve, while the 
 northerly prevail during the period of most 
 rapid fall. The easterly winds predominate 
 during the maximum, and the westerly during 
 the minimum epochs in the atmospheric pres- 
 sure. The double wind oscillation is as con- 
 spicuous at Calcutta as at Bombay. This 
 oscillation, in conjunction with the alternate 
 increase and decrease of pressure, demonstrates 
 the existence of a daily flux and reflux of -air 
 over very wide areas. Eiippell observed some- 
 thing similar at Gondar, in Abyssinia; for, 
 during his stay there, in the rainy season, the 
 wind was N.E. in the morning, veering round 
 to S.E. before 9 A.M., becoming S.W. by noon, 
 and N.W. during the afternoon. At sunset the 
 wind ceased. At Pola, in Illyria, there is a 
 daily variation in the direction of the wind ; 
 it starts from a point E. of S. at 5 A.M., and 
 gradually veers till it reaches its most Avesteiiy 
 point about 6 P.M., from which time it shifts 
 back to its starting point. The wind force 
 also shows a diurnal periodicity. Thus at Pola 
 the force is nearly double as strong from 
 11 A.M. to 6 P.M. as it is from 9 P.M. to 6 A.M. 
 The elaborate observations by Osier at Bir- 
 mingham give the following interesting results. 
 In winter the force of the wind undulates about' 
 220 from midnight until 8 A.M., rises to a 
 maximum of 390 at 1 P.M., sinks to 350 at 
 7 P.M., and then declines till midnight. In the 
 
ESSAY I. 
 
 ON THE DIURNAL PERIODICITY. 
 
 spring it starts from 90 early in the morning, 
 reaches the maximum of 3uO at 1 P.M., sinks 
 rapidly to 160 at 6 P.M., and then more slowly 
 to 90. In the summer the rise is from 70 in the 
 morning to 260 at 3 P.M. ; and then a fall to the 
 minimum. In the autumn the maximum of 
 260 is reached at 2 P.M. Many lakes have 
 their morning and evening breezes, which 
 sometimes blow with such astonishing regu- 
 larity as almost to constitute a measure of 
 time, as for instance on the Te Anau lake in 
 New Zealand (McKerrow). At Geneva the daily 
 fluctuations of the land and lake breezes are 
 of a decided character. Plantamour has found 
 that in December, when there is no perceptible 
 difference in the temperature of the land and 
 the lake, there is no prevalent lake breeze. In 
 January the lake breeze sets in, and increases 
 from month to month as the days lengthen and 
 the temperature increases. The wind presents 
 a periodicity in its other aspects, such as the 
 time when violent storms commence. At St. 
 Blaise, in Switzerland, the Peters family care- 
 fully noted the particulars respecting 260 
 storms of wind. Only sixteen of these began 
 between 4 A.M. and noon, while 135 were 
 initiated between noon and 8 P.M., and 70 
 between 8 P.M. and 4 A.M. 
 
 18. Inclination would induce us to give the 
 confirmatory details afforded by the diurnal 
 periodicities of rainfall, thunderstorms, dis- 
 tribution of the maximum and minimum in- 
 tensity of atmospheric electricity, hailfall, ozone, 
 and the chemical action of light. There is an 
 abundance of material for this ; but we retrain 
 from further consideration of the subject, in 
 
 order that we may avoid exhausting the patience 
 of the reader. 
 
 19. The conclusions to be drawn from the 
 foregoing facts are : that each element of 
 climate is liable to a regular daily change, 
 primarily dependent upon the earth's rotation 
 and the consequent exposure to the sun, the 
 amount and degree of which varies with every 
 locality ; that in some the increment and de- 
 crement constituting the period is regulated by 
 the light or heat, so that the maximum is 
 attained soon after the hottest hours; that in 
 others the period is regulated by the action of 
 heat converting water into vapour, so that the 
 maximum is produced during the coldest hour 
 of the day ; that the hour of greatest heat or of 
 greatest cold differs according to the height 
 above the ground, causing a vertical oscillation 
 of the period between the ground and the cloud 
 zone ; and, lastly, that when heat alone and 
 heat acting by the agency of aqueous vapour, 
 co-operate, the maximum effect produced by 
 each separately is so counteracted by the other, 
 that the combined result of their co-operation is 
 to produce a minimum effect, while the maxi- 
 mum occurs when each is at its mean and both 
 act together ; the result of which is an apparent 
 double maximum in the course of the day. The 
 maze of changes may seem very confused ; but, 
 in reality, however complicated the arrangements 
 are, all is in perfect order. Thus having com- 
 pleted the round, the mind recurs to the subject 
 which occupied our thoughts in the opening 
 paragraphs of this essay. 
 
 A* It. 
 
GENERAL REMARKS. 
 
 IN these notes the term general has an in- 
 definite as well as a definite meaning. It in- 
 cludes, as it should do, titles and facts which 
 relate to climate generally, such as "On the 
 Uniformity of Insular Climates ; " and, in the 
 case of districts, those which apply generally to 
 them, such as " The Meteorology of Holland." 
 There are many titles which are expressed gene- 
 rally, but which manifestly apply to some par- 
 ticular district ; as, for instance, " Meteoro- 
 logical Abstract for the Years 1794-1799." As 
 the special district is not stated, such papers, 
 etc., are entered here ; when they have been 
 read the titles are repeated under the name of 
 the districts to which they relate. Particulars 
 respecting the application of telegraphy to 
 meteorological purposes, broad references to 
 cycles, propositions for organised methods of 
 research, notices of the healthiness or unhealthi- 
 ness of places, are considered to be general. 
 In addition to these there are items which can- 
 not be regarded as general, but which, owing to 
 their vagueness, cannot be definitely placed ; 
 so that the only position for them is under 
 general. One instance of this is Fothergill's 
 paper in this number (1805, 2), which may 
 seem to be quite out of place. The only reason 
 for putting it here is the " etc." When this 
 paper has been read, the facts represented by 
 " etc." will be entered in their proper places ; 
 
 but in the meanwhile it is considered to be 
 indefinitely general. Again, certain papers and 
 facts are entered under general, about which 
 there is great uncertainty as to whether they 
 are meteorological at all, as for instance, blood 
 rain, black rain, red snow, showers of frogs, and 
 other strange objects, and similar subjects. 
 Papers of this kind often contain some meteo- 
 rological data. Remarks on storms of the cha- 
 racter of which no specific mention is made are 
 grouped as general. The atmosphere is con- 
 sidered to be distinct from climate ; consequently 
 facts relating to its physical and chemical 
 qualities, which do not concern climate, are not 
 to be found here, but under the section devoted 
 to atmosphere. The papers and paragraphs are 
 numbered so as to facilitate reference. As a 
 matter of convenience the volumes of a serial 
 are entered under the year of publication, but 
 when the date is lumped, and the volumes have 
 not been examined for the purpose of ascertain- 
 ing the year of issue of each volume, the serial 
 is assigned to the general section subordinate to 
 Bibliography. Descriptions of instruments are 
 not considered to be meteorological, except 
 when the statements made bear upon recorded 
 readings. When the volume has a date ex- 
 tending over one year, the title is placed under 
 the latest year mentioned. 
 
 10 
 
GENERAL BIBLIOGRAPHY. 
 
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 11 
 
GENERAL 
 
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 12 
 
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 13 
 
GENERAL 
 
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 14 
 
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GENERAL 
 
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 HY. 
 
 ff- y\ V- * . V- Sa (_ f M r^ . '-- v 
 
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 15 
 
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GENERAL 
 
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 Conductor, 6, Kent Gardens, Ealing, London, W. 
 
 16 
 
ESSAY II. 
 
 ON THE CONNECTION BETWEEN SOLAR PHENOMENA AND 
 CLIMATIC CYCLES. 
 
 BY PROF. E. DOUGLAS ARCHIBALD, M.A., F.M.S. 
 
 PART I. 
 
 " The sun is at once the motor of all things, the agent of light, and the" principle 
 of thought." -Vedas. 
 
 1. THE sun's heat is so manifestly the source of all climates, that 
 changes in the amount of heat radiated from its surface are now 
 regarded as the main cause of the changes in terrestrial weather. 
 Besides the semi-annual and seasonal changes caused by its varying 
 distance from the earth, and relative position with respect to the 
 plane of the equator, it has been suspected that changes occur from 
 time to time in the body of the sun itself, which produce variations in the 
 amount of heat radiated from its surface and thereby affect terrestrial 
 weather. The sun-spots, which are the most striking of the indications of 
 solar disturbance were discovered by the Chinese l in the beginning of the 
 present century, and are now proved by the extensive labours of Schwabe 
 and Wolf, supplemented by the more careful delineations of Messrs. De 
 La Rue, Stewart, and Loewy, to undergo a complete cycle of variation 
 every 11 '11 years. 2 One of the first results of the approximate determina- 
 tion of the foregoing cycle was the discovery by Messrs. Sabine and Wolf 
 of the coincidence of this period with those of the maximum and minimum 
 intensity of terrestrial magnetism and displays of the Aurora Polaris. 
 This coincidence being too marked to be merely fortuitous, it was hence 
 conjectured that, since the majority of the changes in magnetic variation 
 and auroral frequency are probably either directly or indirectly related to 
 corresponding changes in terrestrial meteorological currents, some con- 
 nection might be found to exist between the secular variations in sun-spot 
 frequency and area, and those in the different elements of terrestrial 
 meteorology. The universal principle upon which this conjecture was 
 founded, is that which is emphatically laid down by Herschel in his 
 " Meteorology," viz., " that all periodicity in the action of a cause propagates 
 
 1 Vide * Monthly Notices of the Astronomical Society,' vol. xxxiii. p. 370. 
 
 2 According to De La Kue this period is 11-07 years. The period of increase from 
 minimum to maximum comprising 3'52 yeare, and of decrease from maximum to minimum 
 7'55 years. Lamont makes out the length of the period to be 10'43 years, but this does not 
 accord well with the latest observations. 
 
 PART I. No. 2. o 
 
SOLAK PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 itself into every, even the remotest effect of that cause through whatever 
 chain of intermediate arrangements the action is carried out." * There 
 is, then, some ground for believing a connection to exist between the eleven- 
 year period of solar maculation, and that of some kind of emission dependent 
 upon the particular meteorological or thermal conditions of the sun's 
 surface, with its accompanying train of terrestrial, meteorological, and 
 magnetical effects. It will be noticed that the magnetical disturbances are 
 here assumed for the most part to follow and be dependent upon the 
 meteorological disturbances, and lest such an assumption be thought to be 
 without foundation, it may be stated that it was prominently upheld by 
 so distinguished a physicist as Prof. Balfour Stewart in his presidential 
 address before the British Association in 1875. 
 
 2. From the very earliest times we find a popular tendency to expect 
 the weather to recur in cycles of about ten or twelve years. Mr. Sayce, in 
 an article in Nature,' entitled " The Astronomy of the Babylonians," 2 
 remarks that they used cycles of twelve years, during which they expected 
 the same weather to recur ; and if it is remembered that their years only 
 contained 360 days, it will be found that twelve of their years would corre- 
 spond to about 11 '8 of ours, and therefore nearly coincide with the eleven- 
 year cycle of sun-spots. More recently in 1835, and before the sun-spot 
 cycle was completely established, it was known that frightful droughts in 
 Australia occurred in cycles of from 9 to 10 years, 3 while in Ceylon a 
 weather cycle of 11 years appears to be universally recognised, forming 
 part of a grand cycle of 33 years, and oscillating in length between 10 and 
 12 years, and perhaps in this very element of uncertainty, corresponding 
 all the more correctly with the spot cycle and its unequal periods of 
 variation. 4 
 
 3. Before, however, entering upon the question of weather-cycles, or 
 alluding to the numerous attempts that have been made to exhibit a con- 
 nection between solar and terrestrial meteorology, it may be as well to 
 examine briefly the nature, peculiarities, and supposed origin of sun-spots 
 as revealed to us by the telescope and spectroscope, in order to see how far 
 we are justified in assuming, a priori, that they are capable of exerting any 
 appreciable effect upon terrestrial temperature and weather. 
 
 The only way in which we will at present suppose them capable of 
 affecting terrestrial climate, is by their presence tending to increase or 
 diminish solar radiation, and to this test all results of our enquiry must be 
 applied. 
 
 1 Herschel's ' Meteorology,' p. 137. Stanley Jevons calls this the principle of " Forced 
 Vibrations." The Principles of Science,' p. 451. 
 
 2 'Nature/ vol. xii. No. 310. 
 
 3 Westminster Keview,' July, 1835. No. 45. 
 
 4 Dr. Wolf who has been collecting information regarding sun-spots for the last 40 years, 
 has recently found the average divergence of the sun-spot period from the mean period of 
 11-11 years to amount to as much as 2-03 years ; the time which elapses between two 
 consecutive maxima being sometimes as long as 15 or 16 years, while at other times it 
 amounts to only 7 years. 
 
 18 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 4. First as regards observations with the telescope. From the researches 
 of Messrs. De la Eue, Stewart, and Loewy, as to the nature and position of 
 the spots in the sun's photosphere, by the help of the telescope and photo- 
 heliographs, we learn (1) " that the umbra of a spot is nearer to the sun's 
 centre than the penumbra;" (2) "that solar faculse and probably also the 
 whole photosphere, consist of solid or liquid bodies of greater or less magni- 
 tude, either slowly sinking or suspended in equilibrium in a gaseous 
 medium;" (3) "that a spot including both umbra and penumbra is a 
 phenomenon which takes place beneath the level of the sun's photosphere." 1 
 It is also found that the luminous flakes called "Nasmyth's willow 
 leaves " (or " Huggins's granulations ") of which the photosphere, and the 
 faculsa (which appear to be denser and more elevated portions of the photo- 
 sphere in the vicinity of the spots) are composed, are scarcer and more 
 rarified in the neighbourhood of the spots than in the other portions of the 
 photosphere. These willow leaves were somewhat fancifully supposed by 
 Sir John Herschel to be organisms of some peculiar and amazing kind, but, 
 whatever they might be, he thought, they were evidently the immediate sources 
 of the solar light and heat. 
 
 5. Telescopic observation further shows, that the formation of a spot is 
 usually preceded and accompanied by the appearance of faculse, from which 
 we may conclude, that though there is a palpable decrease in the amount of 
 light emitted by a spot, compared with that emitted by the photosphere 
 itself, it is partially, if not entirely made up for by that emitted from the 
 facula, or region of increased brightness by which it is surrounded. Amongst 
 other telescopic observations during the present century, Mr. Carrington 
 observed : 
 
 (1) " A motion of the spots towards the equator ; " 
 
 (2) " That this motion is in a direction contrary to that of the sun's 
 rotation ; " 
 
 (3) " That spots appear to get divided by a certain whirling motion of 
 their parts ; " 
 
 (4) " That new spots more readily appear where others have previously 
 disappeared ; " 
 
 (5) "That there is a periodicity in the frequency of sun-spots, the last 
 maxima being 1828, 1837, 1848, 1860, and 1872." 
 
 M. Chacornac likewise noted the wonderful rapidity with which small 
 spots are precipitated into large ones, amounting occasionally to as much 
 as 599^ miles per second. 
 
 6. Messrs. De La Eue, Stewart, and Loewy, among the numerous 
 results of their organised researches at the Kew Observatory, not long ago 
 announced a discovery to the effect that during periods of great disturbance, 
 there is a tendency in the spots to change from the northern to the southern 
 hemisphere, the period of such change being about twenty-five days, and 
 that outbreaks occur in pairs at the ends of the same solar diameter, after 
 
 1 Proctor, ' The Sun,' p. 217. 
 19 c 2 
 
SOLAK PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 an interval of about thirteen days. Prof. Langley, of Pittsburgh, from a 
 careful study of the sun's surface, considered the spots to be places where 
 we see the general structure of the photosphere in sections, owing to the 
 filaments composing it being here inclined. He also recognised the pre- 
 sence of both horizontal and vertical cyclones within the spots. 
 
 7. As has already been mentioned, it was observed by Mr. Carrington 
 that spots nearer the solar equator move more rapidly in the direction of 
 rotation than those more remote. He was thus led to assign to them a 
 proper motion of their own. 1 This motion has to be considered in 
 measuring the sun's period of rotation by observations of their successive 
 appearances and occultations. Herr Sporer arrived independently at the 
 same conclusion, and deduced the mean period of rotation from observations 
 of spots near the solar equator to be 25'3 days. The spots are however 
 found to be mainly confined to a zone extending some 30 each side of 
 the equator, very few being observed in higher latitudes, and fewer at the 
 equator itself, than in the adjacent zones on each side of it. 
 
 8. The size of the spots is not unfrequently very great. Capt. Davis 
 made a drawing of one in 1839 which had a double nucleus, and whose 
 superficies, including the penumbra, was about 25,000,000,000 square miles. 
 It may help us in endeavouring to form some idea of the immense size of 
 these cavities to learn that the earth, if projected into the interior of a spot 
 like this, would appear no larger than a fragment of rock rolled into the 
 crater of a volcano ! 
 
 9. The faculae which generally precede and accompany the spots, from 
 recent investigations by Messrs. Balfour Stewart, and De La Eue, are found 
 to be disposed more frequently to the left of the spots than to the right, 
 that is behind as regards the direction of rotation. In fact, out of 1137 
 spots photographed at Kew, Mr. De La Eue found 584 which showed 
 faculse to the left, 508 had them disposed symmetrically on either side, and 
 only 45 exhibited them on the right that is, in front, as regards the 
 direction of the rotation. 
 
 10. Quite recently, M. Janssen, of the Paris Observatory, has succeeded in 
 taking some very fine photograms of the sun, from which it appears that, 
 in addition to the granulations noticed by Huggins and others, the entire 
 photosphere exhibits a reticulated structure, being made up of a series of 
 figures " which have in general rounded contours, but are often almost 
 rectilinear, thus forming polygons." " The dimensions of these figures are 
 very variable ; some are even 1' in diameter (over 25,000 miles)." " Between 
 these figures the grains are sharply defined, but in their interior they are 
 almost effaced, and run together as if by some force." M. Janssen also 
 observes with respect to the granulations, that the most luminous particles, 
 or those to which the solar light is chiefly due, occupy only a small fraction 
 of the solar surface. 
 
 11. One of the most remarkable phenomena connected with the telescopic 
 1 Observations of spots from Nov. 1853 to March 1861 at Eedhill, by E. C. Carrington. 
 
ESSAY II. SOLAR PHENOMENA AND CLIMATIC CYCLES. 
 
 study of the spots was the discovery by Mr. Carrington of the tendency of 
 the limiting parallels between which the spots were found, to contract pre- 
 viously to the minimum, and soon after this epoch the commencement of 
 two fresh belts of spots in high latitudes north and south, which have in 
 subsequent years shown a tendency to coalesce, and ultimately to contract 
 as before. This phenomenon was what mainly suggested to Sir J. Herschel, 
 the meteoric ring theory of the origin of sun-spots, in which these bodies 
 forming a cam-like ring were supposed to impinge upon, and perforate the 
 photosphere, its period of revolution corresponding with that between two 
 similar phases of the spots, and the sudden appearance of the spots in high 
 latitudes accounted for by the above peculiar distribution of the meteors in 
 the ring. 
 
 12. Though the preceding discovery is as remarkable as any that have 
 been obtained by a long and patient study of the changes that occur on 
 the sun's surface, and will probably be of material assistance in helping 
 to unravel the secret of the origin of the spots, it has been recently well- 
 nigh eclipsed by the discoveries of the Kew observers with reference to the 
 apparently complete dependence of the apparition and movements of the 
 sun-spots upon the relative positions of the nearer planets, Mercury and 
 Venus. Prof. Balfour Stewart thus sums up the facts hitherto ascertained : 
 First, when either Venus or Mercury is between or nearly between our 
 earth and the centre of the sun, as the sun-spots are carried round by 
 rotation nearer to the planet, they become less, and as they are carried away 
 from the planet, they became greater ; secondly, when Venus or Mercury is 
 at the extreme right of the sun, the spots diminish in size all the way across; 
 thirdly, when Venus or Mercury is on the other side of the sun, exactly 
 opposite the earth, the spots have their maximum in the centre ; and finally ^ 
 if Venus or Mercury be at the extreme left, the spots augment in size all 
 the way across ; in short they are always least in the immediate neighbour- 
 hood of Venus or Mercury and greatest when that portion of the sun to 
 which they are attached is carried by rotation to the position farthest 
 from the influencing planet. 1 
 
 More recently still, Prof. Stewart has found periods of sun-spot activity of 
 about twenty-four days' duration, so definitely ^marked and so regular, that 
 he can tell their period to within ten minutes. These periods both he and 
 Dr. Buys Ballot attribute to the influence of intra-mercurial planets. They 
 are also found by Prof. Stewart to exist almost as markedly in the diurnal 
 temperature ranges at Toronto, which is the only place he has at present 
 examined. The relation between the two phenomena is of such a character 
 that an increase of sun-spots corresponds to an increase of diurnal tempe- 
 rature range. 
 
 So little, however, is known at present concerning the particular agency 
 by which the planets can be supposed to affect the production and subsc- 
 
 1 It may be remarked, if only as a mere coincidence, that the recent prolonged period of 
 minimum sun-spot, 1875-9, was remarkable as an epoch of conjunction of several of the larger 
 planets. 
 
 21 
 
SOLAE PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 quent motions and appearance of a sun-spot that we are forced to abandon 
 the question for the present until it is somewhat more simplified by 
 further discoveries. Although from the preceding brief resume of the 
 results of telescopic observation of the spots, it is evident that a careful 
 telescopic study of the sun's surface is likely to be attended with valuable 
 additions to our existing knowledge of the conditions which regulate the 
 changes in the appearance and distribution of the spots, it is plain that 
 with regard to the question whether their presence or absence is likely to 
 be attended with an increase or decrease in solar radiation, or solar tem- 
 perature (which need not necessarily co-exist in the same degree), no 
 positive evidence seems likely to be obtained. From the recent telescopic 
 observations of the Kew observers, however (according to Mr. J. N. Lockyer), 
 evidence is not wanting to show that in years of minimum sun-spot 
 there is a less amount of cold absorbing atmosphere above the photosphere, 
 and consequently a smaller tendency to the downrush of cold matter in 
 large quantity. 1 In years of maximum sun-spot, on the contrary, the 
 absorbing envelope is denser, and therefore assuming that the internal heat 
 is not increased to an extent sufficient to counterbalance the effect of the 
 increased absorption, both general throughout the photosphere, and general 
 and selective in the region of the spots, it may be conjectured that in such 
 years the solar radiation ought to be less powerful than it is in years when 
 few spots are visible ; an hypothesis which, as will be seen hereafter, is 
 susceptible of a large amount of direct as well as indirect proof founded 
 upon the results of comparing observations of solar radiation and terrestrial 
 air temperatures and other elements for different years of the spot cycle. 
 
 13. It must be borne in mind, however, that the preceding hypothesis 
 presupposes the existence of a downrush of cold absorbing atmosphere in 
 the region of the spots, the existence of which, though inferred from the 
 telescopic observations of Lockyer, has only been finally placed beyond 
 the possibility of doubt through the evidence afforded by the use of the 
 spectroscope. On this, as well as on many other points, the evidence given 
 by the telescope alone with respect to the nature, peculiarities, and possible 
 origin of sun-spots, is now so amply supplemented by that derived from 
 spectroscopic analysis, that theories formed solely from observations with 
 the former are of little real value unless they are compatible with, and 
 conclusively borne out by, the results obtained through the assistance of 
 the latter. The preceding theory of a downrush in a spot, and the rival 
 theory of an uprush, the former being that held by the Kew observers, 
 and the latter that of M. Faye, have been subjected to the rigorous 
 method of analysis afforded by the spectroscope. The result has been to 
 confirm the former theory in the most decided manner. M. Faye has in 
 consequence renounced his theory, and has adopted one in which cyclonic 
 action is considered to be the prime producer of the spots. Mr. Lockyer 
 further remarks : " A suggestion has also been made by the Kew observers 
 
 1 'Solar Physics,' by J. N. Lockyer, F.K.S., p. 481. 
 22 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 to account for the change in the density of the absorbing layer [noticed 
 above], which promises to be one of great value, in assisting towards the 
 discovery of the causes of the periodicity of the occurrence of the spots. 
 It is this, that assuming the photosphere to be the plane of condensation of 
 gaseous matter, the plane may be found to be subject to periodical elevations 
 and depressions, and that at the epoch of minimum sun-spot frequency the 
 plane might be uplifted very high in the solar atmosphere, so that there 
 was comparatively little cold absorbing atmosphere above it, and therefore 
 great difficulty in forming a spot." l This idea has since received partial 
 confirmation at the hands of Mr. Lockyer and Professor Tacchini, but can 
 scarcely be regarded as definitely settled at present. The Kew observers, 
 whose theory of a downrush is thus strongly supported by spectroscopic 
 evidence, apply it to explain the proper motion of the spots noticed by 
 Carrington in the following terms. " May not the falling behind of the 
 faculas be the physical action of the spots noticed by Carrington, so that 
 while the current passing upwards falls behind, carrying the luminous 
 matter with it, the current coming down moves forward, carrying the spot 
 with it, and may not this current coming from a colder region account for 
 the deficient luminosity which characterises a spot? 3 ' This idea is strongly 
 supported by collateral evidence, and fully explains the appearance of 
 vertical cyclones as observed in the interior of the spot. 
 
 Before concluding this brief notice of the results of telescopic enquiry, it 
 may be finally remarked, that in a group of spots which are gradually 
 breaking up, the one which is furthest advanced in the direction of rotation 
 disappears last. This is a point which certainly deserves careful notice, 
 especially if in dealing with the question of their origin, we can ever hope 
 to build up any satisfactory theory with regard to sun-spots. 
 
 14. On bringing the spectroscope to bear upon the spots to use the 
 words of Professor Tait of Edinburgh, " the normal solar spectrum is seen 
 only with this difference, that the absorption lines are thicker and darker 
 than from sun-light as a whole ; so that it appears that there is associated 
 with the sun-spot something which produces an excess of absorption" This 
 widening of the spectral lines, however, may be due to at least two distinct 
 causes. If the increase takes place equally on both sides, as Lockyer and 
 Frankland have shown, it indicates an increase in the pressure and density of 
 the layers composing the spot ; if, on the contrary, the line undergoes an un- 
 equal expansion, sometimes on one side and sometimes on the other, it is 
 most probably due to the presence of gaseous tornadoes within the spot, 
 in which portions of gas are descending and ascending with tremendous 
 velocity. 2 
 
 15. With regard to the explanation of the abnormal appearances 
 presented by the spectrum of a sun-spot, Schellen says : " From the results 
 of the spectrum observations of Secchi, Lockyer, and Young, it may be re- 
 
 1 ' Solar Physics,' by Lockyer, p. 481. 
 
 2 Lockyer says that the velocity is about 38 miles a second. 
 
 23 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 garded as certain that the phenomena of increase in the width and 
 intensity of the Fraunhofer lines are produced by t\& increased absorptive 
 power exercised by the substances of which the spot is formed" ' 
 
 16. On the whole therefore the evidence given by the spectroscope 
 concerning the solar spots, confirms the idea that they are due to the 
 existence of masses of relatively cool vapours at a lower level, and there- 
 fore relatively more compressed than the vapours elsewhere existing in 
 the solar atmosphere. At the same time it throws little additional light 
 upon their extraordinary movements over the sun's surface as revealed to 
 us by the telescopic researches of Carrington and others. 
 
 17. These movements are in many ways so similar to those of terrestrial 
 cyclones that the spots have in consequence frequently been called solar 
 cyclones. Sir John Herschel, and more recently Mr. Herbert Spencer, have 
 formed theories to account for them on this supposition, that they are 
 really cyclones in the solar atmosphere, the latter applying rules to them 
 very similar to those which hold for their terrestrial analogues. 
 
 18. It would be unnecessary if not impossible for us to attempt to 
 enter into a detailed account of the various theories that have been pro- 
 pounded from time to time by distinguished physicists, regarding the 
 nature of sun-spots. Kirchoff, De La Rue, Stewart, Loewy, Carrington, 
 Sir J. Herschel, Lockyer, Young, Respighi, Secchi, Zollner, Faye, Huggins, 
 Dawes, Sporer, Lalande, Chacornac, Eayet, Tacchini, Weber, Weisse, and 
 others, have by their laborious investigations,- with the help of both the 
 telescope and spectroscope, contributed immensely towards our knowledge 
 of these phenomena; but though much has been elucidated with regard 
 to their nature and peculiarities, much is still involved in uncertainty. 
 
 19. Lockyer considers them to be deep recesses in the surface of the 
 solar body, filled with concentrated masses of those substances (iron, 
 calcium, barium, magnesium, sodium, and hydrogen), the lines of which 
 undergo an increase of breadth and intensity in the spectrum, and over 
 which floats the lighter hydrogen gas. 2 Zollner appears to hold somewhat 
 similar views, and regards them as the sequelae of hydrogen eruptions con- 
 sisting of a kind of scoria, which sinks by its own weight a certain depth 
 into the photosphere or outer portion of the sun, and partially intercepts 
 the light from the lower stratum of the photosphere ; therefore presenting to 
 us an appearance of a dark mass projected upon the disk of the sun, in 
 the same way as the exceedingly intense light of the oxy-hydrogen lime. 
 
 1 Schellen, ' Spectrum Analysis,' p. 290. 
 
 2 Mr. Lockyer has recently (Oct. 26, 1880) communicated a brief note to the Royal Society, 
 (Proc. Roy. Soc. vol. xxxi. No. 207) on the spectra of some iron lines in a sun-spot observed 
 on August 31, 1880, from which it appears that "when the iron line at 5207'6 (wave- 
 length) was doubly contorted, indicating an ascending and descending velocity of about 15 
 miles a second, the two adjacent lines at A 5203-7 and 5201'6 visible in the same field of view 
 were unaffected." This affords strong confirmation of the opinion put forward by Mr. Lockyer 
 in December 1878, that iron, like other so-called elements, is in reality a compound, which 
 by the enormous heat of the sun is resolved into its elementary molecular groupings, of 
 whicli he thinks there are no less than three. 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 light appears black when seen against the sun. M. Gautier of Geneva holds 
 precisely similar views to those of Professor Zollner, and says that they 
 appear to him to be the only ones which neither contradict the ordinary laws 
 of physics nor well-known facts. Secchi also appears to hold almost iden- 
 tical views with Zollner as far as he ventures to go. Thus in ' Le Soleil,' 
 2nd part, p. 184, where he sums up his idea of the nature of sun-spots, he 
 says : " La conviction a laquelle nous sommes arrives apres celle longue serie 
 d'etudes est celle-ci : la tache est formee par la matiere meme que 1'eruption 
 projette sur le disque solaire; la region obscure est due a 1'absorption 
 exercee par les vapeurs qui sont sorties du sein du corps solaire et sont 
 interposees entre 1'observateur et la photosphere." On the whole it appears 
 somewhat difficult to account for the multifarious peculiarities in the 
 nature, formation, and disappearance of sun-spots by adopting any one 
 single theory regarding their nature. Nevertheless from the results of the 
 most recent investigations, both telescopic and spectroscopic, we may safely 
 entertain the following general conceptions with respect to their probable 
 nature and influence. 
 
 (1.) That they are phenomena of condensation rather than of expansion, 
 and therefore due more to the action of external than internal forces. 
 
 (2.) That they exercise a general absorption, as indicated by a general 
 thickening of all the Fraimhofer lines in the spectrum, plus a selective 
 absorption indicated by the abnormal thickening of the dark lines of those 
 substances barium, magnesium, sodium, etc. which are consequently 
 supposed to occupy their deepest recesses. 
 
 (3.) That though they do not by any means indicate regions of total 
 darkness]. 1 they still exhibit a marked deficiency in the number of Kasmyth 
 willow-leaves and luminous flakes, of which the photosphere appears to be 
 mainly composed. 
 
 (4.) That they, exhibit strong indications of cyclonic indraught and 
 outrush, and are associated with periods of more than ordinary solar dis- 
 turbance, including a greater number of jets and prominences in the 
 chromosphere. 
 
 (5.) That though their maxima phases appear to be associated with a 
 greater number of prominences in the chromosphere, the district where the 
 latter occur most frequently, lies between N. and N.W., at about 45 north 
 solar latitude, a region where solar spots are rarely seen. The two 
 phenomena have consequently been hitherto considered quite distinct. 
 Not long ago, however, Secchi came to the conclusion that the spots 
 and faculse were both secondary phenomena, similar to one another in 
 their mode of formation, both being the cooled gaseous products of solar 
 eruptions sinking back upon the photosphere, the spots being the sequelse 
 of metallic, and the faculse of hydrogen eruptions. The spots being 
 composed of heavy metallic vapours, generally occupy cavities of displaced 
 
 1 The light emitted by the blackest umbra has been found by Professor Langley to be 
 equal to at least 5000 times that of the full moon (Vide ' Nature,' vol. xii. No. 307). 
 
 25 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 photospheric matter. The faculse, on the other hand, being composed of 
 the lighter hydrogen gas, exist above the general level of the photosphere, 
 their abnormal brightness being due to the greater transparency of the 
 hydrogen, of which they are composed, for the photospheric rays, than that 
 of the usual layer of metallic absorbing vapour which it has displaced. The 
 greater obscurity of the spots is accounted for as usual, by the greater 
 absorbing influence of the cooled metallic vapours composing them. 
 Secchi differs from most other physicists in attributing the formation 
 of the spots solely to the action of the gases composing the metallic pro- 
 tuberances. According to him, therefore, we must consider the period of 
 maximum sun-spot, to be one in which a larger proportion of absorbing metallic 
 vapour exists above the photosphere than at the period of minimum sun-spot. This 
 accords very well with the fact already mentioned, as noticed by Lockyer, 
 and to which his attention was first attracted, by observing that the spectral 
 absorption lines were generally thicker throughout the solar disk at the 
 former than at the latter period. Further, in looking for the origin of the 
 sun-spots, we must remember that according to this view they are merely 
 secondary phenomena, and that what must really be sought out is the prime 
 cause of, and conditions of variation in, the metallic protuberances 
 themselves. 
 
 20. If we leave the path of results founded upon direct observation, and 
 endeavour to penetrate far enough into the domain of conjecture to furnish 
 ourselves with an answer to the question What is the influence that gives 
 rise to the sun-spots, or, rather, the prominences of which they appear to be 
 the after-effects, and regulates the sub-annual and secular variations in both 
 phenomena ? we shall find ourselves involved in an exceedingly perplexing 
 labyrinth of mystery and confusion. Various and conflicting are the theories 
 which have been propounded from time to time to account for the 
 appearance of sun-spots. Several of them, however, owing to their being 
 inconsistent with facts established by recent researches in solar physics, 
 have been necessarily abandoned. One theory, based on their well-ascer- 
 tained eleven-year cycle of variation, is worthy of notice, and endeavours to 
 account for them by the influence of planetary attraction. Messrs. De La Rue, 
 Stewart, and Loewy sometime back endeavoured to show that this period 
 was in some way connected with, and dependent upon, the period of Jupiter's 
 revolution in his orbit. The sun-spot cycle, however, according to Wolf, 
 is fixed at 11*11 years, a period differing too much from that of Jupiter's 
 revolution to accord with this hypothesis ; for, as Proctor says, " We have 
 not to go far back to find periods of spot maxima corresponding with 
 Jupiter's position (1) at aphelion; (2) at perihelion; (3) at his mean 
 distance." 1 They have, however, as has been already briefly remarked, 
 succeeded in discovering traces of the influence of both Venus and 
 Mercury upon the behaviour of sun-spots. This influence appears to be of 
 such a nature that the sun-spots attain their maximum size when carried 
 
 1 'Science Byways,' p. 125. 
 26 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 into positions as far as possible remote from the influencing planet. They 
 also notice that when one of these planets passes across the plane of the 
 sun's equator, it drags as it were the spots into the equatorial region of the 
 disk ; they spread towards the poles on the contrary when the planet passes 
 away from the equatorial plane. 1 The theory, nevertheless, of their being 
 entirely due to planetary influence, gives no satisfactory explanation of 
 several peculiar phenomena in connection with the appearance of sun-spots, 
 amongst others the apparent downrush and condensation that takes place 
 in their interiors, and the appearance of greater brightness in the inner, 
 compared to the outer edge of the penumbra. KirchofFs theory of their 
 being dense agglomerations of vapours superimposed on the photosphere, 
 which for some time obtained numerous adherents, is now finally discarded, 
 chiefly in consequence of the fact which recent spectroscopic investigations 
 have brought to light, viz. that instead of the photosphere being surrounded 
 by a cool atmosphere (assumed to exist in order to account for the degree of 
 condensation requisite for the production of clouds), it is surrounded by an 
 intensely hot stratum of gas, which forms what is generally known as the 
 Sierra chromosphere. 2 
 
 21. It may be remarked that though a dense agglomeration of vapours 
 relatively cool enough to be visible as a dark mass, could hardly quietly 
 float about in the chromosphere, a sudden irruption of cooled vapours from 
 regions beyond the chromosphere, such as those shot out by the prominences, 
 might temporarily exist as a dark spot, not only in the chromosphere, but 
 below the level of the photosphere. Indeed, the very fact that spots form 
 cavities in the photosphere, would seem to show that the cooled gases are pro- 
 jected (probably fall back) upon it with sufficient velocity to maintain their 
 low temperature, unaffected for a time at least by their surroundings. Mr. 
 Herbert Spencer's theory, a full account of which is given in Louis 
 Figuier's ' Day after Death,' avoids the error into which Kirchoff is found 
 to have fallen, in assuming the spots to be clouds suspended above the 
 photosphere, and supposes them to be clouds of metallic vapour formed by 
 the rarefaction, and consequently refrigeration, which takes place in the 
 interior of a solar cyclone. He likewise accounts for the peculiar aspect of 
 the penumbra already alluded to. by supposing that for some distance 
 round a cyclone there will be a drawing in of the superficial gases towards 
 the vortex. " All the luminous spaces of more transparent clouds, forming 
 the adjacent photosphere, will be changed in shape by these centripetal 
 currents, they will be greatly elongated, and those peculiar aspects which 
 the penumbra present will be so produced." This theory doubtless seems 
 to be satisfactory in so far as it avoids placing the clouds when it has been 
 shown they could not possibly exist ; but at the same time it attempts no 
 explanation of the cause of the solar cyclones upon the assumption of 
 whose existence it is alone founded. 
 
 1 ' Researches in Solar Physics,' by De La Eue, Stewart, and Loewy. 
 
 2 Vide Scliellen, 'Spectrum Analysis,' p. 415. 
 
 27 
 
SOLAE PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 22. A comparatively new theory, and one which disposes of many 
 difficulties connected with the explanation of the violent eruptive forces 
 displayed by the jets and prominences in the Sierra, has been propounded 
 by Professor Young, of Dartmouth College, Hanover, U.S., in which he 
 considers the Sun to be an immense gaseous bubble, the external envelope 
 of which is formed of metallic rain falling from the photosphere of luminous 
 clouds which floats above it. This rain, on approaching the Sun's strongly 
 heated interior, becomes revaporised, thus forming a nearly continuous 
 envelope, through which the eruptions which form the jets and prominences 
 take place. Proctor says : " In other words the Sun according to this view 
 is a gigantic bubble, whose walls are gradually thickening, and its diameter 
 diminishing, at a rate determined by its loss of heat. It differs, however, 
 from ordinary bubbles in the fact that its skin is constantly penetrated by 
 jets and blasts from within." l 
 
 According to this theory the spots are supposed to be places where the 
 photospheric clouds are thrust aside, by the cyclonic downrush of matter 
 from without, and the metallic rain thus rendered visible through the 
 opening. The luminous clouds 'thrust aside by this assumed downrush, 
 being heaped closer together, would naturally shine with greater intensity, 
 and consequently appear as faculae lining the regions of the spots. This 
 theory likewise accounts for the peculiarity previously alluded to in the 
 penumbra, viz., that it is brighter at its inner than at its outer edge ; that 
 is to say, if, according to Proctor, we assume that the lower limit of the 
 showers falling all round a spot lie closer than the upper ones (which 
 appears likely owing to the indraught caused by the whirling gases), we 
 should expect to find, as we actually do in reality, that the lines of rain 
 will come closer together, and therefore appear brighter as they converge 
 towards the centre of a spot. Proctor appears to consider this coincidence 
 so important as " to throw serious doubts upon all the other theories which 
 have hitherto been propounded in explanation of spot phenomena." 2 
 
 23. M. Faye formerly held a theory somewhat similar to that of Pro- 
 fessor Young, and agreed with him in considering the photosphere to be 
 the effect of partial condensations, but attributed the spots to vertical 
 ascending and descending currents within the photosphere, spots being 
 produced where the former predominate, and the luminous matter of the 
 photosphere is temporarily dissipated, while the retardation of the different 
 zones of the photosphere, noticed by Carrington and Laugier, was accounted 
 ior by the rupture of equilibrium produced by the currents. 2 Professor 
 Young, however, in dealing with the sun's spots, evidently assumes according 
 to his theory that the primary movement commences from without in the 
 form of a downrush. 
 
 24. The question, then, whether the primary movement commenced from 
 within, or without, was for some time the chief point of difference between 
 
 1 'Science Byways,' by Proctor, p. 123. 
 
 2 ' Sur la Constitution physique de Soleil,' par M. Faye. Comptes Eendus, Paris 
 . 28 
 
ESSAY II. SOLAK PHENOMENA AND CLIMATIC CYCLES. 
 
 the two rival thories. As I have already had occasion to remark, however, 
 M. Faye has been forced to renounce his idea of the primary movement 
 commencing from within, owing to the incompatibility of this condition with 
 the evidence afforded by spectroscopic analysis. Professor Young's theory 
 on the other hand, does not by any means preclude the possibility of the 
 co-existence of an outrush of gas from the spot, but rather makes this 
 phenomenon a necessary consequence of the downrush. Altogether it 
 appears to coincide very well with Secchi's and Zollner's notion that the 
 spots are the sequelae of eruptions of gas from the jets and prominences in 
 the Sierra, the condensed gas or scoria sinking into the photosphere by its 
 own gravity. 
 
 25. There is, however, an addition which may be made to Professor 
 Young's theory, effecting a slight modification in it without affecting its 
 intrinsic worth, from which the peculiarly limited area occupied by the 
 spots on the solar disk, the constancy of the sun's light and heat, and the 
 phenomenon of downrush have been hitherto thought to flow as necessary 
 consequences. I allude to what is generally known as the meteoric theory 
 of solar heat, a theory which was started a few years ago by Mayer, Water- 
 ston, and Sir W. Thomson, in which the sun-spots are supposed to be perfora- 
 tions in the photosphere caused, or at any rate aided in their production, by a 
 periodic rain of meteors, or the straggling meteoric masses, in the'train of some 
 yet undetected comet travelling in an orbit of eleven years round the sun. 
 
 26. If we accept Schiaparelli's theory of the common origin of shooting 
 stars and comets, and combine it with Professor Tait's notion of the consti- 
 tution of comets, which he considers to be " swarms of stones or meteors 
 from which stragglers are continually falling into the sun, owing to their 
 tangential velocity being checked by the collisions that are constantly 
 taking place amongst them," x we shall have little difficulty in under- 
 standing how even comets, ordinarily known as such, might during their 
 perihelion passage assist the body or bodies of undetected meteors already 
 alluded to in producing the solar spots. In proof of a general connection 
 between sun-spots and comets, the zones which the former occupy on the 
 solar photosphere are found to correspond in general with the curves in 
 which tangent planes to the cone of cometary orbits, if produced, would 
 intersect the sun. It may however be objected to this theory, that no 
 meteoric or cometary system can pour a steady hail of meteors on the sun, 
 for he is their ruling centre, and therefore under ordinary circumstances 
 their orbits should pass round him without intersecting his substance. It 
 must be remembered nevertheless, as Proctor says, " that they are infinitely 
 more crowded in the neighbourhood of the sun than at a distance from him, 
 and therefore at perihelion an indefinite number of meteoric orbits must 
 intersect, and collisions be continually taking place between different 
 members of countless systems." 2 
 
 1 Tait's ' Kecent Advances in Physical Science.' 
 
 2 ' Other Worlds than Ours.' Proctor. 
 
 29 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 In the sun's immediate vicinity, therefore, we may expect to find the 
 conditions fulfilled for a constant rain of meteors (probably increasing and- 
 diminishing periodically according to the density of the streams) upon 
 particular zones of the sun's surface. 
 
 The preceding hypothesis has since been abandoned by one of its earliest 
 promoters (Sir W. Thomson), as being incompatible with a well-ascertained 
 fact, the impossibility of the existence of a resisting medium in the imme- 
 diate neighbourhood of the sun. 
 
 It has, however, been remarked that such a medium is not essential to the 
 theory, since the same cause which accelerates the motion of Encke's comet is 
 capable in the long run of precipitating meteoric streams on the sun's surface. 1 
 
 It is also in accordance with the now universally held theory of the 
 origin of the sun and other members of the solar system, that they have 
 been formed by the continual aggregation of meteoric matter. Further, it 
 has been recently shown that the majority of the substances composing 
 meteors are found by their spectra to exist in the sun. Prof. Maskelyne, 
 for example, has proved that thirteen out of the twenty-four elements which 
 have been found in fallen meteorites, exist in one or other of the solar 
 envelopes, while the rest, as Mitscherlich, Angstrom, Wiillner, Secchi, and Zoll- 
 ner have shown, may also exist there, though their lines are not apparent in 
 the solar spectrum. 2 The meteoric theory, besides, accounts satisfactorily 
 for the position of the spots on the solar disk, the relative position of the 
 faculae, heaped up behind the spots by the inrush of meteoric matter in a 
 direction contrary to that of the solar axial rotation, the spot farthest 
 in advance being the last to disappear, owing to its being in the most 
 favourable position for catching the meteors that remain as the stream is 
 gradually thinning off. Perhaps we might even venture to suppose that 
 the sun's spots, once formed by the fall of external meteors, would subsequently 
 become the channels by which the condensed residue of the jet eruptions 
 found its way again into the sun's heated interior. 
 
 27. Even if the meteoric andcometary theory of sun-spots is unsupported 
 by direct evidence, it must be allowed, as Proctor says, to be a strange 
 coincidence, that in 1843, a year of minimum sun-spot area, a remarkable 
 sun-spot, 74,000 miles in diameter, made its appearance on the Sun's disk 
 three months after the perihelion passage of Hubbard's comet a phenomenon 
 which Schwabe regarded as an anomaly, and not to be looked for as the 
 general cause of the spots of his cycle. 3 
 
 It is also noticeable, as somewhat confirmatory of a connection between 
 sun-spots and comets, that in general unusually large numbers of comets 
 precede or accompany the years of maximum sun-spot, very few non-periodic 
 comets being visible at the time ot minimum sun-spot. 4 It has besides 
 
 1 The acceleration of this comet is, I believe, still " sub judice." 
 
 2 Schellen, ' Spectrum Analysis,' p. 411. 
 
 3 * Light Science.' Proctor. Vol. ii. 
 
 4 Hahn, ' Ueber die Beziehungen der Sonneufleckenperiode zu meteorologischen Erschei- 
 nungen,' p. 178. 
 
 30 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 been calculated that chemical action is insufficient to account for the pro- 
 tracted emission of the sun's enormous heat and light, whilst meteoric 
 action depends on independent evidence. Sir W. Thomson said (before he 
 abandoned the theory), that the former could only generate 3000 years' heat, 
 while the latter would account for 20,000,000 years' solar heat. Helmholtz 
 has endeavoured to explain this continued emission of heat upon the assump- 
 tion that the sun is constantly contracting, and has shown that the shrinking 
 of the sun's diameter by T^-Q-O-O- P art f i ts present length would generate 
 an amount of heat competent to cover the total solar emission for 2000 years. 
 Proctor unites the two theories, and appears to think " the combined effect 
 of contraction and the arrival of meteoric supplies would account for that 
 steadiness of emission which forms so important a characteristic of solar 
 action." l 
 
 It must be remarked that if, as the meteoric and cometary theory 
 assumes, the sun-spots are regarded as perforations in the photosphere, through 
 which the sun is fed, as it were, with meteors, a process strikingly analogous 
 to that of firing-up in a furnace, the accompanying eruptive phenomena of 
 jets and prominences in the Sierra may be assumed to be caused by the 
 increased tension of the gases within the solar bubble, produced by the 
 introduction of such quantities of foreign material. 
 
 28. So far the arguments in favour of the meteoric origin of sun-spots 
 would appear to be fairly satisfactory. There is, however, one apparently 
 insuperable objection to the notion that the sun's heat is chiefly derived 
 from the fall of meteors, viz., the discovery by the late well-known French 
 astronomer, Leverrier, that the amount of intra-Venusial matter capable of 
 being projected into the sun does not amount to more than would suffice 
 to maintain the total solar radiation for four j'ears ! It may, however, be 
 argued on the other hand that the sun is continually moving in space, and 
 therefore probably meeting with fresh supplies of meteoric matter, so that 
 it need not necessarily be dependent merely upon the small amount that 
 exists at any given moment in its immediate neighbourhood. Besides, it is 
 quite possible that though the sun's heat may be principally due to contrac- 
 tion, the periodic secular variations in it, such as those which are believed 
 to accompany the different phases of sun-spot activity, may be caused, 
 though not necessarily instantaneously, by fluctuations in the supply of 
 meteoric matter. Though the meteoric theory in its original form has 
 been abandoned by its chief promoter, Sir W. Thomson, it has lately 
 been revived in a modified form by Dr. Arthur Schuster, F.K.S., a well- 
 known solar observer, by whom no doubt it will be further developed 
 in the future. 
 
 29. Meanwhile Professor Young's theory of the constitution of the solar 
 envelopes, and the mode in which sun-spots are formed, may be provisionally 
 adopted as the one which best accords with the facts hitherto ascertained. 
 It may be observed that Professor Young's notion that the sun-spots are 
 
 1 The Sun.' Proctor, p. 459. 
 
 31 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 openings in the photosphere caused by the descent of matter from the region 
 above it, coincides with those of Secchi and Zollner, which regard them as 
 places where the matter erupted from the metallic protuberances, sinks back 
 upon the photosphere and occupies the cavities or depressions in the photo- 
 spheric matter displaced by its own gravity. The only thing still wanting 
 to complete the theory, is a satisfactory answer to the question What is 
 the cause of the approximately regular sub-annual and secular fluctuations 
 in the frequency of, and area occupied by, the solar spots? No theory of 
 sun-spot formation can be considered perfect, until it accounts satisfactorily 
 for these periodical changes, and as the preceding theory makes them out 
 to be secondary phenomena directly depending for their production on the 
 metallic protuberances, the problem is in this case merely transferred to 
 the latter phenomena, the variations in whose frequency and area approxi- 
 mately correspond with those of the spots themselves, thus affording an 
 additional proof of the close connection between the two. 1 The question 
 therefore finally resolves itself into the following, viz. : " What are the 
 causes which lead to the semi-annual and secular changes in the number and 
 size of the protuberances and jet eruptions ? When this question receives a 
 satisfactory and eonclusive answer, the whole science of solar physics will 
 have advanced an immense step beyond the position it at present occupies. 
 
 30. But it may be asked, how does the preceding resume of the facts and 
 theories connected with sun-spot formation help us to discover in what way 
 they, or rather the physical changes in the solar atmosphere which regulate 
 their frequency and area, affect the meteorology of the earth. In reply to this, 
 we would remark, that several of the facts alluded to are decidedly calcu- 
 lated to favour the notion of an inverse relation between the amount of solar 
 radiated heat and the frequency and area of sun-spots. First, the fact already 
 noticed regarding the amount of absorbing vapour above the photosphere, 
 at the different epochs of protuberance and spot frequency, and secondly an 
 induction from a consideration of the probable proportion of solar energy 
 transformed into radiant heat at the different epochs of solar activity, and 
 therefore of sun-spot frequency. In regarding this latter point we may 
 assume, to start with, that the total amount of available solar energy is 
 practically constant during finite periods. For even if we imagine the 
 solar energy to be maintained by continuous contraction, we must suppose 
 it to go on regularly, and not by fits and starts. 
 
 Now, how does this available solar energy manifest itself? In two 
 ways. First, in the activity by which the heated metallic vapours and 
 hydrogen gas are elevated above the general level of the photosphere, from 
 whence after their temperature has been considerably lowered by their 
 increased radiative capacity in these regions, they subsequently sink back 
 
 1 The parallelism is not absolute, however, nor could this be expected, since certain pro- 
 tuberances being purely hydrogen have nothing to do with the spots. If the metallic 
 protuberances be considered alone the correspondence is more complete. The time 
 of minimum sun-spot, for example, is characterised by an almost total absence of large 
 metallic protuberances. 
 32 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 to form the spots and faculae respectively ; secondly, in radiant heat and 
 light. 
 
 31. Now if this available solar energy remains constant, it can readily 
 be understood how an excess in either of the two ways in which it is 
 manifested, necessarily implies a corresponding defect in the other, and 
 vice versa. According to this notion therefore, we should expect to find 
 the radiation in excess of the average in years of small activity, i.e. in 
 years of minimum sun-spot, and in defect of the average in years of great 
 activity, that is in years of maximum sun-spot. 
 
 32. It seems, then, that most of the evidence hitherto adduced from 
 observations of the physical condition of the solar surface favours the pre- 
 ceding hypothesis. We shall have occasion subsequently to bring forward 
 evidence from the physical conditions that prevail on the terrestrial globe, 
 amongst others an induction from Messrs. Blanford and Eliot's recent theory 
 of cyclone generation, which powerfully supports the same hypothesis. It 
 may be remarked that several leading physicists, notably Professor 
 Balfour Stewart, and Mr. J. Norman Lockyer, strongly incline to hold the 
 opposite view, viz., that solar radiation is greatest when there are most spots, 
 and vice versa. They arrive at this conclusion by supposing in the first 
 place, that greater solar activity, as evinced by a greater number of promi- 
 nences and sun-spots, indicates more rapid combustion in the solar furnace 
 and therefore more radiation; and secondly, that the greater number of 
 cyclones in the tropics (and other storms in the extra-tropics according to 
 Professor Stewart) implies greater activity in terrestrial meteorological 
 conditions, and so the. expenditure of more direct solar heat to produce it. 
 The relations between barometric pressure in the tropics and the frequency 
 and area of sun-spots recently established by Mr. F. Chambers, are also cited 
 in favour of the same hypothesis, but the considerations involved with regard 
 to this element, we propose discussing later. In the meantime it is evident 
 that while the majority of physicists, are in favour of some connection 
 between the different phases of solar activity and a variability in the 
 amount of solar radiation, there is at present a marked division of opinion 
 as to whether the relation is direct or inverse. 
 
 33. For the present we will abandon any further reference to theories 
 founded on telescopic and spectroscopic observation alone, and proceed to 
 examine what progress has been made towards a solution of this interesting 
 problem, by direct observation of the amount of solar radiation, and by 
 comparison of air-temperature and other meteorological elements indirectly 
 due to solar radiation, for different years of the sun-spot cycles. We must 
 not forget, however, that in dealing with the question of any presumed con- 
 nection between solar and terrestrial meteorology, there are certain terres- 
 trial phenomena, notably terrestrial magnetism and the Aurora Polaris, which 
 appear to have both a direct and indirect connection with the sun ; and also 
 that, in endeavouring to trace a connection between solar and terrestrial 
 phenomena, we cannot confine our attention solely to a diagnosis of sun- 
 
 PART I. No. 2. D 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 spots, and the possibly very limited changes which the solar physical con- 
 ditions contemporaneous with their periodical variations produce in 
 terrestrial climate. 
 
 34. The connection between the sun and the earth is a very complex 
 one, and besides the regularly recurring (1) diurnal, (2) seasonal, and 
 (3) annual effects due to (1) the force of attraction, and the diurnal rotation 
 of the earth, (2) the fixed inclination of the earth's axis to the plane of 
 the ecliptic, and (3) the change in the absolute distance of the sun from the 
 earth due to the eccentricity of the orbit, embraces effects due to (1) the 
 period of solar axial rotation, (2) the relative position of the sun and moon 
 with respect to the earth, and (3) the physical condition of the sun's 
 surface with respect to spots, jets, and prominences, height of atmosphere, 
 brightness of photosphere, &c. ; which, though in some cases subject to 
 regularly recurring periods of variation, in others are liable to abrupt 
 changes, which occasionally are evidently related to equally sudden and 
 abnormal phases of terrestrial meteorological, and magnetical phenomena. 
 In attempting, therefore, to estimate what terrestrial effects can be 
 regarded as having a well-established connection with sun-spots or any 
 other periodically recurring condition of the solar surface, we should 
 expect to find any one effect due to a single cause, so masked by effects due 
 to variations in several of the other influences at work, as to necessitate our 
 enquiring into all the effects due to each disturbing influence respectively, 
 and endeavouring to separate from the complex total the precise effects 
 both qualitative and quantitative, corresponding to that one cause alone. 
 
 35. The importance of discovering the true origin and nature of sun- 
 spots and the causes of their periodicity, would however be considerably 
 increased, were we to find any decided and universal coincidence between 
 their phases and those of terrestrial weather ; for even granted that such a 
 coincidence did not necessarily imply the existence of any direct correlation 
 of cause and effect, we might still search for some common ' vera causa ' 
 capable of producing or influencing both phenomena simultaneously. 
 
 36. We have already alluded to the connection found to exist between 
 the secular variations in terrestrial magnetism and the eleven-year period of 
 solar spots. This forms but a portion of a still larger cycle of 55 J years, which 
 exists in an equally marked degree in both phenomena. This connection, 
 first noticed by Wolf and Sabine, was for some time discredited, but has now 
 been proved beyond all possibility of doubt by Professor Loomis of Yale 
 College, U.S., 1 and still more recently by Professor Hermann Fritz of 
 .Zurich in his magnificent prize essay written for the Haarlem Society 
 of Sciences in 1878. 2 Such an intimate connection between periodic 
 variations in terrestrial magnetism and solar spots, is a strong col- 
 lateral proof in favour of the existence of some similar connection 
 
 1 American Journal of Science and Arts,' 1870-73. 
 
 2 Ueber die Beziehungen der Sonnenflecken zu den meteorologischen und magnetischen 
 Erscheinungen der Erde, von H. Fritz. Haarlem, de Erven Loosjes, 1878. 
 
 34 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 between variations in terrestrial weather and solar disturbances. I have 
 already observed that according to Professor Balfour Stewart, the majority 
 of the meteorological disturbances produce and govern the corresponding 
 variations in terrestrial magnetism. It matters little to us, however, in 
 our present incomplete knowledge of these elements, which is the cause 
 and which the effect, so long as the connection between them is strong 
 enough to enable us by examining the periods of magnetic variation to 
 know where to look for corresponding meteorological disturbances. In 
 any case it is probable that to nearly every period of magnetic variation 
 (and they are sufficiently numerous and far more easy to determine than 
 their meteorological analogues), there is a corresponding meteorological 
 period, and thus by a process of induction, having learned where to look for 
 our meteorological periodicities, we may, after hunting them out, be able 
 finally to trace them back to their primary cosmical causes. 
 
 Through what agency meteorological disturbances cause similar dis- 
 turbances in the intensity and direction of terrestrial magnetism is but 
 partially understood. In fact, as regards this subject we are, as it were, 
 on the threshold of one of the unknown, though still possible developments 
 of the meteorology of the future. It has, however, frequently been observed 
 that the magnetic pole, the pole of greatest cold, and the pole of the winds, 
 are nearly coincident. The equatorial calms or wind equator, together with 
 the magneto-dynamical and thermal equators (the two latter in addition to 
 the general correspondence of their intermediate lines of equal magnetic 
 and thermal intensity), also exhibit a remarkable coincidence. 
 
 It is possible, therefore, as Professor Balfour Stewart thinks, that the 
 rarefied upper convection currents oi the atmosphere, generally denomi- 
 nated the " Anti-trades," which are known to exhibit a tendency to converge 
 towards the pole of the winds, may act as conductors of electricity from 
 the magnetic equator to the magnetic poles. As the regions of greatest 
 auroral intensity are approximately coincident with the magnetic poles, 
 the idea entertained by De La Rive, the great Swiss electrician, that this 
 phenomenon is due to the meeting and silent discharge between the 
 opposite electricities with which the equatorial currents arid the earth are 
 respectively charged, is in complete accordance with, and to all appearance 
 a natural consequence of, the theory held by Professor Stewart. According 
 to this view the Aurora Polaris should, ceteris paribus, approximately con- 
 stitute a measure of the amount of electricity conveyed to the wind- and 
 magnetic-poles by the equatorial convection currents. Any increase, 
 therefore, in the amount of electricity conveyed by these currents should 
 be indicated by a corresponding increase in the number, brilliancy, and 
 magnitude of the Aurora Polaris. The conditions under which this 
 quantity should rise to a maximum are not easy to determine. Either 
 an excess or defect of solar radiation may be the cause. .Professor Loomis 
 evidently thinks the former, for he thus explains the cause of the annual 
 inequality of auroras. " The unequal frequency of auroras in the different 
 35 D 2 
 
SOLAE PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 > M6nths'oT y ^ year depends partly upon the amount of electricity present 
 ' in tne-' upp'er aij, and partly upon the humidity of the air by which this 
 electricity. may be discharged. The supply of electricity must be greatest 
 when the evaporation is most rapid, that is in summer, and this is pro- 
 bably the reason why in North America auroras are more frequent in 
 summer than in winter." 1 The secular maximum, however, which is coinci- 
 dent with the maximum of solar spots, he does not attribute to the 
 indirect effect of any increase of temperature and evaporation, but rather 
 to disturbances in the solar electric currents, directly causing both 
 frequency of spots and abnormal displays of the aurora. The question 
 here naturally suggests itself, Why not attribute the secular changes in 
 auroral frequency to a secular variation in the same influences as those by 
 which the annual changes are supposed to be caused, instead of having 
 recourse to a direct solar magnetic influence ? Did we do s'o at once on 
 the hypothesis put forward by Loomis to account for the annual inequality, 
 we should infer that temperature and evaporation were greatest in years of 
 maximum auroral frequency, i.e. in years of maximum sun-spot. 
 
 It may, however, be objected to Professor Loomis's hypothesis, that it 
 leaves out one very important factor in the production of auroral displays, 
 viz., the presence of ice. Humidity and a high temperature are doubtless 
 necessary for the production of the electricity and its discharge, but the 
 visibility of the phenomenon depends of course on its luminosity, and this, 
 according to De La Kive, is a direct function of the resistance which the 
 reunion of the two electricities encounters, on account probably of the 
 congelation of particles suspended in the air, which constitute the haze 
 invariably accompanying this phenomenon. M. De La Eive even infers 
 that secular changes in the auroral frequency may be caused b} T secular 
 changes in the accumulations of ice in the neighbourhood of the polar 
 regions. For the Aurora Polaris being only the luminous effect of the 
 electric discharges which take place around the poles between the ground 
 and the vapours that are carried thither, it is necessary, in order to the 
 production of this effect, that the discharges should meet on their route 
 with icy particles, and that consequently the ground itself must be covered 
 with ice. At periods therefore when the regions situated round the magnetic 
 pole are covered with less ice than usual, the discharges may take place, 
 but they will be little or not at all luminous. 
 
 On the other hand, an unusual accumulation of ice in these regions 
 would without any additional supply of vapour probably cause a decided 
 increase in the frequency and brilliancy of the visible Auroras, and from the 
 irregularity of the discharges introduced by the increased resistance give 
 rise at the same time to those large deviations of magnetic declination 
 which usually accompany these phenomena. 2 It seems quite possible then 
 
 1 Loomis's Meteorology/ p. 198. 
 
 2 It has been remarked in connection with the same idea that the neighbourhood of the 
 Alps may influence the frequent displays of Aurora seen in Northern Italy. 
 
 36 
 
ESSAY II. SOLAE PHENOMENA AND CLIMATIC CYCLES. 
 
 that the secular changes in auroral and magnetic disi 
 correspond directly with the secular changes in sun-spot fc$bKrjcy|j^V ^' 
 partly due to variations in the amount of polar ice intro j " *-- * 
 secular meteorological changes. Accordingly we should ex] 
 preponderance of ice at the maximum epoch of sun-spots, and a corresponding 
 deficiency at the minimum epoch. 
 
 Now from the investigations of Dr. Chavanne, of Vienna (Petermann's 
 Mittheilungen, 1874, pp. 134-245), as reviewed by Professor Fritz in his 
 monograph already referred to, as well as other tables furnished by 
 different investigators for the amount of ice round the pole, in northern 
 rivers, and floating in the Atlantic, the above relation is found to be 
 generally true. Moreover the results obtained by Drs. Koppen and Hahn 
 from a comparison of the air-temperature in different years for a large 
 portion of the Northern hemisphere naturally lead to the same conclusion. 
 
 It would, of course, be absurd to suppose that a variation in the amount 
 of ice near the poles is the sole cause of changes in the magnitude and 
 frequency of a phenomenon like the aurora, and the magnetic disturbances 
 which accompany it, both of which often have a" true cosmical character, 
 the former being manifested at the poles, and the latter all over the globe 
 at the same absolute time. It is quite possible, however, that the presence 
 of ice may favour the visibility and magnitude of the phenomenon, while 
 the main causes that contribute towards its production may be partly of an 
 indirect meteorological and partly of a direct magnetic nature. 
 
 Inability to follow up with precision a line of inductive proof like the 
 preceding only arises from our imperfect knowledge of the way in which 
 magnetic and meteorological phenomena react upon one another, and by no 
 means argues the inability of observing the numerous instances that exist 
 of analogous periods of variation in the two phenomena. 
 
 37. By accumulating correlative analogies of this description we may 
 ultimately furnish ourselves with such an array of proofs of the exact cor- 
 respondence between the two phenomena, that when the method by which 
 the one produces or affects the other is thoroughly understood, we may 
 without hesitation regard the variations in the one as a complete index to 
 similar variations in the other. Before long, therefore, we may come to 
 regard the magnetic needle as a sort of meteorological index, the variations 
 of which may be taken to indicate corresponding changes in terrestrial 
 weather, either coincident with, or following upon, those conditions of the 
 convection currents of the atmosphere, which, according to Balfour 
 Stewart, directly affect the weather and indirectly the magnetism of the 
 globe. 
 
GENERAL BIBLIOGRAPHY. 
 
 6. Dove, H. W. Ueber der Vertheilung de 
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 the r,^ /-,,,v4.~1 4- T. 
 
 
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 . . 
 
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 , J . T _ . . 1..: ~ Ql3A UC? i , T _ l^ _ 1 . 
 
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 Schweigger, Journ., Ixi. p. 360-367 
 
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 . (2) p. 74-114. 
 38 
 
 De 1'influence des 
 Mem. Soc. Phys. 
 
 Lombard, H. C. 
 
 saisons sur la mortalite. 
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GENERAL 
 
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 BIBLIOGRAPHY. 
 
 1834. 
 
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 sur I'atmosph&re terrestre, determinde par les 
 observations mete'orologiques. Quetelet, Cor- 
 resp. Math., viii. p. 257-275. Froriep, Notizen, 
 xlii. cols. 166-168. 
 
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 valent disorders contemporaneous and in sup- 
 posed connection with volcanic emanations. 
 A. N. H., vii. p. 193-202 ; 289-308 ; 609-630. 
 
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 7. Gunther, J. J. Witterungslauf vor 
 und wiihrend der letzten Erscheinung der Hal- 
 leyschen Cometen im Jahre 1759, wo er am 
 13. Marz seine Sonnennahe erreichte. Kastner, 
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 9. Huard. Pluie de Crapauds. L'Institut, 
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 10. Huber-Burnand. Lettre sur quelques 
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 14. Meyer, G-. F. Osservazioni meteoro- 
 logiche. Mem. Accad. Agric. Verona, xv. p. 
 291-312. 
 
 15. Morin, 3?. E. Instruction sur la maniere 
 de faire des observations meteorologiques. 8vo. 
 pp. 20. Paris. 
 
 16. Murphy, P. The Anatomy of the 
 Seasons, Weather guide-book, and perpetual 
 companion to the Almanack. 8vo. London. 
 
 17. Peltier, A. Pluie de Crapauds. L'In- 
 stitut, ii. p. 346-347. 
 
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 Am. Jl. Sci., xxv. p. 122-135. Froriep, Notizen, 
 xl. cols. 257-266. 
 
 19. S. Fall of Fish (Clupea cultrata). Journ. 
 As. Soc. Bengal, iii. p. 367. 
 
 20. Segesser. Ueber die Witterungskunde. 
 Verhand. Schweiz. Gesells., p. 25-27. 
 
 21. Stevelley, John. An attempt to 
 connect some of the best known phenomena of 
 meteorology with established physical principles. 
 Brit. Ass. Rep. p. 564-566. 
 
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 iii. p, 353-354. 
 
 1835. 
 
 1. Clarke, W. B. Instances of the effects 
 of Forest vegetation on Climate. A. N. H., 
 viii. p. 473-482. Froriep, Notizen, xlvi. cols' 
 161-168. 
 
 2. Clarke, W. B. On certain, etc. fas in 
 1834, 2.] 
 
 3. Dove, H. "W". Eine Bemerkung iiber 
 die Witterung dieses Jahres. Pogg. Ann., xxxvi. 
 p. 318-320. 
 
 4. Emerson, G. On the influence of the 
 moon upon the weather. Journ. Franklin Inst., 
 xv. p. 238-243. 
 
 5. Hutchinson, G. Causes and principles 
 of meteorological phenomena. Glasgow. (Lib. 
 Geog. Soc. Meteor. Soc.) 
 
 6. Mackenzie, Sir George. On certain 
 points in Meteorology and Magnetism. Phil. 
 Mag. vii. p. 355-356. 
 
 7. Marcet, F. ' Note, etc. [as in 1834, 12]. 
 Am. Jl. Sci., xxvii. p. 192-195. 
 
 8. Merian, P. Bemerkungen iiber die 
 meteorologischen Verhaltnisse des Jahres 1834. 
 Bericht Basel, i. p. 41-43. 
 
 9. Peltier, A. Nouvelle observation me"- 
 teorologique et electrique. Bull. Soc. Sci. Nat., 
 p. 90-91. 
 
 10. Redfield, W. C. On the evidence of 
 certain phenomena in tides and meteorology. 
 Am. Jl. Sci., xxviii. p. 310-318. 
 
 11. Schrb'n, L. Meteorologische Beobach- 
 tungen des Jahres 1833. Nova Acta Acad. 
 Caes. Leop., xvii. Supp. 
 
 12. Schrb'n, L. Meteorologische Beobach- 
 tungen des Jahres 1834. Nova Acta Acad. 
 Caes. Leop., xvii. Supp. 
 
 13. "White, W. H. Remarks contributive 
 to the elucidation of meteoric and atmospheric 
 phenomena. A. N. H., viii. p. 97-99. 
 
 14. White, W. H. Notices of 184 observa- 
 tions on Aurora Borealis made during a period 
 of thirteen years with the state of the weather 
 immediately subsequent. A. N. H., viii. p. 
 343-355. 
 
 15. White, W. H. Notices of solar and 
 lunar haloes, parhelia, paraselenae and meteors 
 as harbingers of falling weather. A. N. H., viii. 
 p. 501-504. 
 
 16. Essay on the Indian Summer. Ain. Jl. Sci., 
 xxvii. p. ,140-147. 
 
 1836. 
 
 1. Atkinson, Joseph. On Sir G. S. Mac- 
 kenzie's remarks on certain points in meteoro- 
 logy. Phil. Mag., viii. p. 187-189. 
 
 2. Bellani, A. Degli aeroliti, delle piogge, 
 e nevi rosse, e delle nebbie o esalazione secchie, 
 e di altri fenomeni atmosferici. Cattaneo, Biblio 
 di Farm., v. pp. 217-223; 282-287; vi. pp. 51- 
 57 ; 116-124. 
 
 3. Bouvard, E. De 1'influence, etc. [as in 
 1834, 1]. Spongia, Com. Med., ii. p. 495-511. 
 
 4. Couch, J. Tables of the thermometer 
 and the weather. Trans. Polyt. Soc. Cornwall, 
 p. 66-67. 
 
 5. David, Aloys. Resultate aus den Witte- 
 rungs Beobachtungen. Prag, Neue Schriften, iv. 
 (2), p. 148-188. 
 
GENERAL 
 
 18371838. 
 
 BIBLIOGRAPHY. 
 
 6. Everest, Robert. On the influence of 
 the moon upon atmospherical phenomena. Bibl. 
 Univ., ii. p. 369-371. Froriep, Notizen, xlix. 
 cols. 177-178. 
 
 7. Green, Charles. Ueber meteorologische 
 Beobachtungen in Luftballon. Froriep, Notizen, 
 1. cols. 245-247. 
 
 8. Harless, C. F. Die Meteorologie in 
 ihrer Anwendung auf die Medicin und insbe- 
 sondere auf die Krankheits Constitutionen und 
 herrschenden wie durchlaufenden Krankheiten 
 und was ihr Noth thut. Hufeland u. Osann, 
 Journ. Arzn., Ixxxiii. p. 7-37 ; Heft 2, p. 3- 
 32. 
 
 9 Kamtz, L. P. Lehrbuch der Meteoro- 
 logie. 3 Bde. 8vo. Halle, 1831-1836. 
 
 10. Merian, P. Meteorologische Uebersicht 
 des Jahres 1835. Bericht Basel, ii. p. 68- 
 71. 
 
 11. Murphy, P. Meteorology considered 
 in its connection with Astronomy, Climate and 
 the geographical distribution < of Animals and 
 plants, equally as with the seasons and changes 
 of the weather. 8vo. London. (Lib. Met. Soc.) 
 
 12. Ponton. Lettre sur une pluie de 
 Crapauds. Comptes Rendus, iii. p. 54-55. 
 Bibl. Univ., vi. p. 414-415. 
 
 13. Raguse, Marshal Due de. Ob- 
 servations de Meteorologie et de climatologie 
 faites pendant un voyage en Orient. Comptes 
 Kendus, ii. p. 210-216. 
 
 14. Tatem, J. G. An advocation of the 
 prosecution of meteorology ; and considerations 
 on lunar halo as a prognostic of weather. A. N. 
 H., ix. p. 357-359. 
 
 15. White, W. H. Some discussion on the 
 principles on which clouds are suspended, with 
 a recommendation that those, who pursue 
 meteorology do so co-operatively. A. N. H., ix. 
 p. 247-251. 
 
 16. Reports of the Joint Committee on Meteoro- 
 logy of the American Philosophical Society and 
 the Franklin Institute. Journ. Franklin Insti- 
 tute, xvih p. 286-321. 
 
 1837. 
 
 1. Caresme. Sur l'e"tude de la meteorologie. 
 Amiens, Mem., p. 49-69. 
 
 2. Crahay, J. G. Sur la Met^orologie. 
 Mem. Acad. Sci. Bruxelles, x. 
 
 3. David, Aloys. Resultateans denWitte- 
 rungs Beobachtungen. Prag, Neue Schriften, v. 
 (1) p. 113-154; v. (2), p. 157-194. 
 
 4. Dove, H. W. Meteorologische Unter- 
 suchungen. 8vo. Berlin. 
 
 5. Emmett, A. Experiments made during 
 a voyage and at Bermuda on the carbonic acid 
 in the atmosphere. Meteorological observations, 
 etc. Phil. Mag , xi. p. 225-227, 449-452. 
 
 6. Goethe, J. W. von. Meteorologie. 
 Werke, v. p. 402-419. Stuttgart. 
 
 7. Hall, G. W. On the connection of the 
 weather with the tides. Brit. Ass. Rep. for 
 1836, Notices, p. 41. 
 
 8. Howard, Luke. Seven Lectures on 
 Meteorology. 12mo. Pontefract. 
 
 9. Kelly, W. On the effects of clearing 
 and cultivation on climate, and on the situation 
 
 40 
 
 most favourable to the deposition of hoar-frost 
 and dew. Trans. Lit. Soc. Quebec, iii. p. 309-312. 
 
 10. Lange, Eduard. Welchen Einfluss 
 hat das Ausroden der Waldungen auf das Clima 
 und die Vegetation einer Gegend ? Altenburg, 
 Mittheil., i. p. 180-187. 
 
 11. Limouzin-Lamotte. Notice sur les 
 previsions atmosph^riques. Publ. Seances Acad. 
 Sci. Bordeaux, p. 60. 
 
 12. Madler, J. H. Ueber den Einfluss des 
 Mondes auf die Witterung. Oken. Isis, cols. 
 400-401. 
 
 13. Morin, P. E. Memoires composes au 
 sujet d'une correspondance meteorologique 
 ayant pour but de parvenir a predire le temps 
 beaucoup a 1'avance sur un point donne de la 
 terre. Tome i. Mems. 1-6. 8vo. Paris. (Lib. 
 Met. Soc.) 
 
 14. Quetelet, L. A. J. Sur la Meteoro- 
 logie. Mem. Acad. Sci. Bruxelles, x. 
 
 15. Russegger, Joseph. Physikalisch- 
 meteorologische Beobachtungen. Baumgartner, 
 Zeits., v. p. 495-511. 
 
 16. Swain, Jas. Electro-meteorological 
 observations. Am. Jl. Sci., xxxii. p. 304-307. 
 
 17. Reports, etc. [as in 1836, 16] Journ. 
 Franklin Institute, xix. p. 17-21. 
 
 1838. 
 
 1. Bellani, A. Degli aeroliti, etc. [as in 
 1836,2]. Cattaneo, Bibl. di Farm., x. p. 115 
 122; 173-183; 242-248; 306-311; 357-365. 
 
 2. Carlini, F. Sulla distribuzione e sull' 
 uso delle osservazioni meteorologiche. Effem. 
 Astro. Milano, p. 65-100. 
 
 3. Chassay. Faits et observations relatives 
 aux pluies de Crapauds. Mem. Soc. Linn. Nor- 
 mand., vi. p. 280-281. 
 
 4. David, Aloys. Resultate aus den Witte- 
 rungs Beobachtungen. Prag, Neue Schriften, vi. 
 (1), p. 129-170. 
 
 5. Dove, H. W. Ueber die geographische 
 Verbreitung gleichartiger Witterungserschei- 
 nungen. Berlin, Abhandl., p. 285-416. Berlin,- 
 Bericht., p. 75-83. 
 
 6. Dupuits de Maconex. Meteorologie, 
 Ann. Soc. Agric. Lyon, i. p. 493-502. 
 
 7. Lovelace, E. of. On climate in con- 
 nection with husbandry, with reference to a 
 work entitled ' Cours d'Agriculture, par le 
 Comte de Gasparini.' Journ. Agricult. Soc., 
 ix. p. 311-339. 
 
 8. Herschel, Sir J. F. "W. Instructions 
 for making and registering meteorological ob- 
 servations in S. Africa and other countries in 
 the South Seas, and at Sea. 8vo. Privately 
 printed. (Lib.- Met. Soc.) 
 
 9. Hombres-Firmas, L. A. d*. Recueil 
 de Memoires et d'observations de physique, de 
 meteorologie, d'agriculture et d'histoire naturelle. 
 8vo. p. 308. Nismes. 
 
 10. Lawson, Henry. Meteorological 
 register for 1836-7. 8vo. Hereford. 
 
 11. Murphy, P. The Weather Almanack 
 for the year 1838. London. (Lib. Met. Soc.) 
 
 12. Quetelet, L. A. J. De 1'influeuce des 
 Saisons sur la mortalite aux differeuts ages. 
 Mem. Acad. Sci. Bruxelles, xi. 
 
GENERAL 
 
 18391841. 
 
 BIBLIOGRAPHY. 
 
 13. Redfield, W. C. Meteorologies 
 
 sketches. Am. Jl. Sci., xxxiii. p. 50-65 ; 261- 
 265. 
 
 14. Sopwith, Thomas. On an easy way 
 of recording the state of the weather. Trans 
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 15. Report on Meteorology embodying the 
 facts relative to the storm of the 16th, 17th, and 
 18th March, 1838. Journ. Franklin Institute, 
 xxii. p. 161-175. 
 
 1839. 
 
 1. Arago, D. F. J. Rapport concernant 
 les observations de Meteorologie et de Physique 
 du globe qui pouvaient etre recommandees aux 
 Expeditions Scientifiques du Nord et de 1'Algerie. 
 Bureau des Long. Ann. Paris, p. 411-440. 
 
 2. David, Aloys. Resultate aus den Witte- 
 rungs Beobachtungen. Prag, Neue Schriften, vi. 
 (2), p. 105-145. 
 
 3. Lees, J. C. Meteorological Journal for 
 the years 1838 and 1839. Folio. Nassau, 
 Bahamas. 
 
 4. Matteucci, C, Sur 1'action des grands 
 feux pour pre'venir la formation des orages. 
 Comptes Rendus, ix. p. 605-606. 
 
 5. Meteor. Soc. London. Trans., vol. i. 
 8vo. (Lib. Soc. Met.) 
 
 6. Morrison, P. J. Considerations on the 
 principles, general bearings and utility of me- 
 teorology, with some account of atmospheric 
 electricity. Trans. Meteor. Soc., i. p. 60-66. 
 
 7. Murphy, P. The Weather Almanack 
 for the year 1839. (Lib. Met. Soc.) 
 
 8. RoweU, G. A. On Meteorology. Proc. 
 Ashmol. Soc., xvi. p. 12-15. 
 
 9. Ruskin, John. Remarks on the pre- 
 sent state of meteorological science. Trans. 
 Amer. Sci., i. p. 56-59. 
 
 10. Woods, R. C. Directions for making 
 meteorological observations on land or at sea, 
 with some remarks on the subjects of meteoro- 
 logical research. Trans. Meteor. Soc., i. p. 
 1-55. 
 
 11. A collection of miscellaneous and detached 
 registers kept at various places during 1839 
 (Lib. Met. Soc. MSS.) 
 
 1840. 
 
 1. Bravais, Aug., Lottin, et Ch. Mar- 
 tins. Observations concernant la Physique du 
 Globe et la Meteorologie faites dans le cours 
 d'une expedition aux Regions Arctiques. Comptes 
 Rendus, x. p. 289-302. 
 
 2. David, Aloys. Resultate aus den Witte- 
 rungs Beobachtungen. Prag, Neue Schriften, 
 vii. (1), p. 114-150, 
 
 3. Delezenne. Note sur un point de 
 me"teorologie. Mem. Soc. Sci. Lille, p. 5-9. 
 
 4. Dove, H. W. Ueber die aus der re- 
 lativen Lage des Meeres gegen die Continente 
 entstehender Unterscheide in der meteorologi- 
 schen Verhaltnissen der Ostkiiste Nord-Amerikas 
 uud der Westkiiste der Alten Welts. Berlin, 
 Bericht, p. 149-151. 
 
 5. Gaylord, W. Formation and dispersion 
 of a thunder storm ; parhelia, and a meteoro- 
 
 logical register. Am. Jl. Sci., xxxix. p. 59-64. 
 Bibl. Univ., xxv. p. 423-424. 
 
 6. Goethe, J. W. von. Sammtliche 
 Werke, xl. p. 309-382. Stuttgart. 
 
 7. Goethe, J. W. von. Versuch einer 
 Witterungslehre. Sammtliche Werke, xl p 253- 
 382. Stuttgart. 
 
 8. Holland, Sir H. On the influence of 
 the weather in relation to disease. Edin. New 
 Phil. Journ., xxix. p. 28-54. 
 
 Lottin. See 1840, 1. 
 
 9. Mahlmann, W. Ueber die 9- tind 19- 
 jahrige Witterungsperiode. Monats. Ges. Erdk 
 Berlin, i. p. 102-104. 
 
 10. Mahlmann, W. Ueber die Tem- 
 peratur einiger Meeres-Stromungen und ihren 
 Einfluss auf das Clima der anliegenden Kiisten. 
 Monats. Ges. Erdk. Berlin, i. p. 208-218. 
 
 Martins, Ch. See 1840, 1. 
 
 11. Meyer, G. F. Osservazioni meteoro- 
 logiche. Mem. Accad. Agric. Verona, xvi. p. 235- 
 
 12. Morin, P.E. Me'moire sur cette question: 
 Peut-on arriver a prevoir le temps au moins 
 un an a 1'avance ? Dans le cas de 1'affirmative 
 quels sont les progres faits en meteorologie qui 
 tendent a la faire croire, et quelle marche doit- 
 on suivre pour y arriver ? Congres Sci. France 
 viii. p. 329^362. 
 
 13. Murphy, P. The Weather Almanack for 
 the year 1840. 8vo. London. (Lib. Meteor. Soc.) 
 
 14. Richard, A. Rapport sur les manu- 
 scrits de Meteorologie et de Botanique, et sur 
 les collections d'Histoire naturelle faites dans 
 1'Inde. Comptes Rendus, xi. p. 186-195. Rev 
 Zool., p. 250^252. 
 
 15. Royal Soc. Report of the Committee 
 of Physics, including meteorology, on the 
 objects of scientific inquiry in these sciences. 
 Approved by the President and Council of the 
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 16. Sauvanau. Essai de me'teorologie com- 
 pared. Annal. Soc. Agric. Lyon, iii. p. 373 
 418. 
 
 17. Selby, P. J. On the effects produced 
 upon animal and vegetable life by the winter 
 of 1838. A. N. H., v. p. 334-340. 
 
 18. Simonin, Edmond. Sur la metdoro- 
 logie. Mem. Soc. Sci. Nancy, p. 421-439. 
 
 19. Sykes, W. H. On a shower of grain. 
 Brit. Ass. Rep., pt. 2, p. 44-45. 
 
 1841. 
 
 1. David, Aloys. Resultate aus den Witte 
 rungs Beobachtungen. Prag, Neue Schriften, 
 vii. (2), p. 202-237. 
 
 2. Forbes, J. D. Supplementary Report 
 n meteorology. Brit. Ass. Rep. for 1840, p. 37- 
 
 .OO. 
 
 3,. Friedrichsthal, E. Geographical and 
 neteorological observations. Journ. Roy. Geog. 
 3oc., xi. p. 258-263. 
 
 4. Fusinieri, A. Sopra alcuni fenomeni 
 neteorologici che hanno rapporto collo sviluppo 
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 Mem. Soc. Ital. Modena, xxii. p. 48-75. 
 
 41 
 
GENERAL 
 
 18421843. 
 
 BIBLIOGRAPHY. 
 
 5. G-raeger, N. Beitrage zur Meteorologie. 
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 45 
 
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 47 
 
THE SCIENTIFIC ENQUIRER. 
 
 Correspondence is invited on science matters of all kinds. In all cases 
 names and addresses should be given; but these will not be published without 
 the writer's consent. The Conductor will not be responsible for the opinions ex- 
 pressed by Correspondents. All communications should be addressed to the 
 Conductor, 10, Bouverie Street, London, E.G. 
 
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 55 
 
GENERAL 
 
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 56 
 
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GENERAL 
 
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 57 
 
GENERAL 
 
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 48. Meteorology. Annalen d. Hydro- 
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 Berlin. 3s. 
 
 49. Meteorology. Bureau central mete'o- 
 rologique de France. Instructions meteorolo- 
 giques. 8vo. Paris. 2*2 marks. 
 
 50. Meteorology. Fortschritte d. Meteo- 
 rologie. 1877-1879. Edited by H. J. Klein. 
 8vo. Koln. Pp. 126. 2s. 
 
 51. Meteorology. Jahrbuch, etc. [as in 
 1873, 36.] Edited by Guido Schenzl. Bd. vii. 
 8vo. Budapest. 10s. 
 
 52. Meteorology. Repertorium f. Meteo- 
 rologie. Ed. by H. Wild. 4to. Bd. vi. Heft 
 1. 7-7 marks. Heft 2. Pp. 426. 17 marks. 
 
 53. Meteorology. Schweizer meteorolo- 
 gischen Beobachtungen. Bd. xvi. Edited by R. 
 Wolf. 4to. Zurich. 9s. 
 
 54. Meteorology. Symons's Monthly 
 Meteorological Mag. 8vo. London. 
 
 55. Meteorology. Zeitschrift etc. [as in 
 1866, 27.] Bd. xiii. Edited by J. Hann. 8vo. 
 Wien. 12s. 
 
 56. Mohn, H. Grundziige d. Meteorologie. 
 Die Lehre d. Wind u. Wetter. 2nd ed. 8vo. 
 Berlin. 5'4 marks. 
 
 57. Moseley, H. "N. Notes by a Naturalist 
 on the Challenger. 8vo. London (rv). 
 
 58. MUller-Pouillet. Lehrbuch d. Physik 
 u. Meteorologie. 8th ed. by Pfaundler. Bd. 
 ii. 8vo. Braunschweig. 
 
 59. Neumayer, Geo. Denkschrift u'ber 
 einige Vorschlage zur Durchfuhrung des in dem 
 Punkte 31 des Programms fur den zweiten inter- 
 nationalen Meteorologen-Kongress angeregten Ge- 
 dankens, mit besonderer Beziehung auf die Ge- 
 genden der Erde in hohereu sudlichen Breiten. 
 4to. Hamburg. (Lib. Met. Soc.) 
 
 60. P. Pigeons and weather warnings. * Na- 
 ture,' xx. p. 363 (rv). 
 
 61. Fernet, J. Bericht iiber die Frage 16 
 des Programms fur den Meteorologen-Congress 
 in Rom, 1879. 8vo. Leipzig. (Lib. Met. 
 Soc.) 
 
 Pfaundler. See 1879, 58. 
 
 62. Pittei, C. Congresso Internazionale di 
 Meteorologia a Roma. Rivista Marittima. (Lib. 
 Met. Soc.) 
 
 63. Pittei, C. Rapports 'presented au deu- 
 xieme Congres mdteorologique international de 
 Rome. Svo. Florence. (Lib. Met. Soc.) 
 
 64. Poey, A. Comment on observe les 
 images pour prevoir le temps. 3rd ed. Svo. 
 pp. 5 and 176. Paris. 4s. 6d. (Lib. Met. Soc.) 
 
 65. Preston, Rev. T. A. Report on the 
 phenological observations for the year 1878. 
 Q. Journ. Meteorol. Soc., p. 42-64. [England.] 
 
 66. Rossi, M. S. de. La Meteorologia 
 endogena. 8vo. Milano. 7s. [Earthquakes.] 
 
 Schenzl, Guido. See 1879, 51. 
 
 67. Schultz, A. Bemerkungeu z. d. Be- 
 
 richte u'ber d. Organisation e. meteorolog. Dien- 
 stes in Interesse d. Land- u. Forstwirthschaft. 
 8vo. Berlin. 6s. 
 
 Scott, R. H. See 1879, 34. 
 
 68. Sidler, W. Z. Entwicklungs- Geschi- 
 chte d. modern. Meteorologie. Svo. 
 
 69. Smyth, Piazzi. Weather past and to 
 come. ' Nature,' xix. p. 338 (rv). [Temperature.] 
 
 70. Spooner, W. C. The seasons and the 
 crops ; their mutual relations. Svo. Dorchester. 
 (Lib. Met. Soc.) 
 
 Strachan, R. See 1879, 34. 
 
 Symons, G. J. See 1879, 34; 1879, 54. 
 
 71. Tissandier, G. Observations meteoro- 
 logiques en ballon. Resume de 25 ascensions 
 aerostatiques. Svo. Paris. Pp. 55. Is. Qd. 
 
 72. Wettstein, H. Die Stromungen d. 
 Festen, Flu'ssigen und Gasfbrmigen und ihre 
 Bedeutung fur Geologie, Astronomic, Klimato- 
 logie und Meteorologie. Svo. Zurich, 1880. 
 [Published in 1879.] 8s. 
 
 Wild, H. See 1879, 52. 
 
 73. Wild, H. Rapports succincts sur quel- 
 ques articles du programme du deuxieme Con- 
 gres international des meteorologistes a Rome en 
 1879. 4to. St. Petersburg. 
 
 74. Williams, W. Mathieu. A possible 
 consequence of our present weather. l Nature,' 
 xxi. p. 130-131 (rv). 
 
 Wolf, R. See 1879, 53. 
 
 75. Instructions to meteorological observers 
 issued by the Meteorological Committee. Svo. 
 Cape Town. (Lib. Met. Soc.) 
 
 76. The Meteorological Congress at Rome. 
 ' Nature,' xx. p. 57-59 (rv). [Nothing for these 
 notes.] 
 
 77. Meteorological Notes. ( Nature,' xx. p. 
 270, 271 (rv). [The subjects referred to are : 
 Loomis's observations on wind and areas of low 
 barometric pressure in New England and on 
 Mt. Washington ; the observations at Stony- 
 hurst ; and the rain results for New S. Wales.] 
 
 78. Meteorological Notes. 'Nature,' xxi. 
 p. 48-49 (rv). [The subjects dealt with are : 
 temperature in London ; connection between 
 weather and rate of mortality in the Australian 
 colonies ; the weather in Iceland and in Vic- 
 toria.] 
 
 79. "Meteorological Notes. ' Nature,' xxi. 
 p. 142 (rv). [Subjects : typhoon in the China 
 and Japan seas ; the weather of Missouri ; the 
 temperature of the Atlantic and of the British 
 Isles.] 
 
 80. Meteorological Organisations. ' Nature,' 
 xix. p. 514 (rv).. 
 
 81. Weather Charts for the Northern Hemis- 
 phere. Nature,' xx. p. 381-383 (rv). 
 
 82. * Nature,' vol. xix. p. 189 to end (rv) ; 
 vol. xx. (rv); xxi. p. 1-196 (rv). 
 
 83. Royal Society. Catalogue of Scientific 
 Papers, vol. viii. (rs). 
 
 84. The Weather and its Prediction. Quar- 
 tei-ly Review,' Oct. 
 
 1880. 
 
 1. Aratus. The skies and weather forecasts. 
 Translated by E. Poste, M.A. , Svo. London. 
 3s. 6ef. 
 
 75 
 
GENERAL 
 
 1880. 
 
 BIBLIOGRAPHY. 
 
 2. Bruhns, C. Die Benutzung der Me- 
 teorologie fur landwirthschaftliche Arbeiten. 
 Mittheil. oekon. Gesells. Sachsen. (Lib. Met. Soc.) 
 
 3. Bruhns, C. Bericht iiber das meteoro- 
 logische Bureau fur Wetterprognosen im Konig- 
 reich Sachsen, 1879. 8vo. Leipzig. (Lib. 
 Met. Soc.) 
 
 4. Bureau Central M6te"orologique 
 de France. Instructions pour Pobservation 
 des phenomenes periodiques des animaux et des 
 ve'gdtaux. 4to. Paris. (Lib. Met. Soc.) 
 
 5. Cantoni, G. Su le osservazioni me- 
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 6. Descroix, L. Resume meteorologique 
 des annees agricoles 1873-1880. Ann. de 1'Obs. 
 de Montsouris pour 1'an 1881. (Lib. Met. Soc.) 
 
 7. Houzeau, J. C. Traite e"lementaire de 
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 8. Jenkins. On a connection between me- 
 teorological phenomena and the time of arrival 
 of the earth at perihelion. Atti Accad. Lincei, 
 May. 
 
 9. Ley, Rev. W. C. Aids to the study 
 and forecast of the weather. 8vo. London. 
 (Lib. Met. Soc.) 
 
 10. Loomis, E. Contributions to Meteoro- 
 logy. 12th No. Am. Journ. Sci., Feb. 
 
 11. Loomis, E. Contributions to Meteoro- 
 logy. 13th No. Ann. Journ. Sci., July. 
 
 12. M., H. The U.S. Weather Charts. 
 * Nature,' xxiii. p. 147 (rv). [Nothing in it for 
 these notes.] 
 
 13. Marcet, Wm. On the influence of 
 altitude with reference to the treatment of pul- 
 monary disease. Brit. Med. Journ. Oct. 2. 
 Read to Brit. Med. Assoc. at Cambridge, Aug. 
 (ra). 
 
 14. Mari6 - Davy, H. Meteorologique 
 ngricole. Ann. de 1'Obs. de Montsouris pour 
 1'an 1881. (Lib. Met. Soc.) 
 
 15. Mascart. Sur 1'inscription des pheno- 
 menes meteqrologiques, en particulier dc 1'elec- 
 tricite et de la pression. Ann. Soc. Met. France, 
 xxviii. (Lib. Met. Soc.) 
 
 16. Meteorology. Repertorium fur me- 
 teorologie. Bd. vii. Ed. by H. Wild. 
 
 17. Parkin, John. Epidemiology ; or the 
 cause of epidemic disease, of murrains, of blight, 
 of hurricanes, and of abnormal atmospherical 
 vicissitudes. 2nd ed. 8vo. 
 
 18. Porro, S. On some recent studies in 
 agrarian meteorology. * La Natura,' iv. 
 
 Poste, E. See 1880, 1. 
 
 19. Preston, Hev. T. A. Report on the 
 phenological observations for the year 1879. 
 Q. Journ. Meteorol. Soc., p. 1-28. (Lib. Met. Soc.) 
 
 20. Ramsay, A. On the diurnal periodicity. 
 The Scient. Roll : Climate, i. p. 2-9. (Lib. Met. 
 Soc.) 
 
 21. Ramsay, A. General bibliography of 
 climate, 1485 to 1830. The Scient. Roll, i. p. 
 11-16. (Lib. Met. Soc.) 
 
 22. Renou, E. Note sur 1'hiver de 1880. 
 Ann. Soc. Met. France, xxvii. (Lib. Met. Soc.) 
 
 23. Scott, R. H. Weather forecasting. 
 Brit. Aim. and Comp. for 1881. 
 
 24. Tayler, W. B. Henry and the tele- 
 graph. Smiths. Report for 1878. 
 
 76 
 
 25. Tridon, L. Considerations sur les 
 explorations aeriennes a de grandes hauteurs. 
 Ann. Soc. Met. 'France, xxviii. (Lib. Met. Soc.) 
 
 26. Wilson, Wm. The ocean as a health 
 resort. 8vo. London. 
 
 27. W^ragge, C. L. Forecasting the wea- 
 ther. (Lib. Met. Soc.) [? date. About 1880.] 
 
 28. What is the climate most favourable to 
 the development of civilisation? Annuaire de 
 PObs. Bruxelles. 
 
 29. Ciel et Terre. 8vo. Brussels. [A 
 popular journal of astronomy and meteorology. 
 Published fortnightly.] 
 
 30. International monthly chart for April, 
 1878. ' Nature,' xxi. opp. p. 304 ; May, 1878, 
 same vol., opp. p. 377 ; June, 1878, same vol., 
 opp. p. 500 ; July, 1878, same vol., opp. p. 565 ; 
 August, 1878, xxii., opp. p. 36; for September, 
 
 1877, same vol., opp. p. 100 ; Sept. 1878, same 
 vol., opp. p. 249 ; Oct. and Nov. 1878, same vol., 
 opp. p. 516. Dec. 1878, xxiii., opp. p. 39. 
 
 [The maps are loose ; the reference to pages may 
 not therefore be correct for some copies. They 
 show the mean temperature, pressure, direction, 
 and force of wind for each month at 7 P 35 A.M. 
 (Washington time) for a large portion of the 
 northern hemisphere, and for a few places in 
 the southern hemisphere.] 
 
 31. Intercolonial Meteorological Conference at 
 Sydney. ' Nature,' xxii. p. 160 (rt>). [Nothing 
 in it for these notes ; relates mainly to arrange- 
 ments for weather warnings.] 
 
 32. International Meteorology. 'Nature,' 
 xxii. p. 307 ; 471-472 (rv). 
 
 [The first article is the programme of the 
 International Meteorological Committee meeting 
 at Berne and of the Conference meeting at 
 Vienna. The second gives results of the Berne 
 meeting and the resolutions adopted.] 
 
 33. Meteorological Notes. ' Nature,' xxi. 
 p. 265-266 (rv). [Clouds, temperature, and 
 pressure ; wind charts of the Pacific, Atlantic, 
 and Indian oceans, and waterspout off' Cape 
 Spada.] xxi., p. 384-385 (rv). [Meteorology of 
 Bombay; pressure, rainfall, and wind; tempera- 
 ture and rainfall of Austria and Hungary.] 
 xxi., p. 503-504 (rv). [Tay Bridge storm; 
 weather of Canada ; atmospheric pressure in 
 U.S. ; rates of progress of storm centres.] 
 xxii., p. 132-133 (rv). [Sweden ; Tasmania.] 
 xxii., p. 253-254 (rv). [U.S. Missouri ; wind 
 and rainfall ; Maiden island in 4 2' S.] xxii., 
 p. 594 (rv). [Thunderstorms, temperature, and 
 barometer ; United States ; Scotland.] xxiii., 
 p. 183-184 (rv). [The U.S. weather maps ; 
 Canada, U.S., and British Isles ; temperature ; 
 barometric pressure in London ; Falkland 
 Islands.] 
 
 34. The United States weather maps. ' Na- 
 ture,' xxi. p. 304-305 (rv"). [United States.] 
 
 35. The United States weather maps, April to 
 July, 1878. 'Nature,' xxi. p. 565-567 (rv). 
 
 36. The United States weather map, Aug. 
 
 1878. 'Nature,' xxii. p. 36-37 (rv). 
 
 37. The United States weather maps. Sept. 
 
 1877. Nature,' xxii. p. 100 (rv). 
 
 38. The United States weather maps. Sept. 
 
 1878. ' Nature,' xxii. p. 253-254 (rv). 
 
GENERAL 
 
 18801881. 
 
 BIBLIOGRAPHY. 
 
 39. The United States weather maps for Oct. 
 and Nov. 1878. ' Nature,' xxii. p. 516, 517 (rv). 
 
 40. The United States weather maps. De- 
 cember, 1878. Nature,' xxiii. p. 39, 40 (rv"). 
 
 41. ' Nature,' vol. xxi. p. 197 to end (rv) ; 
 xxii. (ro) ; xxiii. p. 1-212 (rv). 
 
 42. Rapport des discussions et des resolutions 
 de la Conference internationale pour la meteo- 
 rologie agricole et forestiere tenue a Vienne 
 en Autriche du 6 au 9 septembre 1880. 8vo. 
 Vienna. (Lib. Met. Soc.) 
 
 43. The Scientific Roll. Climate. Vol. i. 
 p. 1-16. 8vo. (Lib. Met. Soc.) 
 
 1881. 
 
 1. Archibald, E. D. On the connection 
 between solar phenomena and climatic cycles. 
 Ft. i. The Scient. Roll : Climate, i. p. 17-37. 
 (Lib. Met. Soc.) 
 
 2. C., H. W. The recent severe weather. 
 < Nature,' xxiii. p. 329 (rv). [Weather = tempe- 
 rature in Brit. Isles.] 
 
 3. C., H. W. The recent severe weather. 
 
 ' Nature,' xxiii. p. 363-364 (rv). [Temperature 
 cycles.] 
 
 4. F. M. S. The recent severe weather. 
 'Nature,' xxii. p. 363 (rv). [Temperature cycles.] 
 
 5. Looxnis, E. Contributions to meteoro- 
 logy. Am. Journ. Sci. Jan. [Wind.] 
 
 6. Meteorol. Council. Report for 1880. 
 8vo. Pp. 118. (Lib. Met. Soc.) 
 
 7. Meteorology. Revista mensual climato- 
 logica. Tomo i. 4to. (Lib. Met. Soc.) 
 
 8. M. R. I. A. The recent severe weather. 
 ' Nature,' xxiii. p. 411 (rv). 
 
 9. Preston, Rev. T. A. Report on the 
 phenological observations for the year 1880. 
 Q. Jouru. Meteorol. Soc., vii. p. 13-39. [Eng- 
 land.] 
 
 10. Ramsay, A. General bibliography of 
 climate, 1831 to 1881. The Scient. Roll: Climate, 
 i. p. 38-47 ; 49-7-7. 
 
 11. Meteorological Notes. ' Nature,' xxiii. p. 
 322-323 (rv). [Wind; Mauritius: Europe.] 
 
 xxiii. p. 470-471 (ro). [Europe ; Cobham 
 
 in Surrey ; British Islands : Scotland : England.] 
 
 12. The Scientific Roll: Climate. Vol. i. p. 
 17-80. 8vo. 
 
 
GENEEAL NOTES. 
 
 1607. 
 
 Davis, John. The Voyages and Works of John Davis, the Navigator. Hakluyt Soc. 
 Edited by A. H. Markham, 1880. The Seaman's Secrets, (TV). 
 
 (Page 308.) A climate is the space included between two parallels wherein the day 
 is sensibly lengthened or shortened half an hour ; the climates take the names from 
 such famous places as are within the said climates. The 1st passeth through Meroe, 
 between 12 45' and 20 30' ; 2nd, Syene, 20 30' and 27 30' ; 3rd, Alexandria, 27 30' 
 and 33 40' ; 4th, Ehodes, 33 40' and 39 ; 5th, Eome, 39 and 43 30' ; 6th, Boris- 
 thenes, 43 30' and 47 15' ; 7th, Ehipaan Mountains, 47 15' and 50 20'; 8th, Masotis, 
 or London, 50 20' and 52 10' ; 9th, Denmark, 52 10' and 55 30'. 
 
 1833. 
 
 Ainsworth, W. Journal of Hie Royal Geographical Society. I. (for 1831). 2nd ed. 
 
 (1833) (rv). 
 
 (Page 211.) Capt. Beechey's expedition noticed that in the Arctic regions in 1826, 
 (Page 112) when the weather was settled, the aurora generally began in the w.x.w., 
 and passed over to the N.B., until a certain period, after which it as regularly commenced 
 in the N.E. and passed to the N.W. ; whilst in 1827 the appearances of the meteor were 
 as uncertain as the season was boisterous and changeable. The period when this change 
 in the course of the light took place coincided very nearly with that of the equinox. 
 
 1851. 
 Alexander, J. H. (B. 4.) 
 
 [He says weather on the third day before new moon regulates that on each quarter- 
 day, and that generally of the whole period.] 
 
 1853. 
 
 Maclaren, C. Art. America. Encyclopedia Britannica, vol. ii. (ra). 
 (Page 670.) The latitude and elevation of the land in every country, its position in 
 reference to the sea, with the direction of the prevailing winds, are the chief circum- 
 stances which determine the nature of the climate. 
 
 1859. 
 
 English Cyclopaedia. (B. 4.) 
 
 (Col. 921.) Almost as soon as the barometer was discovered, it was observed that 
 changes in the height of the mercury corresponded to changes in the weather. The 
 (Col. 933) water barometer (1 in. bore) is affected by the weather one hour sooner than 
 the ordinary barometer with half an inch bore, and this one hour before a barometer 
 with ' 15 in. bore. 
 
 English Cyclopaedia, (B. 4.) 
 
 (Col. 967.) The climate of the Greeks corresponded roughly to our latitudes. They 
 indicated in a general way the comparative temperature which a country enjoys by 
 78 
 
GENERAL 18601861. NOTES. 
 
 reason of its smaller or greater distance from the equator. The modern term climate 
 has a wider meaning. It implies all the phenomena which affect vegetation and render 
 a country a fit abode for men and animals. Heat and moisture, properly speaking, 
 constitute climate ; but the latter is dependent on the former, while that itself varies 
 originally according to distance from the equator and height above the level of the sea, 
 the results of both co-ordinates being themselves subject to variation from other causes. 
 The other phenomena, such as wind, electricity, &c., affect these constituents of 
 climate ; but they require a separate consideration as modifiers of it, according to the 
 view we take of the subject. 
 
 1860. 
 English Cyclopaedia. (B. 7.) 
 
 (Col. 599.) Meteorology in its extended sense embraces all physical causes which 
 affect the state of the atmosphere or are affected by it. Hence it is connected with the 
 phenomena of heat and cold, dew, rain, hail and snow, clouds, winds, aurora} boreales 
 and australes, haloes, parhelia, &c. The sense in which Aristotle uses it is still more 
 extensive, comprehending, in addition to what are now called meteors, every affection 
 common to the air and water, with the character of the different parts of the earth and 
 their affections, as winds and earthquakes, and everything incident to such moods of 
 motion. 
 
 Grey, Earl de. (B. 9.) 
 
 (Page cxlv.) Meteorology has approached to the character of an exact science. It is 
 now by no means difficult to estimate the climate of any place of which the geographical 
 position is known. The hours of highest and lowest temperature and barometric 
 pressure, the normal height of the mercurial column, and the prevalence of moist air, 
 rain or dryness, much or little wind, can be predicated approximately for any part of the 
 world, although in that particular place no observations may yet have been made, 
 (page cxlvi) Dampier, De Foe, Capper, Flinders, are amongst the contributors to 
 meteorological science. Instruments have been lent by Government to upwards of 
 thirty fishing villages. 
 
 1861. 
 English Cyclopaedia. (B. 16.) 
 
 (Col. 165.) Mountains arrest the fleeting clouds ; their influence on local climate is 
 all-powerful, and depends upon the direction in which they lie as regards the sun's 
 course, their height, their position upon the surface of the globe, their proximity to or 
 remoteness from the sea, the winds they arrest or give passage to, etc. They have also 
 a climate, or rather a great variety of climates, of [their own. Thus, in ascending from 
 the sea towards the summit of the Andes almost every kind of climate is passed through, 
 nearly as completely as if the traveller were to proceed from the equator towards the 
 poles. 
 
 [In the latter part of this passage climate seems to mean little more than temperature, 
 while in the former its meaning is more extensive. A. K.J 
 
 English Cyclopaedia. (B. 16.) 
 
 (Col. 428.) The phenomena of the seasons may be divided into those which occur 
 yearly and those which are different in different years. We have in every year the same 
 succession of longer and shorter days, with a summer and winter, while the summer of 
 one year is of a higher temperature and is accompanied by finer days than that of another. 
 The unvarying phenomena can be explained by what we know of the sun's (or earth's) 
 motion ; the varying phenomena belong to meteorology, and depend upon atmospheric 
 and other circumstances with which we have little or no acquaintance. The earth's 
 axis preserves its direction throughout the whole of the yearly motion. The consequence 
 
 79 
 
GENERAL 1861. NOTES. 
 
 is that places which are distant from the equator have very unequal days at different 
 times of the year. The accompanying figure [not reproduced here], which is generally 
 given in connection with the subject, represents the earth in its four principal positions, 
 the sun being at S., and N. being the north pole of the earth ; A is at the vernal 
 equinox ; the intersection of the equator and ecliptic passes through the sun, and 
 (col. 429) days and nights are equal all over the world. B is the summer solstice, 
 when the sun is most above the equator on the northern side ; the diurnal circles have 
 more day than night, and have their longest days, and vice versa. C being the 
 autumnal equinox, the phenomena of A are repeated. D is at the winter solstice, when 
 the sun is farthest from the equator on the southern side : the phenomena of B are now 
 reversed, the days being shortest on the north side of the equator. This figure very 
 well explains the variation of days and the main reason for the phenomena of seasons in 
 the extra-tropical parts of the earth. It is evident, speaking of the northern hemisphere, 
 the sun being above the equator gives not only longer days, but greater altitudes, more 
 powerful light and heat, and more of it in duration. It does not serve for the tropical 
 climates, as the days and nights are so nearly equal throughout the year that seasons 
 are caused more by the effects of the winds (which are very regular, and depend mainly 
 upon the sun's position) than by changes in the direct action of the sun's light and 
 heat. The seasons are not so much a summer and winter as a recurrence of dry and 
 wet periods two in each year. 
 
 FitzRoy, R. (B. 17.) 
 
 (Page cli.) Simultaneous daily observations were started in 1857 at a number of 
 stations in the British Isles and on the Continent. Storm-warnings were suggested 
 (page clii) before 1836, but were not commenced till September 1860. The first warn- 
 ings were given on Feb. 6th, 1861. 
 
 Galton, P. (B. 18.) 
 
 [His paper is simply a suggestion of a method of making meteorological charts so as 
 to give a bird's eye of the various phenomena of rain, &c.] 
 
 NOTE. B. is the contraction fol- bibliography : the number is that of the item under the yp.ir 
 
 * 
 
 THE SCIENTIFIC ENQUIRER. 
 
 Correspondence is invited on science matters of all kinds. In all cases 
 names and addresses should be given; but these will not le published without 
 the writer's consent. The Conductor will not be responsible for the opinions 
 expressed by Correspondents. All Communications should be addressed to the 
 Conductor, 10, Bouverie Street, London, E.G. 
 
GENERAL NOTES. 
 
 1863. 
 Beardmore, W. (B. 2.) 
 
 (Page 1.) The British Meteorological Society was founded in 1850. Continuous. 
 (Page 2) observations are made at many stations. Brookes's photo-recording system is 
 (Page 3) a great improvement. The perturbations in the sun's photosphere appear to 
 react on the earth's atmosphere. Wolf has discovered a secular period of eleven years 
 in the sun's spots. The method of recording and signalling by telegraph simultaneous 
 readings which prevail over wide areas has of late years assumed a very prominent 
 position. In July 1856 Le Verrier introduced the system of having the state of the 
 weather at different points in France telegraphed to the Imperial Observatory, where 
 the observations were reduced and issued in the form of a daily bulletin, and soon after 
 (Page 4) he extended his area for returns over a large portion of Europe. It was soon 
 found that the principal meteorological disturbances were propagated in a direction 
 from W. to E. ; and that it was important that Great Britain should be included in the 
 scheme, a matter which was accomplished by Adm. FitzRoy early, in 1860. [See 
 * Notes,' 1861, FitzRoy.] Synchronous observations are of especial importance. 
 Regular observations are made by Quetelet, in Belgium. Kreke and Buys-Ballot 
 collect observations from 11 stations in the Netherlands. In Sweden there are 21 
 (Page 6) stations. In Norway three or four. Denmark is represented by Oersted. In 
 North Germany there are 90 or 100 stations. Austria has about 140, and Russia 30. Ob- 
 servations are made at Athens. Sinobas has established about a dozen stations in Spain. 
 There are many in France, as also in Switzerland. Lisbon has an observatory. North 
 America has upwards of 500 stations. Canada has its observatories. Scotland has 
 (Page 8) about 60, and Ireland several stations. In 1861 the spring, summer, and 
 autumn were warm, dry, and genial over Europe and North America. At the head- 
 waters of the Nile and in India there were deluging rains. In 1860 North America and 
 Europe had both cold and wet summers, while the plains of India experienced a severe 
 drought. 
 
 Bellingham, W. (B. 3.) 
 
 (Page 111.) He believes that a belt of vapour passes alternately from pole to pole in 
 about forty days, and that this gives rise to periodicity of atmospheric phenomena at 
 intervals, varying according to the locality. At London it is ten and thirty days. 
 
 Tomlinson, C. (B. 36.) 
 
 [The title of the paper is not as given at p. 55. It should be : An experimental 
 examination of the so-called storm-glass.] The storm-glass did not, I believe, hold 
 (Page 93) rank as a scientific instrument until it was introduced by Admiral FitzRoy. 
 In the Report for 1862, issued by the Meteorological Department of the Board of Trade, 
 it is stated that the chemical mixture in a so-called storm-glass varies in character with 
 the direction of the wind and electrical tension ; and that temperature affects the 
 (Page 94) mixture much, but not solely. In the article on Camphor Storm-glasses iri 
 (Page 95) Ure's Dictionary of Arts, edited by Mr. Robert Hunt, it is stated on the 
 G 81 
 
GENERAL 18631864. NOTES. 
 
 authority of Dr. Parrion that the weather-predicting qualities of the instrument are 
 false ; light and temperature being the conditions which affect it. Some years ago I 
 purchased a storm-glass at an instrument maker's shop, and received with it a paper 
 which stated that it would correctly indicate the coming rain, high wind, storm or 
 tempest ; that the indication for fine weather was that the substance would be low and 
 smooth at the bottom ; and that experience had proved the instrument to be useful in 
 (Page 96) the prognostics of the changes that take place in the weather, if properly 
 made. I have been in the habit of observing this instrument for some years past, and 
 had long ceased to regard it as of any value as a weather indicator. While experi- 
 menting on camphor I was induced to conclude that heat only was concerned in the 
 storm-glass phenomena. [A series of experiments are described in support of this 
 view, which need not be detailed here, since they have no bearing on meteorological 
 (Page 108) phenomena.] The conclusion drawn from these experiments is that the 
 storm-glass acts as a rude kind of thermometer, inferior to that in ordinary use for most 
 of the purposes of observation. 
 
 Willis, B. (B. 38.) 
 
 (Page Iv.) The system of simultaneous meteorological observations was organised in 
 1840. The meteorological department of the Board of Trade was created in 1854. The 
 Kew Observatory was commenced in 1842. 
 
 1864. 
 
 Buchaii, Alex. On the weather conditions which produce large crops of turnips and 
 cereals. Journ. Scot. Meteorol. Soc., I. pp. 149-154. No. IV. Oct. (rv). 
 
 [The paper refers to Scotland, but is of general application, except as regards the 
 periods. There are no particulars for general notes, but some will be found under 
 several of the elements.] 
 
 Forbes, Sir J. S. Address on Meteorology. Journ. Scot. Meteorol Soc., I. pp. 104-116. 
 Eead Jan. 1864 ; published in July, 1864 (rv). 
 
 (Page 107.) The first < Barometer Guide, and how to foretell the Weather,' was 
 (Page 109) published by Admiral FitzBoy in 1857. Espy's 'Fourth Report' was 
 (Page 110) published in 1854. Human health and life are servile to all the skyey 
 (Page 113) influences. Since March 1862 there have been 45 warnings issued by 
 Admiral FitzRoy almost uniformly followed by gales more or less serious. The stations 
 directly communicated with now by telegraph amount to about 80, and from these 
 more than twice as many receive messages. Instruments have been lent to many 
 thousand selected merchant vessels since 1854, from whose logs trustworthy observations 
 extending over many years have been obtained. It is remarkable that nothing has 
 been done to obtain reliable data for calculating the average return from the soil under 
 different circumstances of the weather or at different dates. 
 
 Garner, R. (B. 8.) 
 
 (Page 114.) An increasing deterioration of the atmosphere in towns and mining 
 districts may be estimated by means of plants thus : 1. In the smallest degree of 
 impurity trees are destitute of the leafy lichens ; and Ericas, the Scotch fir and the 
 larch die. 2. Next, the common laurel, the Deodara cedar, the Irish arbutus, the 
 laurestinus and the yew die. 3. The Araucaria, the Thuja, the common cedar, the 
 mezereon and the Portugal laurel die. 4. The common holly, the rhododendron, the 
 oak and the elm die. 5. Annuals still live, and the almond, poplar and many roses 
 thrive, fruit trees are barren, and peas unproductive. 6. Hieracia, Reseda lutea, the 
 
 82 
 
GENERAL 1864. Meldnim. NOTES 
 
 elder, some saxifrages and sedums thrive, while many syngenesious and cruciferous 
 weeds still luxuriate. 
 
 Meldrum, C. Proc. and Trans. Meteorol. Soc. Mauritius, VI. Report read Dec. 29, 
 
 1862 (rv). 
 
 (Page 64.) The total number of members in the Meteorological Society of Mauritius 
 is 80, or nearly double what it was three years ago. Within the last few years the 
 science of meteorology has received more attention than it ever did before. There is 
 not a civilised country in the world which is not through its government, its scientific 
 bodies and numerous observers, busily engaged in meteorological pursuits both on land 
 and at sea. This was in a great measure brought about through the exertions of 
 Captain Maury. At his suggestion a conference of meteorologists was held at Brussels 
 in September 1853, the object of which was to adopt a uniform and universal system 
 of observation at sea over the whole globe. The result was that the governments of 
 the various countries represented on that occasion, such as Great Britain, France, 
 America, Denmark, Prussia, Holland, &c., adopted measures to carry the recom- 
 mendations of the conference into effect. Special offices were created for the 
 purpose of obtaining observations, collecting and discussing them, and publishing 
 (Page 65) the final results ; and already a large body of highly useful information has 
 been published, especially in England, under the direction of Admiral FitzEoy. But 
 meteorological research is not confined to the sea. All along the coasts of Europe and 
 America, as well as at numerous inland stations meteorological observations are either 
 being already taken or observatories being established. By means of the electric wire 
 the central observatory, or meteorological office, of each country is in daily and hourly 
 communication with a network of smaller observatories extending to the remotest 
 corners of the land and constantly keeping those at head- quarters informed of the 
 changes of wind and weather that are taking place on all sides of them. The central 
 observatories again are in electric communication with each other ; so that at certain 
 hours on each day it is known in London, Paris, &c., what winds and weather were 
 experienced a few hours previously over the greater part of Europe. If there should be 
 reason to suppose that a gale or storm is at hand despatches are sent to all the sea- 
 ports warning the shipping of the threatened danger. Meteorology is thus becoming a 
 science of the highest practical utility to navigation, agriculture and other national 
 interests. These are powerful motives for establishing and maintaining so many 
 observatories and transmitting the results to a central station from which they are 
 again sent forth to the world. In this instance considerations of public and private 
 welfare come to the aid of science. But besides this incentive to meteorological observation 
 over an extensive area, there is also the pleasure derived from tracing effects to their 
 causes, and extending our knowledge of the laws of nature. In this point of view 
 meteorology is likely to become one of the most popular and interesting of the physical 
 sciences. jSTqt many years ago it would have seemed absurd to suppose that it was 
 possible that a person in London should have placed before him every morning a chart 
 showing the barometric pressure, the temperature of the air, the direction and force of 
 (Page 66) the wind, and the state of the weather at all the principal towns and sea-ports 
 of Europe on the previous day ; and yet we now know that this is not only practicable, 
 but that, if it has not already been effected, it has at least been strongly recommended, and 
 will, no doubt, be carried into execution. Now what could be more interesting than by 
 means of such charts to watch the atmospheric changes occurring from day to day over 
 thousands of miles ; to observe the respective tracts of high and low temperature, and high 
 and low atmospheric pressure ; where cloud and sunshine respectively prevailed ; where 
 rain fell and where it did not fall ; where tempests and thunderstorms took place, and where, 
 on the other hand, the sky was serene ; to note the varying force and direction of the 
 aerial currents with their attendant phenomena ; to trace the rise and progress of gales, 
 2 83 
 
GENERAL 1864. Meldrum. NOTES. 
 
 storms, and hurricanes ; .in short, to be the daily spectator over a wide area of the 
 operations of nature in that wonderful laboratory the atmosphere. Nor is it to Europe 
 and America that the system of meteorological inquiry set on foot some years ago is 
 confined. India had long ago been distinguished for its labours in this branch of science, 
 observatories having been established at many stations, and many otficers, civil and 
 military, co-operating in a general plan of observation, and these observatories are still 
 busily at work. Within the last few years also the subject has been taken up by the 
 Australian Colonies, in which several observatories have been established at the public 
 expense, with numerous branch observatories in connection with them ; the whole being 
 placed under the general superintendence of officers appointed and paid by the Government. 
 And it appears that a few months ago a meteorological commission appointed at the 
 Cape of Good Hope to report upon the meteorology of that colony, recommended that 
 ten stations should be supplied with instruments for systematic observations by 
 competent persons, who, we learn, have already entered upon their duties. By increasing 
 the number of observatories and extending the system to all parts of the habitable world, 
 (Page 67) while at the same time observations are daily and hourly taken in all 
 navigated parts of the ocean, the day will come when the atmosphere can be contemplated 
 as a whole, and the mutual relations of the phenomena occurring in it be more clearly 
 perceived and understood. All that is wanted in the first place is to have a sufficient 
 number of reliable observations taken at the same moments of absolute time at numerous 
 points over the whole accessible globe, and to have them continued for a lengthened 
 period. It is towards the realisation of this object that the efforts which are now being 
 made in so many and so widely distant countries are tending, and when it shall have 
 been attained, meteorology will become one of the most useful of the modern sciences. 
 (Page 68). It is universally admitted that the future progress of meteorological science 
 will depend upon the active co-operation of all countries, each contributing towards the 
 general result. From its special position Mauritius is one of the most important of all 
 (Page 69) the meteorological stations. The Meteorological Society of Mauritius 
 (Page 74) was established on August 1, 1851. 
 
 (Page 80.) Every phase of weather has its meaning, which only requires to be read 
 aright to convey important information. 
 
 Meldrum, C. Proc. and Trans. Meteorological Soc. Mauritius, VI. Paper read June 3 r 
 
 1863 (rv). 
 
 (Page 177.) Mauritius is so favoured by geographical position that with a knowledge 
 of the atmospheric changes which take place in the neighbouring seas we can, so far as 
 the experiment has yet been tried, tell with certainty' when a storm exists, where it 
 exists, and often in what direction it is travelling, although its distance from us may be- 
 nearly 2000 miles. As yet there has not been a single exception to this rule. 
 
 Scoresby- Jackson, R.E. On the Importance of the Study of Medical Climatology. 
 Journ. Scot. Meteorol. Soc., I. pp. 25-40. Published Jan. 1864 (rv). 
 
 (Page 25.) Meteorology is closely allied to the science of medicine; it holds a 
 prominent position in social science ; and it enters into the calculations of the political 
 (Page 27) economist. Uniformity of action must be observed, which may be most 
 easily attained by following the instructions at the back of each schedule. The 
 instruments used should be in good order and subject to frequent comparison with 
 standards. [The details given as to the influence of climate on disease belong to Man.] 
 (Page 28) Five day means are best adapted to medical climatology. Averages of a 
 number of years, or of seasons, or of months, are not safe guides in medical meteorology. 
 There is occasionally a tendency on the part of observers who are wedded to certain 
 
 84 
 
GENERAL 18641865. NOTES. 
 
 localities to hide little climatal defects by drawing averages from long periods. Hence it 
 happens that what are called exceptional years frequently occur at such places. 
 
 Scoresby- Jackson, R.E. Report of the Medico- Climatological Committee. Journ. Scot. 
 Meteorol Soc., I. pp. 120-121 (published July, 1864) ; pp. 154-157 (published Oct.) (rj). 
 [Nothing in them for general notes.] 
 
 1865. 
 Becquerel, A. C. Journ. Scot. Meteorol. Soc. t I. Published July, 1865 (rv). 
 
 [The name is there misprinted Becqueral, and the paper is the translation of one in 
 * Comptes Rendus,' Ix. p. 136.] 
 
 (Page 235.) The influence of forests upon climates depends (1) on the extent of the 
 forests; (2) on the height of the trees and their species, according as they have 
 deciduous or persistent leaves ; (3) on the power of evaporation possessed by their 
 leaves ; (4) on their capacity of being heated or cooled like any other body placed in the 
 air ; (5) on the nature of the soil and subsoil. The climate is improved by bringing the 
 (Page 237) land under cultivation, by draining unhealthy marshes, and by planting 
 trees on mountains and on all soils not suited for pasture and tillage. 
 
 Dumas. (5. 15.) 
 
 (Page 950.) Lavoisier fully appreciated the method of foretelling weather by means 
 of simultaneous observations. He thought the weather could always be foretold twenty- 
 four hours in advance. He had no idea of the telegraph. The proposal to use telegraph 
 was first started in 1852. 
 
 Leverrier, U. J. J. (IB. 28.) 
 
 (Page 1318.) The intention of collecting observations by telegraph was to use them 
 for forecasts. The first collection of simultaneous records in France was on February 19, 
 1855. I dispute the statement as to the direction from which Italian storms usually 
 come. 
 
 Matteucci. (5.30.) 
 
 (Page 892.) The idea of having a central office for collecting simultaneous observa- 
 tions by telegraph for purposes of prediction was started in 1858. I started a similar 
 plan for Italy in 1864. The great storms which attack the British Isles from the west 
 rarely fail to reach Italy, so that nearly all predictions of these come right. Those 
 threatening from Spain rarely extend to Italy. 
 
 (Page 1314.) First forecast issued was on July 31, 1861. Two years after, Leverrier 
 followed FitzRoy's example in France. Strongly in favour of forecasting storms only. 
 
 Poey, A. (5.36.) 
 
 (Page 1279.) Early in the 17th century simultaneous meteorological observations were 
 organised by the Accademia del Cimento. The Meteorological Society of Mannheim 
 first organised an extensive meteorological correspondence, and several plans of the same 
 kind have since been carried out in France, United States, &c. In 1840 the Royal 
 Society proposed the establishment of as many meteorological observatories as possible in 
 all parts of the world. 
 
 Scoresby-Jackson, K.E. Report of the Medico-Climatological Committee. Journ. Scot. 
 Meteorol Soc., I. pp. 182-183 (published in Jan.) ; pp. 210-212 (published in April); 
 pp 241-243 ; p. 244 (published in July) ; pp. 276-277 (published in Oct.) (rv). 
 
 [Nothing for general notes.] 
 
 85 
 
GENERAL 1866. Leverrier. NOTES. 
 
 1866. 
 Becquerel, A. C. (B. 2.) 
 
 [The translation of this paper given in the Journ. Scot. Meteorol. Soc. was published 
 in July, 1865 ; and the notes are entered under 1865. The volume is dated 1866, but 
 contains the quarterly numbers issued from Jan. 1864 to Oct. 1866.] 
 
 Buchan, A. (5.5.) 
 
 [This paper was published in July 1865. It refers mainly to Scotland, and contains 
 nothing for general notes.] 
 
 Buchan, A. (B. 6.) 
 
 [This paper was published in Jan. 1866. It refers to various European countries, and 
 contains nothing for general notes.] 
 
 Buchan, A. Hints to Observers regarding Instruments. Journ. Scot. Meteorol. Soc., I. 
 pp. 300-303. Published in Jan. (rv). 
 
 [Nothing for general notes.] 
 
 Buchan, A. Meteorological Characteristics of the Winter of 1865-6. Journ. Scot. Meteorol. 
 Soc., I. pp. 358-366. Published in July, 1866 (rv). 
 
 [There is nothing for general notes. It refers mainly to European countries.] 
 
 Forbes, Sir J. S. (5.13.) 
 
 [This paper was published in Jan. 1864, under which year the notes are entered.] 
 
 Leverrier, U. J. J. On Storm Signals and Weather Warnings. Journ. Scot. Meteorol. 
 Soc., I. pp. 366-368. From Bulletin International, April 26. Published in July (rv). 
 
 (Page 366.) On Jan. 16, 1860, a letter was sent to the Minister of Marine in 
 which it was stated that to signal a storm as soon as it should appear at any point of 
 Europe, to follow it in its march by means of the telegraph, and to send warning of its 
 approach in good time to the coasts which it will visit, should be the ultimate end to 
 be reached by the system which we carry out. The means for carrying out this scheme 
 were not granted. Some time after, FitzKoy began a system of warnings on a different 
 principle. He undertook to foretell the probable weather for the following day to the 
 coasts of the United Kingdom. About the middle of 1863 M. Duruy promised the 
 (Page 367) required assistance. While organising a service operations were limited to 
 the system of forecasts begun by FitzKoy. The system of absolute forecasts is beset 
 with difficulties which prevent its being adhered to entirely. We cannot tell the 
 direction the storm will take; hence we cannot send definite forecasts to particular 
 localities. Hence we have adopted a system intermediate between the warning of an 
 approaching storm and prevision thereof. We receive daily observations made at 8 A.M. 
 in winter and 7 A.M. in summer from 21 French and 42 foreign stations. We receive in 
 the evening observations made at 6 P.M. ; twelve being from French stations. This 
 second series is necessary as a check on the first. It indicates any change that may 
 have taken place since the morning in those parts over which it is particularly desirable 
 to keep an outlook. When no atmospheric disturbance has occurred the observations 
 of the evening, in their relation to those of the morning, enable us in general to forecast 
 (Page 369) the weather of the following day. A greater number of evening despatches 
 are wanted. Telegrams are sent to 73 French ports. 
 
 86 ' 
 
GENERAL 
 
 18661867. 
 
 NOTES. 
 
 Mitchell, A. Journ. Scot. Meteorol. Soc., I. Published in Jan. (rv). 
 
 (Page 304.) The c Ark o' the Cluds ' is not always regarded as a forerunner of bad 
 weather. When it runs north and south the aftercome is not so much dreaded as when 
 it is stretched between any of the other points (Galloway). The weather-gaw sometimes 
 indicates good weather. When it is seen in the east its consequences are less dreaded. 
 
 The weather's taking up now, 
 For yonder is the weather gaw ; 
 How bonny in the east now ! 
 Now the colours fade awa'. 
 
 (Page 305.) 
 
 (Page 306.) 
 
 Grumphie sees the weather, 
 And grumphie sees the wun', etc. 
 
 Gif the lavrock sings afore Cannelmas, 
 She'll mourn as lang after it. 
 
 Ne'er trust a July sky. 
 
 (Galloway). 
 
 (Galloway). 
 
 (Shetland). 
 
 Mottez. (B. 29.) 
 
 (Page 620.) Latent electricity enters into the constitution of water, but in different 
 quantities in the three conditions. Probably all meteorological phenomena are explicable 
 by this principle. 
 
 Scoresby-Jackson, H. E. Report of the Medico-Climatological Committee'. Journ. Scot. 
 Meteorol. Soc., I. pp. 306-307 (published in Jan.) ; pp. 335-336 (published in April) ; 
 pp. 370-371 (published in July) ; pp. 388-389 (published in Oct.) (TV). 
 
 [Nothing for general notes.] 
 
 Journ. Scot. Meteorol. Soc. Number of Meteorological Stations established in different 
 
 Countries in Europe. I. p. 368. Published in July (rv\ 
 (Page 368.) 
 
 36 
 109 
 32 
 89 
 
 
 Norway and 
 Denmark 
 Holland 
 Belgium 
 Scotland 
 England 
 
 wede 
 
 n 
 
 
 
 11 
 11 
 9 
 9 
 
 81 
 54 
 
 19. 
 
 France . 65 
 
 Prussia, etc. .. 
 
 Austria 
 
 Italy 
 
 Switzerland 
 Spain and Portugal 
 Turkey . . 
 Greece 
 Malta ., 
 
 10 
 3 
 1 
 1 
 
 1867. 
 
 Buchan, A. (B. 6.) 
 
 (Page 1.) Meteorology was originally applied to the consideration of all appearances 
 in the sky, astronomical as well as atmospherical, but the term is now restricted to that 
 department of knowledge which treats of the phenomena of the atmosphere that relates 
 to weather and climate, their relations to each other, and the laws to which they are 
 subservient. Owing to the complexity of the phenomena and the manifold influences by 
 which they are modified and determined, it would be beyond the power of the human 
 intellect to give a perfectly satisfactory explanation of them. From the nature of the 
 subjects which make up the science of meteorology, we may infer that they occupied 
 (Page 2) men's minds from a remote antiquity. The splendid panorama of the sky 
 and the variations of temperature through the days and seasons, together with the other 
 atmospheric changes constituting the weather which affect in so powerful a manner the 
 necessities and comforts of man, are of a nature well-fitted to arrest his attention. 
 
 87 
 
GENERAL 1867. Buchan. NOTES. 
 
 Hence the appearances which were found by experience to precede changes of weather 
 were eagerly recorded and handed down in the sententious form of weather-proverbs. 
 In this way many valuable facts were ascertained and passed current from hand to hand, 
 so that there is perhaps no science of which more of the leading facts and inferences 
 have been so long incorporated into popular language. Aristotle was the first who 
 collected, in his work ' On Meteors,' the popular prognostics of the weather. A number 
 of these were derived from the Egyptians who had long studied the science as a branch 
 of astronomy, while a large number were the fruit of his own observation. Theophrastus, 
 one of Aristotle's pupils, next took .up the subject, classifying the commonly received 
 opinions of the weather under four heads, viz., the prognostics of rain, wind, storms, 
 and fine weather. He made no attempt to explain phenomena. Cicero, Virgil, and a 
 few other writers also wrote on the weather, but made no substantial additions to our 
 knowledge. The treatise ,of Theophrastus contains nearly all that was known down to 
 comparatively recent times. Partial explanations were attempted by Aristotle and 
 Lucretius, but their explanations were necessarily vague owing to ignorance. No 
 progress was made until proper instruments were invented for making real observations 
 with regard to the pressure, temperature, humidity, and electricity of the atmosphere. 
 (Page 3) Torricelli's discovery of the barometer in 1643 was undoubtedly the first step 
 in the progress of meteorology to the rank of a science. The value of the barometer as 
 an indicator of the weather gave an additional impetus to the study of the science. 
 Sanctorio's invention of the air thermometer in 1590 laid the foundation of a salutary 
 revolution in the science, since it pointed to an exact determination of the temperature 
 of the air, which is by far the most important element of weather in relation to our 
 welfare. Fahrenheit was the great improver of the thermometer. The hygrometer is 
 an instrument of great value in meteorology as indicating the quantity of vapour in the 
 (Page 4) air, and inferentially the changes of weather dependent thereon. From the 
 period of the invention of these instruments the number of meteorological observers was 
 greatly increased, and a large body of well authenticated facts of the utmost value began 
 to be collected. The climates of particular parts of the earth were inquired into and 
 compared together, and the science made great and rapid advances by the investigations 
 undertaken .by distinguished philosophers into the laws which regulate atmospheric 
 phenomena. The publication of Dalton's ' Meteorological Essays,' in 1793, marks an 
 epoch in meteorology. It was the first instance of the principles of philosophy being 
 brought to bear on the explanation of the complex and varied phenomena of the atmosphere. 
 (Page 5) Well's * Theory of Dew ' (1814), must always be regarded as one of the greatest 
 contributions to meteorology. In 1823, Daniell published his * Meteorological Essays and 
 (Page 6) Observations.' It is to be expected that the discovery of the relations of 
 atmospheric vapour to heat, will soon be turned to account in explaining many 
 questions of meteorological enquiry. Humboldt's treatise on 'Isothermal Lines,' 
 published in 1817, marks an important epoch in experimental meteorology. The 
 temperature of one country differing materially from that of neighbouring countries, 
 has an important influence in causing unsettled and stormy weather in both countries 
 at that time. The establishment of meteorological societies during the last twenty 
 (Page 7) years, has contributed in a high degree to the solid advancement of the 
 science which, more than any other, depends on extensive and well-conducted observa- 
 tions. In this respect, the United States stands pre-eminent, the observers there 
 numbering about 800. Great Britain has about 150. In Austria, Switzerland, 
 France, Prussia, Italy, Russia, the Netherlands, and other European countries, meteoro- 
 logy is being widely cultivated. Austria has 108 stations, and Switzerland, 83. A 
 special object of meteorological enquiry, is to ascertain the degrees of heat, cold, and 
 moisture peculiar to different localities, and the usual periods of their occurrence, with 
 a view to discover their effects on the health of the people, and on different agricultural 
 (Page 8) products. One fruit of the multiplication of meteorological stations, is the 
 88 
 
GENERAL 1867. Buchan. NOTES. 
 
 prediction of storms, and the foretelling of the weather. It is impossible to over- 
 estimate the value of storm warnings to the shipping interest. In the north temperate 
 zone, observation shows that storms almost invariably come from some westerly point, 
 and thence follow an easterly course. Hence, in the United States, it is easy to warn 
 seaports of the approach of storms. America is thus favourably circumstanced for 
 carrying out effectually the system of storm warnings. On the contrary Great Britain, 
 France, and the rest of W. Europe, are unfavourably situated to allow of timely warn- 
 ing being given of coming storms, because, if no warning be sent till the storm has 
 made its appearance, it is too late for the western seaports. But in Europe, stormy 
 weather is almost always accompanied with a diminution of atmospheric pressure, the 
 centre of which, after traversing more or less of the Atlantic ocean, arrives on the coast 
 of Europe. The existence of this depression is made known by the barometer when 
 the maximum is still at a considerable distance out at sea ; and collateral informa- 
 tion pointing to an advancing storm is to be obtained from the direction of the 
 {Page 9) wind, and the cirrus clouds. Here, then, we have materials for foretelling 
 the approach of storms on the west coast of Europe. For 'though we cannot arrive 
 at the degree of certainty of the American predictions, and telegraph to the coasts 
 that a storm is actually seen advancing on them, yet from the premonitions 
 afforded by the barometer, the wind, and the cirrus cloud, we can warn them to prepare 
 for a storm which is likely to visit them. The giving effect to this idea constitutes 
 the splendid contribution to practical meteorology made by Admiral FitzRoy in 
 February, 1861, by the system of storm warnings which has since been adopted 
 by almost every country in Europe. Owing to the present state of our knowledge, 
 a degree of uncertainty is inseparable from the storm warnings based on these premoni- 
 tions, which does not attach to predictions, based on storms actually observed. The 
 c Bulletin International,' of Le Verrier, published daily, must be regarded as the latest 
 (Page 10) important step taken in the progress of meteorology. In the schools of the 
 United States of America, meteorological observations and the keeping of meteoro- 
 logical registers form a part of the common education of the people. Also in the higher 
 schools of France, and some other European countries, systematic instruction is com- 
 municated on this subject ; but in this country, meteorology is generally neglected in 
 our educational system. There are a few exceptions. Meteorology has been taught 
 for upwards of thirty years in the Dollar Institution, and the example has been 
 followed at Stonyhurst, the Grammar School of Aberdeen, and at other places 
 (Page 75). It is this [viz., the degree of divergence of extremes], which makes the 
 most important distinction among climates, both as regards animal and vegetable life. 
 On man, especially, the effect is very great. The severity of the strain of extreme 
 climates, is shown in a striking manner by .the rapidly increasing death rate, according 
 as the difference between the July and January temperatures is increased. Thus the 
 mortality is 8 per cent, greater in England than in Scotland, the climate of the latter 
 country boing more equable or insular in its character ; and it is found that on ad- 
 vancing into the continent of Europe, that the more extreme the climate becomes, so 
 much the more is the death rate increased. [Climate here means temperature.] Since 
 (Page 105) clouds are subject to distinct modifications from the same causes which 
 produce the other atmospheric phenomena, the face of the sky may be regarded 
 as indicating the operation of those causes. The ancient meteorologist was content 
 with discerning the face of the sky in order to predict the coming weather. It is 
 to this chiefly that the weather-wise sailor and farmer still look, and their predictions 
 are frequently more correct than those made solely by instruments. The best 
 (Page 106) system of weather prediction comprises both methods. Small groups of 
 regularly-formed and arranged cirrus scattered over the sky often accompany fair 
 weather and light breezes. When a storm of wind has passed and the sky has cleared, 
 should a few fine cirrus clouds be seen slightly blown back at their eastern ex- 
 
 89 
 
GENERAL 1867. Buchan. NOTES. 
 
 tremities, the storm Las in all likelihood really past, and fair weather may with 
 some confidence be expected, since the dry polar current has already begun to 
 prevail overhead. When cumuli are of moderate size and height, well defined 
 (Page 107) curved outline, and appear only during the day, they indicate a continuance 
 of fine weather. The gradual lifting of the stratus from the ground, its conver- 
 sion into cumuli, and the disappearance of these indicate a continuance of the finest 
 (Page 140) and serenest weather. As synchronous charts present the principal 
 elements of the weather at a given instant, they may be regarded as successive 
 (Page 165) photographs of storms in their passage across the earth's surface. An 
 examination of weather changes over large portions of the surface of the globe 
 from day to day leaves a deep and lasting conviction on the mind of the essential 
 unity of the earth's atmosphere, and a fortiori the oneness of comparatively so 
 small a portion as that of Europe in respect of the intimate relations of its different 
 parts, and their absolute dependence on each other. We have seen waves of tem- 
 perature creeping over that continent apparently so vast that only a mere fragment 
 of one of them could be exhibited by the whole continent at one time ; and the 
 same remark applies with equal force to the waves of barometric pressure which 
 pass across it. We are very ignorant of the causes of these vast atmospheric changes. 
 Meteorology is eminently the science of observation and averages, and before those 
 inquiries now raised regarding the general movements of the atmosphere can be 
 satisfactorily and adequately discussed, it is indispensable that the field of observation 
 be extended, so as to embrace the whole of the northern hemisphere. The present state 
 of our knowledge of the science may be thus put. Given in any locality an excess or 
 diminution of atmospheric temperature, and an excess or diminution of atmospheric 
 moisture, we know the atmospheric changes which will take place in restoring the 
 equilibrium thus disturbed, and can to a considerable extent turn this knowledge to 
 account in predicting the weather. But as regards the specific conditions out of which 
 those great atmospheric disturbances take their origin we know little or nothing ; and 
 it is to acquire this all-important knowledge that we urge the extension of the field of 
 observation so that synchronous charts of the northern hemisphere might be constructed 
 (Page 180) which would supply the information desiderated. More magnetic observa- 
 tories are wanted, so that synchronous magnetic charts might be made for comparison 
 with similar meteorological charts. If this was accomplished, and the relation between 
 these atmospheric elements discovered, the magnetic and electric states of the atmos- 
 phere and the aurora might take their place among the most valuable prognostics of 
 the weather. Weather is the condition of the air at any time as regards heat, moisture, 
 wind, rain, cloud, and electricity, and a change of weather implies a change in one or 
 more of these atmospheric elements. The craving of the public for a knowledge of 
 these changes is indicated by the prognostics of every country, which, amid much that 
 is shrewd and of practical value, embody more that is vague and not a little that is 
 absurd; and by the readiness with which newspapers seize upon prognostications of 
 fine or of stormy weather weeks or months beforehand. No prediction of the weather, 
 at least in the British Isles, can be made for more than three or perhaps only two days 
 (Page 190) beforehand, and any attempt at a longer prediction is illusory. Still, 
 guesses may be formed which are not without value. All prediction based on solar 
 or other astronomical causes, if not misleading, is useless. The only safe guide we 
 can have in attempting to forecast the weather for some time are averages based 
 on terrestrial observations. Of this class may be mentioned the interruptions 
 which occur in the regular march of temperature in the course of the year. 
 
 Rikatclieff. (B. 55.) 
 
 (Page 5.) In 1865 FitzKoy's system of meteorological observations and telegraphing 
 was established in Kussia. 
 90 
 
GENERAL 1868. Buchan, NOTES. 
 
 1868. 
 Buchan, A. (B. 4.) 
 
 (Page 1.) Meteorology is the science of the weather. Meteorology took its modern 
 (Page 3) rise from the invention of the barometer by Torricelli in 1643, the ther- 
 mometer by Sanctofio in 1590, Fahrenheit's improvements in 1714 and De Saussure's 
 (Page 9) researches on hygrometers. Austria has 110 stations. Monthly isobarometric 
 (Page 43) lines may justly be regarded as furnishing the key to all questions of mete- 
 (Paye 129.) orological inquiry. The year 1867 was so remarkable for illustrations of 
 violent alternations of heat and cold, drought and rain, brilliant sunshine and the dullest 
 weather, as well as for the many great storms which swept all parts of the globe, that it 
 (Page 138.) may well be regarded as the annus mirabiUs of meteorology. Though all 
 meteorologists now agree in thinking that daily telegrams should not be attempted, yefe 
 a great deal of positive information regarding the suitableness of the coming weather 
 for travelling, farming operations, the growth and ripening of crops, and for other objects 
 and purposes of human life, may be most certainly concluded from daily weather 
 telegrams received from a wide field of observations. It will be evident from the rela- 
 tions of the pressure and temperature of the atmosphere and of the winds, that daily 
 observations, particularly barometric, from a number of well-selected points in Europe, 
 would supply sufficient data from which really trustworthy conclusions could be drawn 
 regarding the weather from day to day over any part of Europe in which for the time we 
 might take an interest. If Eeuter and private individuals would add particulars of the 
 weather to their telegrams we might form a tolerably accurate estimate of the probable 
 (Page 331) productiveness of the harvest in grain-producing eountries. Investiga- 
 tions appear at present to point to a connection between the position of the planets 
 on one hand and the sun's spots, terrestrial magnetism, and the aurora on the other. 
 Nothing, however, could be inferred from such a connection, even were it conclu- 
 sively established, that could be turned to account in predicting the weather 
 (Page 332) likely to occur in a particular country within a specified time. It is 
 an opinion which has been long and popularly entertained that the changes of the 
 moon have so great an influence on the weather, that they may be employed with 
 considerable confidence in prediction. That the moon's changes exercise an in- 
 fluence so strongly marked as to make itself almost immediately felt in bringing 
 about fair, or rainy, or settled, or stormy weather, an examination of meteorological 
 (Page 335) records sufficiently disproves. The next class of prognostics are of 
 a more certain character, being taken from those indications or appearances which 
 experience has shown to be the precursors of a change of weather, or rather they are the 
 first indications or beginnings of these changes. Perhaps the very earliest indication 
 of a change from dry to wet weather might be obtained from observations of the polari- 
 (Page 339) sation of the atmosphere. It is by a careful observing and recording of the 
 lesser changes of the weather from day to day, that the approach of the greater changes, 
 included under storms of wind, rain or snow, may to some extent be known beforehand. 
 It is not by a single observation made at one time that an isolated observer can best 
 draw conclusions regarding the weather likely to happen, but from the character of the 
 changes which have been silently going forward for some time. Hence it is desirable to- 
 set down in a pictorial form the different observations as they are made, so that the eye 
 may take in at once the whole of the changes which are going forward. The Kev. K. 
 Tyas's handy little annual, ' How to use the Barometer,' is calculated to be popularly 
 useful for recording pictorially and in tables the successive changes of the weather from 
 (Page 341) day to day. Mr. Meldrum sent a note to the daily papers when it was 
 concluded from the Mauritius observations that a storm was abroad, stating its position 
 and probable course from day to day. No case of failure has occurred since these notices 
 
 91 
 
GENERAL .'. - . . -4868. Buchan. NOTES. 
 
 . i : * .^ 
 
 began to be sent to the press. l This shows what may be done at an isolated station in 
 the ocean ; in other words what may be done by ships at sea. The reduction of the 
 ocean statistics of meteorology has now become a question of pressing importance. In 
 discussing meteorological ocean statistics referring chiefly to tropical and subtropical 
 regions, the most important points to be determined are the following : 1. The daily 
 range of the barometer for the different months as applicable to the different parts of the 
 ocean, or, better still, the law of its variation according to season, latitude, and proximity 
 to large masses of land. 2. The mean monthly barometric pressure of the different seas 
 chiefly traversed by ships given for every '05 in., or, if possible, every -025 in. of mean 
 pressure. 3. The deviation from the mean pressure -of the month which may be 
 regarded as an amount of disturbance sufficient to be considered as indicative of a storm 
 (Page, 342) at no great distance. 4. The mean direction and force of the wind for the 
 different months. This is no doubt a vast problem, which it will take many years to 
 work out. In regions such as Great Britain an isolated observer cannot with a like 
 certainty draw conclusions from his own observations regarding the approach of storms 
 and other weather changes. But he may almost, if not altogether, attain to the same 
 degree of certainty if he be assisted by a sufficient staff of observers well distributed over 
 W. Europe ; and be able, when he considers it necessary, to communicate with them 
 through the telegraph. In his letter of June 15th, 1865, to the Board of Trade, Gen. 
 Sabine states that he had examined the warnings given on our coasts during the two 
 years ending March 31st, 1865, and found that in the first year 50 per cent., and in the 
 second year 73 per cent., were right. The improvement he ascribes to increased 
 (Page 343) experience. A number of the places warned were not favourable situations 
 for receiving timely warnings, being too near the west coast ; but if the warnings sent 
 to places more favourably situated were examined fewer failures would appear. Thus, 
 of 100 warnings sent to the north coast of France in the winter of 1864-5, 71 were 
 realised ; and in the winter of 1865-6, 76. Of 100 storms which occurred 89 were 
 signalled during the first winter, and 94 during the second winter. The first and chief 
 source of failure was the want of a day and night watch maintained on the west coast of 
 Ireland; whereas this is the first requisite of any system of storm warnings for the 
 British Isles, as pointed out by K. Russell. With observations at 7 a.m. and 2 p.m. 
 only, some storms would have passed some stations before warnings could be issued. 
 {Page 344) The occasional late arrival or non-arrival of telegrams was also a source of 
 failure. There were too few stations on the Continent to the east and south-east of 
 Great Britain. If, then, allowance be made for the failures which arise from these 
 causes, we have the explanation of every one of the ten storms which were not 
 signalled out of the 93 which occurred on the N. coast of France in the winter of 
 1864-5, and of the 6 not signalled out of the 99 which occurred during the following 
 winter. Hence it follows that, practically, the approach of any storm which 
 visits Great Britain may be signalled some time before it reaches the different 
 ports. There is thus no difficulty in carrying on a system of storm warnings 
 {Page 345) in this direction. The practical difficulty lies in securing that no warn- 
 ing be sent except to those places at which the wind will rise to the force of a gale. 
 If this happened uniformly over the whole region included at any time within the low 
 barometric pressure, marking out the atmospheric disturbance of which the wind storm 
 is one of the accompaniments, or if a certain wind force invariably attended on a certain 
 pressure in each storm, then the problem of storm warnings might be regarded as 
 completely solved. But the force of the wind at a particular place depends upon the 
 relative differences of pressure as observed simultaneously at two other places between 
 which it lies. To determine these relations for any place for the next 30 hours, so that 
 from the result warnings might be framed for that place, is a problem which admits 
 only of an approximate solution ; any exact solution, and exact rules framed from such 
 solution, to guide us in issuing storm warnings being impossible. It suffices if the number 
 92 
 
GENERAL 1868. Strachan. NOTES. 
 
 of successful warnings be sufficient to warrant the Uract&e of^Itfog'^^eiifjj What is 
 wanted are : (1) a day and night watch at Yalenti^Wg^^iep^legijaphing to London 
 immediate notice of storms in N.-W. France and Sjfen^Sv. Ireland, W. and N. 
 Scotland ; (3) power to use the telegraph wires at discretion. The only difficulty in 
 carrying it out is the expense. 
 
 Strachan, R. (B. 37.) 
 
 (Page 3.) Weather forecasting depends upon definite principles. FitzRoy gave ample 
 (Page 4) explanation of the principles involved in forecasting the weather, in official 
 reports on the Meteorological Office, but especially in his c Weather Book.' Fine weather 
 (Page 14) occurs with uniformly high pressure. If the law of barometric variations 
 (Page 15) were known, or if any law as regards barometric maxima and minima could 
 be established, then the forecasting of weather could be reduced to a very accurate 
 (Page 16) system it would be a simple mechanical problem. Sir John Herschel long 
 ago saw this. No such law is yet recognized. FitzRoy has practically proved that 
 great storms can be predicted from one to three days beforehand in the present state of 
 meteorology. In the British Isles the transition from a maximum to a minimum of 
 atmospherical pressure does not take place generally in less than 24 hours, while it fre- 
 quently extends over many days. The diurnal range is trifling and not taken into account. 
 Hence the probabilities of being able to rely on the transitions for one day and of fore- 
 casting weather therefrom must be great ; but for two days they must be less, for three 
 days much less, while for more than three days they can have very little dependence. 
 (Page 17.) Forecasts depend upon: 1. Law of wind direction in relation to pressure. 
 2. Extent of barometric differences. 3. Rate and direction of barometrical changes. If 
 we suppose the probabilities in favour of each of these conditions as 9 to 1 ; the value of 
 
 the probability of a daily forecast being correct will be -JA = J or 7 to 3 
 
 nearly. If two days be taken the probabilities for No. 3 must be reduced. Let it be 
 supposed 7 to 3 then the value of a forecast for two days would be 6 to 4 nearly, or 
 
 567 . If three days be attempted the probabilities for No. 3 will be, say 5 to 5. Then 
 
 JL.\)\)\) 
 
 the value of a forecast for three days will be tr~r~> that is, oftener wrong than right. 
 
 No importance is attached to this hypothetical calculation. [It applies to British 
 (Page 18) weather, but may be taken to be of general application.] The forecasting of 
 rain, snow, hail or fog, of cloudy overcast or clear sky, of hot or cold weather and such 
 like weather features, must be rather a matter of shrewd guessing. The direction and 
 strength of the wind, the most important characteristics of weather, may be considered 
 (Page 20) to be within the scope of rule. The key to FitzRoy's method of forecasting 
 weather was identical with the law of wind in relation to pressure, as stated by Ballot. 
 (Page 24) Meteorological knowledge is not yet sufficiently systematized. There is- 
 abundance of material, but books continue to be crammed with assumed rules. Hence 
 it is more than ever needful to sift facts by resting all laws, principles and rules on demon- 
 stration. J. D. Forbes (Brit. Assoc. Rep. vol. i.) said what is true yet, that there is pre- 
 valent a too generally erroneous notion that meteorology as a science has no other object 
 but an experimental acquaintance with the condition of those variable elements which 
 from day to day constitute the general and vague result of the state of the weather at 
 any given spot ; not considering that while such heterogeneous elements can be of little 
 avail, when viewed as groups of facts towards forwarding any one end of the science or 
 giving us any precise knowledge regarding it, yet that the careful study of the individual 
 points when grouped together with others of the same character may afford the most 
 valuable aid to scientific generalization. 
 
GENERAL 1870. Ansted. NOTES. 
 
 Zenger, C. W. (5.43.) 
 
 (Page 433.) Argues that the moon influences temperature and pressure according to 
 the moon's position relatively to the earth and sun ; the temperature is highest and 
 pressure lowest when the obliquity of the moon's orbit is greatest and vice versa. The 
 period is half a lunar year [=9i solar years]. 
 
 1870. 
 A. (B. 1.) 
 
 (Page 600.) The spots [of the sun] are only one of the known evidences of changeful 
 activity going on in the great central luminary. The form, disposition and dimensions 
 of the prominences, and the distribution of chromosphere are visibly undergoing con- 
 stant alteration. May these phenomena not also have their periods of recurrence ? and 
 may not they, equally with the spot outbreaks, stand in some relation to what formerly 
 used to be considered purely terrestrial phenomena, 'namely, magnetism, electricity, 
 humidity, temperature and rainfall? To carry the hypothesis one step further: If 
 there is a physical relation between the solar changes and meteorological occurrences, 
 and if the solar changes are subject to laws which cause them to recur in regular series, 
 have we not in this arrangement a clue by means of which climatic variations may be 
 studied with greatly increased effect ? 
 
 Ansted, D. T. (.2.) 
 
 (Page 103.) Hills can never be safely neglected in reference to climatal questions. 
 (Page 111) The difference [between low plains and plateaux] greatly affects climates. 
 (Page 112) But it is only in large tracts of lands that plains and plateaux attain 
 (Page 144) dimensions sufficiently extensive to influence climate. Changes of weather 
 are very rapidly and distinctly indicated by the colours of the sea water. These may be 
 due to the movements of minute animal organisms, or they may be produced by changes 
 (Page 150) in the state of the atmosphere. The ocean stream currents are of great 
 (Page 151) importance to climates. The great currents are those which chiefly affect 
 (Page 287) climates [Climate then means temperature]. Climate is a very complex 
 matter, and one dependent on a great variety of conditions. It includes the temperature 
 of the air at various times and seasons, the range and variation of temperature, the force 
 and direction of the winds that prevail, the liability to storms, the amount of humidity 
 in the air at various seasons, the quantity of cloud, mist and rain, the distribution of 
 rain and the varieties of electrical condition. These to some extent affect and depend on 
 each other, but all may ultimately be traced to certain general causes connected with 
 physical geography. Among such causes are : 1. The position of the station in latitude. 
 2. The size and figure of the land on which the station is situated, whether detached 
 island, archipelago or continent. 3. The elevation of the station above sea. 4. The 
 position of the land on which the station is placed with reference to the neighbouring 
 land. 5. The position, distance, direction, magnitude and elevation of the nearest con- 
 tinent. 6. The nature, magnitude and direction of the nearest great marine current to 
 (Page 291) the shores. The climate of the south hemisphere is marine and insular ; 
 that of the northern hemisphere continental. The former is extreme, the latter average. 
 (Page 292) There are no means of generalizing in meteorology without abundant facts, 
 (Page 294) and the facts are of no value unless the instruments be accurate. The 
 (Page 298) pressure of the atmosphere is another element of climate. The vicinity of the 
 ocean and the constant freshening of the air by intermixture with other air that 
 has passed over a large extent of sea seems favourable to life, while the influence of a 
 large tract of land seems unfavourable. Islands are therefore, cceteris paribus, more 
 healthy than places far removed from the sea, although there is no doubt that some 
 islands, especially in the tropics, where the decay of organic matter is extremely rapid, 
 
 94 
 
GENERAL 1870. Ansted. NOTES. 
 
 are among the least healthy localities. Electric storms are generally regarded as leaving 
 the atmosphere in a more healthy state than before the storm. So many matters com- 
 bining to produce a certain kind of climate, it is clear that even in the same very 
 small tract of land there may be differences in this respect. It would be difficult at 
 present to say why these differences exist, but the fact is notorious. Climate is 
 {Page 299) so affected by winds that the direction of a mountain chain scarcely 
 visible on the horizon, the position of a large tract of distant lowland, the presence at 
 special seasons of icebergs floating in a sea a thousand miles away, or the fact of a 
 current of water crossing, by a marine current, some great ocean that washes the 
 shores these are the simple elements from which the general climate of a country may 
 be deduced ; while the level of the land, the course of a river, the range of a few low 
 {Page 300) hills, will any of them be sufficient to produce a local modification sufficient 
 to alter the details of climate and greatly affect health and vegetation. And if 
 in the course of ages a change should take place in any of these elements by the 
 alterations that are constantly being produced by great natural forces always at work 
 on the earth, it is clear that the climate must undergo a corresponding modification. 
 Thus the diversion of the Gulf Stream up the Mississippi valley would render Europe 
 {Page 301) colder and drier. Changes of climate and changes of the earth's surface are 
 simultaneous, and both have certainly been produced ever since the earth was subjected 
 to those influences of air and water that seem to us to be essential to its very existence. 
 {Page 302.) Climate may and does change by the influence of man and cultivation. 
 Weather is the condition of the climate of any particular country or district. It varies 
 from day to day in most parts of the temperate zones, but in the tropics and in some 
 special, but limited, areas, it is constant, and may be entirely depended upon during 
 {Page 303) the whole dry season. A fine day in a fine season involves a goodly 
 variety of conditions. On such a day we have a bright sun, but the sun's heat is not 
 scorching, nor its light glaring ; the sky is clear, and the clouds, if any, are light and 
 high, not streaky or in heavy cumbrous masses during the day, and towards evening 
 they clear away leaving only a few that are rosy and pink at sunset. The colour of 
 the sky is blue, but not too intense, and not extending quite to the horizon. Distant 
 objects are visible, but not quite so sharply defined as to appear unusually near. The 
 atmosphere is really heavy, as shown by a high state of the barometer ; but to the 
 feelings it is light and elastic. The air feels dry, but not harsh. The temperature is 
 seasonable. There is a motion in the air, but not enough to be called wind. It pro- 
 ceeds from a quarter generally favourable for fine weather in the place of observation. 
 The electricity of the air is in a state of equilibrium. There is a fair supply of ozone, 
 and there is no disturbance of the magnetic force. An average number of such days, 
 occurring at intervals separated by cloudy and rainy weather of no long duration and 
 not accompanied by violent and continued wind, electric or magnetic storm, or sudden 
 and frequent changes in the temperature and pressure of the air, characterize a fine 
 season ; and several fine seasons following each other produce a cycle or period of fine 
 weather. A certain amount of electric storm and hail in summer, intervals of heavy 
 rain, wind and storm near the vernal and autumnal equinoxes, and an average of snow, 
 frost and magnetic storms in winter are by no means incompatible with fine seasons. 
 Bad weather and bad seasons are the opposite of fine. They also recur occasionally in 
 {Page 304) cycles and alternate with fine weather and fine seasons. The general 
 average of the weather represents the climate of the district, and in this sense it may 
 be said that hardly any two places a few miles apart have precisely the same climate. 
 In a general sense, however, the climate of England is spoken of as one thing, that 
 of France as another, and so on. It is quite conceivable, and even probable, that the 
 climate of a place may, in the course of a comparatively short time, undergo a change, 
 although it takes a large number of observations to prove it. But though climate may 
 change we may almost assert it as an axiom, in most parts of the world in temperate 
 
 95 
 
GENERAL 1870. Ansted. NOTES. 
 
 latitudes, that the weather must change. There are places where these changes are 
 excessively small, but we may safely assert, in a general sense, that weather is change- 
 able and climate uniform. Climates are different in different places, whereas the 
 weather, though changeable in any one place, may be the same at the same time in 
 many places. The weather is often extremely different on the two sides of a mountain 
 chain, across a narrow channel occupied by water, even in two localities on land a few 
 miles distant from each other. It follows that while there are causes which influence 
 weather of exceedingly wide operation, there are others altogether local. The prog- 
 (Page 305) nostication and causes of change of weather must evidently be studied with, 
 reference to this important difference. There is a third condition of weather when, as 
 in the case of storms, it travels over land and sea at a nearly even pace, occupying and 
 affecting a narrow belt. During cyclones the weather travels in this manner. The, 
 signs and causes of this travelling weather are somewhat different from those of the 
 other two kinds. The weather is essentially the state of the air at the place and time. 
 of observation, and change of weather involves the action of some external cause 
 altering the condition of the atmosphere. The pressure of the air is constantly varying 
 from a multitude of influences. The temperature of the air also changes every hour 
 of the day. The moisture of the air varies with the temperature. The electrical state 
 varies from many causes. The direction of the wind frequently changes. There is 
 thus a great complication of phenomena. By observation of the external world or by 
 (Page 306) combining these with notices of the habits and instincts of animals, any; 
 one may acquire an almost instinctive perception of weather-changes. The state 
 of the air is one of the first things that may be studied with reference to the 
 weather. There is hardly a more certain prognostication of coming change 
 than an unusual clearness of distant objects. Generally in all temperate climates it 
 is followed by bad weather within twenty-four hours, or if continued for some days, 
 severe weather is almost inevitably at hand. The quantity, mode of arrangement, 
 and form of clouds are all matters greatly to be looked at if we would foretell the 
 weather a little in advance. Yery light, lofty clouds, but detached from each other, 
 and often crossing each other's directions, are frequently the first signs of change and 
 coming wind after continued fine weather. These cirrus clouds are called cats' tails, 
 and the sky covered with such clouds a mackerel sky : in summer they announce rain, 
 in winter thaw. By degrees the clouds descend and become more prominent ; they pass 
 either into heaped masses of cumulus or into dense horizontal stratus, forming at sunset 
 and disappearing at sunrise. Both kinds pass into grey, formless, leaden clouds, which 
 (Page 307) at last empty themselves in rain. A very sudden alteration of form or shifting 
 of the place of clouds, or a sudden obscuration of the sky without clouds in motion, 
 is an indication of a state of the air generally belonging to changeable weather. When, 
 the round, heaped clouds appear early in the morning, they often gradually disappear as 
 the day advances, and after noon the sky is clear ; but when they come on after noon 
 and increase during evening, obscuring the sunset, they generally terminate in rain. 
 Any violent and rapid motion amongst the clouds, owing to various currents of air at 
 different altitudes, indicates the approach of changeable weather. At a few thousand 
 feet above the earth there is a cloud stratum which forms a kind of dividing plane, and 
 the more immediate changes of weather no doubt commence there, while the more 
 distant alterations require a longer time to perfect. A fine sunset is a valuable indica- 
 tion of the weather of the succeeding day. It requires, however, some experience to 
 appreciate the exact state of the clouds in this respect, and the probability of interference 
 by changes of wind or temperature. Among signs of fine weather an early and heavy 
 dew has often been noticed. Hail in summer is generally preceded by great heat and 
 followed by cold weather. The state of the air in which smoke rises vertically and to 
 a considerable height is known to be frequently followed by fair weather, whilst the 
 opposite state, in which the smoke is beaten down and refuses to rise, is unfavourable. 
 96 
 
GENERAL 1870. Ansted. NOTES 
 
 The direction of the wind and the direction of the change when the wind veers round 
 are among the most valuable indications of weather open to the general observer. The 
 {Page 308) latter is the more important as a prognosticating sign. A large amount of 
 weather news is obtained by watching the animals and the conditions of vegetation, 
 such as the flight of birds and insects, the departure of fishes from their usual haunts, 
 the movements of cows and sheep in the fields, or of domestic animals in the house. 
 Amongst human indicators are the martyrs to rheumatism and neuralgia, persons who 
 have old and imperfectly healed wounds, those with dry consumptive coughs, or those 
 {Page 309) who suffer from bronchial irritation. All the conditions of the air are the 
 result of causes which, if clearly understood in their relative importance and mode of 
 action, would be reducible to direct observation and calculation. They depend on the 
 pressure of the air, the temperature of the air at the surface and at various heights, the 
 dew point, the rainfall, the clear or cloudy state of the upper air, the direction and force 
 of the wind, the electrical state of the air, the presence or absence of ozone, and the 
 {Page 310) magnetic condition of the earth and atmosphere. A temperature continued 
 for some time below or above the average is an almost certain indication of change. 
 The direction of the wind and the agreement or disagreement of the direction with the 
 average of many years at the same period or season is an important observation. When 
 {Page 311) the wind veers the change may be looked on as not unfavourable, but when it 
 backs bad weather may be expected to follow. Settled north-west wind brings cold and 
 fine weather. Auroras are often followed in our latitudes by bad weather, but the 
 precise relations of magnetic disturbance with weather changes are not yet fully under- 
 stood. Peculiarities of weather, however great and strongly marked, must not, even 
 when they extend over many years, be assumed to indicate permanent changes of climate. 
 Although we may not be able to foretell the exact year of change, the general fact of 
 periodicity of weather is clearly established. The power of foretelling is by no means 
 easy to acquire ; it can only be acquired by careful and frequent observations of the 
 barometer and other instruments. It will also appear that, to judge of the weather 
 a week in advance by noticing the hour at which the moon becomes new or full, or by 
 observing the weather at such hour, can only be a very vague and uncertain method 
 subject to various causes of local interference. It is not that valuable suggestions may 
 not be obtained by collecting rules based on these suppositions. All observations and all 
 modes of connecting observations have a certain value, as they may suggest the true 
 explanation, even if they do not give it. But the problem is so complicated that no 
 simple solution can suffice. The prognostications of the weather-wise sailor or shepherd 
 are the result of the life- long observation of small signs, of the nature of many of which 
 he is hardly aware himself, and which combine all that a dozen instruments, and as 
 many careful meteorologists, can discover. Exactly in proportion to the experience and 
 habit of close observation of natural appearances is the value of such an opinion ; and 
 this is all that can be said for the meteorologist's also, for he compares the experience of 
 a large number of persons, and combines their results before he is justified in expressing 
 an opinion ; and his conclusion must fail should he neglect some correction which, how- 
 ever small, may largely influence the result. We may almost recognize the reality of 
 an existence unhampered by material impediments when we find an instantaneous 
 response of our innermost senses and sensations to a material stimulus applied within 
 the burning atmosphere of the sun. Who has not felt the influence of weather in clearing 
 up or. obscuring the intellectual faculties? We attribute this to an indirect action 
 through the state of our health ; but who can say how much of it may not be due to 
 some direct action proceeding from the sun ? Perhaps some of those peculiarities of 
 high nervous organization really owe their origin to a more ready sensibility to natural 
 forces. The tendency of all observations on climates is to show that it is subject to 
 a number of periodic changes, and we are fully justified in believing not only that the 
 periods are many, but that we are by no means acquainted with all. A few years 
 H 97 
 
GENERAL 1870. Somerville. NOTES. 
 
 reproduce some phenomena ; others do not recur for centuries or even thousands of 
 years. Geologists infer from observations that weather in special localities as well as 
 climate must have varied greatly during different periods of the earth's history. 
 
 Somerville, M. (B. 43.) 
 
 (Page 33.) Plants and animals vary with climate. The phenomena of the atmos- 
 (Page 308) phere depend upon the revolution and rotation of the globe, which successively 
 exposes all parts of it and the air which surrounds it to a perpetual variation of the 
 gravitating force of the two great luminaries, and to annual and diurnal vicissitudes of 
 solar heat. Atmospheric phenomena are consequently periodical and connected with one 
 another, and their harmony and the regularity of the laws which govern them become 
 more evident in proportion as the mean values of their vicissitudes are determined from 
 simultaneous observations made over widely extended tracts of the globe. The 
 fickleness of the weather is proverbial, but as nearly the same amount of heat is 
 (Page 309) annually received from the sun, and annually radiated into space, it follows that 
 all climates on the earth are stable ; and that their changes, like the perturbations of the 
 planets, are limited and accomplished in fixed cycles, whose periods are still in many 
 instances unknown. It is possible, however, that the air may be affected by secular 
 variations of temperature during the progress of the solar system through space, or from 
 periodical changes in the sun's light and heat. The spots on the sun must occasion 
 periodical variations both in the light and heat of the sun. Accuracy in meteorological 
 (Page 313) statements can only be obtained by means of averages of large numbers 
 (Page 316) of observations. Observations tend to prove that all the climates on the 
 earth are stable, and have remained so from the remotest historical periods, and that 
 (Page 319) their vicissitudes are only oscillations of greater or less extent, which vanish 
 in the mean annual temperature of a sufficient number of years. [' Climates ' here is 
 (Page 338) apparently restricted to temperature.] The atmosphere is much more 
 unstable in the north hemisphere, with its excess of land, than in the southern, with its 
 excess of water. Rains, fogs, thunder, calms and storms, all occur much more frequently, 
 and are much more irregular as to time and place, on this side than they are on the other 
 (Page 343) side of the equator. In the region of the trade winds the weather is steady 
 (Page 386) and delightful. As the land rose at different periods above the ocean, each 
 part, as it emerged from the waves, was probably clothed with vegetation and peopled 
 with animals suited to its position and climate. And as the position and climate were 
 different at each succeeding geological epoch, so each portion of the land, as it emerged 
 from the ocean, would be characterized by its own vegetation and animals. The plants 
 (Page 425) essential to man have great powers of adaptation to climates, especially the 
 (Page 441) cerealia. The marine faunas are distributed in nine belts which surround the 
 globe, each of which, being under nearly the same circumstances as to climate, has in its 
 different parts either the same or representative species, and therefore it is said to be 
 (Page 442) homoiozoic. The intertropical ocean forms the central homoiozoic belt ; it 
 has four others on each side, of which those at equal distances north and south have 
 faunas mutually representative ; the two last belts are the circumpolar oceans. The 
 lines which bound the homoiozoic belts are climatal and nearly correspond with the 
 isothermal lines on land, so that they are neither parallel to one another nor do they 
 coincide with the parallels of latitude, but are undulating from the effects of the warm 
 (Page 490) and cold currents which come from the tropical and polar oceans. Most 
 animals [ = mammals] perish from change of climate, and many must have inherited 
 (Page 491) their present stations from the first appearance of the land. In the 
 temperate zone of Asia and Europe there are such varieties in size and colour as might 
 be expected to arise from differences of food and climate. In the inter-tropical regions 
 and still more in the south temperate zones, the vertebrated animals are different, but in 
 the similar climates tribes of forms in many respects analogous replace one another. 
 98 
 
GENERAL 18711872. NOTES. 
 
 (Page, 493) Many wild animals adapt themselves to change of climate; after some 
 generations their habits and organizations alter to suit the new conditions. By draining 
 {Page 526) marshes, cutting canals, making roads, turning the courses of rivers, opening 
 communications, clearing away forests in one country and planting them in another 
 man has altered the climate. 
 
 1871. 
 Maury, T.B. (5.24.) 
 
 (Page 390.) To give forewarnings of approaching tempests on the coasts of the 
 Adriatic, the Italian and old Roman castles had on their bastions pointed rods, to 
 which as they passed the guards on duty presented the iron points of their halberts, 
 and whenever they perceived an electric spark they rang an alarm-bell, to warn the 
 fishermen and farmers of the approaching storm. This Italian custom was widely 
 spread over the earth in former ages. In November 1854, the Anglo-French fleet was 
 warned of an approaching cyclone. The fleet withdrew, and the storm broke over 
 Sebastopol at the time predicted. The first idea of making use of the telegraph for 
 conveying information as to weather occurred to Professor Henry in 1847, and he sug- 
 gested it in the Smithsonian Report, published January 6, 1848, and it was further 
 referred to in the Reports for 1848 and 1849, and subsequently, but it was not till 
 1856 that observations were actually collected and posted. It was in full operation 
 in 1858, when weather maps were made from reports received at 10 A.M. America 
 (Page 391) has the credit of first initiating and carrying into successful operation the 
 systematic use of the telegraph for the simultaneous registers of the weather over large 
 (Page 414) areas. The Signal Office of Washington estimated that the probabilities 
 published were fully verified 50 per cent. ; partly, 25 per cent. ; while 25 per cent, 
 failed. Many failures were due to lack of information from places without observers. 
 (Pages 430-432.) Describes Gr. W. Hough's self-recording barometer and meteorograph. 
 (Page 432.) Describes Wild's self-registering barometer. 
 
 B., W. (5.39.) 
 
 (Page 466.) A meteorograph similar to Hough's, and invented by a Swede, was 
 exhibited in the London International Exhibition of 1871. 
 
 1872. 
 Hall,J.J. (5.17.) 
 
 (Page 327-8.) [The Swedish instrument exhibited in the International Exhibition 
 of 1871 was Theorell's printing meteorograph.] 
 
 Howorth, H. H. (5.21.) 
 
 (Page 24.) The increase of land round the poles in recent times must have influenced 
 climates; it would materially alter the mean climate of both hemispheres. [Here 
 climate seems to mean temperature solely or more particularly.] 
 
 Lockyer, J. W. (5.25.) 
 
 (Page 98.) He dwells upon the millions of observations made in the British Isles, and 
 remarks that the enquirers of some centuries hence will give up their examination in 
 despair. In meteorology the thing to hunt down is a cycle ; if no cycle can be found, 
 plant the science firmly on a physical basis, and wait for results. Observation in the 
 absence of method is for research purposes of very inferior value. Mr. Ferguson told 
 me that every one in Ceylon recognized, a 13-year cycle. I suggested the cycle might 
 be 11 years. This conversation led to a letter in the * Ceylon Observer,' which stated 
 H 2 99 
 
GENERAL 1872-1873. NOTES. 
 
 that the weather cycle was 11-yearly ; but not with mathematical regularity, for at one 
 time it may be 13 years, and at another 11 ; giving a grand cycle of 30 or 33 years. 
 
 Murphy, J. J. (5.40.) 
 
 (Page 142.) I do not think the most important question in meteorology is the dis- 
 covery of a cycle ; the chief desideratum is a dynamical theory of barometric waves. 
 
 P., H. (5.41.) 
 
 ' (Page 420.) Prince says few prognostics of seasons can be relied on. 
 
 Scott, R. H., and Win. Galloway. (B. 49.) 
 
 (Page 504.) They made curves based on the records at Stonyhurst ; 30 per cent, of 
 the colliery explosions were unaccounted for on meteorological grounds. They con- 
 clude that meteorological changes are the cause of most of the explosions ; 48 per cent. 
 were attributed to the state of the barometer, and 22 per cent, to the state of the 
 thermometer. 
 
 1873. 
 
 Barrett, W. P. (B. 1.) 
 
 " (Page 23.) One important feature of the translation of Flammarion's * Atmosphere ' is 
 the frequent graphic delineation of data. 
 
 Flammarion, C. (B. 13.) 
 
 (Page xi.) As it exists at the present day meteorology is a new science of recent 
 establishment, scarcely as yet fixed in its elementary principles. The present generation 
 has seen the establishment of meteorological societies throughout the different nations of 
 Europe, and of special observatories for the exclusive study of problems relating to the 
 atmosphere. The analysis of climates, seasons, and periodical phenomena, is scarcely 
 terminated. The science of the atmosphere is the question of the day. Meteorology 
 will be founded in the nineteenth century. The work is intended to collect all that is 
 (Page 9) positively known on the subject. The solar heat keeps in continual work the 
 mighty factory of the terrestrial atmosphere, organizing the permanent system of the 
 (Page 45) vital circulation of the globe. Solar heat gives rise to regular diurnal and 
 monthly variations, the intensity of which differs according to the latitude. It now 
 (Page 200) becomes necessary to ascertain what part of the immense calorific radiation 
 which is incessantly emanating from the sun is at work in the atmosphere. Meteorology 
 is nothing but a great physical problem. We have to determine what are the laws 
 which regulate the manner in which heat, barometrical pressure, vapour of water, and 
 electricity, are distributed in our atmosphere in relation to the movements which the 
 solar heat engenders in the solid, liquid, and gaseous superficial stratum of our globe. 
 This problem, as Father Secchi says, is in reality but an application of the best known 
 laws of physics ; the difficulties of solving it are owing rather to the large number of 
 disturbing causes, and to the incalculable reactions of effects upon causes, than to any 
 real deficiency in the general theory. Hence the necessity of numerous experimental 
 data in order to arrive at a complete solution. 
 
 Maury, J. B. (-B/26.) 
 
 (Page 124.) Meteorologists say the science is as old as Aristotle ; but its progress has- 
 been very slow up to the middle of the present century. Within the past few years it 
 has rapidly developed. 
 
 100 
 
GENERAL 18731875. NOTES. 
 
 Stevenson, T. D. (B. 56.) 
 
 (Page 103.) The elements of time and distance should form part of the meteorological 
 records. The gradient of all the elements should be calculated. There should also be 
 horizontal sections by means of instruments placed at short distances from each other, 
 and also vertical sections. The latter could be effected by having a series of stations on 
 the slopes of a mountain. 
 
 Nature. (5.64.) 
 
 (Page 341.) Even under the present diverse systems of observation much valuable 
 material has been accumulated ; but its value depends .only on its being sufficiently 
 approximate to meet the requirements of some of the more pressing questions, not 
 because it is precise. Where questions require precision and uniformity the present 
 systems of observations are found to be sadly wanting and unsatisfactory. Uniformity 
 is much to be desired. The conference [at Leipzig in 1872] was only a consultative one, 
 preliminary to one proposed for 1874 in Vienna. Twenty-six questions were proposed. 
 (Page 342.) It was recommended that aneroids should not be substituted for the 
 mercurial barometer. 
 
 Nature. (B. 65.) 
 
 (Page 468-469.) [Gives a programme of the subjects discussed at the Vienna Con- 
 gress. It consists of 28 questions.] 
 
 Nature. (5.67.) 
 
 (Page 335.) Professor Chase (Am. Phil. Soc. Philad., July 19, 1872) read a paper on 
 '^Ethereal oscillation: the primordial force,' and stated that certain meteorological 
 observations had been verified which had been based on his observations of the rain- 
 fall at San Francisco. 
 
 (Page 455.) E. H. Scott (Meteorol. Soc., March 19), read a paper 'On Some Eesults of 
 Weather Telegraphy.' The information received was insufficient, both as regards 
 quality and quantity, to give a complete idea of the weather. Serious results arise 
 from the frequency of telegraphic errors. 
 
 Nature. (5.70.) 
 
 (Page 484.) During the year the Signal Service of the United States sent out 187,617 
 bulletins and 203,533 maps. The forecasts up to November 1, 1871, were verified to the 
 extent of 69 per cent ; since that and up to October 1, 1872, to 76'8 per cent. The 
 precautionary signals were verified to the extent of 70 per cent. 
 
 1875. 
 Hopkinson, John. (B. 4*.) 
 
 (Page 34.) Observations of the periodical phenomena of plants and animals alone 
 may furnish climatological data of importance in the operations of the farmer and 
 gardener. Combined with meteorological observations they may afford valuable assist- 
 (Page 35) ance in investigations on climate, for these periodical phenomena both of plants 
 and animals are all more or less regulated by the laws of climate, and the varying 
 influences of the seasons. It is here that union is required. As an example of the 
 information that may be derived from these naturalists' calendars it may be mentioned 
 that by comparing the various records of similar observations made simultaneously upon 
 the species selected at a number of stations in this and other countries, we may dis- 
 tinguish those localities at which the same phenomena occur at the same time, and by 
 drawing lines through these localities we may indicate with clearness the isochronism of 
 the phenomena and therefore of the climatal conditions on which they are dependent. 
 
 101 
 
GENERAL 18751876. NOTES. 
 
 Sayce, A. H. (Nature, xii.) 
 
 (Page 489.) The ' Observations of Bel ' were compiled before B.C. 1700. This treatise 
 shows that amongst the Accadians cycles of 12 solar years were in use, during which th 
 same weather was expected to recur. 
 
 I Stewart, Balfour. (B. 42.) 
 
 (Page 348.) Terrestrial meteorology baffles us owing to the largeness of the scale and 
 (Page 350) the isolation of the observers. An exhaustive catalogue of all that has 
 been done in meteorology in the English dominions has been framed by a British Asso- 
 ciation Committee. It requires to be supplemented by all that has been done abroad. 
 
 Nature. (B. 52.) , 
 
 (Vol. xii. Page 160.) (Acad. Sci. Paris, June 14.) Fautrat read a paper 'On the 
 (Page 264) influence of forests on climate,' etc. (Acad. Sci. Paris, July 19.) On 
 (Page 405) Espy's meteorological essays by M. Faye. (Brit Assoc. Meeting, 1875.) 
 Dr. Hennessy read a paper * On the influence of the physical properties of water on 
 (Page 488) climate.' [It refers to temperature.] Zeits. f. Meteor., August 15, describes 
 Theorell's printing meteorograph. 
 
 (Vol. xiii. Page 56.) (Germ. Sci. Assoc. Meeting, 1875.) Method of representing 
 (Page 140) the various constituents of weather in a short and compact manner, by Dr, 
 'Prestel. (Acad. Sci. Paris, December 6.) Atmospheric perturbations of the hot 
 (Page 160) season of 1875, by M. Bel grand. (Acad. Sci. Paris, December 13.) Atmo- 
 spheric perturbations of the hot season, by M. Belgrand. Meteorological observations in 
 a balloon, November 29, by M. Tissandier. 
 
 1876. 
 Evans, John. (B. 4.) 
 
 (Page 115.) [Refers to meteorological instruments : but has no remarks worth noting 
 connected with climate.] 
 
 Spes. (B. 12.) 
 
 (Pages 169, 170.) [Suggests that meteorology be treated as a distinct science by having 
 professoriates of meteorology.] 
 
 Symons, G. J. (B. 15.) 
 
 (Page 10.) [Simply a. notice that the thermometers established under the auspices of 
 the Meteorological Society are all placed as nearly as possible 4 feet from the ground.] 
 
 Nature. (5.17.) 
 
 (Page 107.) The * New York Herald ' of November 7, publishes a map of the weather 
 of the morning, exhibiting the lines of atmospheric pressure and of the temperature of 
 the United States. The meteorological charting, which was finished at the Central 
 Office in Washington at 10 A.M., was immediately transmitted from Washington in 
 facsimile by telegraph to Philadelphia, where it was received at 10'30 A.M. It was 
 shortly thereafter published in the supplement of the 'New York Herald' of the same 
 day, being the first occasion on which such telegraphing charting had appeared in any 
 newspaper. The fact of telegraphing and printing such charts solves one of the greatest 
 difficulties of exchanges of weather reports. It may now be regarded as only a question 
 of time when the more important newspapers of our British large towns will be in a 
 position to present their readers every morning with a chart of the weather as existing 
 only two or three hours before going to press ; and, indeed, it will not be till this result 
 is effected ^that the practical utility of weather warnings will be properly developed, 
 
 102 
 
GENERAL 18761877. NOTES. 
 
 owing to our close proximity to the Atlantic, and the rate at which our weather changes 
 pass to the eastward. 
 
 Nature. (5.19.) 
 
 {Page 10-11.) [Account of meeting of the Vienna Meteorological Congress. Notice 
 of resolutions made.] 
 
 Nature. (5.21.) 
 
 (Vol. xiii. Page 218.) (Zeits. f. Meteor. Nov. 15.) Wild reviews the work of the 
 Meteorological Congresses of 1873 and 1874. Keprinted from the Annual Report of the 
 (Page 440) Imp. Obs. at St. Petersburg. (Meteor. Soc., March 15.) On the deduction of 
 mean results from meteorological observations by L. F. Kamtz, trans, from Eepert. f. 
 (Page 497) Meteor, by J. S. Harding. (Zeits. f. Meteorol., Dec. 1, 1875.) Wild on the 
 Congresses. The sole result of these it had been urged would be to pile a million useless 
 figures upon a million others already published. Wild admits that comparatively few 
 of the figures are of any use ; but who is to decide which will Or will not be serviceable ? 
 Observations are faulty owing to their deficiencies, inconvenience of form, or variety of 
 arrangement. Published observations are more carefully revised than unpublished. The 
 (Page 491) latter are for the most part useless. 
 
 (Vol. xiv. Page 143.) (Meteor. Soc., May 17.) Remarks on the present condition 
 of maritime meteorology from 1853. Loomis's Contributions to Meteorology, 5th 
 (Page 420) paper. Am. Journ. Sci., July 1876. The * Bothkamper Beobachtungen,' 
 No. 3, contains Lohse's meteorological observations in the year 1873. Montigny 
 (Page 562) (Bull. Acad. Roy. de Belgique, 1876, No. 8) has an elaborate report upon 
 the connection between scintillation and various meteorological elements. 
 
 1877. 
 
 Abercromby, Hon. B. (S. 1.) 
 
 (Page 510.) Meteorology is said not to be a science by Airy, Sir Wm. Thomson, and 
 others ; but a great change has come over the whole aspect of meteorology since the 
 introduction of synoptic charts. Synoptic meteorology shows that the world is covered 
 with shifting cyclones and anticyclones, which have each, subject to local, diurnal, and 
 other variations, a characteristic weather and physical appearance; and one great 
 problem of meteorology is to explain the observed weather over any area at any instant 
 by defining the position of these cyclones and anticyclones. It is also said that the 
 knowledge requisite to issue forecasts cannot be expressed in mathematical formulae or 
 in simple maxims. Mean values or harmonic series will never advance meteorology 
 much as a science. Meteorology is as much a science as geology. 
 
 Broun, J. A. (5.2.) 
 
 (Page 251.) Strachey's true criterion of a periodicity is this. If the differences of the 
 rainfall [the rainfall of Madras is meant, but the remarks apply generally to climate] 
 for each year from the mean of the whole 64 years be taken, and the mean of all these 
 differences (without respect to sign) be called the general mean difference; if we 
 average the yearly rainfall in horizontal series of 11 successive years, and the means for 
 the first, second . . . years be taken, these quantities (periodic means) will show the 
 mean variation in the period of 11 years, if any such exist. If now the differences of 
 the yearly rainfall from the periodic mean for the corresponding years be taken, the 
 means of these, irrespective of sign, may be called the periodic mean difference. His 
 true criterion appears to be that if there be no periodicity the variation in the periodic 
 means will tend to disappear in a sufficiently long series of observations, and the general 
 and periodic mean differences be identical. It seems to me that the disappearance of a 
 
 103 
 
GENERAL 
 
 1877. Stevenson. NOTES. 
 
 variation in the periodic means is here the true criterion of no periodicity. Strachey 
 (Paqe 252) concludes that when the periodic mean difference is much less than the 
 general mean difference, a true period exists. I will show that this is no criterion of 
 periodicity If we represent variations of any quantity for a given time by a curved 
 line and if we have several such lines of exactly the same form placed one over the 
 other, a straight line passing through the curves, with as much space between the 
 straight and curved lines above as below, will represent the general mean. In a simple 
 curve of two branches, the general mean difference will be nearly one-fourth of the 
 amplitude of the oscillation; while as all the oscillations agree with each other, and 
 therefore with the mean oscillation, the periodic mean difference will be zero. If, how- 
 ever, we displace the individual curves so that as many shall be above as below their 
 mean, both the general and the periodic mean differences will increase, and the 
 differences between these quantities will diminish till the individual curves are so sepa- 
 rated from the mean that none of them is cut by it, when the two mean differences 
 will be equal ; between this case and that of general coincidence the two mean differences 
 will have values which will differ more or less from each, according as the individual 
 curves are nearer to or more remote from the mean ; and the ratio of the one mean dif- 
 ference to the other will tend to a constant value as the number of cycles increases, a 
 ratio which will depend for its value on the mode of distribution of the individual curves 
 and of the irregular deviations from the mean. The two-hourly observations of the baro- 
 meter at Simla for six days in Jan. 1845, gave as follows : general mean difference, 
 0634 in. ; periodic ditto, -0615 in. Or if the first five days be taken, we get : general 
 mean difference, "0656 in. ; periodic ditto, '0634. Here we have a large and regular semi- 
 diurnal period where the periodic is not one- thirtieth less than the general mean difference. 
 
 Buchan, A. (B. 3. The reference should be to vol. xvi., not xvii.) 
 (Page 424.) Meteorologists have for some time been aware that the 11 years cycle of 
 sun-spots is coincident with a cycle of atmospheric conditions producing ascertained 
 terrestrial effects. 
 
 Hunter, W.W. (J5. 8.) 
 
 (Page 455.) The cyclic" coincidence may be tested thus. If it really exists there 
 should be a well-marked minimum group at the extremities of the cycle (in the llth, 
 1st, and 2nd years), and a well-marked maximum group in the middle (the 5th and 
 the following years). The years on both sides of the central maximum group should 
 yield intermediate results, and when taken together should form an equally well- 
 marked intermediate group. 
 
 Kinahan, J. H. (B. 9.) 
 (Page 334.) [Nothing for general notes.] 
 
 Stevenson, Thomas. (B. 21.) 
 
 (Page 586.) Prof. Balfour Stewart has separated meteorology into two great divisions 
 physical and climatic. The latter I have proposed to separate into two subdivisions, 
 viz. normal and abnormal. The first of these subordinate branches includes the 
 investigation of the usual states of the atmosphere in different parts of the earth's surface, 
 as ascertained by periodic data derived from the averages of observations continued 
 for a series of years. The second subordinate branch has for its object the investigation 
 of unusual temporary disturbances of the equilibrium of the atmosphere, such, for 
 example, as storms of wind, by means of the comparison of individual observations 
 extending over only a few hours or a few days. Physicists of high standing look 
 with disfavour on meteorology, owing to the want of agreement amongst meteorologists 
 as to the means of determining even the most important fundamental data. One 
 essential condition is uniformity in instrumental observations. No uniform inter- 
 
 104 
 
GENERAL 1877. Stewart. NOTES. 
 
 national system has been established. Glaisher has induced many observers to adopt 
 the uniform height of 4 feet above the ground for thermometers and an uniform screen. 
 The Scottish Meteorological Society has adopted the height of 4 feet, and my double louvre 
 protecting box. The Meteorological Society of England has adopted the same uniformity 
 of boxes, their exposure and hours of observation ; but amongst observers generally 
 and on the Continent there is less approximation to uniformity. Without uniformity 
 the results obtained are not comparable. Climates may be defined as states of the 
 atmosphere due to the joint operation of geographical, geological, and other conditions 
 more or less local, and they are judged of by their effects on animal and vegetable 
 life. They do not depend, therefore, simply on the geographical position on the earth's 
 surface of the district where observations are made, but are largely affected by various 
 conditions, such as the distribution of land and water, the nature of the soil and its 
 covering, and the elevation or depression and character of the land at or adjacent to 
 the place. Climates are therefore frequently of a local nature, that is, of small super- 
 ficial extent. Thus many varieties of climate may co-exist about the same parallel of 
 latitude, and even over a very limited portion of that zone. That such local atmospheric 
 distinctions do exist is shown by the varied distribution of plant-life, which, though 
 no doubt largely affected by the nature of the soil, is nevertheless dependent to a 
 considerable extent on the existence of certain atmospherical conditions. 
 
 Stewart, Balfour. (5.22.) 
 
 {Page 45.) Dr. Arthur Schuster has found that the years of minimum sun spots 
 {Page 46) coincide very nearly with the good wine years in Germany. The temperature 
 ranges at Kew have an apparent reference to the sun ; the ranges being greater at times 
 of maximum sun-spot frequency, but the correspondence is not so great as in the case 
 of the magnetic disturbance. Do these fluctuations occur simultaneously with tha 
 solar fluctuations ? or do the solar fluctuations occur first ? in the latter case we could 
 predict the greater meteorological occurrences. The Kew observations seem to indicate 
 that the temperature fluctuations occur six months after the solar. Meteorologists are 
 beginning to suspect a somewhat ultimate connection between the magnetism and the 
 meteorology of the earth. Baxendell, I think, first pointed out that there is a diurnal 
 inequality in the direction and velocity of the wind apparently connected with the 
 daily changes of magnetic variation. J. A. Broun says that meteorological phenomena 
 are due to solar action; the heating action is one, but there also seems to be a 
 second which introduces forces we cannot at present appreciate. If the sun affects 
 {Page 47) the earth, so also may the moon. It certainly influences the earth's mag- 
 netism, and Mr. Park Harrison has pointed out that its temperature is influenced by the 
 relative position of the sun and moon. I have noticed an unmistakable reference 
 to the phase of the moon in the daily temperature range at Kew. In the summer, 
 when the full moon is low in the heavens, we have a less decided reference, which 
 seems to imply a maximum of daily temperature range about new moon and also about 
 full moon. But in winter, when the full moon is high, we have a very decided refer- 
 ence, showing a maximum of daily temperature range about new moon and a minimum 
 about full moon. The same features occur in the magnetic ranges. He suggests that, 
 as solar research, terrestrial magnetism, and meteorology hang closely together, they 
 should be studied together. 
 
 Stewart, Balfour. (5.23.) 
 (Page 161.) The true test of a physical cycle is its repetition. 
 
 Nature. (5.26,32.) 
 
 (Page 59.) Dr. Williams treats the subject to which his book relates in its climatic 
 relations, and gives a discussion of the data adduced with regard to the therapeutical 
 
 105 
 
GENERAL 1877. Nature. NOTES. 
 
 action of British, Mediterranean, African, Indian, Australian sea voyages and other 
 climates differing widely from each other as regards temperature, humidity, elevation, 
 and exposure to sudden changes of weather. 
 
 Nature. (.31.) 
 
 (Page 263.) Prof. Fritz finds evidence of an 11-yearly period in the hail-storms 
 (Page 458) and high river floods. Prospects of fair weather are increased in pro- 
 (Page 460) portion to the elevation of clouds. The * New York Herald ' has sent seven 
 storm-warnings since the end of February. 
 
 Nature. (B. 32.) 
 
 (Page 171.) (Royal Soc., May 24.) General Strachey 'On the alleged Corre- 
 spondence of the rainfall in Madras with the sun-spot period and on the true criterion 
 of periodicity in a series of variable quantities.' The only signification of the arith- 
 metical mean value of a series of observed quantities is, that it is one above and below 
 which there is an equal amount of deviation in the individual observations. The 
 question is whether the mean values thus obtained can be accepted as showing a 
 definite law of variation from year to year in the cycle. In the case of the Madras 
 rainfall it seemed to make little difference whether the cycle adopted be 11 years 
 (Page 172) or 4, 5, 6, 7, 8, 9, 10, 12, and 14 years. Now, if in any series of 
 quantities there be a '.law of periodicity, each observed quantity may be supposed 
 to be compounded of a periodical and non-periodical element. If we take the sum 
 of a large number of cycles, each of which coincides with the cycle of periodicity, 
 the non-periodical elements will tend to be eliminated and the means for the suc- 
 cessive years of the cycle will indicate the periodical elements for the successive 
 intervals. At the same time the differences of these means from the several original 
 quantities from which they were obtained will be the several non-periodical elements. 
 In proportion as the periodical elements are large or small in relation to the corre- 
 sponding non-periodical elements, so the difference (obtained as above) will be univer- 
 sally less or more different from the differences between the individual observations 
 and the mean of the whole of them ; and if there be no periodicity the two sets 
 of differences would, in a sufficiently long series, be identical. Hence it may be 
 inferred when the differences (taken as before) closely approximate in magnitude to 
 the mean difference ot the original observations from the arithmetical mean of all of 
 them, the periodical elements in these observations must be correspondingly small. 
 The mere circumstance of any series of cyclical means showing a single maximum and 
 a single minimum gives no real indication of such a result being a truly periodical 
 feature. The test of the periodicity is to be sought altogether outside of the particular 
 values of the successive elements of the cyclical means. It is manifest that a com- 
 plication of periodical elements may so mask one another as to prevent positive results 
 being obtained by the examination of the means and differences. (B. 39.) The new 
 (Page 224) Meteorological Council of the Royal Society has no meteorologist on it. 
 [The article is on the constitution of the Council and the disposal of the funds.] 
 (Page 253.) General Strachey contends that a periodicity is not indicated unless the 
 general and periodic mean differences differ by at least 10 per cent. The periodicity 
 represented by the diurnal barometric oscillations at Madras is too simple a test for 
 the new criterion ; it should be tested on such a curve as the barometric oscillations at 
 Valentia for December 1876, which, however, gives a difference between the two 
 means of only l-10th per cent., and not rising to 1 per cent, for any of the 24 hours. 
 The averages for the months, however, show most decidedly the presence of a periodicity. 
 The phenomena of the diurnal oscillations of the barometer are among the most uni- 
 (Page 254) versally accepted and best established periodicities of science. Were 
 Strachey's new criterion accepted, it would sweep from our view scores of periodicities 
 
 106 
 
GENERAL 1878. Abercromby. NOTES. 
 
 now everywhere accepted and prevent enquiry in those departments, in which the non- 
 periodical are very largely in excess of the periodical variations, of which meteorology 
 may be regarded as presenting the most numerous and best illustrations. (Brit. Assoc. 
 (Page 375) Meeting.) Meldrum. The evidence in favour of a cycle has much increased. 
 Confirmatory results have been obtained from the rainfalls at 13 stations in the 
 (Page 452) French colonies from 1832 to 1872. Alluard (Acad. Sci. Paris, Sept. 18) 
 notices that frequently the barometer has risen at Clermont while falling at Puy de 
 Dome. This shows the necessity of studying the atmosphere in vertical layers. 
 
 Nature. (5.33.) 
 
 (Page 113.) ^Dr. Warring (Amer. Journ. Sci., Nov.) discusses the question, Is the 
 existence of growth-rings in the early exogenous plants proof of alternating seasons ? 
 Some exogens form rings at intervals much less than a year; others require several 
 years ; and some form no rings. The presence or absence of rings in exogens occurs in 
 all climates. Large and well-defined rings are formed where there is absolutely no 
 appreciable variation of temperature or moisture throughout the year. An exogen 
 naturally forming rings will continue to form them although the climate become 
 uniform throughout the year. Thus the existence of these markings in the ancient 
 flora gives no information as to the existence at that time of seasons. 
 
 Nature. (B. 36.) 
 
 (Page 399.) [This is a reprint of the Keport.] Meteorology at present stands in 
 (Page 400) need of hypothesis and discussion at least as much as of observations. 
 
 Nature. (B. 37.) 
 
 (Page 51.) The British Meteorological Board have notified that the weather tele- 
 grams will be discontinued on Sundays during the summer. [This no doubt refers to 
 the British Isles.] 
 
 Nature. (5.39.) 
 [This is given under B. 32. See above.] 
 
 Nature. (B. 40.) 
 [Nothing in it for general notes.] 
 
 1878. 
 
 Abercromby, Hon. Halph. On the General Character and Principal Sources of Varia- 
 tion in the Weather at any part of a Cyclone or Anticyclone. Q. Journ. Meteorol. Soc. 
 IV. pp. 1-13. Published in No. for Jan. 
 
 (Page 1.) Two methods have to be combined to obtain a complete idea of cyclone or 
 anticyclone weather. The first, or synoptic, method consists in drawing an isobaric 
 map, and marking on it the position of rain, clouds, &c., by which their position rela- 
 tively to each other and to the cyclone or anticyclone centres can be ascertained; in 
 fact, in making a plan of the weather. The second method consists in recording the 
 sequence of phenomena which occur to a single observer as a cyclone or anticyclone 
 passes over him : in fact of drawing a section of the weather across a cyclone along a 
 line parallel to its path. When this is done, it is found that the mere words rain, 
 clouds, &c., such as alone can well be marked on a synoptic map, convey but a very 
 (Page 2) imperfect idea of their character and surroundings, as the kind of rain and 
 kind of cloud vary much in different parts of a cyclone, and are readily distinguished. 
 Also that the passage of similar parts of different cyclones over an observer does not 
 bring exactly the same weather ; for in one cyclone the sky may be merely overcast, 
 while in another there is heavy rain ; and in one anticyclone there will be thick wet fog, 
 
 107 
 
GENERAL 1878. Abercromby. NOTES. 
 
 while in another dry winds and blue sky will prevail. These two methods, the plan 
 and; section as it were, are so widely different, that it is difficult practically to 
 combine them, and to realise how a difference in a cyclone, on a synoptic map, will 
 affect the sequence of weather as it passes over an observer. The object of the following 
 paper is to define generally the nature and sphere of the principal sources of variation in 
 the weather at each part of any cyclone or anticyclone, and to show how, in spite of 
 endless diversities, certain broad characteristics of each are always maintained. Though 
 the illustrations and details will refer almost exclusively to the weather of Great Britain, 
 the general principles laid down appear to be of universal application in every part of 
 the world. The first source of variation in any cyclone or anticyclone depends on the 
 type of general distribution of pressure to which either belongs. The commonest type 
 of cyclone in this country has the highest pressure some point south of the centre, on 
 which side steep gradients are found, while on the north side the gradients are very 
 slight. In this case the rain and cloud area extends far to the S. and S.E. of the 
 centre, but comparatively little to the N. and N.W., while the hardest weather is 
 generally found to the point of S., where the steepest gradients are. In another less 
 common type the highest pressure is some point to the N.E. of the centre, on which 
 side the steepest gradients are found, while to the S. and S.W. the gradients are slight. 
 In this case the rain and cloud area is very differently shaped from that just described, 
 extending farthest from the centre in the N.E. direction, and less in the S. or W., 
 while the hardest or most severe weather is found to the point of N.E., where the 
 steepest gradients are. If also we consider the position of strongest wind, or the 
 direction of the wind relative to the isobars, or the distribution of temperature relative 
 to the centre, we find that certain general features common to every cyclone undergo 
 considerable modifications, according to the type of pressure distribution to which it 
 belongs. The former of these two types particularly mentioned above may conveniently 
 be called the westerly, and the latter the north-easterly type of cyclone. In anticyclones 
 {Page 3) the influence of type is much less marked than in cyclones. The next source 
 of variation is the difference of what may aptly be called the intensity of any cyclone. 
 In cyclones of the same type the weather differs much in hardness or severity, or in 
 quietness. Thus in the S.E. front the sky may be simply soft and overcast in a cyclone 
 of moderate intensity ; but with increased intensity the overcast sky would develope into 
 soft drizzling rain, or even into a peculiar class of thunder-storms ; but, in spite of all 
 these variations, there is always the close muggy atmosphere and dirty sky character- 
 istic of this part of a cyclone. Again, in the rear, the general character is always a 
 cool, brisk feeling in the air, with a bright and broken sky, which varies according to 
 the intensity, from simply heavy masses of cloud to hard showers, to squalls, or to 
 hail-squalls, with thunder and lightning ; but no difference of intensity can ever alter 
 the fundamental difference in the general character of the S.E. front and rear portions of 
 a cyclone. It is well known that a deepening cyclone is increasing in intensity, while 
 one which is filling up is decreasing. In anticyclones the term intensity is much 
 less applicable to their characteristic weather than in cyclones. The term intensity 
 has been applied by the Eev. W. C. Ley to the difference of weather due to the 
 steepness of gradients, and though that is one, and perhaps the principal source, of 
 variation in intensity, the term is capable of considerable extension of meaning. 
 Short-lived cyclones, forming and disappearing rapidly, or a great development of 
 secondaries, in which gradients are usually slight, though the weather, so far as rain 
 and thunder are concerned, is very severe, are atmospheric conditions to which the 
 term intensity is equally applicable. Another source of variation depends on the size 
 and shape of the cyclone, and is intimately connected with type and intensity. It 
 might obviously be expected that the weather in any part of a large cyclone as, for 
 instance, one of those which sometimes entirely cover the Atlantic Ocean, would be 
 very different from the weather in a small cyclone, which perhaps only just covered 
 108 
 
GENERAL 1878. Abercromby. NOTES. 
 
 the British Isles ; and this is fully borne out by observation. In very large cyclones, 
 the steepest gradients and the bad weather which accompanies them are always found 
 at some distance from the centre. Round the centre itself, when the gradients are very 
 slack, the sky is usually broken with hardish clouds, and there is a cold pleasant feeling 
 of the air. In small cyclones the heaviest rain usually surrounds the centre, and 
 extends more or less to one side or the other, according to the direction of the nearest 
 area of high pressure and the steepest gradients. Another source of variation in the 
 size and extent of a cyclone rain and cloud area has been pointed out by Professor 
 Loomis. His examination of the United States' weather chart points to the conclusion 
 that the rain and cloud area is extended farther in front of cyclones that are moving 
 (Page 4) rapidly than in those moving slowly ; but Mr. K. H. Scott has pointed out 
 that it is difficult to trace this over an area so intersected by sea and land as the British 
 Islands. Another great source of variation is a class of phenomena which has as yet no 
 recognised name, but to which the term diurnal variation seems very applicable. To a 
 single observer the broadest feature of the diurnal variation of the weather in a 
 cyclone is that, starting from early morning, the amount of cloud and the general 
 severity of the weather and rain gradually increase till about 2 P.M., and then 
 gradually decrease till nightfall. Occasionally a type of cyclone occurs in which the 
 rain comes on during the night and takes off or ceases during the day. This is 
 undoubtedly due to some far-distant general causes affecting the origin of the cyclone ; 
 but the few cases I have been able to trace are not sufficient to form any opinion on the 
 subject ; a diurnal variation of the weather is, however, sufficiently well marked, 
 though it is to a certain extent abnormal. (Note. Diurnal variation is also much 
 influenced by the type of pressure distribution. With north-west winds and pressure 
 high to the S. W. of Great Britain cloudy days often culminate with a squall or 
 shower about 4 P.M., and then subside to quiet nights.) In anti-cyclones the diurnal 
 variation presents a marked contrast to that in cyclones. In them a misty or cloudy 
 morning is followed by a great diminution of cloud as the day goes on, while later on in 
 the evening mist and cloud are sometimes again formed. If, besides these broad 
 features of diurnal variation, we consider some of its more minute changes, we observe 
 that in cyclones a cloudy morning often has a short break about 10 A.M., that the 
 weather then becomes much worse, but has a marked tendency to break again about 
 4 P.M. In anti-cyclones a clear morning at 4 A.M. is frequently very cloudy at 
 10 A.M., after which the cloud again decreases till about 4 P.M., when more cloud or 
 mist is often again formed, and last till quite late in the evening. The increase of 
 cloud during the day in cyclones may be generally described as an increase of intensity ; 
 the decrease of clouds in anti-cyclones is not so easily explained, unless it is due to the 
 increased intensity of the descending current found in them ; but the minor changes at 
 4 A.M., 10 A.M., and 4 P.M. are obviously connected with the normal variation of the 
 barometer, and their attentive study may perhaps some day throw light upon that 
 puzzling phenomenon. But whatever modification the diurnal variation may make in 
 a cyclone or anti-cyclone the general character of either is never lost. No diurnal 
 variation can make the clouds and look of weather in front of a cyclone like the clouds 
 in the rear or like the clouds formed from rising mist in an anti-cyclone, the variation 
 being not merely a modifying influence superimposed on a more general effect, but in 
 some cases where the general character is not very strongly marked, the diurnal variation 
 becomes an important feature in a day's weather. Hence, if we take the case of a 
 stationary cyclone, and lay down on a synoptic chart the weather at any part of it, the 
 extent of the cloud and rain areas will extend much farther from the centre at 2 P.M. 
 than at 8 P.M., and in an anti-cyclone much cloud will be found near the centre at 
 (Page 5) 10 A.M., but very little at 2 P.M. (Note. Since writing the above I have 
 seen a number of United States' tri-daily synoptic maps. In some of them the difference 
 of cloud and wind in the same disturbance at different hours of the day is very well 
 
 109 
 
GENERAL 1878. Abercromby. NOTES. 
 
 marked.) Some diurnal variations of the weather seem to take place in every part of 
 the world, as, for instance, the daily thunderstorms which occur in some parts of the 
 tropics. The above details apply to the British Isles only [but still they have a general 
 bearing]. Another very important modification in weather is local variation. It is 
 well known that in any storm the position of showers, squalls, and thunderstorms is 
 very local, and at some places, either from the contour of the ground or other causes, 
 they are much more frequently developed than at others ; so also with the amount of 
 rain-foil, the position of ridges of hills relatively to the prevailing direction of the wind, 
 or the presence of lakes and forests as compared with bare ground, or the position of the 
 sea relatively to the prevailing wind, all seem to have an important influence in 
 regulating its amount. So important is the position of the sea that on our east coasts 
 the worstweather is with east winds, while on our south coasts it is worst with west 
 winds. In anti-cyclones and under any conditions where easy gradients do not give 
 any very general marked character to the weather, the local variation is much more 
 important than in cyclones where the general character is much more strongly marked. 
 Local variation is found in every part of the world ; and in the tropical and equatorial 
 regions, where barometric gradients are usually slight, it becomes a more important 
 element of weather. The last source of modification, I would notice, is the seasonal 
 variation. In this country during winter the cyclones are usually much larger than in 
 summer, and even in cyclones of about the same size and intensity the position of the 
 rain and cloud area is not quite the same. In winter time the clouds and general 
 appearance of the sky are usually softer than in summer, and the rain is more drizzly 
 and less showery, besides many other smaller differences, which are too well known to 
 require minute description. We shall now describe the general phenomena which 
 appear to a single observer as different parts of a cyclone past over him, by which we 
 acquire the knowledge of other important facts not to be deduced from synoptic maps. 
 In a British cyclone of ordinary size the rain area and cloud ring are divided into three 
 well-defined portions which differ much in general character, viz., the N.E. front, the 
 S.E. front, and the W. or rear side. The front is divided from the rear by a line drawn 
 through the centre of the cyclone, in front of which the barometer is falling while in 
 rear it is rising. The passage of this line over an observer, especially its southern half, 
 {Page 6) is marked by a very sudden and striking change in the appearance and feeling 
 of the weather ; the N.E. and S.E. fronts, though they have much in common, are 
 sufficiently different to be classed separately, and are divided by the line drawn through 
 the first, which represents the path of the cyclone ; but this line does not mark the 
 position of any great physical change, as the weather in either front merges gradually 
 into the other. In the N.E. front, when the steepest gradients are somewhere south 
 of the centre, the first symptoms of its approach are a gradual darkening of the sky till 
 it becomes overcast, with very little of the appearance of the formation of true cloud ; 
 or else light wisps or barred stripes of cirrus, moving sideways, appear in the blue sky, 
 and gradually soften into a uniform black sky ; near the centre, light ill-defined showers 
 fall from the uniformly black sky, the wind from some point between south-east and 
 north-east blows uneasily, and though the air is cold and chilly there is an oppressive 
 feel about it. These appearances continue till the barometer begins to rise, when the 
 character of the weather at once begins to alter. In a cyclone where the steepest 
 gradients are somewhere to the north and east of the centre, the general character of the 
 weather is the same as above described, but is much more intense, the wind rising at 
 times to a heavy gale and the ill-defined showers developing into violent squalls. In 
 the south-east front, when the steepest gradients are to some point south of the centre, 
 the first symptoms are likewise a gradual darkening of the sky into the well-known 
 pale or watery sky, with a muggy oppressive air, or else, as in the N.E. front, 
 wisps of cirrus first appear in a blue sky, which gradually become heavier and soften 
 till the sky is uniformly overcast. Nearer the centre, rain, usually in the form of. 
 110 
 
GENERAL 1878. Abercromby. NOTES. 
 
 drizzle, sets in, and the wind, from some point between south-east and south-west, 
 varying in force according to the gradients, drives the cloud and rain before it. But 
 this wind differs from that in the other portions of the cyclone in its way of blowing ; 
 and for the same velocity does not raise so high a sea, or seem to bear so much down 
 on the surface of the earth. In cases of very great intensity, the rain in this portion of 
 a cyclone may come in showers or even in squalls, but the general character is never 
 lost. These characters last till the barometer begins to rise. A line drawn from the 
 centre of a cyclone in that southerly direction, along which the barometer turns to rise, 
 marks out the position of one of the most striking parts of a cyclone. Viewed on a 
 synoptic chart a small secondary cyclone is often formed in some part of it, or else a 
 curious V-shaped depression, which frequently extends to the south of the centre. It 
 would be a point of very great importance to determine accurately how far the line 
 along which the barometer turns to rise is at right angles to the direction of the path of 
 the cyclone. As far as my own researches have gone it seems to be often at right 
 angles to that motion, but frequently it stretches nearly due south of the centre, 
 even when the cyclone is going well to the north of east. It is sometimes very 
 difficult to draw this line accurately, owing to the frequent changes in the depth of 
 any cyclone. As any portion of this line passes an observer, an immediate (Page 7) 
 change comes over the whole appearance of the weather, and the transition is often 
 accompanied either by a very heavy shower, squall, or hail, with a small irregular 
 fluctuation of the barometer. The general character of the west or rear side, which now 
 passes over the observer, is a cool, exhilarating feeling in the air, with a high, hard 
 sky, of which the tendency is always to break into firm detached masses of cloud. The 
 rain which occurs near the centre is usually in cold, sharp, brisk showers or hard 
 squalls, and the general hard look of the weather presents a marked contrast to the 
 dirty appearance of the weather which characterises the whole front of a cyclone. As 
 the centre recedes from the observer, showers or squalls are replaced by simply detached 
 masses of cloud, and these finally disappear, leaving a blue sky. The wind from some 
 point between west and north blows gustily and for the same velocity raises a higher 
 sea than a south-west wind, and seems to bear down more on the surface of the water. 
 The whole of the rear of a cyclone partakes of this general character, but the change of 
 weather along the line drawn north of the centre, along which the barometer turns to 
 rise, is not nearly so strongly marked as along the southern line. In one of the few 
 cases I have been able to observe of weather on the north side of a cyclone going west, 
 the north-west wind, in what was then the front, was dull and oppressive, but when 
 the wind veered to north-east the sky broke to cumulus and the air felt fresh. This 
 seems to suggest the important conclusion that the specific characters of the front and 
 rear are due to some property of cyclone motion and not to the direction of the wind. 
 In secondary cyclones, as viewed on a synoptic chart, the area of rain and cloud some- 
 times appears to cover the area of shallow gradients inside the secondary ; at other 
 times the rain especially seems confined to the partial ring of steeper gradients which 
 surround the secondary on the side of the nearest area of high pressure. The most 
 striking difference between a secondary and primary cyclone is the great amount 
 of rain and cloud with absence of wind developed in the former compared with 
 the less rain and cloud but the greater wind developed in the latter. To a single 
 observer the characteristic features of a secondary are a uniformly overcast sky, with 
 a peculiar stagnant motion of the clouds, and a very gloomy appearance and oppres- 
 sive state of the atmosphere. When the rain comes on it is usually very heavy 
 and falls straight, and in its general appearance and surroundings is very different 
 from the driving drizzling rain, so characteristic of the front of a primary cyclone. 
 Another very marked difference between the rain in a primary and secondary cyclone 
 is the motion of the barometer. In a primary the misty rain in front is accom- 
 panied by a rapidly falling barometer, while the hard rain in rear is accompanied by a 
 
 111 
 
GENERAL 1878. Abercromby. NOTES. 
 
 rising barometer ; but in a secondary the barometer is usually perfectly stationary 
 with a slight but quick motion at the beginning and end of the rain, either up or down, 
 according to the general direction of barometric change. This heavy rain and cloud, 
 with a steady barometer, was long very puzzling, and it is only since the publication of 
 the carefully-drawn charts of the Meteorological Office that its true nature has been 
 (Page 8) discoverable. In anti-cylones viewed on a synoptic chart, the position of blue 
 sky, cloud or fog seems very capricious, but to a single observer a certain general 
 character is readily perceptible ; but as it is much less marked than that in cyclones, it 
 is more easily masked by diurnal, local, and seasonal variations. In a general way the 
 weather is fine or at least quiet ; and though, in the calm centre especially, thick fogs 
 are often found, and cloud in other parts, the surroundings are so different, that they 
 can rarely be mistaken for cyclone weather. There is always a certain coolness in the 
 air, though if the sun shines it is very hot ; in fact the terms " radiation weather " and 
 " radiation temperature " would generally best describe anti-cyclonic weather. There is 
 no doubt that in this country rain sometimes falls in an anti-cyclone, and in France it 
 seems to be tolerably common. To a single observer the rain is usually in short 
 showers, with rather a high sky, and the general appearance is different from that in 
 either primary or secondary cyclones ; the showers are very often accompanied by & 
 slight irregular motion of the barometer, and as they are very short and of small extent 
 are probably due to some local disturbance. [Illustrations are given of the general 
 principles from the weather prevailing on specified days in various parts of the British 
 (Page 12) Isles and contiguous area. The addition referred to below was made in March.] 
 The following are additional illustrations of the term intensity as applied to weather. 
 (Page 13) Take a cyclone of a certain size and shape, and conceive another of the same 
 size and shape moving in the same direction at the same rate, but in which the isobars, 
 instead of representing a difference of '2m., represent a difference of only 'lin., then 
 we should have two cyclones differing in nothing except intensity, which would be 
 greater in the first than in the second. The corresponding difference of weather would be 
 shown in a less continuous area of rain near the centre, in a smaller extension of cloud 
 round the rain, and in a less total rainfall all over the country during the cyclone's 
 motion. Where squalls occurred in the first cyclone they would be replaced in the 
 second by brisk showers, and the weather generally would be more deficient in those 
 properties to which the words hardness or severity are usually applied, but the general 
 character and position of the front and rear would remain unaltered. Thus we see that 
 this kind of intensity depends on the steepness of the gradients in a single cyclone. 
 The other kind of intensity refers rather to that sequence or tract of weather to which 
 the term broken would be applied. From synoptic charts broken weather is found to 
 be either the product of small quick-moving cyclones, which only exist a very short 
 time, or of frequent secondaries ; in contradistinction to the weather produced by large 
 shallow-gradient cyclones, moving slowly and lasting some days, which would be 
 associated with more settled weather. The difference between these two kinds of 
 intensity is analogous to single heavy gusts of wind being as much a sign of great 
 atmospheric disturbance as numerous short puffs, although they proceed from different 
 causes. With regard to the line dividing the front and rear of a cyclone, it can al ways- 
 be approximately determined by drawing a series of sections of pressure across the 
 cyclone, parallel to its path. The line along which each of the sections changes from 
 rise to fall is the line required, and is obviously independent of the deepening or filling 
 up of the cyclone. Sometimes when a cyclone is filling up very rapidly the barometer 
 rises even when the central line is approaching the observer ; and conversely, when a 
 cyclone is deepening rapidly the barometer continues to fall after the central line has 
 passed, but the relation of wind and weather, relative to the cyclone centre, always 
 remains the same. In this fact we have the explanation of many seeming anomalies 
 between the apparent motion of the barometer and the actual state of the weather. 
 112 
 
GENERAL NOTES. 
 
 1878 (continued.) 
 
 Abercromby, Hon. Ralph. On tlie Application of Harlnonic Analysis to the Reduction 
 of Meteorological Observations, and on the General Method of Meteorology. Q. Journ, 
 Meteorol. Soc., iv. p. 141-156. Eead April 18. Published in No. for July, (ra.) 
 
 (Page 141.) The paper illustrates harmonic analysis by taking pressure as an 
 example, and tracing the physical and geometrical meaning of every step from the 
 barographic record till the tabulated records are exhibited in a harmonic series. But 
 comparing this curve with the traces from which it is derived we see that the result of 
 averaging is to eliminate all the information which might have been derived from them 
 relative to the position or passage of cyclones, squalls, etc., as they occur at irregular 
 hours, in fact all that makes up changes of weather, and that only the regular periodic 
 variation is left. Also that this diurnal mean curve is only the graphical representation 
 of the fact that there is a diurnal variation of the barometer, which is usually of a 
 certain magnitude, and occurs usually at certain hours ; but the curve gives no clue to 
 the cause of this variation beyond the obvious inference that as its period is one day, 
 the sun is probably the primary agent. During an arctic winter the resultant curve 
 of daily mean pressure will be an irregular line whose fluctuations have no physical 
 meaning, but represent the fact that the cyclonic variations have not balanced in so 
 short a time. If now we take the same series of figures representing the mean pressure 
 at every hour of the day and combine them by Bessel's formula, we get a harmonic 
 series of the form P = A -f- B (sin + C) + D sin (2 e + E) + etc., and if we plot the 
 curve represented by the above equation with the proper co-efficients we find that it is 
 almost identical with the former curve of mean pressure. In fact this formula gives, 
 in a single expression, the whole of the isolated tabulated values in a very convenient 
 manner ; and as the co-efficients can be calculated for any number of different places 
 it is easy to compare the respective characters of their diurnal variation ; so when mean 
 values are used the harmonic analysis is the most convenient and perfect method of 
 averaging. But it is most important to observe that a harmonic series can be made to 
 fit any arbitrary function whose law is unknown, but of which numerical values can be 
 determined ; that in this case the formula only gives the numerical, but not the physical, 
 law of the variation of the barometer by expressing in mathematical language the fact 
 that at a certain hour the pressure is a certain distance from the mean, without any 
 reference to the physical cause, so that it is merely the algebraic embodiment of a fact. 
 It is also evident that nothing more is learnt from the harmonic series than from 
 inspection of the curve formed by plotting the mean values directly. But there is 
 another totally different view of a harmonic series which has been very strongly 
 advocated by Sir "William Thomson, viz., that when the numerical values of a physical 
 phenomenon are reduced to a harmonic series, each algebraical term corresponds with one 
 of the physical constituents of the total variation represented by the whole series. 
 Each term of such series represents that class of motion called harmonic, which in a 
 simple form he has shown to play a prominent part in physical science; while the 
 more complex harmonic series he has used with great success in tidal investigations. 
 (Page 143.) The general idea seems to be that as a matter of observation harmonic 
 PART I. No. 5. i 113 
 
GENERAL 1878. Abercromby. NOTES. 
 
 action is almost a great physical principle ; and that just as in complex waves the 
 primary wave is naturally subdivided into 1, 2, 3, etc., parts, so in complex harmonic 
 motion the primary is naturally subdivided into motions corresponding to 0, 2 e, 3 0, 
 .... etc. ; so that in thus analysing an unknown function into harmonic constituents 
 we have a great engine of discovery, and not merely a formula that puts into a short 
 compact form a number of isolated facts, or that approximates to an arbitrary function. 
 The author does not feel competent to enter into the general principles involved either 
 in harmonic motions, or the curious analogies which can often be traced between 
 analytic symbols and physical phenomena ; but from a meteorological point of view, 
 and considering only the diurnal variation of the barometer, he would remark, that 
 neither method gives much clue to the physical causes, beyond the probability that it 
 has something to do with day and night. In whichever way we look at harmonic 
 analysis, its value must depend on our estimate of the use of averages, or of the 
 (Page 144) statistical method generally in meteorology. A large and most useful class 
 of statistical results have been derived by taking the statistical value of different 
 elements, and considering their amount locally or by comparison with surrounding 
 places. 
 
 The introduction of statistical methods was a great step in meteorology, but it is 
 now necessary to examine where these methods fail, and why they can never raise 
 meteorology to the rank of an exact science. The failure of statistical methods may 
 principally be referred to three causes : (1) that, when applied to the fluctuations of 
 any one element, they only take hold of periodic phenomena; (2) that of these 
 periodic phenomena averages only give the facts of their variation, and often furnish 
 no clue to their causes or laws : (3) that when applied to the amount of any one 
 element or to the discussion of synoptic maps, phenomena are often classed together 
 which are not really identical, but have only one common property. We will now 
 consider these sources of failure separately. I. The elimination in these results of the 
 effects of cyclones and anticyclones leads naturally to the consideration of what part 
 synoptic charts must play in the future study of meteorology. Though such charts 
 have been constructed for more than twelve years, meteorologists are by no means 
 agreed as to their use or meaning, and the author therefore proposes to make a few 
 remarks on their relation to the general problems of meteorology, and to point out the 
 method of attacking certain questions by their means. In the first place the study of 
 synoptic charts gives an answer to the question " what is weather ?" Weather is the 
 product of the passage of cyclones or anticyclones over any place. In temperate 
 regions the circulation of the atmosphere, the general scheme of which is at present 
 entirely unknown, always takes broadly the form of cyclones or anticyclones, whose 
 position and shape are in a state .of perpetual change, subject to numerous local, diurnal, 
 seasonal and other variations, the weather at any part of either aJUvays possesses the 
 same characters ; so that the weather over any area at any instant is the result of their 
 position, and the sequence of weather over any spot is the result of their motion. 
 Hence the problems for the meteorologist to solve, as regards weather, are : (1) To deter- 
 mine the character of cyclone and anticyclone weather, which would give the explana- 
 tion of the observed weather at any moment over any area a very complete solution of 
 which is certainly possible. (2) To explain the observed sequence and variation of 
 (Page 145) each element over any spot by defining the position and motion of the 
 cyclones or anticyclones that have passed over it. (3) To study the motions of cyclones 
 and anticyclones so as to discover the nature and laws of their changes, so that given 
 their position at any moment, their future course and resulting weather may be fore- 
 cast. Very little progress has been made in this direction. If this general view of 
 \venther be correct, meteorology is essentially an observational science, for the physical 
 conditions are not such as can be reproduced in the laboratory, nor are the results 
 capable of being expressed in mathematical language, or in simple maxims. The views 
 114 
 
GENERAL 1878. Abercromby. NOTES. 
 
 just enunciated point to a great change in the .way of looking at weather prognostics. 
 If every part of a cyclone or anticyclone has a characteristic appearance, then every 
 prognostic must be studied with reference to the synoptic conditions during which it is 
 observed, and all that any such prognostic can do is to enable an observer to identify 
 his position relatively to the cyclone or anticyclone. An observer with telegraphic 
 nforniation could often forecast the result by considering the surrounding pressure. 
 The following is an illustration of an important class of questions whose solution can 
 already be roughly sketched since the introduction of synoptic charts. From them 
 it is easily seen that the positions of persistent anticyclones, and of areas of depression 
 that are constantly traversed by cyclones, are roughly denned by the distribution of 
 land and sea ; and some day, when it is more worked out, it will be possible to say 
 what alteration in climate would be produced by a change in the position of land and 
 (Page 146) sea. For instance, in winter there is usually a persistent anticyclone over 
 Siberia, which stretches across Central Europe, while the North Atlantic is covered by 
 a persistent area of depression, in which cyclones are constantly formed in such a 
 position as to leave England traversed by warm s.w. winds. Observations on the 
 general circulation of the atmosphere show conclusively that the Siberian anticyclone is 
 due to the cold radiation from the land. Hence, if Siberia were submerged, the anti- 
 cyclone would disappear, the Atlantic cyclones would be able to move east, and, with a 
 larger proportion of west winds, the climate of England would grow colder. Again, 
 there is another class of questions that it has been attempted to solve solely by 
 statistics, but which the author ventures to think can only be satisfactorily handled by 
 reference to synoptic charts, viz., the connection of rainfall with sunspots. Take, for 
 example, the rainfall in the north of Scotland for 1872, a year of sunspot maximum. 
 In that year, according to Buchan, the rainfall over a small area in the valley of the 
 Dee was 75 per cent, above the average, while within 120 miles of this area, in a north- 
 west direction round Cape Wrath, there was a large region where the rainfall was below 
 the average. Taken as bald statistics, it would be difficult to say from this whether 
 rainfall was increased or diminished by a sunspot maximum. But if we consider the 
 s ynoptic history of the year we find that it was characterised both by a great diminution 
 in the number of large cyclones moving in a N.E. direction at some distance from Great 
 Britain, which expose our west and N.W. coasts to wet s.w. winds, and leave our east 
 coasts comparatively dry ; and by a great increase of small cyclones and secondaries, 
 both of which are always very wet, crossing our islands in an east or even S.E. direction, 
 thereby greatly increasing the rainfall on our east coasts, and in the case of cyclones 
 going S.E. into the German Ocean, often leaving our N.W. coasts comparatively dry. 
 It appears, therefore, in this case a year of sunspot maximum was associated with a very 
 well marked and readily described variation in the usual synoptic conditions of the 
 whole of western Europe ; and if this is confirmed m future years it will then be safe 
 to connect sunspots with the general circulation of the atmosphere, which can never 
 be done so long as we consider only one meteorological element. In connection with 
 this it may be observed that the year 1877, a sunspot minimum, was remarkable for 
 the small number of secondaries which crossed Great Britain. Similarly with regard 
 to the connection of Indian rainfall and sunspots, it seems doubtful whether pure 
 statistics can ever lead to a satisfactory result. Indian rainfall is so local and so 
 dependent on both monsoons that, unless the rainfall returns are carefully considered 
 (Page 147) from a meteorological point of view, and daily synoptic charts constructed, 
 to show if there is really a cyclical variation in the position or force of the monsoons, 
 we shall never be justified in asserting that there is a real physical connection between 
 sunspots and weather. There is a farther great advantage in this method of treating 
 the question of sunspots. The same synoptic investigation which is required to deal 
 with rainfall also supplies the explanation of the decrease of temperature, increased 
 proportion of west winds, and unusual number of thunderstorms over W. Europe in 
 
 i 2 113 
 
GENERAL 
 
 1878. Abercromby. NOTES. 
 
 1872 What has already been explained with reference to the harmonic curve of mean 
 daily pressure is capable of extension to every algebraic expression, viz, that it only 
 expresses in symbolical letters facts or ideas which might be expressed more cumber- 
 somely in words. Hence it is impossible that there should be an algebraic criterion of 
 fact as a logical touchstone of what is true; that is to say, that letter symbols discover 
 no more than word symbols. Therefore it is evident that if we have two sets of 
 phenomena to compare, which can both be shown graphically in a similar manner, no 
 mathematical combination can either alter or improve the judgment which the eye 
 will form as to their probable coincidence or otherwise. The consideration of the fore- 
 going questions as to change or recurrence of weather brings forward very prominently 
 a great want, which synoptic charts may be used to supply, viz, a description, in 
 synoptic terms, of cold, hot, wet, dry and stormy seasons, etc, or of long tracts of 
 weather, as referred to the position and motion of cyclones and anticyclones. One 
 source of increased cold has been already mentioned as depending on the position of 
 cvclone paths, but much cold in winter is due to the presence of anticyclones with their 
 radiation ; and there are probably other conditions of wet years than those of 1872 ; 
 and till these and similar groups are properly denned and classified, we shall never be 
 able properly to discuss questions of climate, or to say that the recurrence of any one 
 element is more than a mere coincidence. Before leaving this subject the author 
 wishes to make a few remarks on the attempted application of statistics to the 
 discussion of synoptic charts, which up to the present has not led to much result, 
 nor does he think it ever will. We have seen that if there are no constant periodical 
 phenomena a mean value is only the arithmetical result of certain unbalanced 
 observations. For instance the exact direction of the wind at any part of a 
 (Page 148) cyclone is variable, depending principally on the position of the steepest 
 gradient, so that the mean direction of the wind at that point merely signifies that it is 
 usually in that direction, Tout does not say what it would be in any given type of cyclone. 
 Again the mean velocity of a cyclone has no physical meaning, but only states an arith- 
 metical result, and is of no use in forecasting the path of any particular cyclone. To carry 
 out the investigations referred to in this part of the paper it is evidently absolutely 
 necessary to construct synoptic charts for certainly the whole northern hemisphere and 
 probably also for the southern hemisphere, for by no other means will it be possible to 
 discover that general scheme of the circulation of the atmosphere on which the whole 
 science of meteorology appears to rest. 
 
 II. Before dealing with the second reason of the failure of averages, viz, that 
 when applied to periodic variations they only give the facts and not the causes, the 
 author wishes to point out the position of diurnal periodic phenomena generally in 
 meteorology. If we look at any set of synoptic charts we see that the cyclones and 
 anticyclones seem to go on their course tolerably independent of day or night ; while 
 if we look at any set of meteorograms we see that every element has a diurnal 
 variation. In some, as in barometric pressure and direction of the wind, the diurnal 
 variation is small compared to the cyclonic ; while in others, as in temperature and 
 velocity of wind, the diurnal variation is large as compared with the cyclonic. An 
 inspection of any set of barograms shows that the diurnal variation of pressure is 
 simply a small fluctuation overlying either cyclone or anticyclone, and an inspection of 
 synoptic charts for any hour shows that the direction and force of the wind are always 
 determined by the position of cyclones and steepness of gradients; while in a former 
 paper the author has shown that the general character of the appearance of weather is 
 determined by the position of cyclones, though modified by a diurnal variation ; whence 
 the conclusion seems to be that the primary character of weather in its broadest sense 
 \Page 149) is determined by the position of cyclones and anticyclones, while every 
 element has a diurnal variation superimposed on the cyclone character. We have seen, 
 in discussing pressure variation, that the result of taking the mean value for every hour 
 116 
 
GENERAL 1878. Abercromby. NOTES. 
 
 of the day is to eliminate the effect of cyclones and leave only the fact and average 
 amount of the diurnal variation. Also that, whether we consider the variation as an 
 observed fact or as a harmonic component, we have no clue to its cause other than 
 considerations as to the hours of its occurrence may suggest. In the following remarks 
 the author does not profess to solve the question of diurnal barometric variations, but 
 merely to show the means by which only, he believes, the solution ever can be worked 
 out. The method proposed is simply, instead of taking mean values, to take every day 
 on its own merits, and to observe what kind of weather is associated with large diurnal 
 and what with small diurnal variations, and how different kinds of weather affect the 
 times of maxima and minima. For instance, once during the summer of 1877 in 
 London there were several fine days at the edge of an anticyclone, during which, 
 though one would usually have expected a considerable 4 A.M. minimum the baro- 
 graphic trace showed very slight indications, if any; the author observed that on those 
 mornings, there was an unusual amount of wind about 4 A.M., and if this is confirmed by 
 future observation, it would point to the conclusion that wind is not favourable to the 
 formation of the 4 A.M. minimum. Then as to the 10 A.M. maximum, if we look at the 
 barographic trace for May 27, 1877, we see that superimposed on the general rise of 
 the barometer between 4 A.M. and 11 A.M. there is a very slight depression. The 
 author's observations for the day are not very complete, but a similar depression is very 
 common, and in many cases he has observed it to be associated with the temporary 
 formation of heavy clouds about that time of the day. If this also is confirmed by 
 future observation it would point to the conclusion that either overcasting of the sky or 
 the formation of cloud interfere with those statical or dynamical conditions which 
 produce the 10 A.M. maximum. Then as to the 4 P.M. minimum, Bnchan has con- 
 clusively shown that at Valencia and over the North Atlantic generally it is smaller in 
 summer than in winter ; while at Kew and in Continental Europe generally the reverse 
 is the case ; and even within so short a distance as 50 miles the author has observed 
 that the kind of weather which would give a large 4 P.M. minimum in London only 
 gives a small one at Brighton, clearly pointing to the influence of land or water in the 
 production of this variation. The author has also pointed out, in a former paper, that 
 there are critical periods of the formation or disappearance of cloud or fog superimposed 
 on the general cyclone or anticyclone character of weather corresponding with the hour* 
 of diurnal barometric maxima and minima, and by combining the above and many 
 other observations of a similar nature it will certainly be possible some day to explain 
 (Page 150) these diurnal variations. The chief interest of diurnal barometer variation 
 lies in the difficulty of explaining it, for an inspection of the barograms illustrating this 
 paper, and the general argument, will show that it is simply a very secondary 
 phenomenon superimposed on cyclones, and that even if we were now in possession of - 
 its complete explanation we should be no nearer a knowledge of the laws of cyclone 
 motion on which all weather forecasting depends. A similar line of observation will be 
 necessary to discover the cause of the numerous other diurnal variations which are still 
 unexplained by meteorologists, and of which any combination of mean values can only 
 give the facts. Passing from unknown to known causes, the method proposed may be 
 compared to taking the mean temperature of every hour of the day, which we shall 
 find is represented by a single headed curve with a minimum about 4 and a maximum 
 about 2 A.M. and 2 P.M. Then if the recognition of the fact did not suggest the cause, by 
 taking many single thermograms and observing that a small diurnal range is produced 
 by cloud which at night reduces the cold and by day reduces the sun's rays also that 
 a temporary clearing of the sky might make the minimum at almost any hour of the 
 day and that these changes are always secondary to those produced by cyclonic 
 alterations in the direction of the wind we should conclude, even if it were not 
 otherwise obvious, that terrestrial radiation by night and solar radiation by day, were 
 the causes of the diurnal range of temperature. 
 
 117 
 
GENERAL 1878. Abercromby. NOTES. 
 
 III. We now come to the third source of failure in the use of averages to make 
 meteorology a science, viz., that when applied to values or occurrence of any element, 
 phenomena are treated as identical which have really only one common property. Take 
 for instance the occurrence of rain. The commonest occurrence of rain in this country 
 is in cyclone, accompanied, to a single observer, by a sharp fall of the barometer ; but 
 heavy rain also often falls in thunderstorms with a characteristic sharp rise of the 
 barometer, and also more rarely with a flat barometer associated with secondaries, as 
 shown on July 1, 1877 [for London], where rain began about the end of the small step- 
 like fall of the barometer a little before 6 A.M., and continued during the time of steady 
 barometer till the second step-like fall about 4 P.M. We see then that there are 
 certainly three distinct states of atmospheric motion which are associated with rain ; and 
 therefore, deductions drawn from the mean value of rainfall which masses all these 
 sources of rain together, must necessarily fail to be of any scientific value. Again, there 
 are several sources of cold weather in this country ; for it may either come with an 
 (Page 151) east wind and a high pressure over Norway ; or with N.W. wind with high 
 pressure to the N.W. of Scotland ; or else with the calms and radiation of an anticyclone, 
 stretching northwards from France. So if we take the general circulation of the 
 atmosphere, as shown by synoptic maps, to be the ultimate cause of weather, we have 
 at least three different conditions of such circulation, but with one property in common, 
 namely, cold. And if we attempt to generalise on the recurrence of cold merely from 
 records of a low thermometer, without reference to the synoptic conditions of its 
 occurrence, we are treating as identical phenomena which have really only the one 
 common property of cold, and the results can only lead to error and confusion. A 
 similar line of argument might be applied to every meteorological element. The 
 importance of thus discriminating between different kinds of any phenomenon is most 
 seen in discussing questions of cyclical variation and recurrence, as may be seen by 
 reference to what has been said relative to the connection between rainfall and sunspots. 
 "The above method of dealing with questions of rainfall also helps to show very clearly 
 where statistics are useful, and yet fail to make a science. If a distinctive name were 
 (Paye 152) wanted for this method it might be called the "specific" method, since it 
 endeavours to discover causes by dealing with specific instances rather than by massing 
 (Page 154) many results together. Note added June 17. The following are additional 
 illustrations of the idea of harmonic analysis. In the first place it should be noted that 
 in a harmonic series no combination of terms containing can give rise to terms in- 
 volving 2 0, 3 0, etc., so that if the diurnal variation of the barometer is due to the 
 interference of the temperature and pressure of dry and moist air, it could not be 
 expressed in a harmonic series. Also that the whole principle of the propagation of 
 harmonic components involves the independence of the causes represented by 0, 2 0, etc. 
 As this view of the subject is little known, the author may perhaps give the following 
 extract of a letter from Sir William Thomson to himself, dated May 28, 1878, relative 
 to a part of the preceding portion of this paper. " Take for example the barometric 
 variation. This depends entirely on the sun's heat, while the semi-diurnal harmonic 
 constituent largely exceeds the diurnal. Now, in the thermometric variation, the 
 diurnal harmonic constituent greatly exceeds the semi-diurnal. If we could set aside 
 the disturbing influence of cyclones we should probably find that the diurnal harmonic 
 constituent of the barometric variation would be the same as if there were no semi- 
 diurnal variation of either the barometer or thermometer, and the diurnal variation were 
 what it is. So of the semi-diurnal, we should probably see it to depend simply upon the 
 semi-diurnal harmonic constituent of the thermometer. This is undoubtedly a key 
 towards a physical explanation of the barometric variation. It is probable that there is 
 a fundamental mode of simple harmonic vibration of the atmosphere suitable for excita- 
 tion of the semi-diurnal harmonic variation of temperature, whose period agrees much 
 more nearly with twelve hours than with twenty-four hours, the period of a harmonic 
 118 
 
GENERAL 1878. Absrcromby. NOTES. 
 
 vibration suitable for excitation by the diurnal simple harmonic constituent of the 
 thermometer. The subject is at present quite open for mathematical theory ; but the 
 mathematical investigation, if not helped, will at all events be rendered more fruitful by 
 extensive data from observation analysed into the two terms of diurnal and semi-diurnal 
 periods, with proper treatment for the variations of the amplitudes and epochs of these 
 terms for the season of the year." The whole question, then, of the application of 
 harmonic analysis to meteorology turns round how much meteorologists are prepared to 
 accept certain dynamical principles connected with vibrations as an explanation of the 
 observed phenomena ; and whether, up to the present time, any trace of such vibrations 
 has been discovered. Allusion was made in the discussion on this paper to a method of 
 averaging adopted by the late J. C. Bloxam in reducing his sixteen years' observations 
 at Newport. A short account of it in his own words may be acceptable. After 
 pointing out the difficulty to be contended with in determining the mean annual daily 
 (Page 155) temperature by simply ascertaining the mean values belonging to a long 
 series of years for each day, is the liability in the reducing process to obliterate the 
 normal as well as the abnormal irregularities which belong to the secular variation in 
 cycles, he goes on to say that his values were reduced by the following method. There 
 being sixteen consecutive years to deal with, it is better to combine the whole of these 
 together in mean values ; but if there had been twenty or thirty, or any larger number 
 of years, to deal with, it might have been better to dispose of these in successive groups 
 of twelve years each, in the same method as that used for the successive days. The 
 method used is founded on the principle that the mean value of nine or eleven con- 
 secutive days gives more accurately the normal value for the central date of the nine or 
 eleven, as the case may be, than the identical value which may happen to fall on that date ; 
 and so, the value assigned to each day in the year is the mean value of a given number 
 of days on each side of its own date. The number of days adopted for the mean is ten, 
 this being by far the most convenient number for calculation ; and the whole series of 
 365 days are thus made up of decadal means ; the first mean value representing the 
 decade 1-10 ; the second 2-11 ; the third 3-12 ; and so on. The date for the first mean 
 value is 5 ; the second 65 ; and so on. This process having been carried on all 
 through the year, the new series of mean decadal daily values thus obtained is in 
 turn treated in the same way; and now the dates become whole numbers again. 
 This process is reiterated until the resulting values constitute regularly increasing 
 and decreasing quantities, and no longer, except that in consequence of using 
 the number 10, it becomes necessary always to have an even number of reductions 
 in order to obtain whole numbers for the dates. By proceeding in this way the 
 normal irregularities are preserved, whilst the small irregularities which can only 
 be accidental are sufficiently obliterated from the thermometric values by repeating the 
 process four times over. The same is the case with the dew point values, but with the 
 other particulars a twofold reduction is found to suffice ; but, in order to reduce 
 the thermometric values to one line of constant ascent and another of constant descent, 
 it was found necessary to repeat the process twenty-two times. It may elicit some 
 useful facts to carry the process to this extent, but for general purposes, and more 
 especially for the purpose of determining the daily normal value?, it becomes a process 
 of derangement rather than of correct arrangement. Now if we look at any ten days' 
 successive thermograms, it is easy to see what the meaning is of taking the mean 
 temperature for each day, and then the mean of the ten days, namely, that a mean 
 temperature of say 50 tells very little about the kind of weather, for it may either be 
 the result of a maximum and minimum of 65 and 35 in fine weather ; or of 55 and 
 45 in dull, overcast weather, and that massing all ten days together completely 
 destroys their individuality ; but it is very difficult to say what the meaning of a mean 
 decade of the second order would be ; in fact it is very doubtful whether it has any, 
 (Page 156) except an arithmetical significance. The result of the procees is, however, 
 
 119 
 
GENERAL 1- C 78. Abercromby. NOTES. 
 
 easily traced. As a matter, of fact in this country [England] the annual march of tem- 
 perature is not a uniformly ascending and descending line, but has interruptions of cold 
 periods, notably about February 10 and May 14, owing to the occurrence about these 
 dates of cold anticyclones ; and we see that Mr. Bloxam's test of the utility of his 
 process is the disappearance of these important facts. The author finds, for instance, 
 from Mr. Bloxam's own tables, that the mean temperature for Feb. 11, derived from 
 the mean average of the sixteen years, is 36 "94, while the value obtained by a fourfold 
 decadal reduction is 38'66, and that obtained by a 22-fold reduction is 39'43. 
 The result therefore of the process is to destroy what meaning the original curve 
 possessed, and the author believes that a similar result must necessarily attend any 
 other application of the method. If the curve of mean daily temperature is plotted, the 
 periodical irregularities are detected at a glance, and in every case of cyclical recurrence 
 the author believes the graphical to be superior to any arithmetical process. 
 
 Abercromby, Hon. Ralph. Q. Journ. Meteorol. Soc., iv. p. 198 et seq. Published in 
 
 No. for Oct. (ra.) 
 
 (Page 198.) The method hitherto universally adopted in treating of the diurnal 
 variations of the barometer has been to take the mean value of a large number of 
 observations at each hour of the day, and to draw deductions from the average amount 
 of variation thus determined. The diurnal variation is superimposed on larger fluctua- 
 tions, and in order to ascertain the causes of the variations it is desirable to be able to 
 measure the actual amount of variation on any particular day. This cannot be done 
 when the non-diurnal fluctuations are curved ; but when the general motion shown by 
 the barographic trace seems to be a straight line, the amount of diurnal variation which 
 (Page 199) overrides it can be approximately determined in the following way. Find 
 the mean pressure for the day ; mark this height on the noon ordinate, then draw a 
 straight line through this point in such a way that it intersects the two midnight 
 (Page 200) ordinates at the same distance below the trace. The value of the method 
 depends on the diurnal variation being the same at the first as at the second midnight, 
 which is not always the case. The difference is, however, always small. (Note, added 
 in July.) Kamtz suggested a similar method in Q. Journ. Meteorol. Soc., III. p. 130, in 
 the following words : If therefore, at one place, hourly observations have been made for 
 several years, and if for each month, the mean of the temperature observed at the same 
 hour be taken, it is not strictly correct, if we consider these means obtained to be such 
 as belong exactly to this day ; but we have in the numbers found, on the one hand, 
 quantities belonging to the daily period, and, on the other hand, the variations which 
 correspond to the march of temperature from the end of the previous to the beginning 
 of the following day. If we draw the yearly temperature curve from many years' 
 observations, the portion which corresponds to April is nearly a straight line, therefore 
 the temperature rises from one day to the following day about the same quantity. If 
 then, according to these observations, the 1st of May was 6 warmer than the 31st of 
 March, the mean of each day would be about 0'2 warmer than the previous day ; if we 
 distribute this over the hours each would take = 0'0083 ; if the hours are 
 reckoned from 1 to 24, indifferently as to which hour 1 corresponds, the 24th is, owing 
 to this circumstance, 0'19 warmer than that indicated by 1, and in a strict calculation 
 of the period regard must be paid to this change in each individual calculation. 
 (Page 201.) Kamtz's method is correct where averages are used, which give the level 
 of variation; and in general idea is the same as the method employed in this paper. 
 Still the author believes there is a certain amount of novelty in the paper, as it is the 
 first attempt that has been made to determine diurnal variation from observations of a 
 single day, and to dispense altogether with the use of averages ; and secondly, that 
 120 
 
GENERAL 1878. Archibald. NOTES. 
 
 there is some novelty in the method of finding the level of variation. [The method is 
 applied by the one author to the barometric condition of the air, and by the other to 
 temperature; but its application is more general than this. Moreover, the method 
 itself might have a more general scope, the principle being the superposition of curves 
 of periodicities of all lengths upon straight lines representing the general direction of 
 longer fluctuations. In Kamtz's case, the diurnal curve is superimposed on the annual 
 line for a month; in Abercromby's, the diurnal curve is superimposed on the larger 
 variation and mean lines for the day.] 
 
 Archibald, E. D. (B.I.) 
 
 April 23. (Paye 3.) The sun's heat is notoriously the source of all climates, and 
 changes in the amount of heat radiated from its surface are now regarded as causing for 
 the most part the changes in terrestrial weather. The solar spots, according to Schwabe, 
 Wolf, De La Rue, Stewart and Loewy, undergo a complete cycle of variation every ll'll 
 years, or according to De La Hue more accurately 11/07 years; the period of increase 
 from minimum to maximum comprising 3'52 years, and of decrease from maximum to 
 minimum 7*55 years. Lament gives 1O43 years as the length of the period. As there 
 is a close connection between the solar changes and the periods of terrestrial magnetism, 
 it has been conjectured that if such magnetic changes are due to corresponding changes 
 in terrestrial meteorological currents, some connection might be found to exist between 
 the secular variations in sun-spot frequency, and those in the different elements of terrestrial 
 meteorology. There is then some ground for believing that a connection exists between 
 the eleven-year period of solar maculation and some kind of emission dependent upon 
 the particular meteorological or thermal conditions of the sun's surface with its accom- 
 panying train of terrestrial meteorological and magnetical effects. It is here assumed 
 that the magnetical disturbances follow and are dependent on the meteorological, an 
 assumption supported by Balfour Stewart in his address to the British Association in 1875. 
 From the earliest times we find a popular tendency to expect the weather to recur in 
 cycles of about 10 or 12 years. Sayce, in ' Nature/ No. 310, says the Babylonians used 
 cycles of 12 years, during which they expected the same weather to recur, and as their 
 years only contained 300 days, this would correspond to 11*8 of our years. [The 
 remainder of the paper deals mainly with solar physics and the probable close connection 
 between these, terrestrial magnetism, and terrestrial meteorology.] 
 
 Broun, J. A. 
 
 (Page 126.) I propose considering some of the questions raised by Faye. He 
 decides that the moon does not influence weather; but then his conclusion is based 
 (Page 127) solely on the weather register kept at one place, Vigevano. Faye decides 
 that the moon does not reflect heat sufficient to make a change of ToVo tn f a degree 
 Fahr. If then the moon's action does dissipate clouds, it must act otherwise than by 
 heat. 
 
 Buchan, A. (B. 3.) 
 
 (Page 506.) To test the value of Meldrum's method of inquiry as to the relation 
 of rainfall cycles with sun spots, I have treated Woll's relative numbers of sunspots 
 as follows : 
 
 121 
 
GENERA^ 
 
 1878. Collins. 
 
 NOTES. 
 
 
 1 
 
 1-6 
 
 8-1 
 
 26-3 
 
 13-1 
 
 7-7 
 
 31-4 
 
 14-7 
 
 .. 
 
 
 
 2 
 
 4-9 
 
 1G-2 
 
 9-4 
 
 *19-8 
 
 5-1 
 
 14-7 
 
 11-6 
 
 1 14-9 
 
 
 
 3 
 
 12-6 
 
 35-0 
 
 13-3 
 
 38-3 
 
 22-9 
 
 8-8 
 
 21-8 
 
 2 25-4 
 
 
 
 4 
 
 16-2 
 
 51-2 
 
 59-0 
 
 59-6 
 
 56-2 
 
 3G-8 
 
 46-5 
 
 3 48-8 
 
 
 
 5 
 
 35-2 
 
 G2-1 
 
 119-3 
 
 97-4 
 
 90-3 
 
 78-6 
 
 80-5 
 
 4 77-0 
 
 
 
 6 
 
 46-9 
 
 G7-1 
 
 136'9 
 
 124-9 
 
 94-8 
 
 131-8 
 
 100-4 
 
 5 91-1 
 
 
 
 7 
 
 39-9 
 
 67-0 
 
 104-1 
 
 95-4 
 
 77-7 
 
 113-8 
 
 83-0 
 
 G 83-0 
 
 
 
 8 
 
 29-7 
 
 50-4 
 
 83-4 
 
 G9-8 
 
 Gl-0 
 
 99-7 
 
 65-7 
 
 7 65-G 
 
 
 
 9 
 
 23-5 
 
 26-3 
 
 61-8 
 
 63-2 
 
 45-4 
 
 67-7 
 
 48-0 
 
 8 49-0 
 
 
 
 10 
 
 1G-2 
 
 9-4 
 
 38-5 
 
 52-7 
 
 45-2 
 
 43-1 
 
 34-2 
 
 9 34-6 
 
 
 
 11 
 
 6-1 
 
 13-3 
 
 23-0 
 
 38-5 
 
 31-4 
 
 18-9 
 
 21-9 
 
 10 24-G 
 
 
 
 12 
 
 3-9 
 
 59-0 
 
 13-1 
 
 21-0 
 
 14-7 
 
 11 -a 
 
 20-5 
 
 11 22-5 
 
 
 
 13 
 
 2-6 
 
 119-3 
 
 19-3 
 
 7-7 
 
 Q Q 
 
 8 
 
 7-0 
 
 27-5 
 
 
 
 1 2 3 
 
 1 = 1811-1823. 
 2 = 1824-183G. 
 3 = 1832-1844. 
 
 456 
 
 4 = 1843-1855. 
 5 = 1855-1 8G7. 
 6 = 1SG5-1877. 
 
 7 8 
 
 7 Means. 
 8 Meaii Cycle. 
 
 * 19 -8, iu 5th col., 2nd line, is evidently a misprint for 19-3. 
 
 Collins, J. J. ' (B. 8.) 
 
 (Page 4.) The weather predictions cabled by the ' New York Herald' to its London 
 office, commenced February 14, 1877, and a large percentage were fulfilled. Except in 
 (Page 5) few cases recent works on meteorology are barren of original information. They 
 are chiefly made up of quotations from earlier works and the experience of isolated 
 observers. We find in America that many branches of trade are seriously affected by 
 weather changes, and that timely warnings are calculated to insure against losses that 
 would in their absence be sustained. The great-grain producing districts of the Western 
 States send their produce to the eastern sea-board. Sudden and severe storms affect the 
 conditions of the roads, and thus cause delays, at the same time that the produce is liable 
 to damage. Hence both producer and dealer welcome all information as to weather. 
 The same state of feeling must exist wherever trade flourishes and agriculture repre- 
 sents wealth. To the seaman a timely warning is of paramount importance. Timely 
 storm-signals are useful to an army on campaign, and the variations in the conditions 
 of the weather must be recognized in all the operations of an army, otherwise great 
 disasters may overtake it. Many difficulties incidental to warfare would be avoided by 
 having a special military service of meteorologists. 
 
 Meldrum, C. (B. 20.) ? 
 
 (Page 448.) From an examination of the rainfall (1872 to 1875) at 144 stations in 
 different parts of the world, the conclusion is drawn that there is a rainfall-cycle of the 
 same duration as the sunspot-cycle, and nearly coincident with it, both the sun-spots 
 and the rainfall attaining a minimum in the eleventh, first, and second years of the 
 cycle, and a maximum in the fifth. As Hunter found this to be so, I examined his 
 method. A remarkable rainfall-cycle had been previously obtained for Bombay nearly 
 coincident with the sun-spot cycle, as also for Anjarakandy, Calcutta, and Nagpur. 
 Hunter's method was to commence with 1876, and taking backward as far as the 
 122 
 
GENERAL 1878. Meldrum. NOTES 
 
 T^ 
 
 register extended for periods of eleven years each, and then fijIjdMgne .mean 
 each series of years in the common period. My method bein|\ cfifllrJn\, ftjij& requite 
 not comparable. The sun-spot period being one of about eleven, ^^exs. and the maxi- 
 mum epoch occurring on an average 3*7 years after the previous" Baaximuni, and the 
 next minimum 7*4 years after the maximum, I found the best way was to start either 
 from a maximum or a minimum year, and then to take the proper number of years 
 before and after the epochal year. Commencing with a maximum year for instance, I 
 (Page 449) took five years before it and seven years after it. Then, with a view of 
 reducing the effects of the so-called non-periodic variations, I took a mean of the rainfall 
 iii the first and third of the thirteen series, and a mean of that mean and of the rainfall 
 in the second series, and so on. This gave me eleven new means, which I called the 
 " mean cycle." Again, starting with a minimum year, I took eight years before and 
 four after it, and found eleven other new means in the same way. To each set ot 
 results, or to a combination of them, I then applied interpolation formulae, and found a 
 well-marked coincidence between the sun-spot and rainfall variations. This is illus- 
 trated by means of the Madras rainfall, which shows a double oscillation during a sun- 
 (Page 450) spot period. Dr. Hunter considers that the evidence as regards European 
 and American rainfall is against a periodicity, but it seems to me it indicates a periodi- 
 city which closely corresponds with that of sun-spots. Thus the mean for about 
 128 stations in Europe and America are these : 
 
 Years of cycles.. 123 45 6 789 10 11 
 
 Sunspots .. .. -31-7 19'5 3-5 +28'8 39-5 29'5 10-4 -4'9 14-8 21-2 19-4 
 Rainfall Variation 1-9 1-43 -09 +'71 -fc2 1-26 1-46 '78 -1 '65 '55 
 
 Having worked at the subject for six years, I have concluded that the whole evidence 
 is satisfactory as to the existence of a connection between sun-spots and terrestrial 
 magnetism. 
 
 Meldrum, C. (Nature, xviii.) 
 
 (Page 561.) [He gives tables of sun-spots from Wolfs relative numbers, having the 
 maximum years in the sixth line, and the minimum years in the eighth line. The first 
 is the same as that given by Buchan, with the following differences : 
 
 3rd column Gth line 67'2 
 
 8th 59-4 
 
 5th 2nd , 19-3 
 
 Mean cycle column 5th line 91-9 
 
 He adds a variation column as follows : ] 
 
 1 - 33-9 
 
 2 - 23-4 
 
 3 0-0 
 
 4 + 28-2 
 
 5 + 43-1 
 
 6 + 34-2 
 
 7 + 16-8 
 
 8 + 0-2 
 
 9 - 14-2 
 
 10 - 24-2 
 
 11 - 26-3 
 
 The second table gives the sun-spot numbers from 1816 to 1872, arranged so that the 
 minimum years are in the eighth line. 
 
 123 
 
GENERAL 
 
 1878. Nature. 
 
 NOTES. 
 
 No. 
 
 1816 
 vo 
 1828. 
 
 1826 
 
 to 
 
 1838. 
 
 1836 
 
 to 
 1848. 
 
 1849 
 to 
 1861. 
 
 1860 
 1872. 
 
 Means. 
 
 Mean 
 Cycle.. 
 
 Variation. 
 
 1 
 
 46-0 
 
 35-0 
 
 119-3 
 
 95-4 
 
 94-8 
 
 78-3 
 
 
 
 2 
 
 39-9 
 
 51-2 
 
 136-9 
 
 69-8 
 
 77-7 
 
 75-1 
 
 73-1 
 
 + 23-3 
 
 3 
 
 29-7 
 
 62 1 
 
 104-1 
 
 63-2 
 
 61-0 
 
 64-0 
 
 64-3 
 
 + 14-5 
 
 4 
 
 23-5 
 
 67-2 
 
 83-4 
 
 52-7 
 
 45-4 
 
 54-4 
 
 54-6 
 
 + 4-8 
 
 5 
 
 16-2 
 
 67 
 
 61-8 
 
 38-5 
 
 45-2 
 
 45-7 
 
 44-2 
 
 - 5-6 
 
 6 
 
 6-1 
 
 59-4 
 
 38-5 
 
 21-0 
 
 31-4 
 
 31-3 
 
 30-8 
 
 - 19-0 
 
 7 
 
 3-9 
 
 26-3 
 
 23-0 
 
 7-7 
 
 14-7 
 
 15-3 
 
 17-3 
 
 - 32-5 
 
 8 
 
 2-6 
 
 9-4 
 
 13-1 
 
 5-1 
 
 8-8 
 
 7-8 
 
 12-7 
 
 - 37-1 
 
 9 
 
 8-1 
 
 13-3 
 
 19-3 
 
 22-9 
 
 36-8 
 
 20-1 
 
 24-4 
 
 - 25-4 
 
 10 
 
 16-2 
 
 59-0 
 
 38-3 
 
 56-2 
 
 78-6 
 
 49-7 
 
 51-6 
 
 + 1-8 
 
 11 
 
 35-0 
 
 119-3 
 
 59-6 
 
 90-3 
 
 131-8 
 
 87-2 
 
 80-7 
 
 + 30-9 
 
 12 
 
 51-2 
 
 136-9 
 
 97-4 
 
 94-8 
 
 113-8 
 
 98-8 
 
 94-6 
 
 + 44-8 
 
 13 
 
 62-1 
 
 104-1 
 
 124-9 
 
 77-7 
 
 99-7 
 
 95-7 
 
 
 
 Meyer, A. G. (B. 31.) 
 
 (Page 621-625.) [Gives description of the weather-case, directions for reading it, and 
 
 its uses.] 
 
 Neumayer, G. (B. 32.) 
 
 (Page 313.) The people generally take little interest in meteorology. The greatest 
 progress has been made by the United States ; next come England, Holland, France, 
 and Denmark. The German Seewarte does its share in the international work. 
 
 Preston, Rev. T. A. Q. Journ. Meteorol Soc. No. for Jan. (ra.) 
 
 (Page 55.) From the first table [which gives the dates of flowering of many plants 
 at numerous localities in England] may be gathered the difference of climate between 
 two stations. [The immediate context shows that climate here means temperature, 
 and to a certain extent moisture.] 
 
 Nature. (Vol. xvii.) 
 
 (Page 211.) Faye, in the 'Annuaire du Bureau des Longitudes,' denies that any 
 connection exists between either sun-spots, magnetic disturbances, or the motions of the 
 moon, and variations of the weather. 
 
 Nature. (Vol. xviii.) 
 
 (Page 63.) Much diversity of opinion exists regarding the climatic effect of the sun 
 (Page 83) upon the earth at the present time. (Meteor. Soc., April 17.) Hon. K. 
 Abercromby. The meaning of the harmonic analysis is shown in reference to average 
 barometric pressure by tracing the geometrical and physical significance of every step 
 from the barogram till the tabulated results are combined in a harmonic series. 
 Whether we regard this series as an algebraic embodiment of a fact, or as a series of 
 harmonic components, it is simply a method of averages, and our estimates of its value 
 must depend upon the use of averages at all in meteorology. The failure of averages 
 to make meteorology an exact science is traced to three causes : 1. That the process of 
 (Page 84) averaging eliminates the variable effects of cyclones and anti-cyclones, on 
 which all weather from day to day depends, and on this are based some general remarks 
 on the use of synoptic charts, not only in explaining and forecasting weather, but also 
 in attacking such problems as the influence of changes of the distribution of land and 
 water on climates, and the cyclic recurrence of rain or cold. 2. That deductions from 
 averages only give the facts, not the causes, of any periodic phenomena. The position 
 of diurnal and other periodic variations in the general scheme of meteorology is then 
 124 
 
GENERAL 18781879. Archibald. NOTES. 
 
 pointed out, and it is shown that their causes can only be discovered by careful study 
 of meteorograms from day to day. 3. That in taking averages, phenomena are often 
 classed as identical which have not [=but] one common property. For instance, rain in 
 this country is associated with at least three different conditions of atmospheric dis- 
 turbance, and it is necessary to discriminate between these kinds before meteorology 
 (Page 430) can be an exact science. During the eclipse of 1878 the corona was much 
 (Page 431) less brilliant than usual. Associated with this are a small number of spots 
 and a famine period. In 1871 there were many spots and a heavy rainfall, which were 
 (Page 600) associated with a large corona. In all earthquake countries it is believed 
 the weather is affected by such phenomena. Observations should be recorded showing 
 (Page 619) the influence of earthquakes upon the weather. Mr. F. Chambers believes 
 it probable that all abnormal meteorological variations are due to causes similar to, if 
 not identical with, those which produce the normal variations. Indeed, says Chambers, 
 (Page 620) the inference that most of the unusual variations of weather in tropical 
 climates are induced by corresponding variations in the absolute heating power of the 
 sun in the same manner that the seasonal variations are induced by those changes of 
 heating power which depend on the relative motions of that body seems almost irre- 
 sistible. If, then, the absolute variations of the sun's heat are fitful in their occurrence, 
 and do not obey periodical laws, it will, perhaps, never be possible to predict by more 
 than a few days in advance the unseasonal variations of weather induced by them ; 
 while if such laws can only be discovered, the possibility of our being able to predict 
 their consequences is equally certain. 
 
 Nature. (B. 43.) 
 
 (Page 178.) Ley. The form and movements of the clouds are intimately connected 
 with the relation of wind and weather to the distribution of barometric pressures. 
 Changes in the clouds indicate to us alterations of wind and weather. From the use of 
 weather maps a new science of the winds has originated, on which all attempts at 
 weather forecast must be based. 
 
 1879. 
 
 Archibald, E. D. (B. 1.) 
 
 (Page 626.) Professor Piazzi Smyth evidently infers (' Nature,' xx. page 431) that 
 changes in the condition of the sun must needs affect every part of the earth in the same 
 way, whereas we have many meteorological analogies which favour the notion that 
 totally opposite effects may arise in different parts of the earth from the action of the 
 same primary cause. For example, it is generally assumed that the same tropical heat 
 which gives the primary impulse to the desiccating N.-E. trade wind of subtropical 
 latitudes furnishes the energy which exhibits itself in the almost constant precipitation 
 under the equator. Any variation in the degree of this heat should consequently affect 
 localities situated in the region of the trades and the equatorial calm belt in a diametrically 
 opposite manner. Moreover, the notion that the British and Indian rainfalls vary 
 together now is altogether inconsistent with the well-known want of similarity between 
 them, both as regards seasonal distribution and annual quantity, in the past. Induction 
 should be made from results which are derived from trustworthy data, and anticipated 
 by a knowledge of admitted physical principles. As an example of the latter I would 
 (Page 627) mention the secular period traced by S. A. Hill in the barometrical pressure 
 of Calcutta. So far as we have gone in India we find years of few sun spots characterized 
 by higher temperatures, greater wind velocity, and greater range of barometric pressure 
 than those of many spots. 
 
 Baker, H. B. In Annual Eeport of the Michigan State Board of Health for the year 1878. 
 8vo. Lan&ing. 1879. (ra.) 
 
 (Page 213.) Meteorological conditions are known to have great influence on the health 
 
 125 
 
GENERAL 1879. Baker. NOTES. 
 
 of the people; and certain groups of such conditions are known to be coincident with, 
 and are believed to cause, directly or indirectly, a very great many deaths during each 
 year ; such, for instance, as a large proportion of the deaths from diseases of the bowels 
 in summer ; and of deaths from croup, bronchitis, inflammation of the lungs, etc., in 
 winter. Any study of the causes of disease with a view to their prevention must 
 therefore include comparisons of their rates with statements of the meteorological con- 
 ditions existing at the same time, or immediately preceding. Such comparisons can be 
 made by years, by seasons, and by months, and will be facilitated by noting those 
 years, seasons, or months, which are exceptional in any of the meteorological con- 
 ditions observed, and ascertaining whether there were any exceptional facts concerning 
 any disease which appear to correspond therewith ; and if so, whether comparisons for 
 scries of years, seasons, or months, show such correspondence to be constant. Conversely 
 exceptional times of disease supply peculiarly favourable opportunities for studying 
 meteorological conditions which may influence the disease. In considering the question 
 to what extent they are only incidental, all other conditions which can have influence 
 in causing or modifying the disease must be kept in mind, or be separately considered. 
 In order to eliminate the evidences of unknown or unconsidered influences, and of those 
 which are only indirect or incidental, comparison must be made by different periods of 
 time ; as for instance, if a given disease is found to prevail most in years when certain 
 {Page 214) meteorological conditions prevail, it is needful to learn whether it also prevails 
 most in months when the same meteorological conditions prevail ; because the disease 
 might be caused by something coincident with such conditions, and which only occur 
 once in a year, and can therefore be coincident only by years. Conversely it is useful 
 to compare by years where a disease has been found coincident with certain meteoro- 
 logical conditions by months. Because of the interdependence of the several meteoro- 
 logical conditions it is usually the fact that when certain meteorological conditions are 
 found to bear a more or less constant relation to a given disease, certain other meteoro- 
 logical conditions are found also to have nearly or quite as constant a relation, so that 
 the cause of the disease is not certainly reached by means of this knowledge alone. 
 Technical knowledge is requisite to appreciate the bearing of the evidence. There is 
 much, however, that may be done in advancing this study by the meteorologist or 
 physicist alone ; because it not unfrequently happens that the usual harmony in the 
 meteorological conditions is not maintained, some one or more being exceptionally pro- 
 minent or absent as the case may be. 
 
 Burgess, A. H. (B. 7.) 
 
 (Page 313.) Suggests the establishment of a meteorological buoy in the track of 
 storms at a distance from exposed coasts, and connected with them by telegraph wires, 
 which will record the readings of the barometer and wind gauge. One might be 
 (Page 314) placed 80 miles or so from Valenita. If found successful other readings 
 could be taken, and other floating observatories established at certain distances apart 
 This would give warnings of storms which would be almost sure to visit the coast. 
 
 Griffith, Rev. C. H. Q. Journ. Meleorol Soc., V. No. for Jan. 
 
 (Page 62.) I am convinced that all insects might with advantage be observed as 
 weather indicators. The geometrical spiders are gifted with a remarkable perception of 
 probable future conditions of the atmosphere, indeed M. Q. D' Tijonval has suggested 
 that they are so accurate as weather guides as to be as good as barometers. There is 
 no doubt but that the spiders, as well as the insects, give so good a general idea of the 
 increase of temperature of spring that their reappearance is at all times worthy of 
 observation. There is no doubt that the whole class is very susceptible of the return 
 of genial weather ; as Spallanzani has observed, their restlessness after so long an absence 
 126 
 
GENERAL 1879. Ley. NOTES. 
 
 from food, and their irritability due to their desire to lay eggs or propagate their kind, 
 induces them to emerge from their hiding-places, at even a considerably lower tempe- 
 rature than that at which they hybernated in the previous autumn, thus becoming good 
 (Page 63) indicators of alterations of the changes of the seasons. At the same time I 
 do not attach much importance to the appearances of Trichocera hiemalis, as they may 
 be observed all the year through, even in the depth of winter if the air be at all dry or 
 quiet. 
 
 Ley, Rev. W. C. Clouds and Weather Signs, pp. 102-13G. (B. 34). (r.) 
 
 (Page 103) Aratus and Virgil would find themselves almost on a level with some 
 meteorologists of the present day upon the subject of weather signs derived from cloud 
 (Page 110) observations. The most valuable of weather signs are obtained not so much 
 (Page 111) from the shape of the clouds as from the direction from which the clouds of 
 different levels are observed to travel, and it is these weather signs which, in the 
 present state of our knowledge, can be most readily reduced to definite rules. From 
 the use of synchronous weather maps there has sprung up in recent years a new science 
 of the winds. With the principles of this science all the more reliable rules of weather 
 forecasting are most intimately connected. In judging of coming weather we invariably 
 refer to rules already deduced from the long study of weather maps. The man who 
 ignores these rules had better, in my opinion, leave all attempts at weather forecasting 
 (Page 114) alone. The old observers were quite right in telling us that we know 
 a great deal about coming weather from the appearances and forms of the clouds. 
 They comparatively neglected the prognostics to be obtained from the movements of 
 those bodies. We must give our attention both to form and movement, but more 
 (Page 122) especially to the latter. The motions of cirrus clouds round depressions 
 (Page 123) are of great importance in making forecasts of the weather, and in judging 
 of the probabilities of storms. 
 
 Mann, R. J. TJie Physical Properties of the Atmosphere. In Modern Meteorology, p. 1-28. 
 
 (B.3L) (r<) 
 
 (Page 1.) The word Meteorology is from the Greek term pcrt'capos, which signified 
 elevated or soaring. The name has not been adopted because meteorologists at one time 
 busied themselves with observing falling stars. The word was used by Aristotle in very 
 much the same sense as that in which it is now applied. In a treatise which he composed 
 under the title MerecopoXoyixa, he dealt with all that was at that time known concerning 
 water, air, and earthquakes. At the present time the object of meteorology is properly 
 the scientific study of atmospheric phenomena and the investigation of weather and 
 (Page 2) climate. The base of the science is therefore an exact acquaintance with the 
 physical properties of the atmosphere. 
 
 Marie*-Davy, H. (B. 35.) 
 [Describes the instruments at Montsouris.] 
 
 Marriott, Wm. (B. 3G.) (ra.) 
 [Nothing for general notes.] 
 
 Meldrum, C. (Nature, xxi.) 
 
 (Page 167.) At any given place there are exceptions to every meteorological cycle, 
 [Examples are given from temperature and barometric pressure.] 
 
 Moseley, H. N. (B. 57.) 
 
 [Nothing for general notes.] 
 
 P. (B. 60.) 
 [This is a misprint in ' The Scientific Roll.' It should be E.] 
 
 127 
 
GENERAL 1S79. Scott. NOTES. 
 
 R. (B. 60.) 
 
 (Page 363.) Suggests that as carrier pigeons can fly 270 miles in less than six hours, 
 they could be utilized for weather warnings by being despatched from outward-bound 
 ships with weather news out at sen. 
 
 Scott, R. H. The Nature, Methods, and General Objects of Meteorology, pp. 166-186. 
 
 (B.34.) (m) 
 
 (Page 16G.) Meteorology is the science of the atmosphere, of TO. /^re'copa the things 
 (Page 167) above the earth as Aristotle has it. It has even yet hardly made good its 
 title to a place among the exact sciences. The reason of this is easily explained. 
 Firstly, we live at the bottom of the atmospheric ocean, and of this the upper layers 
 are all but inaccessible to us, so what half-knowledge we can gain of their condition 
 is mostly derived from conjecture. We know really nothing of any phenomenon 
 occurring above the level of the stratum which we inhabit. Secondly, the observations 
 we make of the physical state of the air are affected to such a desree by local accidents, 
 such as the elevation, contour, and slope of the ground, nay, even by the very character 
 of the soil, that we meet with material variations of meteorological circumstances, even 
 within the limits of a single county. In meteorology phenomena are not the same 
 (Page 168) at two different points of observation. The temperature of the air and 
 the motion of the wind in the street outside [Great George Street] differ appreciably 
 from what is being experienced in the middle of Hyde Park, and a fortiori, from what 
 is felt outside the city, as at Kew or Greenwich. Hence we see the necessity for 
 covering the country with a network of independent meteorological stations for climato- 
 logical purposes, as the observer at each place cannot do more than record the phenomena 
 exhibited by the actual particles of the atmosphere which come in contact with his 
 instruments. If we seek to investigate the climate of a thinly-peopled region, like one 
 of our Australian colonies, we are thankful if we secure stations even 250 miles apart ; 
 but when we come to the consideration of our own climate at home we find that a 
 distance of 50 miles is still too great to ensure that no special peculiarities shall escape 
 (Page 169) our notice. In all this multiplication of stations we must not hold that 
 quantity will in any way replace quality. The results from one bad station will often 
 throw doubt en the figures of most conscientious observers. In more than one instance 
 of recent times it has come out that results obtained by laborious calculations have been 
 proved to be almost worthless, owing to the disregard in former times of obvious precautions 
 to ensure accuracy in the observations and their registration. Good observers are required 
 as well as good instruments, and good substitutes during the absences of the usual observers. 
 (Page 178.) There are few recognized observatories of which the registers of uniformly 
 high character go back for fifty years. The accurate records at each spot simply cor- 
 respond with the period of office at the place of individual observers. When each died 
 or. left the place the chain was broken. If we find difficulty in securing accurate 
 information for the climate of our highly civilised Europe, what are we to say about 
 our knowledge of the climates of the other continents ? This is scanty enough if we 
 look for data of high scientific value. On a recent occasion our Secretary, Mr. Symons, 
 published a valuable summary of the existing statistics of the climate of our colonies, 
 but full as were the details in that paper, it showed us how much we have yet to learn 
 before we can pretend to have gained a really comprehensive insight into the meteoro- 
 logical condition of the globe. The earliest systematic effort to obtain this information 
 was the scheme organised in this country by the Committee of Physics and Meteorology 
 of the Eoyal Society in 1840, and managed by Sir E. Sabine. A similar system was 
 (Page 171) conducted in Eussia under Kupffer. The results obtained at these colonial 
 observatories have, in the few instances in which they have been discussed, thrown a 
 flood of light on the condition of the atmosphere in widely different parts of the globe. 
 It is a great pity that this system has not been continued. Of the four of our colonial 
 128 
 
GENERAL 1879. Scott. NOTES. 
 
 observatories only two, Cape Town and Toronto, survive. The Russians, however, have 
 at all events maintained their stations. We are therefore compelled to admit that any 
 accurate knowledge we possess of the meteorology of the globe is in a great measure 
 derived from observations taken over a comparatively limited portion of the northern 
 hemisphere. Still there is abundance of material in existence for any one who wishes 
 (Page 172) to discuss it. Information from sea stations is wanted, but ships are seldom 
 at rest. Hence we see the comparative fruitlessness of the attempts to deduce means 
 of any value from the log of a single ship, no two observations having been made under 
 exactly the same circumstances, except when she was at anchor. What we have to do 
 is to take a definite area, say a one-degree square, in any part of the sea, and deal with 
 all the ships which pass through it. Suppose that these ships have similar instruments 
 and equally qualified observers, we are met at once by this difficulty. Suppose that 
 this square really had seven days of easterly wind in each of two months, and that 
 only one ship passed through in each of two months. A, bound to the eastward, 
 would probably record twenty observations of the east win'd as she would be beating 
 against it, and detained in the square ; while B, bound westwards, would fly through 
 the square, and probably only put down the east wind twice. What is the true record 
 of the wind for either month ? C, again, may have been becalmed in the square for 
 three days in an anticyclone, with his barometer ranging above 30*5 inches, while D, 
 (Page 173) on another occasion may have been hove to in a winter gale with his 
 barometer below 29 inches. In every one of these cases the local conditions will affect 
 the observations taken, and any means obtained in their discussion. The problem is a 
 tough one to solve, but we think that we have partially solved it for some small areas. 
 The complication is even worse than I have described when we wish to deal with thf 
 climate of the sea at large, for we find that information cannot be got from unfrequented 
 parts of the sea, unless ships are sent on purpose to get it. We see that in dealing 
 with ocean meteorology it is nearly hopeless to look for a complete representation of 
 the geographical distribution of meteorological conditions, and that no matter how care- 
 fully we collect and discuss our information, a large part of the isobars and isotherms 
 which have been drawn over the sea are mere approximations. Still when we look at 
 the great amount of meteorological knowledge which has been deduced from the logs of 
 our marine observers, we take courage and feel that, although it may be long before 
 absolute truth is obtained, we are yet bringing out valuable approximations for the use 
 (Page 174) of the navigator, as well as for the physical geographer. There is another 
 direction in which the subject of observing stations may be prosecuted, and of which 
 the importance cannot be overrated, that is, the study of the weather. We may almost 
 say that this is a new science, rendered possible by the facilities of communication 
 afforded by the electric telegraph. This branch of inquiry demands heavy expenditure 
 and a great amount of discipline and organisation, so that it cannot be prosecuted by 
 individual observers, or at isolated stations. There is one broad feature of distinction 
 between climatology and weather study as regards the collection of observations. In 
 the former case we seek above all things for continuous records from the same spot. 
 In the latter geographical position and freedom from conditions which will affect the 
 character of the observations, especially of wind, are of paramount importance. If an 
 opportunity occurs of obtaining a report from a new station which will give us earlier 
 (Page 175) and surer intimation of coming changes of weather, we reject those from 
 the most ably served observatory in the district. As regards synoptic work on a laro-e 
 scale, the importance of which to the meteorology of the future is being daily more and 
 more acknowledged, it is evident that the records of the oldest established station are 
 of no higher value than those of a ship on her rapid passage over the ocean. Here we 
 boldly ask for more records, not from civilised countries, but from the unsurveyed 
 world of Africa, Central Asia, Australia, South America, and our own North-West 
 American territories. Meteorological processes go on whether men be present to register 
 PART I. No. 5. K 129 
 
GENERAL 1879. Strachan. NOTES. 
 
 them or not, and could we get it, a knowledge of what is going on at present over at 
 least the whole northern hemisphere would be necessary for the complete elucidation of 
 the agencies which produce our weather. We do not want more synoptic stations 
 in these islands, for we have far too many already. At the present moment one good 
 (Page 176) station on Spitzbergen or Jan Mayen would be worth ten in W. Europe. It 
 is to be regretted that Wilczek and Weyprecht's far-seeing scheme of girdling the 
 North Polewith a belt of observing stations, does not exhibit many symptoms of 
 vitality. The methods of meteorological science are not by any means satisfactorily 
 settled as yet. Some meteorologists decry all attempts of International Congresses to 
 introduce uniformity of procedure and publication, while others insist upon uniformity 
 to the regulations enforced in their own special organisation. The fact is great differ- 
 (Page 177) ence of opinion and practice exist. The Russians call for siphon tubes ; we 
 prefer Fortin's or Kew pattern barometers. For thermometric exposure the battle of 
 the screens is raging with its full fury. Minute accuracy in results is impossible with 
 such wide difference of procedure. As regards methods, we are still in want of sug- 
 (Page 178) gestions from experienced physicists. As regards hours of observation we 
 are no nearer uniformity than our fathers were a generation ago. The ultimate uses 
 (Page 184) of meteorology are twofold. Firstly, there is the strictly scientific 
 (Pagel&S) use ; and, secondly, its immediately practical use in the foretelling of weather. 
 In marine meteorology we search for true mean values to indicate where a seaman may 
 find a fair wind and a favourable current. There is not a profession, not a handicraft, not 
 a process in animal or vegetable life, which is not influenced by meteorological changes, 
 and there is not a human being to whom a knowledge of coming weather would not be 
 of value. Had we a quarter of a century ago known the rigour of the Crimean climate, 
 who would have dared to have sent out an army unprepared to meet the hardships of a 
 Black Sea winter? Ask the physician at what price he would value the power of 
 giving timely warning of a :< cold snap " to his patients. Ask the builders of London 
 what they have lost in the last ten years by sudden frosts or unexpected downpours of 
 rain. Above all things go to the farmer, and ask what he would freely pay to know at 
 seed time what weather he might really expect in harvest. The roll is endless a 
 knowledge of meteorology is of the very first importance in every stage of human life, 
 civilised or uncivilised. 
 
 Strachan, Richard. (B. 31.) 
 
 (Page 73.) Readings of the Torricellian column [practically a barometer] were taken 
 daily by Pascal at Paris, by Perrier at Clermont, by Chanut and Descartes at Stockholm 
 during the years 1649-50 at the same time, in order to see if anything could be dis- 
 covered by confronting them with one another. Pascal was thus the pioneer of 
 (Page 78) synchronous observations. If it be admitted that every wind has its 
 weather ; then, to observe the direction and force of the wind is the first step to observe 
 (Page 79) the weather. The practice has been to relate changes of wind and weather 
 to the state of the barometer ; and innumerable rules have been propounded to enable 
 every-one to become weather wise by the aid of the barometer. Torricelli began them, 
 Pascal and Perrier added to them, Halley, Patrick, and Saul extended them. Some- 
 thing to do in this line was left to Dalton, Jenyns and Glaisher. I have not found a 
 single rule among them. By rule I mean a mode of arriving at certain results from 
 determinate conditions. They are all mere connotations of the weather with the 
 heights and movements of the barometric column. When the behaviour of barometers 
 in different regions and countries came to be known, these connotations were thrown into 
 (Page 80) a little confusion. The latest connotators introduced some reasoning, 
 especially Glaisher. He says : " It is the changes which constitute the barometer 
 an indicator of approaching weather." Galton's charts, in his * Meteorographica " 
 (Page 85) (1863), were the earliest of weather-maps, and to him also we are indebted 
 130 
 
GENERAL 1879. Symons. NOTES. 
 
 for the main features of our daily weather-charts, lithographed as we get them by post, 
 (Page 95) In 1859 Maury wrote that one of the great practical questions of the age 
 was a daily system of weather reports between Europe and America. We have not 
 accomplished this yet. The warnings sent by the ' New York Herald ' are possibly 
 based on information derived from ships arriving at New York, which enables it to 
 telegraph the approach of storms before they have reached the coast of W. Europe. 
 (Page 99) The law of pressure in relation to wind affords no means of foretelling 
 weather by itself. Fixing attention on areas of pressure, either high or low, merely : 
 the weather changes which attend them are only to be forecast by such data as their 
 extent and gradient always, and either (J ) rate and direction of progress ; (2) rate of 
 veering of the wind ; or (3) rate of barometric change. The latter two may be either 
 for one place or for several distant places. The problem has thus a variety of phases ; 
 but generally it may be stated thus. Given the barometric pressure, wind and 
 weather at a place or region, at a definite instant, to estimate the change during a 
 (Page 100) succeeding interval, as a day or two days. Either the translation of the 
 air, the veering of the wind, or the change of pressure, must be assumed or known for 
 the interval, and all the rest results as a matter of course. Barometrical observations 
 appear to me to afford the most precise data for investigating the sunspot cycle as 
 connected with the weather. There are no a priori reasons known to me for sup- 
 porting that theory, and I consider the whole thing as a wild-goose chase. If it should 
 be proved that the sunspot maximum coincides with a barometric minimum, and the 
 sunspot minimum with a barometric maximum in India, there must be a region or 
 (Page 101) regions where the law is the reverse ; otherwise we should have to account 
 for an abstraction from our atmosphere in some years, and an accession to it in others. 
 The opinion of myself and most other meteorologists is that statistical results tend to 
 show that there is a correlation between the meteorological elements considered either 
 synoptically or statistically, that is to say, both in relation to geographical distribu- 
 tion as well as regard to a single station, and therefore it follows that the key to 
 prediction is a foreknowledge of some one of them. 
 
 Symons, G. J. (B. 34.) 
 
 (Page 150.) In constructing a table of rainfall, there are two evils between which 
 it seems necessary to choose. The longer the period of observation, the more trust- 
 worthy is the mean deduced from it, but if one is only to work up long registers, there 
 (Page 151) will be large' tracts of country without any. If one works with short 
 registers, the means are liable to be in error through exceptional seasons not being 
 adequately neutralised. I have adopted two ways of surmounting these difficulties. 
 One is by taking first only the long registers, determining their true means, and the 
 ratio which the fall in each year bears to the mean of the long period. Then by 
 applying these ratios to the observations which were made for only a few years, one 
 obtains a very close approach to the true mean for those stations. Another plan is to 
 take several long registers, and to hunt through them for a short group of years, of 
 which the average is nearly the same as the average of a long period. . The great need 
 (Page 165) of rainfall work, as of every other branch of meteorology, is neither more 
 observations nor more money (though neither of these is to be despised), but more 
 brains, more hard workers, more deep thinkers. 
 
 Williams, W. M. (B. 74.) 
 
 [He suggests that systematic observations be made on the variations of the Gulf 
 Stream, with a view to obtaining forecasts of the coming season in W. Europe.] 
 
 Nature. (B. 80.) 
 
 (Page 514.) Dr. Gustav Hellmann reports on the meteorological organizations in the 
 chief countries of Europe in the 'Journal of the Eoyal Statistical Bureau of Prussia' for 
 
 K 2 131 
 
GENERAL 1879. Nature. NOTES. 
 
 1878. He describes the systems in France, Great Britain, Belgium, and Holland. 
 Diverse hours of observation are still practised. 
 
 Nature. (5.81.) 
 
 ( Page 381.) The monthly International Weather Chart of the Northern Hemisphere/ 
 based on simultaneous observations, marks an important step in meteorological progress. 
 It originates from the proposal at the Vienna Congress of 1873, that synoptic charts be 
 formed, based on reports from Algiers, Austria, Amsterdam, Belgium, Great Britain, 
 China, Central America, Denmark, France, Germany, Greece, Greenland, India, Italy, 
 Ireland, Japan, Mexico, Morocco, the Netherlands, Norway, Portugal, Russia, Spain, 
 Sweden, Switzerland, Turin, British North America, the United States, the Azores, the 
 Sandwich Islands, Malta, Mauritius, the West Indies, South Africa, and South America. 
 On July 1st, 1875, the daily issue of a printed bulletin exhibiting these international 
 simultaneous reports was commenced at the Signal Office of the United States, and has 
 since been maintained. It combines for the first time the work of nations for mutual 
 benefit. A ship at sea becomes one of the best of stations for a simultaneous system. 
 The value of the record is enhanced by the change in the ship's location every twenty- 
 four hours. Every ship ought to carry meteorological instruments, both for its own sake 
 and for that of others. The duty of observing requires but little effort. One hundred 
 observations are made daily at sea. The average number of daily simultaneous 
 observations now made in foreign countries [the remarks are from the United States 
 Signal Office report] is 293. The total number of stations on land and on vessels at sea, 
 from which reports are entered in the bulletins regularly, is 557. On July 1st, 1878, 
 the issue was commenced of a daily international weather map. The charting embraces 
 the whole northern hemisphere. The questions as to the translation of storms from 
 (Page 383) continent to continent and of the times and directions they may take in 
 such movements ; the movements of areas of high and low barometer ; the conditions of 
 temperature, pressure, and wind direction existing around the earth at a fixed period of 
 time, permitting thus the effects of day and night to be contrasted ; the distribution and 
 amount of rainfall and other studies, many and valuable, only suggested by this 
 enumeration, may be by such studies settled. This simultaneous system enables studies 
 by normals to be made. The inter-comparison of these normals with the normals 
 taken at other places simultaneously with the first, and under the similar condition that 
 the normals to be found for those places are from observations taken at those places at a 
 fixed time and on every day, gives results reliable and different from those to be had by 
 the use of normal readings arrived at in any other way. Normals for the year, for the 
 season, and for the month may be determined by such procedure. The comparison of 
 such normals will show, in the case of abnormal changes in any district or section for any 
 season, whether and how they are compensated by compensating variations elsewhere. 
 There are interesting studies as to what sequences there may be to follow such 
 atmospheric variations occurring over any region or country either in that region or 
 country or elsewhere and how and where the compensating variations occur, and with 
 what concomitants or sequences of meteoric changes. 
 
 Nature. (B. 82.) 
 
 (Vol. xix. Page 232.) Professor Forster gave in on Dec. 22 a report on weather- 
 warnings to the Bern Economical Society. He sketched the developments of these 
 warnings in Europe and pointed out the importance of the Service Agricole, established 
 between France and Austria, by which daily telegrams are sent advertising the coming 
 weather: 85 per cent, of these prognostications have been perfectly true, 7 per cent, 
 approximately true, and only 8 per cent, untrue. The first steps for the establishment 
 (Page 236) of such a service has been made in Switzerland. Biot said, "It is in the 
 high regions of the air that meteors are formed, rain, snow, and hail. There the 
 
GENERAL 1880. Ley. NOTES. 
 
 thunder rolls and the lightning traces its furrows. There are the upper currents which 
 chariot the clouds. It is to these elevated regions that the inquiries of meteorological 
 science ought to be directed. It has been recently discovered in France, by observations 
 at Montsouris, that dust of various kinds is at most seasons of the year floating in the 
 atmosphere, consisting of spherules so minute as to be discernible only by the microscope 
 or by chemical tests ; and that which so floats is not always the same in the higher as 
 in the lower regions of the air." The bearings of this new information on epidemics 
 affecting both animal and vegetable life is awakening much attention among continental 
 physicists. High stations will furnish early intimation of changes in the weather. 
 (Page 293.) In the article Atmosphere (' Encyclopaedia Britannica') it has been justly 
 remarked that one of the most important steps that could be taken towards the develop- 
 ment of the science of meteorology would bean extensive series of observations from such 
 countries as India, which offers splendid contrasts of climate at all seasons, has a surface 
 covered at one place with the richest vegetation, and at others with vast stretches of 
 sandy deserts, and presents extensive plateaux and sharp ascending peaks, all which 
 conditions are indispensable for the solution of atmospheric physics. In working 
 out this problem it is necessary, owing to its extreme complexity and difficulty, to 
 give attention not merely to questions immediately bearing on the physics of the 
 atmosphere, but to climatic and other practical inquiries which may be handled with 
 comparative ease, and which afford results that contribute indirectly, but very mate- 
 rially, to the solution of the higher problem. The mean monthly pressure for each hour 
 of observation is an essential requisite for the presentation of the data required in 
 discussing various of the more important problems of international meteorology. The 
 tables given by H. F. Blanford in ' Report on the Meteorology of India in 1876,' are 
 entirely suited for the discussion of climatic questions of an international character, with 
 the exception perhaps of the lumping of the wind observations into the monthly mean. 
 (Page 329.) Professor Asa Gray (Amer. Journ. Sci.) takes it for granted that the 
 indigenous plants of any country, particularly the trees, have been selected by climate. 
 [Here and in the subsequent part of the article climate means temperature.] 
 (Page 446.) A system of weather- warnings has been established in Switzerland, 
 (Page 447.) The prognostics are correct in 8 cases out of 10. 
 
 (Vol. xx. Page 100.) (Q. S. Nat. Acad., April 1879.) J. Weir Mitchell. 'The 
 relation of Neuralgic Pains to Storms and the Earth's Magnetism.' (Meteorol. Soc. 
 (Page 282.) June 18.) 'Report on the International Congress held at Rome, April 
 (Page 434.) 1879.' By R. H. Scott. The Collegio Romano has issued, in a volume of 
 282 pp. (Rome, 1879), a French nccount of the Reports, &c., of the Congress at Rome. 
 
 1880. 
 Griffith, Kev. C. H. Q. Journ. Meteorol. Soc., VI. No. for Jan. 
 
 (Page 21.) With a difference of more than three months in the recorded first 
 appearance [of insects in s.w. England], but little can be gained in reference to the 
 elucidation of facts in climatology. This difference may be due to want of an 
 (Page 22) adequately systematic observation. The dates of none of the species are 
 sufficiently well marked to hazard any remarks in consequence on climate; local 
 influences are of course great, but I think they ought not to differ so much as they do. 
 
 Ley, Rev. W. Clement. (B. 9.) (rv.} 
 
 (Page 1.) The aids are intended for the use of observers in the British Isles [but 
 many are applicable to other areas ; and it is on account of the general principles 
 (Page 6) involved that the remarks are here given]. Many of the weather signs relied 
 on by shepherds and others whose occupations oblige them to be out of doors in all 
 weathers, are extremely local, and the specially weather-wise men who rightly interpret 
 
 133 
 
GENERAL 1880. Ley. NOTES. 
 
 them in their own district would be quite at a loss if taken out of it and asked to form 
 a judgment of coming weather in a different part of the country from the loc. 1 
 signs known there. Hence it is advised that all rules be mistrusted, and that inferences 
 (Page 7) be deduced from well authenticated local signs. It is commonly said that a 
 rosy sky at sunset presages fine weather, a red sky at sunrise bad, and a grey sky 
 fine weather. This generalisation will be fallacious if applied as a rule, and inferences 
 (Page 10) are not drawn as to the distribution of aqueous vapour in the air. The 
 connection between barometric readings and the condition of the weather is not of a 
 simple character. The several relations which constitute it must be patiently studied 
 (Page 16) if we are to employ our knowledge usefully. Do the laws by which 
 barometric fluctuations are governed fall under our cognisance ? Are we acquainted 
 with the special forms and contours of the variable areas of high and low pressure? 
 Is their movement over the surface of the globe determined by conditions which we 
 know ? And, again, are they characterised by particular and definite states of weather 
 in relation to temperature, state of sky, appearance of cloud, amount of rainfall and 
 the like ? It is obvious that on the answer to be given to these questions depends 
 (Page 17) the whole status of our weather knowledge. If that answer were a simple 
 negative this knowledge would scarcely be above the level of an instinct ; in the place 
 of rules we could have nothing but conflicting experiences. If, on the contrary, the 
 laws of the atmospheric changes lay completely within the circle of our knowledge, 
 weather wisdom might at once claim its place among the exact sciences ; and it would 
 be possible to establish fixed and definite rules, by the aid of which the observer could 
 foretell coming weather with absolute certainty. If, however, as is the case, the truth 
 lies between these extremes, if some of the conditions can be traced, whilst others are 
 unknown, then weather wisdom is neither -mere instinct nor an exact science, but a 
 scientific art, containing both possibilities of instruction and elements of progress, and 
 it becomes advisable to tread as carefully as possible through the border between know- 
 ledge and ignorance. Particular forms of cyclonic and anti-cyclonic areas are attended 
 (Page 26) by their concomitant conditions of weather. The occurrence of secondary 
 [barometric] disturbances is not unfrequently a cause of embarrassment to the observer 
 who attempts to forecast wind and weather from local observations only. However, 
 the weather which accompanies these phenomena has a somewhat distinct character of 
 (Page 30) its own. There are a great many modifications of weather which depend on 
 conditions either unknown or not as yet reducible to definite law or fixed classification. 
 In a general way foul weather characterises the cyclonic and fair weather the anti- 
 cyclonic systems, which corresponds to the old rule that the barometer falls before 
 rain or storm, and rises before fine or calm weather. In the front of a large depression, 
 at its extreme exterior that is to say, considerably outside of its isobars which form 
 (Page 31) closed curves, there commonly stretches a great bank of cirro-stratus. The 
 outside edge of this bank is pretty definite, and its outline in most cases is in rough 
 correspondence with the contour of the advancing isobars. The movement of the upper 
 current which carries the outlying parts of this elevated cloud bank is often nearly 
 tangential to the edge of the cloud bank itself, and nearly opposite to the direction of 
 the wind, which is presently about to spring up at the earth's surface, and in nearly 
 all cases it makes a greater angle than 90 with this wind. It is important to observe 
 that when this movement is very rapid the approaching depression may be expected to 
 be deep and probably attended by strong winds at the earth's surface. As the sheet 
 extends over us the upper current breaks very quickly, and continues to do so over the 
 whole of the front half of the advancing system. As the centre advances towards 
 us we commonly observe composite cloud (nimbus), the rain or snow being 
 accompanied by the new current of air belonging to the depression. This cloud 
 bank extends in most instances nearly over the front half of the system, both on the 
 right hand and left hand of the centre's path, but its character differs very considerably 
 
GENERAL 1880. Ley. NOTES. 
 
 on the two sides. If the centre is passing so as to leave our station on its right, the 
 nimbus usually continues until the centre has almost reached its nearest point to 
 us. Then, usually after a sudden increase of precipitation, the sky clears, the cirro- 
 stratus terminating in an abrupt line, while the wind at the earth's surface begins 
 to veer, slightly if we are at a great distance from the centre, and greatly if we are 
 near it. Up to this time the barometer will have continued to fall (except in those 
 cases in which the whole system is becoming rapidly shallower) but the rapidity of 
 the fall will have depended, as a moment's consideration will show, on four separate 
 elements ; the first, the rate of progress of the system ; the second, steepness of its 
 gradients ; the third, the increase or diminution taking place at the time in this 
 steepness, in other words, on the question whether the depression is becoming deeper 
 or being filled up; and the fourth, on the distance of our station from the centre. 
 Pressure now begins to rise (except in those instances in which the depression is 
 becoming rapidly deeper). The appearance of the sky in the rear of the disturbance, 
 but still on the right side of the centre's course, is usually very unlike that in the 
 front. Comparatively few upper clouds are observed, and the movement of these is 
 commonly observed to be nearly the same w r ith that of the current on the earth's 
 surface. In lieu of cirro-stratus we see fleecy cumulus. Shower clouds are also 
 common over this district. These latter in summer, especially in our more inland 
 regions, often take the form of local thunderstorms. In winter, passing squalls of 
 rain, snow, and hail are common. Those on our western coasts are often attended 
 by lightning. It should be remarked that these showers in the rear of a depression 
 are far more extensive and persistent on exposed coasts and in hilly districts than 
 in inland and more level countries. The atmosphere in this part of the disturbance 
 (Page 32) is in most cases clearer, or more devoid of haze than in the front, and 
 temperature is also commonly lower ; but marked exceptions occur to both these 
 rules. A rapid and excessive decrease of temperature is not uncommon when the 
 wind has begun to veer, particularly near the centre of the cyclonic circulation. 
 Now suppose the barometric minimum in its onward course to leave us on the left. 
 Here the nimbus extends over us, the wind after springing up commences to back, 
 and continues to do so throughout the passage of the disturbance. On this side we 
 very rarely experience the abrupt change from a rainy to a clear sky which is so 
 usual on the right-hand side. As the centre passes, the higher cloud forms gradually 
 degenerate into banks of dreary stratus, often attended with an increase rather than 
 any diminution of haze. As the rear of the system approaches us on this side the 
 bolder forms of cumulus are rarely seen, and in place of the shower clouds we 
 commonly notice gloomy-looking banks of condensed vapour in the middle and lower 
 levels of the atmosphere, while cirrus has usually almost altogether disappeared. In 
 the actual centre of a large depression the sky is often comparatively clear. Shower 
 clouds are frequently visible, but these have usually here a thin soft and disintegrated 
 aspect, while cumulus tends to spread itself into stratus, and cirrus lies in broken 
 though watery-looking patches. The above description applies to the large and more 
 important depressions ; it cannot be applied without considerable modifications to the 
 smaller or more local systems. These latter are more commonly characterised by more 
 unbroken cloud banks, gloomy skies (often with rain or snow) prevailing over the 
 central calm, and even to some extent over the extreme rear of the system. The 
 secondaries are especially marked in most cases by very copious precipitation over the 
 district which they traverse, the rainfall being usually greatly in excess of that which 
 occurs over the rest of the primary disturbance. Irj summer, local depressions, 
 especially if they are secondaries taking a northward direction, are usually associated 
 with heavy thunderstorms. In the front of these last mentioned systems the cirro- 
 stratus is commonly accompanied, and sometimes almost replaced, by the turreted 
 stratus. The occurrence, therefore, of this form of cloud moving from some southerly 
 
 135 
 
GENERAL 1880. Ley. NOTES- 
 
 point over easterly or northerly surface winds is a valuable indication of approaching 
 thunder showers. The weather which characterises anticyclones is in marked 
 (Page 33) contrast to that which belongs to cyclones. It is, however, subject to far 
 greater modifications in relation to the seasons of the year. In summer, and especially 
 m our hotter summers, brilliant weather usually accompanies the anticyclonic circu- 
 lations, the dry atmosphere permitting the sun's rays to exercise their full heating 
 power on the stratum of air near the earth's surface. In the central districts, particu- 
 larly, the sky is often nearly or totally devoid of cloud ; at other times light fleecy 
 cirrus, whose motion is extremely slow, is the principal cloud visible. Near the 
 exterior of the system, especially on its eastern and south-eastern sides, stratus and 
 tine weather cumulus, often accompanied by much haze, are the prevailing cloud forms. 
 At the extreme western and northern borders cirro-cumulus and cirrus are very common, 
 beneath which there is much fog occasionally at the sea coast, but rarely at the inland 
 stations. Near the south-western limit of a large and well-formed summer anticyclone 
 remarkably brilliant and cloudless weather often prevails. In winter the aspect of the 
 sky in these systems is commonly different from that just described. Dry weather 
 stratus is now the most common form of cloud, occasionally covering nearly the whole 
 of the anticyclonic system with an unbroken canopy, the perpendicular thickness of 
 which is very small, though its extent is so immense. Above this, in the higher 
 region of the atmosphere, there is in such instances a remarkable absence of cloud ; 
 while beneath it dense ground fogs very commonly prevail at the inland stations. In 
 some cases the sky is almost devoid of cloud, or the ground fog only prevails. In 
 these latter instances the temperature is very low; whereas in the clouded anti- 
 cyclone we usually experience only a moderately low temperature, the cloud layer 
 checking the radiation. Near the exterior of the system the atmospheric currents 
 usually break up, to a great extent, the canopy of cloud and land fog. On the eastern 
 and south-eastern limits of the system the appearance of the clouds is often very 
 similar to that which prevails in the same district of an anticyclone in the summer, 
 but banks of the dry stratus are even here more common than true cumulus. It is 
 usually in this district that the temperature is lowest in our islands, a fact that is due 
 rather to our geographical position than to any other cause. Occasionally, however, 
 we experience, as in summer, an exceedingly clear sky on the south-western side of a 
 large anticyclone, which in winter is accompanied by an intense frost. It may be 
 said generally that the occurrence in any marked degree of the dry weather stratus is 
 commonly an indication of an anticyclonic movement of the air. Anticyclones are 
 (Page 34) often nearly stationary for a considerable period. It is exceedingly difficult 
 from observations made at a single station to foretell with anything like certainty the 
 ultimate fate of a nearly stationary anticyclone, especially if the atmosphere be not 
 only clouded but foggy. The following are specimens of forecasts taken from a 
 weather diary. 
 
 1. Winter : in the rear, right-hand side., of a depression travelling to E. or N.E. 
 Barometer moderately low, rising rapidly, brisk or moderate N.W. wind ; clear sky 
 between passing showers ; very transparent atmosphere ; no tendency to the formation 
 of a bank of stratus ; little or no cirrus. As depressions commonly follow each other 
 in a series, and as the direction taken by the last, as well as the absence of the more 
 anticyclonic cloud forms, indicates the absence of any anticyclone to the west, we expect 
 the N.W. current shortly to fall calm, and to be followed by a fresh bank of cirro-stratus, 
 decline of pressure, southerly wind and rain. 2. Winter ; after a day or two of chilly 
 w. and N.W. winds ; depression in the north-east taking a south-easterly course. Wind 
 w. or w.s.w., brisk or moderate ; atmosphere mild ; barometer about the mean or below 
 it, falling rapidly ; cloudy, with flying scud, rough looking composite cloud bank or 
 dense cirro-stratus. The rapid decrease of pressure in conjunction with the aspect of 
 the sky, and with the previous weather, makes it probable that the right hand segment 
 136 
 
GENERAL 1880. Ley. NOTES. 
 
 of a cyclonic circulation travelling south-eastwards is about to pass over the station ; 
 N.W. to N. or even N.N.E. gale is therefore to be apprehended, with a great fall of 
 temperature ami brisk recovery of pressure. 3. Summer : after moderately dry 
 weather with westerly winds and barometer about or rather above the mean (northern 
 limit of an anticyclone). Barometer about the mean and steady, or falling but little ; 
 wind s.w. or w.s.w., moderate or light ; overcast with much low cloud. Temperature 
 about or a little above the mean for the season. The right-hand portion of a depression 
 taking a north-eastward direction is probably passing over the station ; no rain, or 
 (Page 35) but slightly drizzling showers, may be expected ; the wind will most pro- 
 bably veer a little shortly with a clearer sky. 4. Winter : extreme rear, right hand of 
 a large depression going E. or N.E. Calm, clear and cold : N.W. wind having died down 
 and cumuli and shower clouds disappeared quickly, sheet of cirro-stratus on south 
 horizon, edge travelling from w. or s.w.; barometer below mean, rising, but rise checked 
 somewhat. If the new cirrus bank had appeared farther in the w. and its edge moved 
 from a more northerly point, the fresh depression which is probably approaching might 
 have been expected to follow nearly in the wake of the previous system. As it is, 
 however, there is risk of its centre passing on the south side of the observer causing a 
 temporary easterly wind, perhaps gale on exposed coasts, with overcast skies, and 
 probably some sleet or snow. 5. Winter : after light winds and dull weather ; 
 barometer much above mean ; totally overcast with- low tranquil stratus, and nearly 
 calm. As this is probably the central portion of an anticyclone no immediate change 
 can be anticipated. 6. Summer : barometer near its mean level ; falling somewhat ; 
 E. or N. breeze; turreted stratus above, with some cirrus travelling rather briskly 
 from a southerly point. A shallow depression is probably about to pass northward over 
 the station ; thunder and rain may be anticipated, followed by a light wind from some 
 westerly point. 7. Summer : after westerly winds with temperature and pressure near 
 the mean. Decided rise of barometer and very high temperature ; extremely clear and 
 brilliant sky with very few, and those only very low soft, clouds. Very light w. or N.W. 
 breeze. The central part of an anticyclone, moving slowly north-eastwards, is likely to 
 pass over the station. A further increase of temperature may be expected, followed 
 probably by bright and hot easterly winds. 8. Winter : extreme rear of depression 
 moving to S.E. Steady rise of barometer : wind veering from N.W. towards N.N.E. ; 
 hazy, with some dry-looking broken stratus, and no cirrus. An anticyclonic system 
 may be surmised to exist over the w. or N.W. Fine and cold, though cloudy weather 
 may therefore be expected with light winds. 9. Winter : after a period of disturbed 
 weather, with cyclonic disturbances going eastwards. Barometer about or rather above 
 the mean, scarcely falling ; continuous calm for some hours, with persistent and rather 
 heavy rains. The observer seems to be near the centre of a very shallow depression, 
 whose course is not distinctly towards E. or N.E. There is therefore a probability that 
 anticyclonic currents are forming in the north. Much drier weather, with a higher 
 barometer, may consequently be with some probability anticipated. 
 
 Marcet, William. (B. 13.) 
 
 [Nothing for general notes.] 
 
 Marriott, Wm. Remarks on the Winter of 1878-9. Trans. Watford Nat. Hist., II., 
 
 pp. 237-240. (ra.) 
 
 [Refers to temperature at Greenwich and other places in England.] 
 Smyth, Piazzi. (Nature, xxi.) 
 
 (Paje 249.) Weather predictions cannot be made years beforehand, owing to 
 uncertainty as to the length of each sun-spot cycle. 
 
 137 
 
GENERAL 1881. NOTES. 
 
 Stewart, Balfour. (Nature, xxi.) 
 
 (Page 542.) The question of periodicity of rainfall may perhaps be solved by the 
 method of deducing unknown inequalities proposed by Dodgson and myself. It consists 
 in a way by which we may numerically estimate the indications of an equality. Let us 
 suppose, for instance, that in ignorance of the diurnal range of temperature, we try to 
 find whether there be a temperature inequality of 26 hours or of 24. We begin by 
 taking a large number of hourly readings of temperature and group them into two 
 series, the one containing 26, the other 24 numbers in a horizontal row. We should 
 thus have 24 vertical columns for the one series and 26 for the other, and we should 
 take the mean of each series as well as the mean of the whole. Now it would speedily 
 be found that an inequality, was indicated by the 24 hourly series and none by the 
 others. The mean amount of the differences might be taken to form a numerical 
 criterion of the presence or absence of an inequality. However, we must bear in mind 
 that this method of detecting inequalities by summing up and averaging the departures 
 from the mean caused by the inequality, likewise sums up and averages the accidental 
 fluctuations. These accidental fluctuations can only be got rid of by a long series of 
 observations. 
 
 Stewart, Balfour. (Nature, xxii.) 
 
 (Page 146.) .There would appear to be a progress of magnetic phenomena from west 
 to east, just as we know there is a progress of meteorological phenomena. As, however, 
 the meteorological phenomena which we can examine occur in the lower atmospheric 
 regions, while the magnetical phenomena are, according to my hypothesis, associated 
 with currents in the higher regions, it does not follow that magnetic and meteoro- 
 logical phenomena should travel from west to east at the same rate. There is reason 
 to believe that magnetic changes lag behind corresponding solar changes just as meteoro- 
 logical changes would do. 
 
 Nature. 
 
 (Vol. -K\i.Page 316.) (Acad. Sci., Paris, Jan. 19.) Influence of climates on the matura- 
 tion of corn, by M. Balland. [Refers to Temperature.] 
 
 (Vol. xxii. Page 229.) Vol. i. of 'Archives of the Deutsche Seewarte ' contains 
 reports on (1) Marine meteorology ; and (2) Weather telegraphy and storm warnings. 
 
 (Vol. xxiii. Page 183.) The adequate discussion of the eight-hourly weather maps of 
 the United States is the next great step to be taken in meteorology. 
 
 1881. 
 
 C., G. [probably George Clinch.] The Weather. Monthly Nat. Hist. Notes, vol. i. p. S. 
 Published in Jan. (rv. to date.) 
 
 [It refers to the advantage of trees being leafless during snow-storms and to tempera- 
 ture in England.] 
 
 Clinch, George. Monthly Nat. Hist. Notes, vol. i. Published in June. (rv. to date.) 
 (Page 51.) It is said that if the new moon be seen very early after the change rough 
 and unfavourable weather is betokened. 
 
 Cordeaux, John. Q. Journ. Meteorol Soc., VII. Published in No. for Jan. (ra.) 
 (Page 47.) The character of the seasons appears to have very little effect on the 
 regular migrating movements of birds. The swift seems even less under the influence 
 (Page 48) of the weather than the swallow. With regard to the early or late nesting of 
 birds as influenced by weather, the data are not sufficient to give any very reliable 
 opinion. 
 138 
 
GENERAL 1881. NOTES. 
 
 Elsden, J. V. Trans. Hertfordshire Nat. Hist. Soc. t I. Head March 16, 1880. 
 Published in March, 1881. (m.) 
 
 (Page 111.) The drift exerts an indirect influence on climate. It is to the drift that 
 we owe the well wooded appearance of our county. Trees exert a most important 
 influence on climate by acting as frigorific causes. [Climate here then means 
 temperature.] 
 
 Hazen, W. B. American Meteorological Observations. Nature, XXIV., p. 189. 
 
 [Explains why the Bulletin of simultaneous meteorological observations is published 
 twelve, instead of six, months after date.] 
 
 Hopkinson, John. Trans. Herts. Nat. Hist. Soc., I. Head April 20, 1880. Published 
 
 March, 1881. (m.) 
 
 (Page 138.) From the phonological observations made in Hertfordshire in 1879, it 
 would appear that animals are not so much affected by the seasons as plants are. 
 
 M. R. I. A. (B. 8.) 
 
 (Page 411.) Granting (1) that solar periodicity produces a corresponding periodicity 
 in any of the elements which make the climate of the earth, as a whole, what it is, and 
 (2) that the expression for that change contains only the two first terms of the general 
 expression, i.e. that there are no secondary . . . periods, both large admissions, it 
 docs not appear how a simple fluctuation of solar temperature recurring, we will say, every 
 11 years, could produce several periodic fluctuations of terrestrial temperature identical 
 in duration but not simultaneous, some one or more being therefore partially or com- 
 pletely opposed in phase to some one or more of the remainder and to the causal fluctua- 
 tion. Farther, we know that the sun-spot period is subject to large and seemingly 
 capricious variation. If then solar atmospheric changes are reflected in marked variations 
 in terrestrial climate, we shall find these latter to be common to the whole earth, and to 
 be represented by a function of the same form. The mere citation of local (for in this 
 connection even Europe may be regarded as local) phenomena which have occurred at 
 intervals approximately equal individually to the average length of a sun-spot period 
 proves nothing in favour of H. \V. C.'s views ; and an analysis of the data given by him 
 which would make the occurrence of great frosts simultaneous, sometimes with sun-spot 
 maxima and at other times with sun-spot minima, seems calculated to weaken his case 
 in a material degree on the supposition of a uniform 11-years cycle. 
 
 Meldrum, Charles. [Circular relating to] Weather Charts and Storm Atlas in the 
 Indian Ocean. Dated April 26. 
 
 It is generally admitted that simultaneous observations over wide areas are the best 
 means for obtaining an insight into the laws of weather changes. Some persons consider 
 that all that is recpuircd for ordinary seamen is a resume of results. But to many others 
 no statement of results can be so satisfactory as daily or hourly details presented in a 
 graphic form. The mere enumeration of results for the benefit of practical men is not 
 so much calculated to advance meteorology as a science. The highest authorities have 
 recommended the synchronous method. 
 
 Meteorology. Report of the Agricultural Meteorology Committee. Q. Journ. Meteorol. 
 Soc., YII. Published in No. for April, (ra.) 
 
 (Page 102.) Q. 1. What are the mutual relations of the meteorological elements on 
 vegetation ; not only those which are proved to exist, but also those which are theo- 
 retically supposed to be practicable ? A. Healthy vegetation depends on due proportion 
 of warmth, moisture and light ; in overcast and moist summers there is luxuriant 
 
 139 
 
GENERAL 1881. NOTES. 
 
 leafage and little flower ; in sunny and dry summers leafage is moderate and flowering 
 great (possibly no great amount of fruit, as the plants may be too much dried). These 
 main points are much modified by circumstances that affect the ground temperatures ; 
 and these ground temperatures are of great importance, as through these, the flow of 
 the sap may be retarded or entirely checked, or may be active in one part of the plant 
 while it is exactly the reverse in the others, i.e. above or below ground as the case may 
 be. The importance of this consideration is practically acknowledged by vine growers. 
 The effect of a mild, overcast and moist summer and autumn or the reverse upon the 
 ripening of the wood of that year and the fruit and leaf buds for the succeeding year is 
 probably considerable, as also the effect on agricultural seeds, especially with regard to 
 the cereal crops, as exemplified in the bread made from corn harvested in bad seasons 
 (notably in 1839), drawing out into long sticky strings. Q. II. What observations of 
 meteorological elements are to be particularly attended to with especial reference to 
 their influence on vegetation ? A. Sunshine ; earth temperatures at depths not exceeding 
 4 feet; air temperature and range, humidity, wind, rain, and terrestrial radiation. 
 Also solar radiation and evaporation, if satisfactory instruments can bo obtained. 
 Q. V. Can, at the present moment, meteorological central offices issue weather forecasts 
 for the use of agriculture with reasonable prospects of utility ? 
 
 Meteorology. Resolutions adopted by the Conference for the Development of Agricultural 
 and Forest Meteorology, held at Vienna in Sept. 1880. Q. Journ. Meteorol. Soc., VII. 
 Published in No. for April, (ra.) 
 
 (Page 102.) Q. 1. [as before in previous paper.] Resolution: 
 
 1. Vegetation is materially dependent on the following meteorological elements ; 
 (a) temperature of the air and soil ; (b) duration and intensity of the illumination ; 
 (c) all the hydrometeors ; consequently, the vapour tension and relative humidity, 
 precipitation (rain, snow, etc.) as well as the other forms of condensation (fog, dew and 
 hoar-frost) ; (d) motion of the air. On the other hand the daily march of pressure and 
 of ozone appears to be of less importance for vegetation. 2. Conversely, the meteoro- 
 logical elements appear to exhibit the influence of vegetation in the following way. 
 Vegetation on an augmented scale, such as pasturage, tilled land, forests and moorland, 
 etc., give rise each in their own districts to special conditions of temperature and 
 atmospheric humidity, and perhaps of rain also, and may therefore exert an influence 
 on the climate of the surrounding country in respect of temperature and hydrometeors 
 and also of springs. 
 
 Q. II. (as before, in previous paper.) Resolution : 
 
 3. On the whole it appears important that on as many rationally managed estates as 
 possible special observations should be carried on of all the elements recognised as 
 important. These observations should be made in different soils, and with different 
 types of culture, and should be compared wfth the crop return year by year, so as to 
 investigate in detail the relation between vegetation and climatic factors. The general 
 mean results published by the several central institutes do not furnish values in 
 sufficient detail for the study of individual types of culture or of local conditions. 
 [Then follow instructions in the method to be adopted for observing the various 
 elements, with remarks on the trustworthiness of instruments, which will be given 
 (Page 119) in connection with each element.] It is advisable to organise the system 
 of radial stations in order to ascertain the effect extensive masses of vegetation, 
 especially forests, exert on the climate of the surrounding region, both in their 
 immediate vicinity and at a distance. This system promises better results the more 
 continental is the character of the region in which it is established. Observations 
 immediatedly above the tree crown are of importance. Q. IV. Would it not be 
 desirable with a view to the special observations which must be undertaken (as, e.g., 
 phonological observations) to prepare a general form of instructions? Resolution 23. 
 140 
 
GENERAL 1881. Stewart. NOTES, 
 
 The Conference thinks it desirable to prepare general instructions for phenological 
 observations. The list of plants to be observed should not be too long. They 
 [members of committee] should deal in the first place with cereals and forage plants ; 
 secondly, with the more important forest and fruit trees ; and lastly, with other plants of 
 importance to agriculture and to the phenomena of animal life. 
 
 Metaorology. Eeports of Observatories. Q. Journ. Meteorol. Soc., VII. Published in 
 
 No. for April, (ra.) 
 
 (Page 127.) In the wind charts for the region near the Cape of Good Hope the 
 Meteorological Council of the Eoyal Society have adopted the principle of natural areas, 
 that is to say, they have treated districts characterized by the same general conditions 
 as wholes, and have abandoned the plan hitherto pursued of dealing with areas bounded 
 by lines of latitude and longitude over which the same meteorological conditions might 
 not prevail. The principle of natural areas has also been adopted by Prof. Buys Ballot, 
 in his ' Maadelijksche Windkarte van dcr Noord Atlantischen Oceaan,' which appeared 
 in 1878. 
 
 Rodwell, G. F. Nature, XXIV. (.) 
 
 (Page 32.) There are forty meteorological stations in the country extending from 
 Mogador in Morocco to Sfax in Tunis. A daily bulletin has been issued since 1875, and 
 it is distributed over thirteen points on the coast. 
 
 Stewart, Balfour. (Nature, xxiii.) (n>.) 
 
 (Page 237.) The evidence is strong in favour of some connection between the state 
 of the sun's surface and terrestrial meteorology, while at the same time it is unmis- 
 takably indicated by all the elements that this connection is of such a nature as to 
 imply that the sun is most powerful when there are most spots on his surface. The 
 problem, Prof. Stokes points out, involves two questions. Firstly, do the changes which 
 (Page 238) take place in the suu's surface correspond to changes in the meteorology 
 and magnetism of the earth, and, if so, does an increase of spotted area denote an 
 increase of solar activity or the reverse ? Another question is whether these solar 
 inequalities bear all or any of the marks of true periodicity. If they do not present true 
 periodicity we cannot hope to predict the state of the sun. If they do present such 
 periodicity we may gain such predicting power. Perhaps Mr. Chambers's method of 
 prevision is not the best. Observations of the sun's intrinsic heat-giving power may 
 perhaps be better. 
 
 Stewart Balfour. Lecture delivered at South Kensington, April 27. Nature, XXIV. 
 
 (Page 116.) The eleven-yearly oscillations of the sun's spots vary in magnitude. 
 They were probably small about the middle of the last century, becoming large towards 
 the end of it ; they were again small about the early part of the present century. 
 They have recently been large, and we may expect that in future there will be again a 
 (Page 150) falling off. The sun is periodically stirred up, and being stirred up there 
 is an increase in the light and heat which is radiated to the earth. This affects the 
 meteorology of the earth. 
 
 Symons, G-. J. The History of English Meteorological Societies. Q. Journ. Meteorol. 
 Soc., VII. pp. 65-98. Head Jan. 19. Published in No. for April, (ra.) 
 
 (Page 65.) The earliest English effort at forming a meteorological society, or at any 
 rate, at securing observations made with comparable instruments, recorded upon a 
 uniform system, was made in 1723 by Dr. James tTurin, in his address given in the 
 Phil. Trans, for that year. On May 4, 1744, Eoger Pickering read before the Royal 
 Society a paper entitled, ' Scheme of a Diary of the Weather, together with draughts 
 
 141 
 
GENERAL 1881. Symons. NOTES 
 
 (Page 66) and descriptions of machines subservient thereunto.' Pickering states that 
 a sense of the importance of observing the weather induced Hippocrates, in his remarks 
 upon the epidemic diseases in Thasos, to premise a general history of the weather 
 preceding them ; and with the same view did Boyle turn his thoughts so closely upon 
 the same subject, whose example, being followed by others, ;both abroad; and at home, 
 has brought the natural history of the air to a surprising degree of perfection. The 
 Royal Society commenced its register in 1774, but neglected it for several years after 
 1781. Daniell, in his ' Elements of Meteorology,' says the Meteorological Society 
 (Page 67) of the Palatinate was established in 1780. One of the first acts of the 
 Association was to write to all the principal universities, scientific academies and 
 colleges, soliciting their co-operation, and offering to present them with all the necessary 
 instruments properly verified by standards and free of expense. The offer was 
 immediately accepted by thirty societies, and observations were made by Hemmer, 
 Weis, Plann, Senebin, Bugge, Van Swinden, Konig, Catte, Egel, Pictet, Toaldo, and 
 Euler. Hemmer sent ample instructions with the instruments. Some idea may be 
 formed of the comprehensive scale of the register, when it is known that it contains 
 observations three times in the day of the barometer, thermometer in the shade and in 
 the sun, hygrometer, magnetic needle, direction and force of the wind, quantity of rain 
 and of evaporation, the appearance of the sky, and in some places the electrical state of 
 the atmosphere, and the presence of disease. The field of observation extended from 
 the Ural Mountains in the east, to Cambridge in the United States in the west, and 
 from Greenland and Norway in the north to Home in the south, as also stations on 
 three high mountains and on the summit of St. Gothard. The observations of each year 
 are summed up and compared with those which precede in copious and most laborious 
 tables of mean and extreme results. Hemmer died in 1790, and from that time the 
 Society appears to have become extinct during the French revolution. Daniell says 
 these volumes contain the first instances of representing barometric oscillations by a 
 curve ; but Dr. Lister was the true originator of this method. From 1781 to 1823 there 
 was no uniformity, nor combination in the observations that were made. In 1823 
 (Page 69) J. G. Tatem proposed the formation of a Meteorological Society. A society 
 was formed and its first meeting held, Oct. 15, 1823, and continued in existence till 
 (Page 72) 1843, but very little work was done. Buskin in his paper pointed out the 
 necessity of the combination of simultaneous observations and the desire of the Society 
 to know at any given instant the state of the atmosphere at every point of the surface. 
 
 Nature, (xxiii.) (tr.) 
 
 (Page 307.) (Meteor. Soc., Jan. 19.) G. J. Symons gave a history of Meteorological 
 Societies from 1823 to 1880. The earliest English effort for securing observations made 
 with comparable instruments upon a uniform system was made in 1723 by Dr. James 
 Jurin. In 1744 another attempt was made by Roger Pickering, who read a paper 
 entitled ' Scheme of a diary of the Weather, together with drafts and descriptions of 
 machines subservient thereto.' The Meteorological Society of the Palatinate was 
 established in 1780. In 1823 the first meeting of the Meteorological Society of London 
 was held. The Society practically came to an end soon after 1841. In 1850-1851 the 
 British Meteorological Society was established. The preliminary meeting was on April 
 3, 1850, the first general meeting on March 25, 1851. Annual reports were published 
 from 1851 to 1861 ; then five volumes of Proceedings ; then six volumes of the Quarterly 
 Journal. The work of the Society is now so large as to require three computers. 
 
 Nature, (xxiv.) (rv.) 
 
 (Page 7.) Prof. Balfour Stewart, in his lecture at South Kensington on Sclar 
 Physics, stated his belief that one great cause of weather change is solar variability in 
 
GENERAL 1881. Nature. NOTES. 
 
 which we have periods of short length as well as others extending over many years. 
 These weather changes are propagated from W. to E. The variations in diurnal decli- 
 nation of magnet are caused by solar variation and are propagated from W. to E., but 
 more quickly than meteorological changes ; hence it would seem possible that the 
 magnetic weather of to-day may be followed by corresponding meteorological weather 
 five or six days hence. Prof. Stewart has tried this and thinks that such is the case. 
 
 (Page 184.) Meteorol. Soc., June 15. The use of synchronous meteorological charts 
 for determining mean values over the ocean by Charles Harding. 
 
 (Page 232.) Acad. Sci. Paris, June 27. On the prolegomena of a new treatise 
 published in Italy by M. Diamilla Miiller, by M. Faye. 
 
 [Refers to winds and atmospheric electricity.] 
 
 (Page 464.) Brit. Assoc. Me'eting, Sept. The effects of gulf streams upon climates. 
 
 [Climates means temperature.] 
 
 ANNOUNCEMENTS. 
 
 The- First Number of Part II. of the ' Scientific Eoll ' will be issued in May, 1882. This 
 Part will deal with Aqueous Vapour. The Subscription for this Part is 2s. 6d., payable 
 in advance to A. Ramsay. As the value of the Part will depend largely upon its degree of 
 fulness, authors would materially aid in the work by sending copies of any papers they 
 may have written bearing on the subject of aqueous vapour in its climatic; relations ; or, if 
 they are unable to do this, by giving reference to their publications. 
 
 2 3 
 
THE SCIENTIFIC ENQUIRER. 
 
 Correspondence is invited on Science matters of all kinds. In all cases, 
 names and addresses sJiould be given ; but these will not be published icithout the 
 writer's consent. The Conductor will not be responsible for the opinions expressed 
 by Correspondents. All communications should be addressed to the Conductor, 
 10, Bowerie Street, London, E.G. 
 
 As no one has responded to this invitntion, a few lines seem to be required to explain 
 why it has been made, and to point out what are some of the possible advantages that may 
 be deiived from its acceptance. There are scores, nay, hundreds, of publications . which 
 devote more or less of their space to questions and answers for the benefit of their 
 correspondents; and, therefore, it may be thought there is no need for another serial 
 having the same feature, more especially one which appears so seldom as once a quurter, 
 whereas most of the above are weekly or monthly. There is no intention here of holding 
 out any promise for the future ; but an attempt will be made to enhance the value of, 
 and facilitate reference to, the subjects that may be dealt with in the correspondence by 
 classifying the information as opportunity occurs. In this way, there will not be so much 
 occasion for the repetition of the same question, and enquirers will be able to find whether 
 any question has been asked more readily than is at present the case, and, if the question 
 has been answered, where the information is given. It may be said that the indexes for 
 the several serials answer this purpose. But considering that these indexes generally are 
 not drawn up on any special plan, it frequently happens that the person consulting them 
 does not hit upon the right key-word ; and it seldom, if ever, is the case that the indexes 
 are compiled in such a way that the consultor can draw a safe conclusion from what he 
 finds that the information he seek& is definitely and inferentially implied to be absent in 
 the work. In short, the purpose aimed at is so to systematise the matter as to make the 
 references more easy, and to apply to queries the same principles as are developed in the 
 'Scientific Koll'with respect to facts. At some future time attention will be given to 
 the classification of scientific workers, with a view to facilitate intercommunication between 
 them. Should a plan of this kind be fairly well organised, questions will raiely fail to 
 find their way to those most competent and willing to answer them. 
 
ESSAY II. 
 
 OX THE CONNECTION BETWEEN SOLAR PHENOMENA AND 
 CLIMATIC CYCLES. 
 
 BY PROF. E. DOUGLAS ARCHIBALD, M.A., F.M.S. 
 
 PART II. 
 
 (Concluded from p. 37.) 
 
 38. Besides the secular variations in terrestrial magnetism, there exist 
 several other minor disturbances of magnetic equilibrium, many of which 
 
 hibit a periodic character corresponding not so much to the spots as to 
 
 certain periods in solar and lunar motion. For example, Mr. J. Allan Broun 
 
 from a long series of observations of the bifilar magnetometer (mostly at 
 
 Trevandruin in Mysore) discovered a twenty-six day period which coincides 
 
 very nearly with the period of the sun's rotation as indicated by Sporer, and 
 
 frequently an action upon the earth's magnetism which depends upon the 
 
 alive position of the sun and moon with respect to the earth. It is at 
 
 least significant to find that meteorological periods analogous to these, 
 
 1 through whose agency they are possibly caused, have already been 
 
 served. Mr. Broun himself found a meteorological period corresponding to 
 
 f be former of them ; five years' observation of the barometer at Singapore all 
 
 ring the period 25'74 days ; while more recently Hornstein of Vienna has 
 
 )wu that the barometric pressure is so decidedly influenced by the aspect of 
 
 the solar surface, that is to say, by the particular solar meridian which faces 
 
 e place of observation, that the time of solar axial rotation can actually 
 
 bo approximately determined from observations of the height of the mercury 
 
 umn near the Equator. 
 
 39. It must, however, be remembered that different parts of the solar 
 face rotate with different velocities, the equatorial regions rotating 
 ter than those near the poles. Herr Sporer found the mean period of 
 sidereal rotation of the entire solar surface to be 25*234 days, and 
 rrington 25*38 days ; the synodic period would be about 1*7 days longer, 
 
 and it is this period which is most likely to be communicated to terrestrial 
 elements affected by the particular longitude of the sun presented to them. 
 
 40. Now there is some evidence that this synodic period is reflected in 
 terrestrial* temperature, and further, what is somewhat remarkable, that the 
 sun-spots undergo a period of precisely the same length. Thus Nervander 
 of Helsingfors in 1844 found from observations of the temperature at 
 
 PART I. No. 6. L 145 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 Innsbruck and Paris a temperature period of 27-26 days. Dr. Buys-Ballot 
 of Utrecht in 1851, employing observations from Dantzig, Haarlem, and 
 Zwanenburg, found a temperature period of 27-682 days' duration, which 
 besides being more carefully determined than Nervander's, coincides most 
 remarkably with a sun-spot period of 27*686 days subsequently determined 
 by Prof. Fritz of Zurich from Wolfs collection of observations of the bun- 
 spots extending from 1612 to 1860. 
 
 41. These observations if they correspond to the synodic period would 
 give for the sidereal mean period of solar rotation a length of 25-74 days, a 
 quantity rather in excess of that given by either Carrington or Sporer. 
 If, on the other hand, we examine the periods of somewhat similar duration 
 determined by Broun and Hornstein for the variations of atmospheric 
 pressure and magnetism, we find the former element gives us a length of 
 25-8 days and the latter one of 26 to 26-33 l days for the synodic rotation. 
 The sidereal rotation according to these results would be accomplished in 
 about 24-13 days, a result widely differing from that derived from the tem- 
 perature and spot periods. 
 
 42. It is possible, however, that we are here confronted by one of those 
 too common obstacles to scientific progress, viz., an approximate coincidence 
 of effects due to different causes. From a recent research of Prof. Balfour 
 Stewart, a note on which was communicated to the British Association last 
 year, it would appear probable that some of these short periods in the sun- 
 !>pots, and therefore also in terrestial magnetism, are due to the conjunction 
 of an intra-mercurial planet whose period is 24-011 days with the planets 
 Mercury, Venus, and Jupiter respectively. If this suimise-be correct, it is 
 difficult to say whether some of the periods we have been considering are 
 really due to solar rotation or to the synodic periods of this yet undiscovered 
 planet. Thus assuming the period of this planet to be 24-011 days, which 
 represents a sun-spot period of more than ordinary regularity, its synodic 
 periods with the planets just referred to are as follows : 
 
 With Mercury 33-025 days 
 With Venus 26*884 days, 
 With Jupiter 24-145 days. 
 
 corresponding to which Prof. Stewart has found the following inequalities 
 in the sun spots : 
 
 A very prominent inequality of period, 32-995 day. 
 A very prominent inequality of period, 26-871 days. 
 A less prominent inequality of period, 24-142 days. 
 
 The final confirmation of the planetary hypothesis would tend to settle 
 ihe point as to whether there were any periods really dependent on solar 
 rotation alone, but until this is accomplished it must necessarily remain 
 somewhat doubtful. 
 
 43. Eegarding the synodic periods of the rnoon with respect to the sun 
 and earth, it has been found by Vice-Admiral Fleuriot de Langle that they 
 are closely associated with corresponding variations in the number and 
 
 1 Hornstein finds the latter period from obseivations at Prague. 
 146 
 
JSSAY II. SOLAK PHENOMENA AND CLIMATIC CYCLES. 
 
 itensity of hurricanes. This idea is, moreover, supported by the researches 
 f Ilerr Schubler of Munich, M. Flaugergues of Viviers, and Herr Luedicke, 
 /ho have all noted barometric changes corresponding to the varying 
 elative position of the sun and moon of such a character as to agree with 
 e Langle's results. It would further seem that the cause is in some way 
 onnected with gravity, since the changes in the moon's absolute distance 
 rom the earth are in like manner reflected in meteorological phenomena, 
 "hus de Langle, on examining the particulars of one hundred and ninety- 
 live hurricanes, found that one hundred and nine took place within three 
 lays of the moon's apogee or perigee, while Herr Luedicke found the 
 greatest excesses and deficiencies in the height of the barometer to occur 
 precisely at or near the same epochs. 
 
 44. It would seem, then, from the preceding remarks, that the sun and 
 moon, by changes in the absolute distance of the latter from the earth, 
 
 >ossibly by the rotation of the former on its axis, and by their relative 
 
 >osition with regard to one another, exert marked influences not only upon 
 
 errestrial magnetism, but also upon terrestrial meteorology; so that in 
 
 attempting to discover what periodical meteorological disturbances are in 
 
 close connection with the peculiar molecular or thermal condition of the 
 
 nn introduced by the presence or absence of spots, we must not lose sight 
 
 - f the fapt that terrestrial weather is also decidedly influenced by or at 
 
 any rate affected contemporaneously with the solar and lunar motions 
 
 above mentioned. That these influences ever exceed those exercised by 
 
 the spots is not very likely, but if they are present at all, they must tend 
 
 o mask, or complicate, the effects produced by the latter. 
 
 45. Besides the magnetic changes which appear to be closely connected 
 with corresponding meteorological changes, there are abrupt variations both 
 in magnetic declination and horizontal intensity, accompanied very often 
 by the Aurora Polaris, which appear to be communicated instantaneously 
 to the earth without the intervention of a medium of meteorological dis- 
 turbance. A well-known and often referred-to instance of this kind occurred 
 in 1859, when a violent magnetic storm, accompanied by brilliant Boreal 
 and Austral Aurora, occurred coincidently with a remarkable outburst of 
 
 nagnesium over a sun-spot, observed simultaneously by Messrs. Hodgson 
 ind Carrington. Mr. Allan Broun found that some of these abrupt 
 variations (generally diminutions of the earth's magnetism) are apparently 
 ;onnected with the period of solar rotation, following one another in many 
 :ases at intervals of twenty-six days or some multiple of twenty-six days 
 ind he hence inferred that the medium through which these actions are 
 transmitted proceeds from the sun, is not uniformly distributed around it 
 nor always distributed in the same way. 1 
 
 46. It is evident, then, that in regarding the several cosmical influences 
 it work upon the meteorology and magnetism of the earth, we must 
 endeavour, as far as we can, to distinguish between those which produce 
 
 1 'Nature,' vcl. xiii. No. 330, 
 
 L 2 147 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 magnetic disturbances indirectly through a medium of meteorological 
 disturbance, and those which act directly upon the magnetism of the earth 
 without the intervention of any kuch medium. Such influences, whether 
 direct or indirect, may produce effects- specifically alike. For while the 
 Aurora Polaris and disturbances of the magnetic needle are phenomena 
 often largely due to the influence of meteorological currents, and therefore 
 exhibit a tendency to lag behind the corresponding meteorological changes ; 
 they are evidently at limes affected instantaneously by disturbances in the 
 physical condition of the solar surface (as, for example, the outburst of 
 magnesium over a sun-spot in 1859 already referred to) as well as by the 
 particular solar meridian which faces the earth (or by the possible intra- 
 mercurial planet just referred to), since, according to Mr. J. Allan Broun, 
 * : o many Auroras accompanying the great magnetic disturbances repeat 
 themselves at intervals of twenty-six days, when the same solar point 
 returns opposite the earth. 1 
 
 47. Electricit} 7 , in fact, is a form of energ}* which gives us little informa- 
 tion regarding the proximate causes of its development in any particular 
 case. It may be caused by almost anything in the shape of a disturb- 
 ance, whether arising from heat, gravitation, tidal strain or friction, or 
 inherent terrestrial and solar magnetism. Professor Adams attributes the 
 magnetic periods corresponding to the relative position of the sim and moon 
 with respect to the earth, to earth currents produced by alterations in the 
 position of magnetic matter in the crust of the earth, caused by variations 
 in the tidal pull of these bodies. The auroral disturbances he, in like 
 manner, endeavours to show are produced by the friction between air and 
 earth, due to atmospheric tides ; but this hypothesis scarcely seems adequate 
 to explain the abrupt disturbances of terrestrial magnetism, which so 
 frequently coincide with solar storms and the Aurora. 2 
 
 Professor Stokes, on the other hand, considers the earth currents to be 
 secondary phenomena, and attributes the entire category of regular and 
 irregular magnetic changes, and simultaneous appearances of the Aurora, 
 to the action of solar radiation on atmospheric electricity, directly produc- 
 ing the Aurora, and indirectly thereby the earth currents which affect the 
 needle. His idea, which was propounded in 1881, in a lecture on solar 
 physics, delivered at South Kensington, is briefly this : He conceives dis- 
 charges of electricity, due to a horizontal difference of potential, to take place 
 across the atmosphere at very high levels (especially at the level of minimum 
 resistance, which, according to De La Rue's experiments, is about thirty- 
 eight miles above the earth's surface) with corresponding return currents 
 on the earth's surface. The former near the poles constitute the Aurora ; 
 and the latter the earth currents. When a solar storm, or an increase 
 in the number and size of the spots occurs, the solar radiation is assumed 
 to increase correspondingly, and so either the quantity of atmospheric 
 
 1 Nature, vol. xiii., p. 329. 
 
 2 Lecture delivered at the Royal Iistitution by Prof. W. G. Adams, Friday, June 3, 1881. 
 
 148 
 
ESSAY II. SOLAR PHENOMENA AND CLIMATIC CYCLES. 
 
 electricity, or the facility by which, it may be discharged; the latter, as 
 Professor Stokes says, possibly by the upper regions becoming relatively 
 more heated than those below, and thus offering less resistance to the 
 passage of the electric discharge. 
 
 48. This hypothesis of Professor Stokes's is something akin to one pro- 
 pounded by Professor Balfour Stewart, when delivering his presidential 
 address -before the British Association in 1875. He said: "It appears to be 
 a tenable hypothesis to attribute at least the most prominent magnetic 
 changes to atmospheric motions taking place in the upper regions of the 
 atmosphere, where each moving stratum of air becomes a conductor moving 
 across lines of magnetic force. ... It thus seems possible that the excessive 
 magnetic disturbances, which take place in years of maximum sun-spot, may 
 not be directly caused by any solar action, but may rather be due to the 
 excessive meteorological disturbances, which are likewise characteristic of 
 such years. On the other hand, the magnetic and meteorological influence 
 which Broun has found to be connected with the sun's rotation points to some 
 unknown direct effect produced by our luminary, even if we imagine that 
 the magnetic part of it is caused by the meteorological." Prof. Stewart 
 therefore evidently thinks it probable that the majority of the magnetic- 
 disturbances which are referable to solar influence alone, are caused indirectly' 
 through an intervening medium of meteorological disturbance, which latter 
 he assumes to be due to (1) the he*t radiated by, and (2) a cyclone pro- 
 lucing influence of, the sun. The specific distinction which Prof. Stewart so 
 carefully draws between the two preceding influences seems scarcely 
 necessary if we remember that, according to the views more recently enter- 
 tained regarding cyclones, these phenomena merely represent disturbances 
 lue to either the condensation of vapour over a local area, or else a local 
 difference of temperature, both of which are primarily due to solar radiated 
 heat. 
 
 49. The hypotheses, however, of Prof. Stewart and Prof. Stokes agree in 
 attributing the majority of the magnetic changes to a medium of meteoro- 
 ogical disturbance, and this is important, because it shows us that if we find 
 )eriods of magnetic disturbance, we have reasonable grounds for expecting 
 o find some traces of analogous meteorological periods. The decennial 
 >eriod in terrestrial magnetism has long been an accepted fact, and it is 
 (pginning to be acknowledged that there is a similar period in meteorology. 
 'he longer periods in magnetism have likewise in all probability analogous 
 eriods in meteorology attached to them, and thus the one element ma}' be 
 sed as a means of discovery for the other. 
 
 50. The general correspondence of sorno periods in magnetism arid 
 'Qeteorology is exhibited in the following table : (See p. 150.) 
 
 51. Since, notwithstanding the other influences already alluded to as 
 itroduced by the moon and planets, the most marked periods botli in 
 lagnetism and meteorology, seem to be those dependent on the physical 
 mdition of the sun, we may conclude that cycles of weather are indeed 
 
 149 
 
SOLAR PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 MAGNETISM. 
 (l) Solar diurnal variation. 
 
 (2) Lunar diurnal variation. 
 
 (3) Variation corresponding to the period 
 of lunar revolution, or the relative posi- 
 tion of the sun and moon with respect to 
 the earth. 
 
 (4) Semi-annual variation in the appearance 
 of the Aurora Polaris, and disturbances of 
 the magnetic needle, with maxima at the 
 Equinoxes. 
 
 (5) 26 day solar axial rotational (?) or intra- 
 mercurial planetary variation (Broun, 
 Balfour Stewart, Hornstein). 
 
 (6) Solar spot period decennial or undecen- 
 nial (?) both in magnetic declination and 
 horizontal force (Wolf, Sabine, Gautier, 
 Broun, Lamont, Fritz). Similar period 
 in the Aurora (Fritz, Loomis). 
 
 {7) 55^ (55 . 6) year period in magnetic de- 
 clination (Fritz) ; in the solar spots (Fritz 
 and Wolf); and the Aurora (Fritz and 
 Loomis). 
 
 (8) 222 year period in magnetic declination 
 (Kamtz, Moser, Kuppfer, Hansteeu) and in 
 the Aurora (Fritz 6 ). 
 
 METEOROLOGY. 
 
 (1) Solar diurnal variation in air-temperature, 
 humidity, wind - force and direction, and 
 barometric pressure. 
 
 (2) Lunar diurnal tidal wave in the ocean, and 
 probably also in the atmosphere. 
 
 (3) Similar period in storms (De Langle) ; 
 height of barometric column (Luedicke) ; 
 the relative frequency of Vesuvian eruptions 
 (Palmieri J ) ; and earthquakes (Perrey 2 ). 
 
 (4) Semi-annual variation in the number of 
 cirrus polar bauds, with maxima at the 
 Equinoxes (Weber 3 ); in solar and lunar 
 halos (Tromboldt) ; in the frequency of gales 
 throughout the world, and to a certain extent 
 traceable in earthquakes. 4 
 
 (5) 26 day variation in the height of the 
 barometer (Broun and Hornstein). 
 
 (6) Variation of same length in solar radiation 
 (Blanford, Baxendell, and Hill) ; and in the 
 numerous other dependent meteorological 
 phenomena, such as air temperature (Kb'ppen, 
 Hahn, Fritz, Piazzi Smyth, Stone) ; rainfall 
 (Meldrum, Lockyer, Hunter, Hill, and Archi- 
 bald); vapour tension (Hill and Blanford); 
 hail (Fritz) ; extension of glaciers (Hahn and 
 Fritz) ; barometric pressure (Chambers, Hill, 
 Blanford, and Archibald) ; cyclones (Meldrum 
 and Poey) ; wind direction (Main and Horn- 
 stein) ; cloud proportion (Schwabe, Hahn, 
 Weber, Fritz) ; thunderstorms (Bezold, Fritz) ; 
 and earthquakes (Kluge). 5 
 
 (7) Similar period in the frequency of cyclones 
 (Hahn) ; air temperature (PfafT) ; and baro- 
 metric pressure (Hornstein). 
 
 (8) No similar period as yet detected in me- 
 teorology, probably through lack of observa- 
 tions. 
 
 in close connection with solar phenomena; and that the day is not far 
 distant when, armed with telescope, spectroscope, and, it may "be, with 
 still more powerful instruments of research, we may be able to predict 
 with confidence, and for some time in advance, the mutations of the 
 weather. 
 
 1 * Vesuvius,' by Phillips, p. 171. 2 ' Force and Nature,' by Winslow, p. 478. 
 
 3 Ueber die Beziehungen der Sonnen-fleckenperiode zu meteorologischen Ersclieinungeu 
 Dr. F. G. Hahn, p. 128. 
 
 4 ' Force and Nature,' p. 171. 
 
 5 The variations in several of these elements do not directly follow those in the sun-spots, 
 that is to say, their critical epochs are often reversed, as in the case of air temperature and 
 barometic pressure. The important point is that the periods are equal in length. 
 
 6 ' Zeitschdft fiir Meteorologie,' 1875, p. 31. 
 
 150 
 
ESSAY II. SOLAK PHENOMENA AND CLIMATIC CYCLES. 
 
 52. The general results of the investigations hitherto made into the rela- 
 tions between the shorter sun-spot period of approximately eleven years and 
 the different meteorological elements may be briefly summed up as follows : 
 
 The temperature of the air is found to vary inversely with the sun-spot 
 area, being higher than the mean in years of maximum sun-spot, and lower 
 than the mean in years of minimum sun-spot. Fruit and wine, whose 
 development depends on a variety of causes temperature and rainfall being 
 the chief are found to vary in price according to the position of the year 
 as regards the sun-spot cycle. In the present century fruit is found to 
 be cheaper in years of maximum sun-spot. Wine is found to be subject to 
 two variations, one in quantity, the other in quality. The maximum 
 quantity occurs at the maximum epoch of sun-spot development, and the 
 best quality occurs shortly after the epoch of minimum sun-spot. 1 
 
 53. With some exceptions in the subtropical zone, probably more numerous 
 than is at present imagined, the rainfall is greater in years of maximum 
 sun-spot than in those at or near the epoch of minimum sun-spot. The 
 rivers and lakes, as one would naturally suppose, aie likewise found to be 
 higher at the former epoch than at the latter. As rainfall constitutes an 
 approximate measure of evaporation and thence of solar radiation, it would, 
 if tested all over the world, probably afford a fairly correct estimate of the 
 variation in solar heat at different times. It is certainly more trustworthy 
 than air-temperature measured near the earth's surface, which, as Blanford 
 has lately shown, 2 is largely affected by the amount of rainfall apart from 
 the interception of the solar rays due to cloud. 
 
 54. Hail is found on the whole to occur more frequently in years of 
 maximum sun-spot. 
 
 55. Regarding barometric pressure, one of the most important elements 
 of meteorology, comparatively little has as yet been done ; but Blanford's 
 researches and those of Hill and F. Chambers in India have shown that 
 barometric changes occur closely connected with those of the sun-spots. 
 These changes, as might be expected in an element whose general sum total 
 must remain tolerably constant over the earth's surface, vary in quality 
 according to locality. Thus, so far, it has been found that over West 
 Siberia the barometric pressure is lowest in minimum sun-spot years, and 
 highest in maximum sun-spot years, while the contrary prevails over Indo- 
 Malaysia. Traces of the same kind of compensatory variation have been 
 found by the writer to occur between the west coast and the eastern central 
 districts of Europe. 
 
 56. With respect to storms, it has long been known that the tropical 
 cyclones occur most frequently in years of maximum sun-spot, while in the 
 temperate regions the opposite apparently holds, at least as regards the 
 
 1 The time of change from minimum to maximum sun-spot is only from three to four years 
 and these are generally warm and dry in Europe, which probably accounts for the above fact. 
 
 8 * Journal of the Asiatic Society of Bengal,' vol. 50, part ii., 1881. ' On the Relations of 
 Cloud and Eainfall to Temperature in India,' etc. 
 
 151 
 
SOLAK PHENOMENA AND CLIMATIC CYCLES. ESSAY II. 
 
 general movement of the air. It seems possible that in the years of 
 minimum sun-spot the general motions of the atmosphere may ibe stronger* 
 and therefore the sum total of the wind's velocity greater; while in 
 maximum years we may have more violent stoi ms, just as in the tropics 
 there are more cyclones, the same cause operating in both cases, viz., a 
 weakening of the general motions of the air at the maximum sun-spot 
 epocb, which, by promoting the local aggregation of vapour, greatly 
 facilitates the formation of cyclones. 
 
 57. Finally, the clouds are found to be generally more abundant at the 
 maximum epoch of the spots, in this respect agreeing, as we should expect, 
 with the variation in the rainfall. The particular variety of cloud called 
 cirrus, associated by some with appearances of the aurora, is likewise found 
 to prevail more at the same epoch. 
 
 58. When the relations between all these different elements are better 
 known than at present, we shall be able to understand by what exact 
 process (whether an increase or decrease of solar heat) the presence of sun- 
 spots affects the conditions of the terrestrial atmosphere. At present we 
 are considerably in the dark about the whole question ; but nevertheless 
 our gropings inevitably lead to the result that there is a most undoubted 
 relation between solar phenomena and climatic cycles, and that this relation 
 may be ultimately developed so as to become of. the greatest scientific and 
 economic value to the world. 
 
 152 
 
EXPLANATORY EEMABKS. I. 
 
 EXPLANATORY remarks will be given from time to time relative to the metlio! 
 of systematising notes. 
 
 On the present occasion it may be observed that the foregoing general 
 notes represent a few books only, and are by no means a complete resume of 
 the literature. This is manifest if a comparison is made between the 
 number of papers and volumes which are marked as having been read and 
 of those which are not so marked. Hence it must be understood that any 
 given statement assigned to a paper has some point of novelty only as 
 regards the books that have been read. 
 
 A few repetitions may be observed, but some of them are intentional, 
 while others are more so in appearance than in reality. The intentional 
 ones arise from the facts being put in a different way, or from their having 
 a different bearing. For instance, in the papers by Abercromby and Ley 
 there are many facts in common, and a certain degree of consensus of 
 opinion ; but, as the papers have broad lines of distinction, it is necessary to 
 repeat the facts in order to show their general bearing. Again, repetitions 
 occur if the publications have been issued in the same year, because it often 
 happens that it is difficult to ascertain which appeared first. 
 
 As an example of apparent repetitions may be instanced the passage in 
 Buchan's ' Handy Book,' relating to the barometer and other instruments 
 on page 3 of both editions. As there seems to be a slight difference the 
 repetition is made ; it being better to err by repeating than by omitting 
 facts of this kind. 
 
 There is another point which requires explanation. Many of the state- 
 ments are not general, but they have or may have a general bearing. It 
 is impossible to enter these in the index as general facts, because the infer- 
 ence is made by reading as it were between the lines, and because no 
 ;eneral application was intended by the original author ; indeed, in some 
 ases, such general application is expressly excluded. One example of this 
 * seen at page 190 of Buchan's ' Handy Book' (N. 1867, B. 6). He says no 
 prediction of the weather, at least in the British Isles, can be made for 
 more than three days beforehand. Nevertheless the statement may be 
 applied to a large part, if not the whole, of the world; although, as a 
 eneral rule, Buchan's conclusions are chiefly based onfebservations in the 
 llritifeh Isles. Again, at page 107, Alluard's observation of the barometer 
 >ing at one level while falling at another, is mentioned as showing the 
 ece^sity of studying the atmosphere in vertical layers. This strictly 
 ifers only to barometric condition ; but as this condition depends on other 
 ifluences the it-mark has a much more general bearing. Care should, 
 
 153 
 
SCIENTIFIC UNION. 
 
 therefore, be taken to distinguish between the actual statements made, and 
 the broader meaning given to them by the position they occupy in these 
 notes. Points of this kind are too subtle for any index to grasp them ; and 
 generally speaking they would escape notice in the original work. 
 
 SCIENTIFIC UNION. 
 
 WE are indebted to Mr. John Hopkinson for the following account of the 
 second annual conference of the delegates from scientific societies, held at 
 York, on September 6, 1881. The undermentioned individuals were the 
 delegates present on behalf of the Societies named. 
 
 Present: Society represented: 
 
 W. WHITAKER, B.A., F.G.S. , . Norwich Geological Society. 
 
 in the Chair. 
 
 DAVID GRIEVE, F.R.S.E., F.G.S. . . Royal Physical Society of Edinburgh. 
 
 HENRY MUIRHEAD, M.D. .... Philosophical Society of Glasgow. 
 
 J. BARCLAY MURDOCH, F.S.A., Scotland . Geological Society of Glasgow. 
 
 \V. IVISON MACADAM, F.C.S., F.I.C. . . Geological Society of Edinburgh. 
 
 ISAAC ROBERTS, F.G.S. .... Liverpool Geological Society. 
 
 WILLIAM E. A. AXON, F.S.S. . . . Manchester Statistical Society. 
 
 RAPHAEL MELDOLA, F.R.A.S., F.C.S. . . Epping Forest and County of Essex Naturalists' 
 
 Field Club. 
 
 W. DENISON ROEBUCK .... Yorkshire Naturalists' Union. 
 JOHN H. GIBSON, M.D. .... Hull Literary and Philosophical Society. 
 JOHN HOPKINSON, F.L.S., F.G.S. . . -: . ) Hertfordshire Natural History Society and Field 
 H. GEORGE FORDHAM, F.G.S. . , . .\ Club. 
 
 SIR WALTER ELLIOT, K. C.S.I., LL.D., F.R.S. . Berwickshire Naturalists' Club. 
 Rev. J. MAGENS MELLO, M.A , F.G.S. . . Chesterfield and Derbyshire Institute of Mining, 
 
 Civil and Mechanical Engineers. 
 
 F. T. MOTT, F.R.G.S. . . . .,,. . . Leicester Literary and Philosophical Society. 
 Rev. JOSEPH H. THOMPSON, B.A. . . . Worcestershire Naturalists' Field Club. 
 THOMAS LISTER . . . . > , . 
 
 W. E. BRADY . . \ Barnsle y Naturalists Society. 
 
 Rev. H. H. WINWOOD, M.A., F.G.S. . . Bath Natural History and Antiquarian Field 
 
 Club. 
 W. PENGELLY, F.R.S. .... Devonshire Association for the Advancement of 
 
 Science, Literature, and Art. 
 Professor H. G. SEELEY, F.R.S. . 
 
 The Minutes of the Conference held at Swansea, August 31st, 1880, were 
 taken as read, confirmed, and signed by the Chairman. 
 
 The Keport of the Committee appointed at Swansea, consisting of 
 Mr. John Hopkinson and Mr. H. George Fordham, was read as follows: 
 " We have to report that we have issued to all the scientific societies in 
 the United Kingdom entitled to send delegates to the British Association, 
 a report of the conference at Swansea, and a circular-letter inviting these 
 societies to send delegates to the York meeting, and that in connexion with 
 154 
 
SCIENTIFIC UNION. 
 
 this we have been engaged in a considerable amount of 
 We have also to report that in order to place these conferences on a firmer 
 basis than could otherwise be done, and to meet the necessary expenditure, 
 we have proposed the appended resolution ; that this resolution has passed 
 the committees of Sections A, C, and D ; and will be brought before the 
 Committee of Eecommendations this day : ' That a committee be appointed, 
 onsisting of Sir Walter Elliot, F.E.S., Mr. H. George Fordham, Mr. John 
 FTopkinson, Mr. G. J. Symons, F.E.S., and Mr. W. Whitaker, to arrange for 
 a conference of delegates from scientific societies to be held at the annual 
 meetings of the British Association, with a view to promote the interests 
 of the societies represented by inducing them to undertake definite 
 systematic work on a uniform plan; that Mr. Fordham be the secre- 
 ary, and that the sum of 5 be placed at their disposal for the purpose. 
 < Signed) John Hopkinson, H. George Fordham." 
 
 The adoption of the Eeport was moved by Dr. Gibson, seconded by 
 VIr. Eoberts, and unanimously agreed to. 
 
 A discussion of the general objects of the Conference and its future work 
 HI sued, in which Sir Walter Elliot, Messrs. H. G. Fordham, W. E. A. Axon, 
 Thomas Lister, F. T. Mott, the Eev. J. M. Hello, and others took part. 
 
 Mr. John Hopkinson gave an account of the operations of the Hertford- 
 ;liire Natural History Society, referring especially to the large number of 
 members who were undertaking the registration of the rainfall ; the record- 
 ing of periodical natural phenomena, such as the time of flowering of plants, 
 the appearance of insects, and the arrival and departure of migratory birds ; 
 ind also the preparation of lists of the fauna and flora of the county. He 
 felt sure that if the Secretaries of Natural-History Societies generally, 
 would induce the members of their Societies to undertake such work, in 
 which all could take part, not only would science be advanced, but a 
 greatly -increased number of members would take an active and permanent 
 interest in their Society ; and to further this end he suggested the prepara- 
 tion and issue, by a committee of the Conference, of instructions to observers 
 in these and other departments of science. 
 
 Mr. H. G. Fordham suggested that the local societies might, from their 
 special local knowledge, and from the fact of their being able to obtain the 
 assistance of a great number of observers scattered over large areas of the 
 country, afford help to the committees appointed by the British Association 
 on such subjects as luminous meteors, the circulation of underground water, 
 erratic blocks, and rainfall. 
 
 Sir Walter Elliot doubted whether very much of this work could be done 
 by the local societies, but the operations sketched out by Mr. Hopkinson 
 were practicable and useful, and he had advocated similar work in Berwick- 
 shire years ago. 
 
 Mr. Axon said that the Conference would be doing a real service to 
 science if they could induce the local societies to take up such work, and 
 also utilise by systematic record the many observations that were being 
 
 155 
 
SCIENTIFIC UNION. 
 
 made throughout the country, and which at present were largely waste 
 and 
 
 Mr. Thomas Lister mentioned that as a result of last year's Conferen 
 the Barnsley Society had begun to print Transactions. 
 
 It being understood that the Committee of Recommendations would mo 
 probably not accept the resolution mentioned in the report just read, it w i 
 moved by Mr. Eoberts, seconded by the Eev. J. M. Mello, and unanimous 
 resolved : " That the gentlemen named in the resolution appended to tl v 
 report take steps to have the Conference of Delegates recognised by tl 
 Council of the British Association." 
 
 In order to meet the necessary expenses entailed by printing and issuir 
 the circulars ordered to be sent out by the Conference, it was agreed tin 
 s. be subscribed by each delegate present, and the sum of 3 10s. w; 
 handed over to the Committee. Further contributions are asked for; ai 
 may be forwarded to Mr. H. George Fordham, Odsey Grange, Royston. 
 
 A resolution was then moved by Mr. Fordham, seconded by Mr. Mott 
 and agreed to : " That it be an instruction to the Committee to send out 
 circular to the various Local Scientific Societies, pointing out the woi 
 undertaken by the Committees of the British Association, and the valuab 
 aid which may be given by these Societies in that and other scientif 
 work.'' 
 
 A vote of thanks to the Chairman closed the proceedings. 
 
 The annual conference of delegates from scientific societies is so entirely 
 in accordance with the objects which the ' Scientific Roll ' seeks to promot< 
 that we willingly give it our heartiest support, and strongly urge upon aL 
 scientific societies the advantages which would accrue to them as well as t 
 science by their sending in their adherence to it. 
 
 The discovery of laws and a foreknowledge of the progress of events in 
 to a certain extent facilitated in proportion as individual efforts are directed 
 by systems which have been adopted as the result of conference between all 
 the observers, either directly or indirectly by means of delegates. Ther 
 are many ways by which these individual efforts can be directed; but it i 
 not our intention at present to make any detailed suggestions. One of th 
 most practical of those proposed above is the issue of instructions on specia 
 questions or lines of inquiry. These instructions should in each case b 
 accompanied by a well-considered set of questions drawn up by som< 
 specialist, revised by a committee, and then amended by the person who 
 originally drew up the questions. If these sets of questions were submitted 
 to all the local societies, some useful results would be obtained. 
 
 Great advantages would be derived from the extension of the system oi 
 registering natural phenomena according to a generally adopted plan. Ab 
 an example we would refer to the rainfall system of observation organised 
 by G. J. Symons. This system, which is admirably conducted, is beyond 
 the energies of the mo-t willing worker. In the case of a few counties., 
 153 
 
SCIENTIFIC UNION. 
 
 such as Berkshire and Hertfordshire, individuals have undertaken the super- 
 intendence of the observers as well as the collection and discussion of the 
 rlata. This is a help so far, but still more help would be rendered if every 
 nmty had similar superintendence. It surely would not be a difficult 
 
 itter to organise a complete system of rainfall superintendence for every 
 )art of the British Isles. 
 
 Other branches of science could be taken up as opportunities offered ; 
 until by persistently pursuing the same plan there would be built up a 
 completely organised system of scientific observation equally adapted for 
 continuous records, and for special enquiries demanding attention for periods 
 of time of variable length. 
 
 We would also recommend the compilation of a classified directory of 
 
 icntific workers; and we should be glad to carry out the recommendation 
 by receiving the names of persons with particulars as to their special 
 scientific pursuits. If complete enough, selections from it would be pub- 
 lished. 
 
 157 
 
THE SCIENTIFIC ENQUIKEK. 
 
 Correspondence is invited on Science matters of all kinds. In all cases, 
 names and addresses should be given ; but these will not be published without the 
 writer's consent. The Conductor will not be responsible for the opinions expressed 
 by Correspondents. All communications should be addressed to the Conductor^ 
 10, Bouverie Street, London, E.G. 
 
 As no one has responded to this invitation, a few lines seem to be required to explain 
 why it has been made, and to point out what are some of the possible advantages that may 
 be derived from its acceptance. There are scores, nay, hundreds, of publications which 
 devote more or less of their space to questions and answers for the benefit of their 
 correspondents; and, therefore, it may be thought there is no need for another serial 
 having the same feature, more especially one which appears so seldom as once a quarter, 
 whereas most of the above are weekly or monthly. There is no intention here of holding 
 out any promise for the future ; but an attempt will be made to enhance the value of, 
 nd facilitate reference to, the subjects that may be dealt with in the correspondence by 
 assifying the information as opportunity occurs. In this way, there will not be so much 
 asion for the repetition of the same question, and enquirers will be able to find whether 
 .y question has been asked more readily than is at present the case, and, if the question 
 has been answered, where the information is given. It may be said that the indexes for 
 the several serials answer this purpose. But considering that these indexes generally ar 
 not drawn up on any special plan, it frequently happens that the person consulting thei 
 does not hit upon the right key-word ; and it seldom, if ever, is the case that the index* 
 are compiled in such a way that the consultor can draw a safe conclusion from what r 
 finds that the information he seeks is definitely and inferentially implied to be absent f- 
 the work. In short, the purpose aimed at is so to systematise the matter as to make tl 
 references more easy, and to apply to queries the same principles as are developed in th" 
 * Scientific Roll ' with respect to facts. At some future time attention will be given *n 
 the classification of scientific workers, with a view to facilitate intercommunication betwc 
 them. Should a plan of this kind be fairly well organised, questions will rarely fail 
 find their way to those most competent and willing to answer them. 
 
 ANNOUNCEMENTS. 
 
 The First Number of Part IT. of the ' Scientific Eoll ' will be issued in May, 1882. Thi 
 Part will deal with Aqueous Vapour. The Subscription for this Part is 2s. 6d., payabl 
 in advance to A. Ramsay. As the Value of the Part will depend largely upon its degree c 
 fulness, authors would materially aid in the work by sending copies of any papers the 
 may have written bearing on the subject of aqueous vapour in its climatic relations; or, 
 they are unable to do this, by giving references to their publications. 
 
 158 
 
INDEX. 
 
 HE Index to the present part is only a subject index. The Conductor 
 
 -ould have desired the addition of indexes of persons, places, and time ; 
 
 ut as these would occupy more space than it seems advisable to allow, he 
 .as not ventured to give them. If there should be any call for such indexes 
 ,11 attempt will be made to supply them. From the nature of the notes 
 many cannot be referred to in the index. And as regards the index its* ', 
 it is to be noticed that it is a tentative effort to base the entries on i 
 
 ibject of the papers rather than upon catchwords occurring in the titles. 
 
 lore are, doubtless, many errors and defects ; but while there is no inten- 
 
 m to make any excuse for these, still it may be observed that difficulties 
 - 1 
 
 often caused by the indefinite, or rather ill-defined, nature of the titles. 
 
 ! . ^ese difficulties are, however, just the same whether catchwords are pr 
 ,i not used. 
 
 159 
 
INDEX. 
 
 CONTRACTIONS. 
 
 Int = Introduction. E = Essay. Re = Remarks. B = Bibliography. N = Notes. The figui 
 immediately following these contractions indicate the numbers of the paragraphs in the case of t's 
 Introduction, Essays, and Remarks ; in the case of the Bibliography they denote the year ai 
 number assigned to each item ; and in the case of the notes the pages of the original. The referenc 
 to the pages of the ' Scientific Roll ' are always preceded by p. and are always placed first. 
 
 ALMOND, as test of purity of air. Garner, 
 
 p. 82, N. 
 AQUEOUS VAPOUR : 
 
 Parrot, p. 12, B. 1802, 4; 1803, 3 as 
 characteristic of different kinds of weather. 
 Ley, p. 134-137, N. changes. Ansted, p. 96, 
 N. 305 different climatic aspects of, p. 6, 
 E. I. 14. 
 
 hygrometer, value of. Buchan, p. 88, N. 3. 
 
 in connection with climate. Glock, p. 63, 
 B. 1870, 13. 
 
 influence of plants. P. 140, N. 
 
 influence on diurnal periodicity of the baro- 
 metric condition, p. 7, 8, E. I. 16 plants, 
 p. 139, 140, N. 
 
 periodicity. Bellingham, p. 81, N. 
 
 periodicity, diurnal, p. 6, E, I. 13. 
 
 tension, periodicity, p. 150, E. II. 
 
 Ireland, Antrim. "Murphy, p. 72, B. 1877, 
 19. 
 AQUEOUS VAPOUR, CLOUDS : 
 
 p. 76, B. 1880, 33. Armand, p. 53, B. 
 1861, 1. Bellani, p. 39, B. 1836, 2 ; p. 40, 
 B. 1838, 1. Forster, p. 14, B. 1823, 2. Ley, 
 p. 73, B. 1878, 43. 
 
 as characteristic of different kinds of 
 weather. Abercromby, p. 107-112, N. 
 
 influence of moon. Broun, p. 121, N. 
 
 influence of sun-spots, p. 152, E. II. 57. 
 
 periodicity, p. 150, E. II. ; p. 152, E. II. 57. 
 
 periodicity, diurnal : connection with that 
 of barometric condition, p. 7, E. I. 16; near 
 large lakes, p. 7, E. I. 15 ; in winter and 
 summer, Geneva. Plantamour, p. 7, E. I. 15. 
 Greenwich, p. 7, E. I. 15. Lucknow, p. 7, 
 E. I. 15. Natal and Maritzburg, Maun, p. 7, 
 E. I. 15. Rome, p. 7, E. 1. 15. Lake Tan- 
 ganyika, Burton, p. 7, E. I 15. 
 AQUEOUS VAPOUR, CLOUDS, 
 CIRRUS : 
 
 influence of sun-spots, p. 152, E. II, 57. 
 
 periodicity, p. 150, E. II. ; p. 152, E. II. 57. 
 AQUEOUS VAPOUR, CLOUD 
 ZONE: 
 
 periodicity, diurnal, p. 6, E. I. 15. 
 
 relation between its distribution and that 
 
 temperature vertically, p. 6, E. I. 15. 
 AQUEOUS VAPOUR, DEW. Kelly, 
 of p. 40, B. 1837, 9. 
 AQUEOUS VAPOUR, DEW-POINT : 
 
 periodicity, diurnal, p. 6, E. I. 15. 
 180 
 
 AQUEOUS VAPOUR, FOG : 
 
 as a characteristic of different kinds - 
 weather. Abercromby, p. 107-112, N. Le' 
 p. 136, N. 
 AQUEOUS VAPOUR, HOA3 
 
 FROST. Kelly, p. 40, B. 1837, 9. 
 AQUEOUS VAPOUR, HUMIDITY 
 influence of h. and electrical condition ( 
 auroras. Loomis, p. 35, 36, 37, E. II. 36. 
 periodicity, diurnal, p. 6, E. I. 14 , 
 winter and summer at Geneva. Plantamou 
 j). 7, E. I. 15 ; at Paris and in France. Flair 
 marion, p. 6, E. I. 15 ; in the Sahara, p. r , 
 E. I. 15 ; of maxynum zone of h., p. 6, E. 1. I; 
 ARAUCARIA, as test of purity of ah 
 
 p. 82, N. 
 ARBUTUS, IRISH, as test of purity c 
 
 air, p. 82, N. 
 ASTRONOMY: 
 
 application of method of least square?. 
 Freeden, p. 55, B. 1863, 13. 
 
 bibliography. Bu'chting, p. 65, B. 1872, 4. 
 in connection with currents. Wettsteiii. 
 p. 75, B. 1879, 72. 
 
 principles. Hann, Hochstetter, and Po- 
 korny, p. 66, B. 1872, 18. 
 
 science; present state. Smalley, p. 59, 
 B. 1866, 34. 
 
 ATMOSPHERE. Flammarion, p. 65, P, 
 1872, 13. 
 
 cold air resting on warm. Iselv, p. 63, B. 
 1870, 17. 
 
 halo. Norton, p. 70, B. 1875, 30. 
 AURORA: 
 
 caused bv electrical discharge, p. 35, E. II. 
 36. 
 
 dependent on electrical and hygrometric 
 conditions, ice and sun. Loomis, p. 35, 36, 
 E. II. 36. 
 
 influence of electrical condition of air, p. 148. 
 E. II. 47 ; sun, p. 33, E. II. 33 ; temperature. 
 p. 148, E. II. 47 ; wind, p. 148, E. II. 46, 47. 
 periodicity. Sabine and Wolf, p. 17, E. II. 1 
 26 day, p. 148, E. II. 46. 
 
 relation to polar ice. Chavanne, p. ">~ 
 E. II. 36 ; role of ice in, p. 36, E. II. 36. 
 AVES : species for phenological observation. 
 
 Newton, p. 70, B. 1875, 29; B. 1875, 54. 
 BAROMETRIC CONDITION, p. 53 
 B. 1861, 5 ; 1861, 6 } p. 57, B. 1865, 10 f p. 76, 
 B. 1881, 33. 
 
BAROMETRIC CONDITION contd. 
 
 as a characteristic of different kinds 
 of weather. Abercromby, p. 108-112, X. 
 Ley, p 1134-137, X. 
 
 at different heights. Allinrd, p. 107, X. 
 
 barometer discovered by Torricelli. 
 Buchan, ]>. 88, X. 3. 
 
 changes. Ansted, p. 96, X. 305 large 
 extent of area affected. Buchan, p. 90, X. 
 1(35. Thomson, p. 118, 119, X. 
 
 connection with colliery explosions. 
 Scott and Gallowav, p. 100, N. wind ; p. 8, 
 E. I. 17. 
 
 dynamical theory wanted. Murphy, 
 p. 100, X. 
 
 guide by Fitz Roy. Forbes, p. 82, X. 
 
 high and low areas, connection. Aber- 
 cromby, p. 115. 
 
 influence of moon; Cotte, p. 11, 12, B. 
 1802, 2. Zenger, p. 94, X moon and sun ; 
 p. 14-7, E. II. 43 rain ; Hann, p (58, B. 1874, 
 5 sun, p. 145, E. 11, 38 sun spots; p. 151, 
 E. II. 55 Strachan, p. 131, X. India ; Archi- 
 bald, p. 125, X. 
 
 observations, ,. 45, B. 1849, 9 in Oct. 
 and Xov. 1864 and weather. Glaisher, p. 57, 
 ;. 1865, 21 method ot recording. Mascart, 
 p. 74, B. 1879, 37 ; p. 76, B. 1880, 15. 
 
 periodicity, p. 150, E. II. ; p. 151, E. II. 
 55. Dove, p. 38, B. 1832, 6. Strachey, p. 
 10(3, X. diurnal. Abercromby, p. 113, 114, 
 117, 120, X. connection with that of clouds ; 
 p. 7, E. I. 16 with those of temperature and 
 aqueous vapour ; p. 7,8, E. I. 16 distribu- 
 tion of amplitudes ; p. 8, E. I. 16 method of 
 measuring amount of variation. Abercromby, 
 p. 120, 121, X. at Greenwich. Ellis, p. 8, 
 E. I. 16. Habana, p. 8, E. I. 16. Leh, p. 8, 
 E. I. 16 Oxford. Rumiell, p. 8, E. I. 16. 
 Valentia, E. I. 16 double diurnal, on equa- 
 tor ; p. 7, E. I. 16 probable causes thereof; 
 p. 8, E. I. 16 maximum : influence of clouds. 
 Abercromby, p. 116, X. minimum: influence 
 of sea. Abercromby, p. 116, X. of seasons. 
 Abercromby, p. 116, X. of wind. Aber- 
 cromby, p. 116, X. 26 day; p. 145, E. II. 38 ; 
 p. 146, E. II. 41. 
 
 relation of pressure in tropics to sun 
 spots. Chambers, p. 33, E. II. 32. 
 
 weather accompanying low barometer. 
 Hailstone, p. 14, B. 1822, 5. 
 
 Antarctic regions. Maury, p. 53, B. 
 1861, 22 Atlantic; p. 66, B. 1872, 56. 
 Symons, p. 66, B. 1872, 52 England, Mid- 
 dlesex, London ; p. 76, B. 1880, 30 Europe. 
 Loomis, p. 73, B. 1878, 18 United States; 
 p. 76, B. 1880, 33. Loomis, p. 73, B. 1878, 
 18. 
 
 BIRDS. See Aves. 
 CEDAR, common and deodara, as tests of 
 
 purity of air, p. 82, X. 
 CITATIONS, acknowledgment deferred, 
 
 p. 1, Int. 7. 
 CLIMATE : 
 
 abnormal meteorology defined. Steven- 
 son, p. 104, X. 
 
 advantages of study. Zantedeschi 
 p. 59, B. 1866, 40. 
 
 PART I. Xo. 6. i 
 
 CLIMATE continued. 
 
 atmosphere, treated as distinct from 
 climate, p. 10, lie. 
 
 application of balloons. Fonvielle arrl 
 Tissandier, p. 62, B. 1869, 14. Valz, p. 4.">, 
 B. 1850, 18 electricity. Dumoncel, p. 47, 
 B. 1853, 5 method of least squares. Freeden, 
 p. 55, B. 1863, 13 physics. Rawson, p. 44, 
 B. 1848, 9 telegraph ; p. 69, B. 1874, 29 ; 
 p. 73, B. 1878, 22 ; p. 107, X. ; p. 138, N. ; 
 Abbe, p. 64, B. 1871, 1; p. 65, B. 1872, 1. 
 Beardmore, p. 81, X. 3. Boguslawski, p. 6<S, 
 B. 1874, 2. Buys-Ballot, p. 45, B. 1849, 2. 
 Dumas, p. 85, X. Fitz Roy, p. 54, B. 1862, 7. 
 Jelinek, p. 60, B. 1867, 32. Leverrier, p. 85, 
 X. Locke, p. 54, B. 1862, 16. Matteucci, 
 p. 85, X. Maury, p. 99, X. Meldrum, p. 83, 
 X. 65. Mohn, p. 69, B. 1874, 31. Xeumayer, 
 p. 70, B. 1875, 28. Scott, p. 101, X. Tarry, 
 p. 73, B. 1878, o9. Tayler, p. 76, B. 1880, 24. 
 Zantedeschi, p. 58, B. 1865, 44; B. 1865, 45 
 telegraphy by Fitz Roy. Beardmore, p. 81, 
 X. 4 by Leverrier. Beardmore, p. 81 , X. 3 
 to agriculture Schiiltz, p. 75, B. 1879, 67 
 to navigation. Galton, p. 67, B. 1878, 12. 
 
 Aristotle's opinions. Grellois p. 56, B. 
 1864, 13. 
 
 astro-meteorology. Schneider, p. 56, 
 B. 1864, 31. 
 
 bibliography, p. 73, B. 1878, 42. 
 Biichting, p. 65, B. 1872, 4. Grellois, p. 56, 
 B. 1864, 12; p. 57, B. 1865, 22 general 
 14851830. Ramsay, p. 76, B. 1880, 21 
 18311881. Ramsay, p. 77, B. 1881, 10. 
 
 calendar. Forster, p. 14, B. 1823, 2. 
 
 causes. Ansted, p. 94, X. 287. Hender- 
 son, p. 56, B. 1864, 15. Maclaren, p. 78, N. 
 cosmical, p. 147, 148, E. II. 46. Broun, p. 72, 
 B. 1878, 2. Faye, p. 72, B. 1878, 10. 
 
 changes. Ansted, p. 96, X. 305. Croll, 
 p. 69, B. 1875, 1. Dufour, p. 63, B. 1870, 
 12; p. 64, B. 1871, 15. Gronau, p. 12, B. 
 1803, 1. Peacock, p. 65, B. 1871,36. Smyth, 
 p. 50, B. 1856, 9 causes. Croll, p. 56, H. 
 1864, 6. Henderson, p. 57, B. 1865, 24. 
 Predieri, p. 62, B. 1869, 38; p. 64, B. 1870, 
 36. Ritter, p. 56, B. 1864, 29 caused by 
 changes of earth's surface. Ansted, p. 95, X. 
 301 by cosmical influences. Davidson, p. 65, 
 B. 1872, 6 by excentricity of earth's orbit. 
 Haughton, p. 58, B. 1866, 16 in high stations; 
 p. 132, 133, X. secular. Ansted, p. 98, X. 
 311 secular: influence of ocean currents. 
 Croll, p. 63, B. 1870, 9. 
 
 chronology. Pistolesi, p. 47, B. 1853, 
 12. 
 
 classification. Stevenson, p. 104, 105, X. 
 
 coincidences. Alexander, p. 45, B. 
 1851, 1. 
 
 complexity. Ansted, p. 94, X. 287. 
 
 connection with Agriculture, p. 77, 
 B. 1880, 42. Bernard, p. 46, B. 1852, 2. 
 Bruhns, p. 76, B. 1880, 2. Buchan, p. 82, X. 
 Cantoni, p. 73, B. 1879, 8 ; p. 76, B. 1880, 5, 
 Daniell, p. 15, B. 1826, 3. Forbes, p. 82, X. 
 Hann, p. 74, B. 1879, 20. Henry, p. 51. 
 B. 1858, 15. Hombres, p. 43, B. 1844, 7. 
 Hoskins, p. 49, B. 1855, 5. Johnston, p. 45, 
 
 161 
 
INDEX. 
 
 CLIMATE connection with contd. 
 B. 1849, 6. Liburnau, p. 74, B. 1879, 29. 
 Lorenz, p. 74, B. 1879, 33. Lorenz and Rothe, 
 p. 69, B. 1874, 11. Marie-Davy, p. 76, 
 B. 1880, 14. Oborny, p. 73, B. 1878, 33, 
 Poiriau, p. 54, B. 1862, 23. Porrp, p. 76, 
 B. 1880, 18. Prestel, p. 57, B. 1865, 37. 
 Simony, p. 64, B. 1870, 41. Spooner, p. 75, 
 B. 1879, 70. Animals: Poey, p. 51, B. 1858, 
 21. Aqueous vapour: Clock, p. 63, B. 1870, 
 13. Astronomical phenomena : Granday, p. 55, 
 B. 1863, 17. Murphy, p. 40, B. 1836, 11. 
 Audibility : Voigt, p. 11, B. 1799, 5. Auroras : 
 Ellery, p. 68, B. 1874, 4. Arctic Regions, 
 1826,7. Beechey's Observations : Ainsworth, 
 p. 78, N. Barometric changes: Skey, p. 64, 
 B. 1870, 42. Cholera: Moffat, p. 61, B. 1868, 
 28. Thomson, p. 49, B. 1855, 20: p. 50, B. 
 1856, 10. Colliery explosions: Scott and Gal- 
 loway, p. 66, B. 1872, 49 ; p. 68, B. 1873, 53 ; 
 p. 100, N. Colliery explosions: 1872: Scott 
 and Galloway, p. 70, B. 1875, 40. Comets: 
 Granday, p. 56, B. 1864, 11. Currents : Wett- 
 stein, p. 75, B. 1879, 72. Death-rate : Cator, 
 p. 59, B. 1867, 9. Diseases : Parkin, p. 76, 
 B. 1880, 17. Earthquakes: Buckland and 
 Milne, p. 43, B. 1844, 1. Mann, p. 62, B. 
 1869, 19. Earth's perihelion distance: Jenkins, 
 p. 76, B. 1880, 8. Electrical 'condition : Fournet, 
 p. 59, B. 1867, 21. Famine in India: Buchan, 
 p. 71, B. 1877, 3. Login, p. 69, B. 1874, 10. 
 Forestry : p. 77, B. 1880, 42. Geographical 
 distribution: Murphy, p. 40, B. 1836, 11. 
 Glaciers: Sonklar, p. 51, B. 1858, 28; p. 52, 
 B. 1859, 16 Health : Scoresby-Jackson, p. 59, 
 B. 1866, 33. Hop crop : Doggett, p. 62, B. 
 1869, 10. Horticulture: Daniell, p. 16, B. 
 1829, 2. Hypsometry: Williamson, p. 61, B. 
 
 1868, 42. Indrustry: Lovelace, p. 40, B. 
 1838, 7. Magnetism : Buchan, p. 90, N. 180, 
 Chacornac, p. 59, B. 1867, 10. Zantedeschi. 
 p: 59, B. 1866, 39. Medicine : Foissac, p. 47, 
 B. 1854, 4. Harless, p. 40, B. 1836, 8. Hos- 
 kins, p. 49, B. 1855, 5. Mitchell, p. 62, B. 
 
 1869, 33. Predieri, p. 47, B. 1854, 11. 
 Scoresby-Jacksou, p. 84, N. 25. Meteors : 
 Coulvier-Gravier, p. 59, B. 1867, 12. Denza, 
 p. 59, B. 1867, 16. Quetelet, p. 60, B. 1867, 
 53. Periodic changes of level of land: Gunn, 
 p. 61, B. 1868, 14. Planetary movements: 
 Silbermann, p. 66, B. 1872,50. Plants: Can- 
 toni, p. 58, B. 1866, 7. Goppert, p. 65, 66, 
 B. 1872, 15. Grisebach, p. 66, B. 1872, 16. 
 Poey, p. 51, B. 1858, 21. Plant distribution : 
 Hind, p. 42, B. 1842, 10. Plant life: p. 68, 
 B. 1873, 63. Political economy: Scoresby- 
 Jackson, p. 84, N. 25. Population and wheat 
 returns in France : Becquerel, p. 58, B. 
 1866, 1. Salt: Rogers, p. 45, B. 1850, 16; 
 p. 56, B. 1864, 30. Scarlatina : Vernon, p. 53, 
 B. 1861, 35. Scintillation: Montigny, p. 103, 
 N. 562. Seasons : Murphy, p. 40, B. 1836, 11. 
 Soil water: Nowak, p. 59, B. 1866, 31. 
 Solar physics: Thompson, p. 65, B. 1871, 46. 
 Springs: temperature. Renou, p. 61, B. 
 1868, 35. Sun : p. 72, B. 1877, 22. Archibald, 
 p. 77, B. 1881, 1. Sun-spots : p. 72, B. 1877, 
 38 ; A. p. 94, N. Archibald, p. 72, B. 1878, 1. 
 
 162 
 
 CLIMATE connection with contd. 
 Fritz, p. 74, B. 1879, 18. Temperature decrease 
 with height and other elements : Baxendell, 
 p. 1865, 2. Terrestrial magnetism : Forssmann, 
 p. 67. B. 1873, 8. Hirsch, p. 55, B. 1863, 18. 
 Riese, p. 54, B. 1862, 27. Secchi, p. 53, B. 
 1861, 32 ; p. 54, B. 1862, 31 ; B. 1862, 32 ; 
 p. 55, B. 1863, 34 ; B. 1863, 35 ; p. 56, B. 
 1864, 32 ; p. 57, B. 1865, 39. Stewart, 
 p. 105, N. Zantedeschi, p. 54, B. 1862, 36. 
 Volcanoes: Silbermann, p. 66, B. 1872, 51. 
 Water : physical properties. Hennessy, p. 60, 
 B. 1867, 26. Weather: Murphy, p. 40, B! 
 1836, 11. Wheat price : Cator, p. 59, B. 1867, 
 9 wind. Hann, p. 63, B. 1870, 14; p. 64, 
 B. 1871, 19. 
 
 contributions. Loomis,p. 71, B. 1876,7; 
 p. 72, B. 1877, 10 ; p. 73, B. 1878, 18 ; p. 74, 
 B. 1879, 31; p. 76, B. 1880, 11; p. 103, 
 N. 143. 
 
 correlation of elements, Strachan, p. 131, 
 N. ; phenomena, Sanno-Solaro, p. 66, B. 1872, 
 48. 
 
 curves. Blanford, p. 64, B. 1871, 5. 
 Fournet, p. 58, B. 1866, 13. Symons, p. 142 r 
 N. Waterston, p. 45, B. 1850, 19. 
 
 data for 1878. De la Rue, p. 71, B. 1877, 
 5. 
 
 diagrams by Flammarion. Barrett, p. 
 100, N. 
 
 disturbances, motion from W. to E. 
 Beardmore, p. 81, N. 4. 
 
 fall of Aerolites, Caribber, p. 63, B. 1870 r 
 7. Gilbert, p. 13, B. 1815, 2 ash. Leps, p. 44 r 
 B. 1847, 8 blood. Homer, p. 13, B. 1814, 1 
 dust. Armand, p. 53, B. 1861, 1, Ehren- 
 berg, p. 44, B. 1847, 5 ; p. 46, B. 1851, 8. 
 Tarry, p. 64, B. 1870, 45 earth. Fougeron, 
 p. 16, B. 1830, 5. Fouriiet, p. 44, B. 1864, 
 12 fishes. Caribber, p. 63, B. 1870, 7. 
 Castlenau, p. 53, B. 1861, 12. Gilbert, p. 13, 
 B. 1815, 2, S. p. 39, B. 1834, 19 fro^s. 
 Chassay, p. 40, B. 1838, 3. Dumeril, p. 52. 
 B. 1860, 5. Duparcque, p. 39, B. 1834, 4. 
 Gilbert, p. 13, B. 1815, 2. Huard, p. 3!i r 
 B. 1834, 9. Jobard, p. 50, B. 1857, 14, 
 Labat, p. 39, B. 1834, 11. Peltier, p. o9, 
 B. 1834, 17. Ponton, p. 40, B. 183(3, 12. 
 Zirkel, p. 39, B. 1834, 22 grain. Goppert, 
 p. 38, B. 1831, 5. Sykes, p. 41, B. 1840, 19 
 insects. Caribber, p. 63, B. 1870, 7 iron. 
 Gilbert, p. 13. B. 1815, 2 jelly. Arago, 
 p. 14, B. 1821, 1 larva?. Heer, p. 49, B. 
 1856, 2 lizards. Caribber, p. 63, B. 1870, 7 
 manna. Colaprete, p. 44, B. 1846, 4 ; p. 45. 
 B, 1849, 3 rain (black). Mease, p, 47, B. 
 1854, 8 rain (red). Caribber, p. 63, B. 
 1870, 7. Ehrenberg, p. 44, B. 1847, 5 ; p. 4, 
 B. 1851, 8. Tarry, p. 64, B. 1870, 45 sand. 
 Bellucci, p. 65, B. 1872, 2 ; B. 1872, 3. Carib- 
 ber, p. 63, B. 1870, 7 snails ; p. 14, B. 1821. 
 8_snow (red). Caribber, p. 63, B. 1870, 7 
 soot. Caribber, p. 63, B. 1870, 7 strange 
 objects. Caribber, p. 64, B. 1871, 8 sugar. 
 Delavand, p. 51, B. 1858, 9 sulphur. Gop 
 pert, p. 38, B. 1831, 5. 
 
 government grant, p. 72, B. 1877, 36. 
 Zeta, B. 1877, 27. 
 
INDEX. 
 
 CLIMATE continued. 
 
 gradients. Stevenson, p. 68, B. 1873, 55 ; 
 p. 101, N. 
 
 importance of deviations from mean. 
 Buys-Ballot, p. 45, B. 1850, 4. 
 
 indications afforded by animals and 
 plants. Gutch, p, 42, B. 1842, 7. 
 
 influence of aqueous vapour. Monck, 
 p. 65, B. 1871, 34 change in axis of earth's 
 rotation ; p. 45, B. 1849, 7 eclipse. Weld, 
 p. 72, B. 1877, 25 eclipse of sun. Glaisher, 
 - p. 51, B. 1858, 12. Fritsch, p. 59, B. 1867, 23. 
 Lowe, p. 52, B. 1859, 17 ether. Wilcocks, 
 p. 58, B. 1865, 43 ; p. 63, B. 1869, 46 ex- 
 cess of radiation in S. hemisphere. Croll, 
 p. 62, B. 1869, 4- forces on earth's surface. 
 Hennessy, p. 45, B. 1850, 9 gulf streams ; 
 p. 143, 'N. hills. Ansted, p. 94, N. 103 
 land. Howorth, p. 99, N. land and water. 
 Hennessy, p. 51, B. 1859, 10 light. Poey, 
 p. 49, B. 1855, 14 locality. Kitter, p. 49, 
 B. 1855, 16. Smyth, p. 49, B. 1855, 18 
 man. Ansted, p. 95, N. 302. Somerville, 
 p. 99, N. 526 moon ; p. 12, B. 1808, 2 ; 1809, 
 7; p. 61, B. 1868, 17; p. 63, B. 1869, 48. 
 Alexander, p. 78, N. Arago, p. 38, B. 1833, 
 1. Beale, p. 46, B. 1852, 1. Bezard de 
 Wouves, p. 63, B, 1870, 5. Bouvard, p. 38, 
 B. 1834, 1 ; p. 39, B. 1836. 3. Breton, p. 56, 
 B. 1864, 3. Broun, p. 121, N. Brumham, 
 p. 62, B. 1869, 3. Buchan, p. 91, N. 331. 
 Casoiii, p. 53, B. 1861, 10; p. 54, B. 1862, 5. 
 Clos, p. 53, B. 1861, 13. Cotte, p. 11, 12, 
 B. 1802, 2. Crum, p. 43, B. 1844, 2. Eisen- 
 lohr, p. 38, B. 1833, 5. Emerson, p. 39, B. 
 1835,4. Everest, p. 40, B. 1836, 6. Fonvielle, 
 p. 55, B. 1863, 11. Frisi, p. 12, B. 1804, 4. 
 Gilpin, p. 47, B. 1854, 6. Guillaume, p. 15, 
 B. 1827, 6. Klein, p. 62, B. 1869, 18. Kreil, 
 p. 42, B. 1842, 11. La Cour, p. 43, B. 1844, 9. 
 Lamarck, p. 11, B. 1797, 1 ; 1800, 3. La Place, 
 p. 14, B. 1823, 3 ; p. 15, B. 1826, 9. Madler, 
 p. 40, B. 1837, 12. Marcet, p. 39, B. 1834, 12 ; 
 1835, 7 ; p. 52, B. 1860, 16. Marchand, p. 67, 
 B. 1873, 25. Marguet, p. 63, B. 1870, 22. 
 Middleton, p. 46, B. 1852, 15. Schiibler, 
 p. 38, B. 1832, 8; 1832, 10. Somerville, 
 p. 98, N. 309. Streintz, p. 65, B. 1871, 44. 
 Verdier, p. 61, B. 1868, 40. Webb, p. 64, 
 ' B. 1870, 48. Zenger, p. 61, B. 1868, 43. 
 mountains, Eng. Cyclo, p. 79, N. obliquity 
 of ecliptic. Croll, p. 59, B. 1867, 13 ; B. 
 1867, 14. Moore, p. 60, B. 1867, 49 ; 1867, 50 
 ocean currents. Ansted, p. 94, N. 150. 
 Mahlmann, p. 41, B. 1840, 10 physical con- 
 ditions; p. 63, B. 1870, 15 plains (high and 
 low). Ansted, p.' 94, N. Ill planets. Ger- 
 dum, p. 14, B. 1818, 1 plants ; p. 140, N. 
 Balfour, p. 45, B. 1851, 2. Woodhouse, p. 12, 
 B. 1802, 5; 1803, 4 plants : cultivation. 
 Kelly, p. 40, B. 1837, 9. Miiller, p. 49, 
 B. 1855, 12 plants: deforesting. Lange, 
 p. 40, B. 1837, 10 plants : forests. Becquerel, 
 p. 58, B. 1866, 2 ; p. 62, B. 1869, 1 ; p. 85, N. 
 - Berber, p. 57, B. 1865, 4. Clarke, p. 39, B. 
 1835, 1. Fautrat, p. 102, N. Fritzsch, p. 59, 
 B. 1867, 22. Klippart, p. 52, B. 1860, 14. 
 Lijffelholz-Colberg, p. 66, B. 1872, 26. Lorenz, 
 
 M 2 
 
 CLIMATE influence of continued. 
 p. 74, B. 1879, 32. Maistre, p. 58, B. 1866, 
 20 ; p. 70, B. 1875, 9. Parish, p. 45, B. 1849, 
 8. Schomburgk, p. 64, B. 1870, 40 forests : 
 Australia. Clarke, p. 71, B. 1877, 4 plants : 
 trees. Elsden, p. 139, N. polar ocean. 
 Miihry, p. 56, B. 1864, 25. Z. p. 14, B. 
 1818, 4 railroad and telegraphic lines. 
 Delalonde, p. 52, B. 1860, 3 snow. Woei- 
 koff, p. 65, B. 1871, 47 sun. Archibald, 
 p. 17-37 ; 145-152, E. II. ; p. 121, N. Beard- 
 more, p. 81, N. 3. Brumham, p. 62, B. 1869, 
 3. Chambers, p. 125, N. M. R. I. A., p. 139, 
 N. N., p. 68, B. 1873, 41. Nature, p. 124, 
 N. 63. Somerville, p. 98, N. 308, 309. 
 Stewart, p. 105, N. ; p. 141, N. sun's rota- 
 tion. Buys-Ballot, p. 51, B. 1858, 8 sun- 
 spots. Buchan, p. 104, N. sun (non-influence 
 of). Crichton, p: 15, B. 1825, 5; 1825,6; 
 1826, 2 sun and moon ; p. 147, E. II. 44 
 water : physical properties. Hennessy, p. 102, 
 N. 
 
 influence on animals. Becquerel, p. 50, 
 51, B. 1858, 3. Somerville, p. 98, N. 33 
 insects. Verloren, p. 55, B. 1863, 37 man. 
 Deville, p. 62, B. 1869, 7 ; p. 63, B. 1870, 11. 
 Foissac, p. 47, B. 1854, 4. Forbes, p. 82, N. 
 Rattray, p. 64, B. 1870, 38; p. 65, B. 1871, 
 40; p. 66, B. 1872,45; p. 68, B. 1873,45. 
 Seguin, p. 13, B. 1814, 2. Smith, p. 53, B. 
 1861, 33 ; p. 54, B. 1862, 34. Swaving, p. 
 43, B. 1844, 14. Vigazza-Rascalla, p. 47, B. 
 1853, 17. Young, p. 13, B. 1813, 1 man : 
 civilisation ; p. 76, B. 1880, 28 man : death- 
 rate. Baker, p. 125, 126, N. Baxendell, 
 p. 63, B. 1870, 4 ; p. 64, B. 1871, 4. Buchan, 
 p. 89, N. 75 death-rate : Australia, p. 78, B. 
 1879, 78 man : development. Foissac, p. 61, 
 B. 1868, 11 man: diseases. Baker, p. 126, 
 N. Clark, p. 16, B. 1830, 3. Haller, p. 52, 
 B. 1860, 10. Haviland, p. 49, B. 1855, 4. 
 Holland, p. 41, B. 1840, 8. Ransome and 
 Vernon, p. 54, B. 1862, 25. Reuss, p. 13, B. 
 1817, 3. Robertson, p. 49, B. 1856, 7. Roche, 
 p. 49, B. 1855, 17. Scoresby-Jackson, p. 55, 
 B. 1863, 33 man : diseases : consumption. 
 Williams, p. 72, B. 1877, 26 man : diseases : 
 method of inquiry. Baker, p. 126, N. man : 
 diseases : pulmonary. Marcet, p, 76, B. 1880, 
 13 man ; female puberty. Robertson, p. 43, 
 B. 1844, 11 man : health. Ballard, p. 59, 
 B. 1867, 3 ; p. 64, B. 1871, 3. Bailey, p. 54, 
 B. 1862, 2 ; p. 55, B. 1863, 1 ; p. 56, B. 1864, 
 1. Foissac, p. 61, B. 1868, 11. Lombard, 
 p. 58, B. 1866, 19. Suard, p. 54, B. 1862, 35. 
 Taylor, p. 71, B. 1875, 47. Williams, p. 105. 
 106, N. Wilson, p. 76, B. 1880, 26 man : 
 health : local. Predieri, p. 45, B. 1850, 12 
 man: morals. Foissac, p. 61, B. 1868, 11 
 man : states. Oczapowsky, p. 69, B. 1874, 36 
 man : states and nations. Kohl, p. 70, B. 
 1875, 6 man : temperature of body. Rey- 
 naud, p. 16, B. 1830, 9 man : urinary system. 
 Smith, p. 53, B. 1861, 33 ; p, 54, B. 1862, 3 I 
 organisms. Jorden, p. 52, B. 1859, 14 
 organisms : distribution. Somerville, p. 98,. 
 99 plants ; p. 139, 14<, N. Becquerel, p. 50, 
 51, B. 1858, 3. De Candolle, p. 65, B. 1872, 
 
 163 
 
INDEX. 
 
 CLIMATE influence on continued. 
 7 ; B. 1872, 8. Kerner, p. 62, B. 1869, 17; 
 p. 63, B. 1870, 20. Russell, p. 52, B. 1859, 21. 
 Sagot, p. 54, B. 1862, 28. Schuppli, p. 55, 
 B. 1863, 32. Seywald, p. 47, B. 1854, 14. 
 Somerville, p. 98, N. 33. Willetscheck, p. 43, 
 B. 1845, 16 plants : corn. Ballard, p. 138, 
 N. plants : crops and health. Buchan, p. 58, 
 B. 1866, 5 plants : distribution. Buhse, 
 p. 59, B. 1867, 7 plants : fruit trees. Chatin, 
 p. 64, B. 1871, 10 plants: mulberries. 
 Fournet, p. 47, B. 1854, 5 plants : resinous 
 trees. Beketoff, p. 62, B. 1869, 2 plants : 
 vine. p. 12, B. 1805, 5. Chatin, p. 50, B. 
 1857, 5. Villeneuve, p. 50, B. 1857, 28 
 plants : wheat crop. Babbage, p. 63, B. 1870, 
 3 sheep. Tanner, p. 62, 62, B. 1869, 42 
 sheep's wool an 1 goats' hair. Roder, p. 55, B. 
 
 1863, 30 silkworms. Drian, p. 59, B. 1867, 
 19. Robinet, p. 45, B. 1850, 15. 
 
 influence of mountain climate on 
 man ; health. Lombard, p. 49, B. 1856, 3 ; 
 p. 50, B. 1857, 17 ; p. 51, B. 1858, 17. 
 
 influence of tropical climate on 
 man. Martin, p. 72, B. 1877, 14 man : 
 health, p. 54, B. 1862, 8. Gaston, p. 56, B. 
 
 1864, 9 plants of temperate regions. Sagot, 
 p. 55, B. 1863, 31. Schomburgk, p. 47, B. 
 1853, 14. 
 
 instruments: descriptions excluded from 
 this section, except when they bear upon read- 
 ings, p. 10, Re. lent to ships. Forbes, p. 82, N. 
 
 isobarometric lines (monthly), the 
 master-key to enquiry. Buchan, p. 91, N. 
 43. 
 
 law of evolution. Poey, p. 65, B. 1871, 
 37. 
 
 literature, p. 50, B. 1856, 14; p. 69, B. 
 1874, 19 Berigny, p. 57, B. 1865, 5 Buchan, 
 p. 88, N. Duprez, p. 165, B. 1872, 10. Fer- 
 rari, p. 74, B. 1879, 14, Hann, p. 66, B. 1872, 
 19; p. 69, B. 1874, 6; p. 71, B. 1876, 5. 
 Klein, p. 75, B. 1879, 50. 
 
 local diiferences. Ansted, p. 95, N. 299, 
 p. 96, N. 304. Scott, p. 128, N. Stevenson, 
 p. 105, N. 
 
 maps, p. 69, B. 1874, 16 ; p. 72, B. 1877, 
 
 15. Cotta and Muller, p. 68, B. 1874, 3. Galton, 
 p. 53, B. 1861, 18 ; p. 55, B. 1863, 15. Kuy- 
 per, p. 69, B. 1874, 9. Locke, p. 54, B. 1862, 
 
 16. Posthumus and Kan, p. 69, B. 1874, 37. 
 Rubenson, p. 70, B. 1875, 35 ; maps, daily, 
 p. 66, B. 1872, 32. 
 
 maps : synchronous : use for sea areas. 
 Harding, p. 143, N. 
 
 maps: synoptic. Abercromby, p. 114- 
 120. Brault, p. 73, B. 1879, 4. Buchan, p. 90, 
 N. 140, 16n. Hoftmeyer and Neumayer, p. 72, 
 73, B. 1878, 14. 
 
 method of investigation, synoptic or 
 specific. Abercromby, p. 118, N. 
 
 meteor term defined. Grellois, p. 54, 
 B. 1862, 11. 
 
 meteorograph. Baumhauer, p. 68, B. 
 1874, 1. (Rysselberghe's) Gloeersen, p. 67, B. 
 1873, 14. Hall, p. 66, B. 1872, 17, p. 99, N. 
 M aury (Hough's), p. 99, N. 430. R. (Theorell's), 
 r . 99, N. 
 164 
 
 JLIMATE continued. 
 
 meteorography, universal system. Rys 
 selberghe, p. 70, B. 1875, 38. 
 
 meteorological committee, p. 54, B 
 1862, 18; p. 63, B. 1870, 27 ; p. 65, B. 1871 
 31 ; p. 66, B. 1872, 34; p. 67, B. 1873, 33 
 p. 69, B. 1874, 23 ; p. 70, B. 1875, 22 ; p. 71 
 B. 1876, 23. Willis, p. 82, N. Kew Com 
 mittee, p. 68, B. 1873, 69. Meteorologica 
 council, Nature, p. 106, N. Stevenson, p. 7 1 
 B. 1876, 13 ; p. 72, B. 1877, 39 ; p. 77, B 
 1881, 6. 
 
 meteorological conference at Brus- 
 sels, p. 46, 47, B. 1853, 3. Meldrum, p. 83 
 N. 64. Quetelet, p. 47, B. 1853, 13 ; B. 1854 
 12 maritime, p. 69, B. 1874, 13; p. 70, B 
 1875, 12. Mann, p. 70, B. 1875, 10 a' 
 Sydney, p. 74, B. 1879, 39 ; p. 76, B. 1880, 31 
 
 meteorological congress : Berne, p. 76 
 B. 1880, 32. Leipzig, p. 66, B. 1872, 28 
 p. 67, B. 1873, 28 ; p. 68, B. 1873, 64. Scott 
 p. 68, B. 1873, 48. London, p. 71, B. 1876, 8 
 Paris, p. 74, B. 1879, 40. Denza, p. 74, P, 
 1879, 10. Rome, p. 71, B. 1879, 41-43, 45 
 p. 75, B. 1879, 76. Blanford, p. 73, B. 1879 
 3. Bruhns, p. 73, B. 1879, 5. Depretis, p. 74 
 B. 1879, 11. Ebermayer, p. 74, B. 1879, 12 
 Hellmann, p. 74, B. 1879, 22. Mohn, p. 73 
 B. 1878, 30. Fernet, p. 76, B. 1879, 61 
 Pittei, p. 75, B. 1879, 62 ; B. 1879, 63. Scott 
 p. 133, N. Wild, p. 73, B. 1878, 41 ; p. 7"> 
 B. 1879, 73. Utrecht, p. 74, B. 1879, 44 
 Vienna, p. 67, B. 1873, 27 ; P. 68, B. 1873 
 65 ; p. 69, B. 1874, 14 ; p. 70, B. 1875, Hi 
 14 ; p. 73, B. 1878, 22 ; p. 76, B. 1880, 22 
 B. 1880, 32. Nature, p. 101, N. ; p. 103, N 
 Plantamour, p. 68, B. 1873. 42. Quetelet 
 p. 68, B. 1873, 43. Rikatcheff, p. 68, B. 187S 
 46. Scott, p. 69, B. 1874, 3. 
 
 meteorological department of Boan 
 of Trade, p. 58, B. 1866, 3. 
 
 meteorological institute (iuterna 
 tional). Koppen, p. 67, B. 1873, 20. (Nor 
 wegian.) Mohn, p. 62, B. 1869, 34. 
 
 meteorological papers. Board o 
 Trade, p. 50, B. 1857, 2; B. 1857, 3- 
 reports. Buys-Ballot, p. 72, B. 1878, ': 
 Espy, p. 44, B. 1846, 10 ; p. 45, B. 1850. G 
 p. 46, B. 1852, 8 ; p. 50, B. 1857, 7 (Espy' 
 fourth report). Forbes, p. 82, N. Hooppei 
 and Wheeler, p. 66, B. 1872, 20. Kreil,p.4t 
 B. 1852, 12 treasury report. Stewart, \ 
 102, N. 
 
 meteorological poles, shifting of 
 Woeikoff, p. 64, B. 1870, 40. 
 
 meteorological society. Beardmon 
 p. 81, N. Symons, p. 142, N. lectures, p. Ta 
 B. 1878, 43 reports, p. 46, B. 1851, 11 ; I 
 1852, 14 ; p. 47, B. 1854, 9 ; p. 49, B. 185; 
 9 ; p. 50, B. 1857, 18 ; p. 51, B. 1858, 18 
 p. 52, B. 1859, 18 ; B. 1860, 18 ; p. 53, I 
 1861, 23. 
 
 meteorological society, Mauritius 
 Meldrum, p. 83, 84, N. 
 
 meteorological society (Scottish 
 address, p. 49, B. 1856, 6 ; p. 50, B. 1857, 2( 
 
 meteorological societies. Buchar 
 p. 88, N. 
 
INDEX. 
 
 CLIMATE continued. 
 
 meteorology, term defined. Buchan, 
 p. 91, N. 1. Eng. Cyclo. p. 79, N. Mann, 
 p. 127, N. Scott, p. 128, N. normal, defined. 
 Stevenson, p. 104, .N. 
 
 notes. Lancaster, p. 74, B. 1879, 28. 
 Sargeaunt, p. 70, B. 1875, 37. 
 
 observations, p. 63, B. 1870, 25 ; p. 66, 
 07, B. 1872, 57 ; p. 71, B. 1875, 55 in 1839, 
 ].. 41, B. 1839, 11 in 1855, p. 51, B. 1858, 
 :U in 1856-1863, p. 56, B. 1864, 34 in 
 18<)0, p. 60, B. 1867, 43 in 1865, 6, p. 60, 
 
 B. 1867, 62 in 1873, p. 67, B. 1873, 32; 
 j). 70, B. 1875, 16 in 1874, p. 69, B. 1874, 
 28. Albany Institute, p. 46, B. 1852, 19. 
 Australia, p. 72, B. 1877, 41. Australia, 
 Victoria, p. 75, B. 1879, 78. Baden (1871- 
 75), p. 72, B. 1877, 30. British Islands, 
 weather report, 1862, p. 63, B. 1870, 28. 
 .July, 1870 March, 1871, p. 66, B. 1872, 35 ; 
 April to September, 1871, p. 68, B. 1873, 37 ; 
 1873 to 1875, p. 70, B. 1875, 23; p. 73, B. 
 1878. 44. England, Stonyhurst, p. 75, B. 
 1879,77. Iceland, p. 75, B. 1879, 78. Munich, 
 p. 73, B. 1878, 25. United States, p. 72, B. 
 1877, 41. U. S., Missouri, p. 75, B. 1879, 79. 
 
 C. S., Naval Observatory, p. 71, B. 1876, 9. 
 Antonelli, p. 47, B. 1854, 1. Argelander, p. 56, 
 B. 1863, 1. Arriens. p. 41, B. 1853,1. Atkin- 
 son, p. 59, B. 1867, 1 ; B. 1867, 2. Bache, 
 p. 52, B. 1860, 1. Beardmore, p. 81, N. 4, 6, 8. 
 Bel grand, p. 102, N. Berti and Namias, p. 57, 
 B. 1865, 6. Blanchet, p. 46, B. 1853, 2. 
 Boden, p. 46, B. 1851, 4. Bolt, B. 1871, 6. 
 Bruhns, p. 63, B. 1870, 6. Buchan, p. 58, 
 B. 1866, 4, B. 1866, 6; p. 86, N. Buddingk 
 ..nd Bing, p. 45, B. 1850, 3. Castello, p. 43, 
 44, B. 1846, 2 ; p. 44, B. 1848, 2 ; p. 46, B. 
 1852, 5 ; p. 49, B. 1855, 2 ; p. 53, B. 1861, 
 11 ; p. 55, B. 1863, 6. Gator, p. 59, B. 1867, 
 9. Chapelas-Coulvier-Gravier, p. 63, B. 1870, 
 8; p. 64, B. 1871, 9. Chretien, p. 42, B. 
 1843, 2. Clerk, p. 44, B. 1846, 3. Cook, 
 p. 51, B. 1850, 3. Crockewit, p. 46, B. 1852, 
 3. David, p. 41, B. 1840, 2 ; B. 1841, 1 ; 
 p. 42, B. 1843, 3; p. 43, B. 1844, 3; B. 
 1845, 3; p. 44, B. 1846, 5; B. 1847, 4; 
 p. 45, B. 1849, 4. Delaunay, p. 64, B. 1871, 
 K5, 14. Denza, p. 65, B. 1872, 9 Denza 
 and Maggi, p. 71, B. 1876, 10. Descroix, 
 p. 76, B. 1880, 6. Dieflfenbach, p. 44, B. 1846, 
 <J. Dove, p. 39, B. 1835, 3 ; p. 55, B. 1863, 
 *; ]-. 58, B. 1865, 8; p. 58, B. 1866, 11; 
 ].. 01, B. 1868, 7 ; B. 1868, 8; p. 62, B. 1869, 
 11. Drian, p. 47, B. 1853, 4. Du Boulay, 
 p. 57, B. 1865, 14. Dumoncel, p. 46, B. 1852, 
 
 6. Ellery, p. 65, B. 1872, 11. Emory, p. 41, 
 B. 1852, 7. Fielding, p. 61, B. 1868, 9. 
 Fischer, p. 62, B. 1869, 12 ; p. 65, B. 1872, 
 12 ; p. 67, B. 1873, 7. Fox, p. 71, B. 1877, 
 
 7. Friedrichsthal, p. 41, B. 1841, 3. Gay- 
 lord, p. 41, B. 1840, 5. Gifford, p. 50, B. 
 1857, 10. Gilliss, p. 49, B. 1856, 1. Glaisher, 
 p. 44, B. 1848, 5. Gorno, p. 54, B. 1862, 9. 
 Giinther, p. 39, B. 1834, 7. Haidinger, p. 44, 
 B. 1848, 6. Heijningen, p. 45, B. 1850, 8. 
 Hoffmann, p. 67, B. 1873, 17. Hoffmeyer, 
 p. 67, B. 1873, 18. Hogan, p. 47, B. 1853, 6. 
 
 CLIMATE observations continued. 
 Hombres, p. 44, B. 1848, 7. Holten, p. 63, B. 
 1870, 16. Hoopell and Wheeler, p. 67, B. 1873, 
 19. Houzeau, p. 70, B. 1875, 5. James, p. 49, 
 B. 1855, 6. Jouan (Pacific Ocean) p. 56, 
 B. 1864, 16. Karsten, p. 52, B. 1859, 15. 
 Kolbing, p. 43, B. 1844, 8; p. 44, B. 1847, 6. 
 Koller, p. 44, B. 1847, 7. Kuhn, p. 50, B. 
 1857, 15. Lachmann, p. 50, B. 1857, 16. 
 Lamont, p. 45, B. 1850, 10 ; p. 66, B. 1872, 
 24. Lamotte, p. 56, B. 1863, 21; B. 1864, 
 18. Lautour, p. 47, B. 1854, 7. Lees, p. 41, 
 B. 1839, 3. Levy, p. 46, B. 1852, 13. Lohse, 
 p. 103, N. 420. Lowe, p. 61, B. 1868, 18; 
 p. 63, B. 1870, 21. Marie-Davy, p. 55, B. 
 1863, 24 ; p. 60, B. 1867, 38; p. .65, B. 1871, 
 22. Martins, p. 61, B. 1868, 19; p. 65, B. 
 1871, 23. Merian, p. 55, B. 1863, 25 ; p. 60, 
 B. 1867, 39. Meyer, p. 41, B. 1840, 11. 
 Mitchell, p. 62, B. 1869, 32. Mohl, p. 56, 
 B. 1864, 24. Moller, p. 43, B. 1844, 10; 
 B. 1845, 10. Morris, p. 65, B. 1871, 35. 
 Newton, p. 69, B. 1874, 34. Pearde, p. 69, 
 B. 1874, 35. Perrey, p. 43, B. 1845, 12. 
 Philippi, p. 43, B. 1845, 14. Preisser, p. 44 r . 
 B. 1846, 16; p. 45, B. 1850, 13. Prozell,, 
 p. 55, B. 1863, 29. Quetelet, p. 43, B. 1843,. 
 10; p. 45, B. 1849, 9. Ragona, p. 49, B... 
 1855, 13. Raguse, p. 40, B. 1836, 13. Rees, 
 p. 44, B. 1848, 10. Renon, p. 56, B. 1864, 28 ; 
 p. 65, B. 1871, 42 ; p. 76, B. 1880, 22. Roch r 
 p. 49, B. 1856, 8. Roth, p. 51, B. 1858, 24. 
 Russell, p. 66, B. 1872, 47. Sands, p. 65 r 
 B. 1871, 43. Schabus, p. 50, B. 1857, 23. 
 Schomburgk, p. 46, B. 1851, 13. Schron, p. 39, 
 B. 1835, 11. Schubert, p. 43, B. 1844, 12. 
 Smallwood, p. 54, B. 1862, 33. Spandri, p. 46 
 B. 1851, 16 ; p. 47, B. 1854, 15 ; p. 49, B. 
 1855, 19. Stamkart, p. 45, B. 1850, 17 ; p. 46, 
 B. 1852, 17. Strachan (London), p. 71, B. 
 
 1875, 43-46. Symons (by Boyle, Hippocrates, . 
 and Roy. Soc.), p. 142, N. Tarry, p. 71, B. 
 
 1876, 16. Tavernier, p. 43, B. 1845, 15. 
 Thomson, p. 73, B. 1878, 40. Toplis, p. 45,. 
 B. 1849, 12. Trechsel, p. 43, B. 1844, 15. 
 Valles, p. 50, B. 1844, 15. Verneuil, p. 53,. 
 B. 1860, 24. Wattenwyll, p. 44, B. 1848, 1. 
 Weber, p. 46, B. 1852, 18. Weisse, p. 45, 
 B. 1848, 12; p. 49, B. 1855, 22. White, 
 p. 39, B. 1835, 14. Wullerstorf-Urbair, p. 71, 
 B. 1875, 48. Yeates, p. 44, B. 1847, 15._ 
 Zamboni, p. 42, B. 1842, 21. 
 
 observations: accuracy essential. Scott,, 
 p. 128, N. 
 
 observations in connection with agri- 
 culture, p. 139-141, N. 
 
 observations: averages, p. 71, B. 1875, 
 53. Abercromby (Bloxam's method), p. 119, 
 120, N. (failure of method); p. 1 13-120 N. 
 (value) ; p. 103, N. ; p. 113-120, N. ; p. 124- 
 125, N. Kamtz (method), p. 103, N. La- 
 mont (method), p. 60, B. 1867, 34. Scoresby- 
 Jackson, p. 84, 85, N. 28. Stewart (method 
 in temperature), p. 138, N. Strachey (value), 
 p. 106, N. Symons (method in rainfall), 
 p. 131, N. 
 
 observations in balloons, p. 72, B. 1877, 
 28. Barral and Bixio, p. 45, B. 1850, 1 ; B. 
 
 165 
 
INDEX. 
 
 CLIMATE observations continued. 
 1851, 3. Flammarion, p. 61, B. 1868, 10. 
 Glaisher, Flammarion, Fonvielle, Tissandier, 
 p. 64, B. 1871, 18. Glaisher, p. 55, B. 1863, 
 16 ; p. 56, B. 1864, 10 ; p. 57, B. 1865, 20 ; 
 p. 58, B. 1866, 15 ; p. 60, B. 1867, 25. Harm, 
 p. 74, B. 1879, 21. Tissandier, p. 61, B. 1868, 
 39 ; p. 68, B. 1873, 59 ; p. 75, B. 1879, 71 ; 
 p. 102, N. 
 
 observations : continuity. Beardmore, 
 p. 81, N. 2. Erman, p. 44, B."l846, 8. Her- 
 schcJ, p. 51, B. 1859, 12. Meldrum, p. 84, 
 N. 67. 
 
 observations : co-operation of observers. 
 White, p. 40, B. 1836, 15. 
 
 observations : daily bulletin. Buchan, 
 p. 89, N. 9. Rodwell, p. 141, N. 
 
 observations : deductions. Drew, p. 45, 
 B. 1850, 5. 
 
 observations : defects. Wild, p. 103, N. 
 
 observations : government grant (report 
 on), p. 72, B. 1877, 18. 
 
 observations : instructions, p. 50, B. 
 1857, 31, 32 ; p. 54, B. 1862, 37 ; p. 56, B. 
 1863, 41 ; p. 71, B. 1876, 20 ; p. 75, B. 1879, 
 
 75. Arago, p. 41, B. 1839, 1. Buchan, p. 86, 
 N. Burnier, p, 47, B. 1854, 2. Central 
 Meteorological Bureau of France, p. 73, B. 
 1879, 6 ; p. 75, B. 1879, 49. Deville, p. 46, 
 B. 1852, 4. Grellois, p. 52, B. 1860, 8 ; 
 }>. 50 ; B. 1864, 13. Guyot, p. 54, B. 1862, 
 13. Herschel, p. 40, B. 1838, 8. Kingston, 
 p. 73, B. 1878, 15-17. James, p. 52, B. 1860, 
 13. Jeliuek, p. 62, B. 1869, 16; p. 63, B. 
 1869, 18. Marriott, p. 72, B. 1877, 13. 
 Moberg, p. 49, B. 1855, 11. Phenological, p. 
 
 76, B. 1880, 4. Preston, McLachlan, and New- 
 ton, p. 70, B. 18?5, 34. Quetelet, p. 43, 
 B. 1843, 9. Regnault, p. 65, B. 1871, 41. 
 Renou, p. 49, B. 1855, 15 ; p. 54, B. 1862, 26. 
 Royal Society, p. 42, B. 1842, 15. Rubenson, 
 p. 72, B. 1877, 20. 'Scott, p. 70, B. 1875, 38. 
 
 .Smithsonian Institution, p. 66, B. 1872, 33. 
 Vignou, p. 49, B. 1855, 21. Wild, p. 69, B. 
 1874, 40. Woods, p. 41, B. 1839, 10. 
 
 observations: instruments. Scoresby- 
 Jackson, p. 84, N. 27. 
 
 observations : magneto-meteorological. 
 Lament, p. 56, B. 1864, 17. 
 
 observations : methods. Deville, p. 71, 
 B. 1876, 3. Stevenson, p. 72, B. 1877, 21 
 adopted by Smithsonian Institution. Guyot, 
 p. 46, B. 1851, 9 of collection for climatology 
 and weather study. Scott, p. 129, N. of 
 making ; p. 39, B. 1834, 15 ; p. 43, B. 1843, 
 11; p. 50, B. 1856, 12; p. 65, B. 1871, 29. 
 Chase, p. 58, B. 1866, 8. Drach, p. 43, B. 
 1845, 4. Dumoncel, p. 48, B. 1851, 6. Diirer, 
 ]>. 57, B. 1865, 16. Galton, p. 59, B. 1867, 
 24. Grisconi, p. 13, B. 1815, 3. Hansteen, 
 p. 43, B. 1844, 4. Howard, p. 14, B. 1821, 5. 
 Jamin, p. 50, B. 1857, 13. Matteucci, p. 58, 
 B. 1866, 22. Poey, p. 51, B. 1858 23. Prestel, 
 p. 54, B. 1862, 24. Sabine, p. 60, B. 1867, 
 56 of measuring periodical ranges, p. 121, 
 
 observations: method of recording. 
 Hoskins, p. 60, B. 1867, 28. Hough, p. 60, 
 166 
 
 CLIMATE observations continued. 
 B. 1867, 29. Mascart, p. 74, B. 1879, 37 ; 
 p. 76, B. 1880, 15. Pleininger, p. 44, B. 
 1847, 12. Prestel, p. 102, N. Sopwith, p. 
 41, B. 1838, 14. Zantedeschi, p. 55, 56, B. 
 1863, 39 variations. Bravais, p. 45, B. 
 1849, 1. 
 
 observations \ on mountains. Hann, 
 p. 74, B. 1879. 21. 
 
 observations : multiplicitv. Wild, p. 
 103, N. 
 
 observations : phenological, p. 67, B. 
 1873, 17 ; p. 140, 141, N. Hopkinson, p. 70, 
 B. 1875, 4* ; p. 101, N. Preston, p. 73, B. 
 1878, 34; p. 75, B. 1879, 65 ; p. 76, B. 1880, 
 19 ; p. 77, B. 1881, 9 ; p. 124, N. Quetelet, 
 p. 61, B. 1868, 33 ; p. 68. B. 1873, 44. Tristan, 
 p. 14, B. 1821, 7. Animals : Hopkinson, p. 
 139, N. Quetelet, p. 57, B. 1865, 38; p. 6u, 
 B. 1867, 54 ; p. 62, B. 1869, 39-40 ; p. 65, B. 
 1871, 38; p. 66, B. 1872, 42. Birds: Cor- 
 deaux, p. 138, N. Newton, p. 70, B. 1875, 
 29. Insects : Griffiths, p. 126, 127, 133, N. 
 McLachlan, p. 70, B. 1875, 8. Plants: Brady, 
 p. 59, B. 1867, 4. Pokorny, p. 56, B. 1864, 
 26. Preston, p. 70, B. 1875, 33 ; B. 1875, 54. 
 Quetelet, p. 57, B. 1865, 38 ; p. 60, B. 1867, 
 54; p. 62, B. 1869, 39-40; p. 64, B. 1870, 
 37 ; p. 65. B. 1871, 38 ; p. 66. B. 1872, 42. 
 Wheeler, p. 60, B. 1867, 60 ; p. 64, B. 1870, 
 49. 
 
 observations : reductions, p. 43, B. 
 1844, 6, Abercromby, p. 113-120. Buchan, 
 p. 92, N. Buys-Ballot, p. 72, B. 1878, 6. 
 Cacciatore, p. 38, B. 1832, 3. De Forest, p. 
 59, B. 1867, 15. Glaisher, p. 44. B. 1848, 4. 
 Kamtz, p. 61, B. 1868, 15. Koppen, p. 67, 
 B. 1873, 21. Marriott, p. 74, B. 1879, 36. 
 Scott, p. 129, N. Secchi, p. 46, B. 1851, 14. 
 Stewart, p. 64, B. 1870, 44. Stoney, p. 69, 
 B. 1874, 39. 
 
 observations : registers. Gazzaniga, 
 p. 15, B. 1826, 7 few good and long. Scott, 
 p. 128, N. registration, phenological. Dyer, 
 p. 70, B. 1875, 4 of secondary phenomena. 
 Vivenot, p. 57, B. 1865, 41. 
 
 observations : at sea ; p. 46, 47, B. 1853, 
 3; p. 73, B. 1878, 22; p. 138, N. Brault, 
 p. 71, B. 1876, 1. Erman, p. 47, B. 1854, 3. 
 Fitz Roy, 49, B. 1855, 3. Fleuriot de Langle, 
 p. 57, B. 1865, 19. 
 
 observations ; spectroscopic. Smith, 
 p. 71, B. 1875, 41. 
 
 observations : stations, p. 132, N. 
 Meldrum, p. 83, N. 65. Poey, p. 85, N. 
 Scott, p. 128, N. Africa, N. Rodwell, p. 141, 
 N. Austria, p. 87, N. Beardmore, p. 81, 
 N. 6. Buchan, p. 88, N. 7 ; p. 91, N. 3. 
 Belgium, p: 87, N. Canada. Beardmore, 
 p. 81, N. 6. Denmark, p. 87, N. England, 
 p. 87, N. foreign. Scott, p. 128, 129, N. 
 France, p. 87, N. Beardmore, p. 81, N. 6. 
 Germany, p. 87, N. Beardmore, p. 81, N. 6. 
 Great Britain. Buchan, p. 88, N. 7. Greece, 
 p. 87, N. Greece: Athens. Beardmore, p. 81, 
 N. 6. Holland, p. 87, N. Beardmore, B. 81, 
 N. 4. Ireland, p. 87, N. Beardmore, p. 81, 
 N. 8. Malta, p. 87, N. Mauritius, Meldrum, 
 
INDEX. 
 
 CLIMATE observations continued. 
 p. 84-, N. 69, 177. Norway, p. 87, X. Portugal, 
 }>. 87, N. Portugal, Lisbon. Beardmore, p. 81, 
 X. 6. Russia, p. 87, N. Beardmore, p. 81, 
 Is. 6. Scotland, p. 87, N. Beardmore, p. 81, 
 N. 8 at sea. Jelinek, p. 60, B. 1867, 33. 
 Jouan, p. 56, B. 1864, 16. Locke, p. 54, B. 
 1862, 16. Moffat, p. 61, B. 1868, 27. Nature, 
 p. 103, X. 143. Prestel, p. 57, B. 1865, 37. 
 Quetelet, p. 47, B. 1853, 13; B. 1854, 12. 
 Scott, p. 129, N. Spain, p. 87, N. Beardmore, 
 1). 81, N. 6. Sweden, p. 87, N. Sweden. 
 Beardmore, p. 81, N. 6. Switzerland, p. 87, 
 .N. Beardmore, p. 81, N. 6. Switzerland 
 Buchan, p. 88, N. 7. Turkey, p. 87, N. United 
 States, p. 81, N. 6. Buchan, p. 88, N. 7. 
 
 observations : special lines of enquiry. 
 Buchan, p. 88, X. 7. 
 
 observations : synchronous. Beardmore, 
 p. 81, N. 4. Buys-Ballot, p. 72, B. 1878, 4. 
 Hazen (bulletin), p. 139, N. Herschel, p. 42, 
 B. 1842, 9 ; B. 1843, 5 ; p. 43, B. 1844, 5 ; 
 B. 1844, 7; p. 44, B. 1846, 13. Meldrum 
 (importance), p. 84, N. 67 (use), p. 139, N. 
 Poey, p. 85, X. Symons, p. 142, X. Willis, 
 p. 82, N. Daily bulletin, p. 132, X. Fitz 
 Boy, p. 80, X. cli. 
 
 Observations : systematic. Meldrum, 
 p. 83, 84, X. Symons, p. 142, X. 
 
 observations : uniformity, p. 46, 47. B. 
 1853, 3; p. 53, B. 1861, 36. Buys-Ballot, 
 p. 65, B. 1872, 5 ; p. 67, B. 1873, 5. Lachlan, 
 p. 52, B. 1859, 16. Maury, p. 52. B. 1860, 17. 
 Meldrum, p. 83, X. 64. Xature, p. 101, N. 
 Poey, p. 57, B. 1865, 36. Rundell, p. 68, B. 
 1873, 47. Scoresby-Jackson, p. 84, X. 27. 
 Scott, p. 130, X. Stevenson, p. 104, 105, X. 
 Symons, p. Ill, 112, X. 
 
 observatories: British Isles, p. 65, B 
 1871, 30. Kew, Willis, p. 82, N. 
 
 organizations: Leverrier, p. 57, B. 
 1865, 29. Hellmann, p. 74, B. 1879, 23; 
 p. 131, 132, X. 
 
 periodicity. Australia, p. 18, E. ii. 2. 
 Ceylon, p. 18, E. II. 2. Ansted, p. 97, 98, X. 
 311. Brumham, p. 59, B. 1867, 5. Chambers, 
 p. 125, X. Cotte, p. 12, B. 1804, 3. Deville, 
 p. 62, B. 1869, 6 ; p. 63, B. 1870, 11. Edmonds, 
 p. 44, B. 1846. 9. Flammarion, p. 100, X. 45 ; 
 G., p. 67, B. 1873, 9. Herschel, p. 17, 18. 
 E. II. 1. Howard, p. 42, B. 1843, 6 ; p. 44, 
 B. 1846, 14. Koppen, p. 66, B. 1872, 22 ; 
 p. 67, B. 1873, 22 ; p. 69, B. 1874, 8. Lamarck, 
 p. 11, B. 1801, 2. Lampadius, p. 16, B. 1829, 
 5. Lockyer, p. 99, 100, X. Mahlrnann, p. 41, 
 B. 1840, 9. Sayce, p. 18, E. II. 2 ; p. 102, X. 
 Secchi, p. 60, B. 1867, 57. Serpieri, p. 46, B. 
 1852, 16. Skalweit (non-periodicity). Skey, 
 p. 64, B. 1870, 42. Somerville, p. 98, X. 308, 
 309. Stewart, p. 141, X. Webster, p. 50, 
 B. 1857, 29 calculation of. Schott, p. 54, 
 B. 1862, 30 causes (non-periodicity). Fried- 
 mann, p. 58, B. 1866, 14 criterion. Broun, 
 p. 103, 104, X. Hunter, p. 104, X. Stewart, 
 p. 105, X. ; p. 138, X. Strachey, p. 106, 107, 
 X. diurnal, p. 2-9, E. I. Abercromby, p. 109, 
 110, 116, 117, X. Fritsch, p. 51, B. 1859, 7. 
 Ramsay, p. 76, B. 1880, 20 eleven year. 
 
 CLIMATE periodicity continued. 
 Archibald, p. 121, X. ; p. 149, 150, E. II. 49-51. 
 Bache, p. 52, B. 1860, 1. Fritz, p. 106, X. 
 M. R. I. A., p. 139, X. 
 
 periodicity : aqueous vapour. Belling- 
 ham, p. 81, X. 
 
 periodicity : exceptions in all cases. 
 Meldrum, p. 127, N. 
 
 periodicity: influence of moon, p. 146, 
 147, E. II. 43 sun ; p. 152, E. II. 58 motion 
 of earth, moon, sun, and planets ; p. 2, E. I. 5. 
 
 phenomena connected with earthquakes. 
 Edmunds, p. 52, B. 1860, 6 remarkable. 
 Gutch, p. 42, B. 1842, 8. 
 
 poles. Denzler, p. 44, B. 1848, 3. 
 
 practical importance. Sopwith, p. 50, 
 B. 1857, 25. 
 
 precipitations : cause. Hann, p. 68, 
 B. 1874, 5. 
 
 predication.' Earl de Grey, p. 79, X. 
 
 principles, p. 72, B. 1877, 42. Ansted, 
 p. 63, B. 1870, 2. Blandet, p. 60, B. 1868, 2. 
 Bocoardo, p. 54, B. 1862, 4. Buchan (Handy 
 Book), p. 59, B. 1867, 6 ; p. 60, B. 1868, 4"; 
 p. 64, B. 1871, 7. Collins, p. 64, B. 1871, 11. 
 Contejean, p. 64, B. 1871, 12. Daubeny, 
 p. 55, B. 1863, 7. Drew, p. 52, B. 1860, 4. 
 Eisenlohr, p. 59, B. 1867, 20. Flammarion, 
 p. 65, B. 1872, 13. Friesenhoff, p. 74, B. 
 1879, 17. Glaisher (text-book), p. 51, B. 1858, 
 13; p. 67, B. 1873, 13. Granday, p. 54, 
 B. 1862, 10. Guillemin, p. 72, B. 1878, 12. 
 Guyot, p. 67, B. 1873, 15. Hennessy, p. 53, 
 B. 1861, 20. Herschel, p. 54, B. 1862, 15. 
 Hochstetter, Hann, and Pokorny, p. 66, B. 
 1872, 18. Houzeau, p. 76, B. 1880, 7. 
 Hutchinson, p. 39, B. 1835, 5. Jelinek, p. 71, 
 B. 1876, 6. Johnston, p. 63, B. 1870, 19. 
 Kamtz, p. 51, B. 1858, 16. Ley, p. 76, B. 
 1880, 9. Lommel,p. 67, B. 1873, 23. Loomis, 
 p. 67, B. 1873, 24. Lorenz, p. 74, B. 1879, 
 32. Mann, p. 72, B. 1877, 11. Mann, Laugh- 
 ton, Strachan, Ley, Symons, Scott, p. 74, B. 
 1879, 34. Mohn, p. 70, B. 1875, 27 ; p. 75, 
 B. 1879, 56. Morris, p. 58, B. 1866, 28. 
 Morrison, p. 41, B. 1839, 6. Mottez, p. 58, 
 B. 1866, 29 ; p. 87, N. Miihry, p. 54, B. 1862, 
 22; p. 57, B. 1865, 34; p. 60, B. 1867, 51. 
 Miiller, p. 44, B. 1847, 9 ; p. 62, B. 1869, 36 : 
 p. 64, B. 1870, 34; p. 66, B. 1872, 38. Muller^ 
 Pouillet, Pfaundler, p. 75, B. 1879, 58. 
 Pietra-Santa, p. 57, B. 1865, 35. Pina-Vidal, 
 p. 62, B. 1869, 37. Quetelet, p. 53, B. 1861, 
 28-29. Reclus, p. 62, B. 1869, 41. Schmid, 
 p. 52, 53, B. 1860, 22 ; p. 54, B. 1862, 29. 
 Scott, p. 68, B. 1873,49-51. Smith (chemical), 
 p. 68, B. 1873, 54. Studer, p. 59, B. 1866, 37. 
 Thomson, p. 45, B. 1849, 11. Waltershausen, 
 p. 57, B. 1865, 42 ; p. 61, B. 1868, 41. Young, 
 Breen, Scoffern, and Lowe, p. 50, B. 1856, 12. 
 
 prognostications, p. 59, B. 1866, 43 ; 
 p. 67, B. 1872, 59; p. 75, B. 1879, 84. 
 Abercromby, p. 115, X. Astre, p. 60, B. 1868, 
 1; B., p. 12, B. 1804, 1. Beddoes, p. 11, 
 B. 1802, 1. Beleguic, p. 56, B. 1864, 2. 
 Blake, p. 73, B. 1879, 2. Bruhns, p. 76, 
 B. 1880, 3. Buchan, p. 88, X. 2. Buller, 
 p. 60, B. 1868, 5. Chambers, p. 60, B. 1868, 
 
 167 
 
1XDEX. 
 
 CLIMATE prognostications. con td. 
 
 0. Claridge, p. 15, B. 1827, 3. Crouzet, 
 p. 57, B. 1865, 12. Clouston, p. 59, B. 1867, 
 11. Drechsler, p. 56, B. 1864, 7. Fonvielle, 
 p. 64, B. 1871, 16. Forster, p. 15, B. 1827,7. 
 Fournet, p. 55, B. 1863, 12. Fritsch, p. 55, 
 B. 1863, 14. Gazzaniga, p. 15, B. 1826, 7. 
 Grainger, p. 61, B. 1868, 12. Grellois, p. 53, 
 B. 1861, 19. Mathieu, p. 73, B. 1878, 19. 
 Muncke, p. 14, B. 1820, 3. P., p. 100, N. 
 Prestel, p. 54, B. 1862, 24. Schmidt, p. 53, 
 B. 1861, 31. Smyth, p. 137, N. Stieffel, 
 p. 43, B. 1844, 13. 
 
 prognostications: by animals. Ansted, 
 p. 96, 97, N. 306, 308. Mitchell, p. 87, N. 
 Thomas, p. 47, B. 1853, 16; B. 1854, 16. 
 Toaldo, p. 11, B. 1799, 4. 
 
 prognostications : by aurora. Ansted, 
 p. 97, N. 311. Ogilvy, p. 61, B. 1868, 30. 
 
 prognostications: by barometer. Gal- 
 ton, p. 64, B. 1871, 17. Gobin,p. 65, B. 1872, 
 14. Ley, p. 134, N. Strachan, p. 130, 131, 
 
 prognostications : by birds. Schiibler, 
 p. 38, B. 1831, 12. 
 
 prognostications : by clouds. Ansted, 
 p. 96, N. 306, 307. Buchan, p. 89, 90, N. 
 105-107. Ley, p. 125, 127, N. Mitchell, 
 p. 87, N. Nature, p. 106, N. 458. Poey, 
 p. 75, B. 1879, 64. 
 
 prognostications : by Gulf Stream. 
 Williams, p. 131, N. 
 
 prognostications : by lunar halo. 
 Tatem, p. 40, B. 1836, 14. 
 
 prognostications : by haloes, parhelia, 
 paraselenae and meteors. White, p. 39, B. 
 1835, 15. 
 
 prognostications : by horse leech ; p. 
 13, B. 1826, 5. 
 
 prognostications : by human system. 
 Austed. p. 97, N. 308. 
 
 prognostications : by moon. Ansted, 
 p. 97, N. 311. Buchan, p. 91, N. 331. 
 Clinch, p. 138, N. 
 
 prognostications: by plants. Hoff- 
 man, p. 51, 52, B. 1859, 13. Thomas, p. 47, 
 B. 1853, 16 ; B. 18.H, 16. 
 
 prognostications : by polarisation of 
 atmosphere. Buchan, p. 91, N. 331. 
 
 prognostications : by sky. Aratus, p. 
 -75, B. 1880, 1. 
 
 prognostications: by sun. Buchan, 
 p. 91, N. 331. 
 
 prognostications : by sunrise and sun- 
 set. Ley, p. 134, X. 
 
 prognostications : by temperature. 
 Ansted, p. 97, N. 310. 
 
 prognostications : by terrestrial mag- 
 netism, p. 37, E. II.. 37. 
 
 prognostications : by visibility. An- 
 sted, p. 96, N. 306. 
 
 prognostications: by wind. Ansted, 
 ?. 97, N. 307, 310, 311. Tastes, p. 65, B. 
 1871, 45 ; p. 68, B. 1873, 58. 
 
 prognostications: Kitz Roy's forecasts 
 and weather returns p. 56, B. 1864, 36. 
 
 prognostications : forecasts, p. 74, B. 
 18:9. : J -8. Aben-'ornbv, p. 11(5, N. i;,o 
 168 
 
 CLIMATE prognostications contd. ' 
 Arago, p. 43, B. 1846, 1. Buchan, p. 90, X. 
 180, 190 ; p. 91, N. 138. Buys-Ballot, p. 56, 
 B. 1864, 4 ; p. 59, B. 1867, 8. Collins, p. 
 122, N. Coulvier-Gravier, p. 58, B. 1866, 9. 
 Dumas, p. 85, N. Fonvielle, p. 72, B. 1878, 
 11 ; p. 74, B. 1879, 16. Forster, p. 132, N. 
 Labrosse, p. 58, B. 1866, 17. Lamotte, p. 40, 
 B. 1837, 11. Leverrier, p. 58, B. 1866, 18 ; 
 p. 60, B. 1867, 35. Ley, p. 76, B. 1880, 9 ; 
 p. 136, 137, N. (use of weather maps) ; p. 
 125, 127, N. Matteucci, p. 85, N. 1314. 
 Maury, p. 99, N. 414. Morin, p. 40, B. 1837 y 
 13 ; p. 41, B. 1840, 12. Nature, p. 101, N. ; 
 p. 133, N. 446. R., p. 128, N. RikatchefY, 
 p. 90, N. Scott, p. 76, B. 1880, 23. Sonrel, 
 p. 59, B. 1866, 35. Steinmetz, p. 59, B. 1866, 
 36. Strachan, p. 61, B. 1868, 37. Strachan, 
 p. 93, N. ; p. 131, N. Wenley, p. 72, B. 1877, 
 24. Wragge, p. 76, B. 1880, 27. Zantedeschi, 
 p. 59, B. 1866, 38 storm warnings; p. 69, 
 B. 1874, 29 ; B. 1874, 43 ; p. 138, N. Bogus- 
 lawski, p. 68, B. 1874, 2. Broun, p. 71, B. 
 
 1876, 2. Buchan, p. 88, 89, N. 89 ; p. 91, 92, 
 N. 341 (defects) ; p. 92, N. 343, 344. (Fitz. 
 Roy's system), p. 89, N. 9. (France), p. 92, 
 N. 343. (Great Britain), p. 92, 93, N. 342- 
 345. Burgess, p. 73, B. 1879. 7 ; p. 126, N. 
 Collins, p. 72, B. 1878, 8. Edwin, p. 72, B. 
 1878, 9. Fitz Roy, p. 80, N. Forbes, p. 82, 
 N. Jelinek, p. 60, B. 1867, 31. Leverrier, 
 p. 86, N. Maury, p. 99, N. Meldrum, p. 83, 
 N. 65 ; p. 84, N. 177. Nature, p. 106, N. 460. 
 Neumayer, p. 70, B. 1875, 28. Scott, p. 71, 
 B. 1876, 11 ; p. 73, B. 1878, 36. Sykes, p. 
 60, B. 1867,58; p. 61, B. 1868, 38 guide 
 by Fitz Roy. Forbes, p. 82, N popular 
 errors ; p. 56, B. 1863, 40 popularity. 
 Buciian, p. 90, N. 180 relative value. Ansted, 
 p. 97, N. 311. 
 
 prognostications : by small weather 
 changes. Buchau, p. 91, N. 339. 
 
 prognostications : warnings by pigeons. 
 R., p. 75, B. 1879, 60 on Sundays; p. 72, B. 
 
 1877, 37. 
 
 prognostications : weather signs. Ley, 
 p. 73, B. 1878, 43. 
 
 purity of air as indicated by plants. 
 Garner, p. 82, 83, N. 
 
 raining trees. Murray, p. 38, B. 1831, 
 9. Schmidt, p. 52, B. 1859, 22. 
 
 researches. Ferrel, p. 71, B. 1877, 6. 
 
 science. [This heading is equivalent to 
 meteorology.] Accurate facts important. An- 
 sted, p. 94, N. 292 accuracy depends on long 
 means. Somerville, p. 98, N. 313 contribu- 
 tors. Earl de Grey, ( p. 79, N. elements. 
 Becquerel, p. 44, B. 1847, 1 essays. Arago, 
 p. 49, B. 1855, 1 facts require more syste- 
 matisiug. Strachan, p. 93, N. 24. Fitz Roy's 
 work. Meldrum, p. 83, N. 65 history. 
 Sidler, p. 75, B. 1879, 68. Silber, p. 38, h. 
 1831, 14 hypotheses and discussions wanted, 
 p. 107, N. importance. Sopwith, p. 52, B. 
 1859, 27 investigation: difficulties. Scott, 
 p. 128, N. Stewart, p. 162, N. Maury 's 
 work. Meldrum, p. 83, N. 64 optical. Hen- 
 nessy, p. 69, B. 1874, 7 popularity. Buchan, 
 
INDEX. 
 
 CLIMATE science continued. 
 
 p. 87, 88, N. 2 practical applications. Buchan, 
 p. 67, B. 1873, 4. Meldrum, p. 83, N. 65 
 present state. Herschel, p. 54, B. 1862, 14 
 present state' in England. Drew, p. 46, B. 
 1852, 5 problems. Abercromby, p. 103, N. 
 Flammarion, p. 100, N. Hann, p. 72, B. 1878, 
 13. Kopp, p. 74, B. 1879, 27 progress ; 
 p. 2, E. I. 3 ; p. 54, B. 1861, 37. Abercromby, 
 p. 103, N. Bryce, p. 52, B. 1860, 2. Buchan, 
 p. 91, N. 3. Flammarion, p. 100, N. Maury, 
 . p. 100, N. Meldrum, p. 83, X. 64. Neuniayer, 
 p. 73, B. 1878, 32 ; p. 124, N. Scarpellini 
 (maritime), p. 53, B. 1861, 30. Scott, p. 128, 
 N. Royal Commission evidence, p. 70, B. 1875, 
 24 in schools. Buchan, p. 89, N. 10 is 
 meteorology a science? Abercromby, p. 71, 
 B. 1877, 1 state of. Smalley, p. 59, B. 1866, 
 34 systematisation. Poey, p. 50, B. 1857, 
 21; p. 51, B. 1858, 22 use. Scott, p. 130, N. 
 
 seasons, p. 14, B. 1822, 4. Eng. Cyclo., 
 p. 79, 80, N. Hofer, p. 60, B. 1867, 27. 
 Mossman, p. 62, B. 1869, 35. Murphy, p. 39, 
 B. 1834, 16. Pirie, p. 70, B. 1875, 31. 
 Proctor, p. 60, B. 1867, 52 changes explained. 
 Sandeman, p. 46, B. 1851, 12 growth rings 
 of trees as indicators. Warring, p. 107, N. 
 map, p. 69, B, 1874, 44 influence of ether. 
 Wilcocks, p. 58, B. 1865, 43 ; p. 63, B. 1869, 
 46 influence of winter on animals and plants. 
 Selby, p. 41, B. 1840, 17 influence on man. 
 Quetelet, p. 38, B. 1832, 7. Smith, p. 52, B. 
 1859, 25 influence on man ; death rate, p. 38, 
 B. 1833, 9. Quetelet, p. 40, B. 1838, 12 
 origin. Mossman, p. 63, B. 1870, 32 relation 
 to vegetation, N. p. 45, B. 1850, 11. 
 
 sections. Stevenson, p. 68, B. 1873, 56 ; 
 p. 101, N. vertical. Nature, p. 107, X. 452. 
 
 signal service. L T . States, p. 68, B. 
 1873, 70. 
 
 stability. Somerville, p. 98, N. 316. 
 
 state of sky. Lamarck, p. 12, B. 1802, 3. 
 
 Storm of salt. Salisbury, p. 12, B. 1807, 
 3; B. 1808, 7. 
 
 storm forces. Hopkins, p. 46, B. 1852, 
 11. Grellois, p. 57, B. 1865, 23. Tomlinson, 
 p. 55, B. 1863, 36 ; p. 81, 82, N. 
 
 Storms. Dondenne, p. 59, B. 1867, 17. 
 Leverrier, p. 61, B. 1868, 16. March, 1838, 
 p. 41, B. 1838, 15. Oct. 1854. Kreuger, 
 p. 49, B. 1855, 8. Oct. 1863. Eaton, p. 57, 
 B. 1865, 17. May 7, 1865. Lermoyez, p. 57, 
 B. 1865, 27. 1866. Jelinek, p. 60, B. 1867, 
 30. Nov. 1866. Dove, p. 59, B. 1867, 18. 
 Jan. 1867. Jelinek, p. 60, B. 1867, 31 of 
 indefinite character, considered to be general ; 
 p. 10, Re. influence on man ; diseases ; neu- 
 ralgia. Mitchell, p. 133, N. prevented by 
 fires. Matteucci, p. 41, B. 1839, 4. 
 
 tables. Boileau, p. 45, B. 1850, 2. Guyot, 
 p. 46, B. 1852, 10; p. 51, B. 1858, 14; B. 
 1859, 9; p. 54, B. 1862, 12. James, p. 52, 
 B. 1860, 13. Kunze, p. 70, B. 1875, 7. 
 Loomis, p. 67, B. 1873, 24. Williamson, p. 61, 
 B. 1868, 42. 
 
 term climate defined. Ansted, p. 95, 
 N. 304. Davis, p. 78, N. Eng. Cyclo. p. 78, 
 79, N. ; p. 10, Re. , Stevenson, p. 105, N. 
 
 Ansted, p. 96, 
 Du Boulay, 
 
 CLIMATE continued 
 
 uniform in character. 
 N. 304. 
 
 vernal equinoctial week. 
 p. 53, B. 1861, 15. 
 
 "weather. It is not practicable to dis- 
 tinguish between what refers to weather as 
 distinct from climate. Therefore search should 
 also be made under the more general term 
 climate : p. 51, B. 1858, 6. Behr, p. 51, B. 
 1858, 4. Buchan (of 1867), p. 91, N. 429. 
 Herschel, p. 57, B. 1865, 26. Meldrum (every 
 phase instructive), p. 84, N. 80. Segesser r 
 p. 39, B. 1834, 20 almanac. Murphy, p. 40, 
 B. 1838, 11 ; p. 41, B. 1839, 7 ; B. 1840, 13; 
 p. 42, B. 1842, 14 anti-cyclone : types. 
 Abercromby, p. 108, 109, 112, N. Ley, 
 p. 136, 7, N. changes indicated by barometer. 
 Eng. Cyclo., p. 78, N. Glaisher, p. 57, B. 1865, 
 21. Hailstone, p. 14, B. 1822, 5. case. 
 Myer, p. 73. B. 1878, 31 ; p. 124, N. changes. 
 Hopkins, p. 52, B. 1860, 12 changes : causes. 
 Hopkins, p. 52, B. 1860, 11 changes indicated 
 by colour of sea. Ansted, p. 94, N. 144 
 changes : world-wide. Buchan, p. 90, N. 165 
 changes : connection with magnetic varia- 
 tions. Stewart, p. 18, E. II. 1 ; p. 35, E. II. 
 36 connection with sun-spots. Archibald, 
 p. 18, E. II. 3 with tides. Hall, p. 40, B. 
 1837, 7 with wind. Marie Davy, p. 72, B. 
 1877, 12 correlation of phenomena. Dell- 
 mann, p. 53, B. 1861, 14 cyclonic character. 
 Abercromby, p. 116, N, Ley, p. 134-137, N. 
 cyclone: primary. Abercromby, p. Ill, 
 112, N. cyclone : secondary. Abercromby, 
 p. Ill, 112, N. Ley, p. 135, N. cyclone : 
 types. Abercromby, p. 108, 109, 110, 111, 
 N. diagrams. Cator, p. 57, B. 1865, 11 
 fine day and season : definition. Ansted, p. 95, 
 N. 303 folklore. Swainson, p. 68, B. 1873, 
 57 influence of earthquakes. Nature, p. 125, 
 N. 600 extra terrestrial causes. Wolfers, 
 p. 44, B. 1847, 13 man. Olbers, p. 14, B r 
 1818, 3 ; B. 1821, 6 moon. Schiibler, p. 38, 
 B. 1831, 11. Toaldo, p. 11, B. 1799, 7 sea. 
 Abercromby, p. 110, N. sun. Archibald, 
 p. 17, E. II. 1. Stewart, p. 142, 143, N. 
 thermic differences. Buchan, p. 88, N. 6 
 influence on plants. Fritsch, p. 42, B. 1843, 
 4. Hoppe, p. 14, B. 1822, 6 not influenced 
 by magnetism, moon nor sun-spots. Faye, 
 p. 124, N. intensity as a character. Aber- 
 cromby, p. 108, 109, 112, N. kinds. Aber- 
 cromby, p. 107-112, N. ' Boitard, p. 55, B,. 
 1863, 5 law paramount ; p. 2, E. I. 2 local 
 differences. Ansted, p. 96, N. local variations 
 as a character. Abercromby, p. 110, N. 
 maps ; p. 71, B. 1876, 17. Dec. 3, 4, 1872, 
 p. 66, B. 1872, 37 ; 1873, p. 67, B. 1873, 32 ; 
 1875, p. 70, B. 1875, 18. Sept. 1877, p. 76, 
 B. 1880, 30. April to Dec. 1878, p. 76, B. 
 1880, 30 remarks ; p. 76, B. 1880, 33, 34. 
 Sept. 1877, p. 76, B. 1880, 37. April to 
 July, 1878, p. 76, B. 1880, 35. Aug. 1878, 
 p. 76, B. 1880, 36. Sept. 1878, p. 76, B. 1880, 
 38. Oct. and Nov. 1878, p. 77, B. 1880, 39. 
 Dec. 1878, p. 77, B. 1880, 40. Galton, p. 80, 
 N. Locke, p. 52, B. 1860, 15. Scott, p. 71, 
 
INDEX. 
 
 CLIMATE weather continued. 
 
 B. 1876, 11. Strachan, p. 130, 131, N. 
 Europe. Hoffmeyer, p. 70, B. 1875, 39. 
 N. hemisphere; p. 75, B. 1879, 81 U. States; 
 p. 72, B. 1877, 29. Loomis, p. 74, B. 1879, 
 30. M., p. 76, B. 1880, 12 maps : daily. 
 Maury, p. 99, N. 390. Meldrum, p. 83, 84, N. 
 1874, p. 69, B. 1874, 8. Europe, p. 72, B. 
 
 1877,35 innewspapers; p. 102, 103, X. use 
 p. 132, N. eight hourly require discussion ; 
 p. 138, N. monthly ; p". 132, N. synoptic ; 
 report. Hofimeyer, p. 74, B. 1879, 26 
 method of study. Abercromby, p. 107 112, 
 N. sequential. Abercromby, p. 107, N. 
 synoptic. Abercromby, p. 107, 108, N. 
 periodicity (diurnal) as a character. Aber- 
 cromby, p. 109, 110, 112, N. principles 
 (weather book). Fitz Roy. p. 55, B. 1863, 9 ; 
 B. 1863, 10 (weather guide). Fitz Roy, 
 
 ' p. 51, B. 1858, 10 ; B. 1859, 6. Murphy, 
 p. 39, B. 1834, 16 problems to be solved. 
 Abercromby, p. 114, N. progressive motion. 
 Ansted, p. 96, N. 305. Stewart, p. 138, 143, 
 N. (lags behind magnetic changes). Stewart, 
 p. 138, 143, N. Saint Swithin. Jenyns, 
 p. 55, B. 1863, 19 seasonal variations as a 
 character. Abercromby, p. 110, N. term 
 defined. Abercromby, p. 114. Ansted, p. 95, 
 N. 302 ; p. 96, N. 305. Buchan, p. 90, N. 
 180 bad, defined. Ansted, p. 95, N. 303 
 uniformity of phenomena in wet seasons, 
 1857, 1858 and 1874. Dove, p. 70, B. 1875, 3. 
 1835. Merian,p. 40, B. 1836, 10. June 20, 
 21, 1861. Quetelet, p. 53, B. 1861, 27 
 Antarctic regions. Maury, p. 53, B. 1861, 22 ; 
 p. 54, B. 1862, 17. Neumayer, p. 75, B. 1879, 
 59 Antilles. Poey, p. 53, B. 1861, 26 
 Arctic regions. Miihry, p. 53, B. 1861, 24 
 as indicated by extinct corals. Fleming, p. 44, 
 B. 1846, 11 Atlantic coast : influence of 
 Oulf Stream. Wynne, p. 50, B. 1857, 30 
 British Isles ; p. 76, B. 1880, 33 ; p. 77, B. 
 1881, 11 Babington ; p. 54, B. 1862, 1 
 Canada; p. 76, B. 1880, 33 Cuba. Poey, 
 p. 53, B. 1861, 26 England; p. 77, B. 1881, 
 1 England: Surrey, Cobham ; p. 77, B. 1881, 
 11 Europe; p. 77, B. 1881, 11 Falkland 
 Isles; p. 76, B. 1880, 33 of future. Murphy, 
 p. 66, B. 1872, 40 at great heights. Nowak, 
 p. 53, B. 1861, 25. Tridon, p. 76, B. 1880, 
 25 India: Bombay; p. 76, B. 1880, 33 
 Chambers, p. 72, B. 1878, 7 Indian summer ; 
 p. 39, B. 1835, 16 islands (uniformity in). 
 Murray, p. 14, JB. 1820, 4 of land areas. 
 Ansted, p. 94, N. 298 mountains ; p. 77, 
 B. 1881, 11. Smith, p. 50, B. 1857, 24 
 mountain : application of mechanical theory 
 of heat. Miihry, p. 63, B. 1870, 33 of north 
 hemisphere. Ansted, p. 94, N. 291. Somer- 
 ville, p. 98, N. 338 of north and south hemi- 
 spheres. Dove, p. 67, B. 1873, 6 of north 
 and south polar lands. Ule, p. 63, B. 1869, 
 44 of oceanic areas. Ansted, p. 94, N. 298 
 at sea: principles. Maury, p. 66, B. 1872, 
 27 ; p. 69, B. 1874, 12 Scotland ; p. 76, 
 B. 1880, 33 ; p. 77, B. 1881, 11 of south 
 hemisphere. Ansted, p. 94, N. 291 south 
 hemisphere. Somerville, p. 98, N. 338 
 170 
 
 CLIMATE weather continued. 
 
 Sweden ; p. 76, B. 1880, 33 Tasmania, p. 76, 
 B. 1880, 33 trade wind region. Somerville. 
 p. 98, N. 343 tropical. Forbes, p. 43, B! 
 1845, 5. Gaston, p. 64, B. 1864, 8 ; p. 56, 
 B. 1864, 9 United States; p. 76, B. 1880, 
 33 u. s., Missouri ; p. 76, B. 1880, 33. 
 
 CLOUDS. See Aqueous vapour. 
 
 CONTRACTIONS explained, p. 1, Int. 8. 
 
 CORRESPONDENCE and inquiries so- 
 licited, p. 144. 
 
 DEW POINT. See Aqueous vapour. 
 
 EARTH : influence of sun on, p. 34, E. II. 
 34. 
 
 EARTH : magnetism. See also under Cli- 
 mate : connection, and Climate : prognostica- 
 tion. 
 
 EARTH : magnetism : connection with sun- 
 spots. Fritz, p. 74, B. 1879, 18 connection 
 between its changes and those of sun-spots. 
 Sabine and Wolf, p. 17, E. II. 1 disturbances 
 precede the meteorological. Stewart, p. 18, 
 E. II. 1 -influence of electrical condition of 
 air ; p. 148, 149, E. II. 47 of sun ; p. 147, 
 E. II 45; p. 148, E. II. 46, 47 sun-spots ; 
 p. 147, 148, E. II. 45, 46 ; p. 148, 149, E. II. 
 47 temperature ; p. 147, E. II. 48 ; p. 148, 
 149, E. II. 47 wind ; p. 149, E. II. 48 ob- 
 servations. Ellery, p. 65, B. 1872, 11 
 periodicity coincident with those of solar 
 spots. Wolf, Sabine, Loomis, Fritz, p. 34, 35, 
 E. II. 36 periodicity, p. 150, E. II. 26 day ; 
 p. 145-148, E. II. 38, 41, 45, 46 poles and 
 equator (coincidence with those of heat and 
 wind) ; p. 35, E. II. 36 variations (connection 
 with meteorological changes). Stewart, p. 35, 
 E. II. 36. 
 
 EARTHQUAKES. Rossi, p. 73, B. 1878, 
 35 ; p. 75, B. 1879, 66 ; periodicity, p. 150, 
 E. II. 
 
 ELDER : as test of purity of air, p. 83, N. 
 
 ELECTRICAL CONDITION, p. 76, B. 
 1880, 33. Miihry, p. 68, B. 1873, 40 ; p. 69, 
 B. 1874, 33. Parrot, p. 12, B. 1802, 4 ; 1803, 
 3 changes. Ansted, p. 96, N. 305 as charac- 
 teristic of different kinds of weather. Aber- 
 cromby, p. 108-110, N.v. Ley, p. 135, 137, N. 
 influence of e. and humidity on aurora. 
 Loomis, p. 35, 36, E. II. 36 observations : 
 method of recording. Mascart, p. 74, B. 1879. 
 37 ; p. 76, B. 1880, 15 report, p. 73, B. 1878, 
 22 thunderstorm. Gaylord, p. 41, B. 1840, 
 5 ; p. 42, B. 1842,'5 ; thunderstorms : periodi- 
 city, p. 150, E. II. thunderstorms : periodicity ; 
 diurnal, p. 38, B. 1832, 9. 
 
 ELM : as test of purity of air, p. 82, N. 
 
 ERICA : as test of purity of air, p. 82, N. 
 
 ETHER: influence of. Wilcocks, p. 58, B. 
 1865, 43 ; p. 63, B. 1869, 46. 
 
 EVAPORATION: See Aqueous vapour. 
 
 FLOODS : prediction of, by temperature. 
 Fournet, p. 55, B. 1863, 12. 
 
 G-EODESY : application of method of least 
 squares. Freeden, p. 55, B. 1863, 13. 
 
 GEOGRAPHY: principles. Hann. Hoch- 
 stetter and Pokorny, p. 66, B. 1872, 18. 
 
 GEOLOGY: in connection with currents. 
 Wettstein, p. 75, B. 1879, 72. 
 
INDEX. 
 
 GLACIERS. Miihry, p. 68, B. 1873, 40 
 p. 69, B. 1874, 33. 
 
 GLACIERS : periodicity, p. 150, E. II. 
 
 HAILFALL. Leverrier, p. 61, B. 1868, 16 
 as characteristic of different kinds of weather. 
 Abercromby, p. 108, 111, N. Ley, p. 135, N. 
 influence of sun spots, p. 151, E. II. 54 
 periodicity. Fritz, p. 106, N. prognostica- 
 tions by temperature. Ansted, p. 96, N. 307. 
 
 HEAT. See Temperature. 
 
 HIERACTA : as test of purity of air, p. 82, N. 
 
 HOLLY : as test of purity of air, p. 82, N. 
 
 HUMIDITY. See Aqueous Vapour. 
 
 ICE : agency of ice in auroral displays, p. 36, 
 37, E. II. 36 relation of polar ice to auroras. 
 Chavanne, p. 37, E. II. 36. 
 
 INSECTS : species for phenological observa 
 tions. McLachlan, p. 70, B. 1875, 8. 
 
 INSTRUCTIONS. See under Climate. 
 
 LARCH : as test of purity of air, p. 82, N. 
 
 LAUREL : common and Portugal ; as test 
 of purity of air, p. 82, N. 
 
 LAURUSTINUS: as. test of purity of air, 
 p. 82, N. 
 
 LAW, in nature defined. Title page regulates 
 what is often assigned to chance, p. 2, E. I. 1. 
 
 LICHENS : as test of purity of air, p. 82, 
 
 LIGHT: influence on plants, p. 139, 140, N. 
 influence of diminution of, on animals and 
 plants. Lowe, p. 52, B. 1859, 17 periodicity ; 
 diurnal : influence of earth's relation and 
 position of sun, p. 3, E. I. 6, 7 at Greenwich. 
 Ellis, p. 74, B. 1879, 13. 
 
 MAGNETISM : science ; present state. 
 Smalley, p. 59, B. 1866, 34. 
 
 MAN. See under Climate. 
 
 MEDICINE: geographical and statistical. 
 Boudin, p. 50, B. 1857, 4. 
 
 MERCURY : influence of, on sun-spots. 
 Stewart, p. 21, E. II. 12. 
 
 METEOROGRAPH. See under Climate. 
 
 METEOROLOGICAL Committee, Confer- 
 ence, Counsel and societies. See under Climate. 
 
 METEOROLOGY. See under Climate: 
 science. 
 
 MEZEREON : as test of purity of air, p. 
 82, N. 
 
 OAK : as test of purity of air, p. 82, N, 
 
 OBSERVATIONS. See under Climate. 
 
 OBSRVATORIES. See under Climate. 
 
 OCEAN : currents. Ploix and Caspar!, p. 70, 
 B. 1875, 32 level ; influence of obliquity of 
 ecliptic. Croll, p. 59, B. 1867, 13 ; tempera- 
 ture. Thomson, p. 64, B. 1870, 47 tide ; 
 periodicity, p. 150, E. II. Pacific : tempera- 
 ture. Wild, p. 72, B. 1877, 25. 
 
 OROGRAPHY : hypsometrical tables. 
 Kunze, p. 70, B. 1875, 7. 
 
 OVIS : influence of heredity. Tanner, p. 62, 
 63, B. 1869, 42. 
 
 PEAS : as test of purity of air, p. 82, N. 
 
 PHYSICS : application of method of least 
 .squares. Freeden, p. 55, B. 1863, 13 ; litera- 
 ture. Duprez, p. 65, B. 1872, 10. 
 
 PLANTS : trees ; advantages of leafless con- 
 dition in winters. C., p. 138, N. 
 
 POPLAR : as test of purity of air, p. 82, N. 
 
 PROGNOSTICATIONS. See under 
 Climate. 
 
 PUBLICATIONS asked for, p. 1, Int. 9. 
 
 RAIN. Bellani, p. 39, B. 1836, 2 ; p. 40, B. 
 1838, 1. Claridge, p. 15, B. 1827, 3. 
 
 RAINFALL : cause of. Hann, p. 68, B. 1874, 
 5 ; as characteristic of different kinds of 
 weather. Abercromby, p. 107-112, N. Ley, 
 p. 134-137, N; connection with sun-spots. 
 Abercromby, p. 115, N. Meldrum, p. 122, 123, 
 N. Trouvelot, p. 68, B. 1873, 60 ; connection 
 with wind. Abercromby, p. 115, N. different 
 synoptic conditions. Abercromby, p. 118, 125, 
 N. influence of sun-spots, p. 151, E. II. 53. 
 Nature, p. 125 influence of opposite tempera- 
 tures in different regions. Archibald, p. 125, 
 N. observations : method of averaging. Mel- 
 drum, p. 122, 123, N. Symons, p. 131, N. 
 origin of equatorial seasons explained. Sande- 
 man, p. 46, B. 1851, 12 periodicity, p. 150, 151, 
 E. II. Meldrum, p. 107, N. Strachey, p. 106, 
 N. periodicity : diurnal. Rome, p. 7, E. I. 
 15 eleven-year. Meldrum, p. 122, 123, N. 
 prognostications by clouds. Ansted, p. 96, 
 N. Australia : Adelaide, Babbage, p. 63, B. 
 1870, 3. Australia : New South Wales, p. 75, 
 B. 1879, 77. Austria, p. 76, B. 1880, 33. 
 Hungary, p. 76, B. 1880, 33. 
 
 RESEDA lutea: as test of purity of air, p. 
 82, N. 
 
 RHODODENDRON : as test of purity of 
 air, p. 82, N. 
 
 RIVERS: floods: periodicity. Fritz, p. 106, 
 
 ROSES : as test of purity of air, p. 82, N. 
 SALT DEPOSITS. See under Climate. 
 SAXIFRAGES : as test of purity of air, p. 
 
 82, N. 
 SCIENCE: facts should be noted and 
 
 classified, p. 1, Int. 1 keys deficient in 
 
 uniformity, p. 1, Int. 2. 
 SCIENTIFIC ROLL: notes follow the 
 
 sense, not always the words, of the original, 
 
 p. 1, Int. 6. purpose of, p. 1, Int. 4. 
 SCIENTIFIC SOCIETIES: report of 
 
 annual conference at York, 1882, p. 154156. 
 SCIENTIFIC UNION, p. 154-157. 
 SEDUM : as test of purity of air, p. 82, N. ] 
 SHEEP. See under Climate and Oms. 
 SNOW: Claridge, p. 15, B. 1827, 2 red. 
 
 Bellani, p. 39, B. 1836, 2 ; p. 40, B. 1838, 1. 
 SNOWFALL : as characteristic of different 
 
 kinds of weather. Abercromby, p. 135, N. 
 SOIL : influence on plants. Kerner, p. 62, B. 
 
 1869, 17 ; influence on plant-distribution. 
 
 Buhse, p. 59, B. 1867, 7. 
 SPRINGS: influence of forests. Maistre, 
 
 p. 58, B. 1866, 20 ; p. 70, B. 1875, 9. 
 SUN: chromosphere, p. 27, E. II. 20, 21 
 
 period of rotation, p. 145, 146, E. II. 39, 41 
 
 energy, manifestations of, p. 32, 33, E. II. 30 
 
 influence on earth, p. 34, E. II. 34 influence 
 
 of solar electrical disturbance on auroras. 
 
 Loomis, p. 36, E. II. 36 parhelia. Gaylord, 
 
 p. 41, B. 1840, 5 photosphere, nature of. 
 
 Kirchoff, p. 27, E. II. 20. Spencer, p. 27, E. 
 
 II. 21. Young, p. 28, E. II. 22 photosphere, 
 
 structure of. Janssen, p. 20, E. II. 10. 
 
 171 
 
INDEX. 
 
 SUNSHINE : See Light. 
 
 SUNSPOTS. Proctor, p. 28, E. II. 22 
 chemical nature. Lockyer, p. 24, E. II. 19 
 cometary theory ; p. 29, E. II. 26. Proctor, 
 p. 30, E. II. 27 connected with faculse ; p. 19, 
 E. II. 5 ; p. 20, E. II. 9 connection with rain- 
 fall and wind. Trouvelot, p. 68, B. 1873, 60 
 connection with solar radiation ; p. 22, E. 
 II. 30 solar temperature, p. 22, E. II. 12 
 terrestrial temperature and weather ; p. 18, 
 E. II. 3 cyclonic nature; p. 23, E. U. 12; 
 p. 27, E. II. 21 ; Spencer and Herschel, p. 24, 
 E. II. 17 direction related to solar energy. 
 Stewart and Lockyer, p. 33, E. II. 32 dis- 
 covered by Chine&e ; p. 17, E. II. 1 due to 
 cyclonic motion. Faye, p. 22, E. II. 12 to 
 descending currents; p. 23, E. II. 12 to 
 downrush of cold matter ; p. 22, E. II. 12 to 
 uprush of matter. Faye, p. 22, E. II. 12 
 formation and motion of; p. 19, E. II. 5; p. 
 19, 20, E. II. 6 ; p. 20, E. II. 7 influence of 
 Jupiter. De La Rue, Stewart and Loewy, 
 p. 26, 27, E. II. 20. Proctor, p. 26, E. II. 20 
 influence of Mercury. De La Rue, Stewart 
 and Loewy, p. 26, 27, E. II. 20 of planets. 
 Stewart, Buys-Ballot, p. 21, E. II. 12 of 
 planetary attraction ; p. 26, 27, E. II. 20 of 
 Venus. De La Rue, Stewart and Loewy, p. 
 26, 27, E. II. 20 meteoric theory ; p. 29, 30, 
 31, E. II. 26, 27. Herschel, p. 21, E. II. 11. 
 Mayer, p. 29, E. II. 25. Thomson, p. 29, E. 
 11. 25 ; p. 30, E. II. 26. Waterston, p. 29, E. 
 II. 25 motion. Chacornac, p. 19, E. II. 5. 
 De la Rue, Stewart, Loewy, p. 19, 20, E. II. 6. 
 Sporer, p. 20, E. II. 7 names of investigators ; 
 p. 24, E. II. 18 nature of; p. 18, E. II. 4 ; 
 p. 24, E. II. 16 ; p. 25, 26, E. II. 19. Faye, 
 p. 28, 29, E. II. 23, 24. Secchi, p. 29, E. H. 
 24. Young, p. 28, 29, E. II. 22, 23; p. 31, 32, 
 K. II. 29. Zollner, p. 29, E. II. 24 observa- 
 tions, p. 19, E. II. 5 ; p. 20, E. II. 7. Schellen, 
 p. 23, E. II. 15. Tait, p. 23, E. II. 14 order 
 of disappearance ; p. 23, E. II. 12 periodical 
 latitudinal range. Carrington, p. 20, 21, E. 
 II. 11 periodicity ; p. 32, E. II. 29. Stewart, 
 p. 141, N. Wolf, p. 26, E. II. 20. Wolf, 
 Sabine, Loomis and Fritz, p. 34, 35, E. II. 36 
 periodicity : cycles. Archibald, p. 17, E. 
 II. 1. De la Rue, Stewart and Loewy, p. 17, 
 K. II. 1. Lamont, p. 17, E. II. 1. Schwabe. 
 p. 17, E. II. 1. Wolf, p. 17, E. II. 1 ; p. 18, 
 E. II. 2 periodicity : eleven year. Archibald, 
 p. 121, N. Buchan, p. 121, 122, N. Mel- 
 drum, p. 123. 124, N. periodicity : influence 
 of planets, p. 146, E. II. 42 24 day : influence 
 of intramercurial planet. Stewart, Buys- 
 ballot, p. 21, E. II. 12 relation to solar 
 energy, p. 33, E. II. 31 relation to tropical 
 barometric pressure. Chambers, p. 33, E. II. 
 32 relation to weather; p. 34, 35, E. II. 
 35 size. Davis, p. 20, E. II. 8 ; views held by 
 Gautier, p. 25, E. II. 19; view held by Secchi, 
 p. 25, 26, E. II. 19 ; view of Zollner, p. 24, 
 K. II. 19 ; surface eruptions, nature of, p. 31, 
 E. II. 27 ; temperature, connection with spots, 
 ]). 22, E. II. 12 temperature, contraction 
 theory. Helmholtz, p. 31, E. II. 27 tem- 
 perature ; influence of chemical and meteoric 
 172 
 
 SUNSPOTS continued. 
 
 action. Proctor, p. 31, E. II. 27 temperature : 
 non-influence of chemical action. Thomson, 
 p. 31, E. II. 27 temperature : influence of 
 meteoric action. Thomson, p. 31, E. II. 37 
 temperature : meteoric theory : objections ; 
 p. 31, E. II. 28 variation in sun's tempera- 
 ture the main cause of terrestrial weather. 
 Archibald, p. 17, E. II. 1 variation and 
 periodical change in. Archibald, p. 17, E. II. 
 1 variation in level of condensation plane. 
 Lcckyer, p. 23, E. II. 12. 
 
 SYSTEMATIZATION of notes recom- 
 mended, p. 1, Int. 3. 
 
 SYSTEMATISED notes more fluent in 
 ideas than in language, p. 1, Int. 5; explana- 
 tory remains, I. p. 153, 154. 
 
 TEMPERATURE. Bloxam, p. 55, B. 1863, 
 4. Chambers, p. 72, B. 1878, 7. Croll, p. 70, 
 B. 1875, 2. Laughton, p. 73, B. 1878, 43. 
 Poireau, p. 54, B. 1862, 23. Stewart, p. 73, 
 B. 1878, 38 changes. Howorth, p. 66, B. 
 1872, 21. Rae, p. 66, B. 1872, 43 connection 
 with sun-spots. Archibald, p. 18, E. II. 3 
 influence of excessive radiation in S. hemi- 
 sphere on climate. Croll, p. 62, B. 1869, 4 
 influence on insects. Verloren, p. 55, B. 1863 ? 
 37 influence of sun-spots on diurnal range. 
 Stewart, p. 21, E. II. 12 observations, 1848. 
 Quetelet, p. 45, B. 1849, 9 periodicity. 
 Renou, p. 66, B. 1872, 46 periodicity : diur- 
 nal ; p. 6, E. I. 13 ; p. 7, 8, E. I. 16 (methods 
 of reduction) ; p. 4, E. I. 9 (theoretically and 
 actually) ; p. 3, E. I. 8 (in temperate zone) : 
 p. 5, E. I. 10 (on land and at sea in tropics) ; 
 p. 5, E. I. 9 (in vertical direction) ; Dines, 
 Hamberg, Glaisher, p. 5, 6, E. I. 12 (Ant- 
 artic Ocean). Moseley, p. 5, E. I. 11 (Gon- 
 dar, Abyssinia). Riippell, p. 5, E. I. 10 
 (Limpopo Basin). Erskine arid Baines, p. 4, 5 r 
 E. I. 9 (Octanata River, New Guinea). 
 Miiller, p. 5, E. I. 9 (Pacayacu, Ecuador). 
 Spruce, p. 5, E. I. 9 (Para, Brazil). Orton, 
 p. 5, E. I. 9 (Paris) ; p. 5, E. I. 10 (Ply- 
 mouth) ; p. 5, E. I. 10 (polar regions) ; p. 5, 
 E. I. 11 (Quito). Orton, p. 5, E. I. 9 
 (Rigaf). Watson, p. 4, E. I. 9 (Victoria 
 River, Australia). Wilson, p. 5, E. I. 9 
 (Stonyhurst) ; p. 5, E. I. 10 -(Trevandrum). 
 India, p. 5, E. I. 9 (Wassaw, Gold Coast). 
 Skertchly, p. 5, E. I. 9 (Yarkand, Tibet). 
 Hayward, p. 5, E. 1. 10 daily march of t. 
 and light in harmony; p. 5, E. I. 11 pe- 
 riodicity : eleven year. Kb'ppen, p. 69, B. 
 1874, 8 poles and equators : coincidence with 
 those of magnetism and wind ; p. 35, E. II. 36 
 possible conditions in former times. Heu- 
 nessy, p. 57, B. 1865, 25 relation of decrease 
 with height to other elements. BaxendelJ, 
 p. 57, B. 1865, 2 relation between its ver- 
 tical distribution and that of the cloud zone ; 
 p. 6, E. I. 15. 
 
 TERRESTRIAL MAGNETISM. See 
 under Earth. 
 
 THUJA, as test of purity of air, p. 82, 
 N. 
 
 TREES : raining. Murray, p. 38, p. B. 1831, 
 9. Schmidt, p. 52, B. 1859, 22. 
 
INDEX. 
 
 VENUS I influence on sun-spots. Stewart, 
 p. 21, E. II. 12. 
 
 "WEATHER. See under Climate. 
 
 "WIND, p. 57, B. 1865, 9 ; p. 76, B. 1880, 33 ; 
 p. 77, B. 1881, 11. Claridge, p. 15, B. 1827, 
 3. Hopkins, p. 52, B. 1860, 12. Leverrier, 
 p. 61, B. 1868, 16. Lommel, p. 67, B. 1873, 
 23. Loomis, p. 74, B. 1879, 30; p. 75, B. 
 1879, 77 ; p. 77, B. 1881, 5. Mohn, p. 70, B. 
 1875, 27 ; p. 75, B. 1879, 56 antitrades, path 
 of electrical auroral discharge. Stewart, De 
 La Rive, p. 35, E. II. 36 changes. Ansted, 
 p. 96, N. 305 as characteristic of different 
 kinds of weather. Abercromby, p. 108-112, 
 N. Ley, p. 134-137, N. connection with 
 barometric condition. Abercromby, p. 115, 
 X. connection with climate. Hann, p. 63, 
 B. 1870, 14 connection with terrestrial mag- 
 uetism. Stewart, p. 105, N. connection with 
 weather. Strachan, p. 130, N. connection 
 with weather changes. Marie-Davy, p. 72, 
 1877, 12 course of northerly explained. 
 Sandeman, p. 46, B. 1851, 12 cyclones, p. 
 150, E. II. cyclones ; connection with sun- 
 spots ; p. 151, 152, E. II. 56. Trouvelot, 
 p. 68, B. 1873, 60 cyclones: periodicity; 
 p. 151, 152, E. II. 56 cyclones : relation to 
 solar heat. Stewart, p. 33, E. II. 32 hurri- 
 canes : influence of moon, p. 146, 147, E. II. 
 43 influence of sun-spots : India, Archi- 
 bald, p. 125, X. influence on man. Kohl, 
 p. 70, B. 1875, 6 influence of polar wind 
 on man. Mitchell, p. 62, B. 1869, 32 ; B. 
 1869, 33 maps: natural areas adopted, p. 
 141, X. method of investigation : synoptic. 
 Abercromby, p. 116, N. periodicity, p. 150, 
 
 WIND continued. 
 
 E. II. ; periodicity : diurnal ; on lakes, p. 9, 
 E. I. 17 (lake Geneva). Plantamour, p. 9, 
 E. I. 17 (lake Te Anau). McKerrow, p. 9, 
 E. I. 17 periodicity; diurnal: force (Bir- 
 mingham). Osier, p." 89, E. I. 17. Pola, p. 8, 
 E. I. 17 periodicity ; diurnal : rotation of 
 direction (Bombay). Chambers, p. 8, E. 1. 17. 
 (Calcutta), p. 8, E. I. 17 (Gondar). Ruppell, 
 p. 8, E. I. 17. (Pola), p. 8. E. I. 17 on sea 
 coast, p. 8, E. I. 17 tropics, p. j E. I. 17 
 poles: coincidence of magnetic, heat, and wind 
 poles and equators, p. 35, E. II. 36 prognos- 
 tications by clouds. Ley, p. 125, X. prog- 
 nostications of storms. Krecke, p. 53, B. 
 1861, 21. Prestel, p. 54, B. 1862, 24 rates 
 of progress of storm centres, p. 76, B. 1880, 
 33 relation to cold in spring. Volta, p. 14, 
 B. 1817, 4 rotation. Buys-Ballot, p. 59, B. 
 1867, 8 at se'a. Ploix and Caspari, p. 70, 
 B. 1875, 32 storm beginnings ; periodicity, 
 diurnal ; Switzerland. Peters, p. 9, E. I. 17 
 storms ; theory. Mercurius, p. 39, B. 1834, 
 13 trade. Muh'ry, p. 68, B. 1873, 40 ; p. 69, 
 B. 1874, 33. Typhoon : China Sea, p. 75, B. 
 1879, 79 typhoons : Japanese Sea, p. 75, B. 
 
 1879, 79 waterspout : Cape Spada, p. 76, B. 
 
 1880, 33 Antarctic regions. Maury, p. 53, 
 B. 1861, 22 Atlantic Ocean, p. 76, B. 1880, 
 33. Indian Ocean, p. 76, B. 1880, 33. Pacific 
 Ocean, p. 76, B. 1880, 33. Scotland, Tay 
 Bridge, p. 76, B. 1883, 35. 
 
 YEW : as test of purity of air, p. 82, X. 
 ZODIACAL LIGHT : influence of ether. 
 
 Wilcocks, p. 58, B. 1865, 43 : p. 63, B. 1869, 
 
 46. 
 
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 p. 73, col. 1, line 26. Delete /. 
 
 p. 74, col. 1, lines 47, 51. For Hellman read Hellmann. 
 p. 75, col. 1, line 47. For P. rend R. 
 ]>. 76, col. 1, line 30. For Ann. read Am. 
 p. 78, line 16. For 112 read 212. 
 
 line 22. For 4 read 1. 
 p. 80, line 28. Insert view after ^bird's eye. 
 p. 88, line 36. For Well's read Wells' a. 
 p. 100, line 32. For J. read T 
 p. 119, last line. For procees read process. 
 p. 123, line 26. Insert' as after is. 
 p. 124, line 18. For Meyer read Myer. 
 p. 126, line 40. For Valenita read Valentia. 
 p. 140, line 51. For immediatedly read immediately. 
 
AQUEOUS VAPOUK: REMARKS. 
 
 UNDER this head will be grouped facts relating 
 to the geographical distribution of aqueous 
 vapour, both that which is invisible and that 
 which is partially condensed, as in clouds, 
 fogs, mists, dew and kindred phenomena. The 
 properties will be given under Water, not 
 under Climate, except in a few cases for the 
 purpose of explaining climatic phenomena. The 
 aqueous vapour notes also deal with otherpoints, 
 such as the absolute amount of aqueous vapour 
 in the atmosphere, the humidity or degree of 
 saturation, and the variation of both these with 
 height above the sea and the ground, season, and 
 period of day. They also take into account 
 discussions as to the rate of evaporation accord- 
 ing to circumstances, and clouds. The notes 
 further embrace facts relating to all the causes 
 which modify the amount and rate of variation 
 of evaporation, such as areas of water, nature 
 of ground, whether covered with vegetation or 
 not, and other collateral matters. Plants and 
 animals in many cases afford some indications of 
 the state of the air of a locality as regards 
 moisture, and hence facts relating to these which 
 seem to have a bearing on the subject are ad- 
 mitted here. 
 
 The explanation of the contractions for the 
 
 various periodicals and books will be given when 
 the first volume has been completed ; the follow- 
 ing, however, may be mentioned here. Every 
 item, whether it be a paper, or a volume, or a 
 series of volumes, which has been examined, and 
 the facts afforded by it placed in the magazine, 
 is marked ra, if the article only has been read ; 
 ru, if the volume has been analysed ; and r$, if 
 the series has been searched ; but when such item 
 has been perused too late for the insertion of the 
 facts in their proper place in the previously 
 published portion qf the magazine, p is appended 
 to these. In this case they become rap, rvp, or 
 rsp. These unpublished entries are entered in 
 the manuscript notes, and will be available for 
 the next edition. The date following the number 
 of the volume in parentheses, is the date given 
 on the titlepage of the volume. In the case of 
 serials the separate numbers were published 
 earlier. When the dates of these are known the 
 notes are entered under the year of publication 
 of the number. 
 
 The bibliography for the years 1875 and 
 onwards is deferred in order to allow of pub- 
 lishers and authors sending in copies or notices 
 of their more recent publications which relate 
 to the subject of the present part. 
 
 AQUEOUS VAPOUE: BIBLIOGRAPHY. 
 
 Dates unknown. 
 
 1. Geddes, G-. Rain, evaporation, and filtra- 
 tion. 8vo. (Lib. Geog. Soc.) 
 
 2. Russell, H. C. Table to facilitate finding 
 the humidity of the air. Diagram. London. 
 (Lib. Met. Soc.) 
 
 3. Stewart, Balfour. Remarks on meteoro- 
 logical reductions, with especial reference to the 
 element of vapour. 8vo. (Privately printed.) 
 (Lib. Met. Soc.) 
 
 1682. 
 
 1. Hobbes, Thomas. Seven philosophical 
 problems. London. 1682 (rr). 
 
 1732. 
 
 1. Gersten, C. L. Tentamina systematis 
 novi ad mutationes Barometri et natura elateris 
 aerei demonstrandas, cui adjecta .... Dissertatio 
 roris decidua errorem antiquum et vulgarem per 
 observationes et experimenta nova excutiens. 
 8vo. Francofurti. 1732. 
 
 1766. 
 1. Saul, Rev. Edward. 
 
 An historical 
 
 and philosophical account of the barometer or 
 weather glass. 3rd Ed. 1766. (Lib. Met. Soc.) 
 |rt). 
 
 PAKT II. No. 7. 
 
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 1. Saussure, H. B. de. Essais sur 1'hy- 
 grometrie. 4to. Neuchatel. 1783. 
 
 1784. 
 
 1. Saussure, H. B. de. Versuch fiber die 
 Hygrometrie. 8vo. pp. xii. 432. Leipzig^ 
 1784. [German translation.] 
 
 1786. 
 
 1. De Luc, J. A. Idees sur la mete'orologie. 
 Tome 1. 8vo. London. 1786. 
 
 2. Franklin, Benjamin. On hygro- 
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 1786 (n>). 
 
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 1786 (HJ). 
 
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 1. De Luc, J. A. Neue Ideen iiber die 
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 Stettin, 1787. [Translation from French.] 
 
 2. De Luc, J. A. Idees sur la meteorologie. 
 
 Tome 
 
 8vo. London. 1787. 
 
 177 
 
AQUEOUS VAPOUR 
 
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 1. Eason, A. On the ascent of vapour. 
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 etc. Bibl. Britannique (Agric.), xvii. p. 274 
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AQUEOUS VAPOUR 
 
 18141830. 
 
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 metry, and their connexions with the phenomena 
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 xxxiii. p. 291-303. 1812. 
 
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 dopo a quelli che scaricarono grandine. Brugna- 
 telli, Giornale, x. p. 17-27. Ann. de Chimie, iv. 
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AQUEOUS VAPOUR 
 
 18721874. 
 
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 188 
 
AQUEOUS VAPOUR: NOTES. 
 
 1682. 
 
 Hobbes, Thomas. (P. 1682, 1.) 
 
 (Page 26.) It is by the motion of the sun that fluid bodies are made to exhale out of 
 the earth. 
 
 A. 'Tis very probable that the same action of the sun is that which from the sea and 
 moist places of the earth, but especially from the sea, fetcheth the water up into the 
 clouds. 
 
 (Page 45.) A. What is the original cause of rain ? 
 
 B. The motion of the air, tending to the disunion of the parts of the air, must needs 
 cause a continual endeavour of whatsoever fluids there are upon the face of the earth 
 and sea to supply the place which would else be empty. This makes the water, and 
 also very small and loose parts of the earth and sea, to rise and mingle themselves with 
 the air, and to become mist and clouds, of which the greatest quantity arise there where 
 there is most water, namely, from the large parts of the ocean : which are the South Sea, 
 the Indian Sea, and the sea that divideth Europe and Africa from America, over which 
 the sun for the greatest part of the year is perpendicular, and consequently raiseth a 
 greater quantity of water, which afterwards gathered into clouds falls down in rain. 
 
 A. If the sun can thus draw up the water, though but in small drops, why can it not 
 as easily hold it up ? 
 
 B. It is likely it would also hold them up if they did not grow greater by meeting 
 together, nor were carried away by the air towards the Poles. 
 
 A. What makes them gather together? 
 
 B. It is not improbable that they are carried against hills, and there stopt till more 
 overtake them. And when they are carried towards the north or south, where the force 
 of the sun is more oblique and thereby weaker, they descend gently by their own weight. 
 And because they all tend to the centre of the earth, they must needs be united in their 
 way for want of room and so grow bigger, and then it rains. 
 
 (Page 56.) A. What breaketh the clouds when frozen ? 
 
 B. In very hot weather the sun raiseth from the sea and all moist places abundance of 
 water, and to a great height. And while this water hangs over us in clouds, or is again 
 (Page 57) descending, it raiseth other clouds, and it happens very often that they press 
 the air between them and squeeze it through the clouds themselves. [He seems to have 
 no idea of vaporisation. The essay is in the form of a dialogue, the interlocutors in 
 which are called A and B.] 
 
 1766. 
 
 Saul, Rev. Edward. (B. 1766, 1.) 
 
 (Page 16.) Boyle proved that the pressure is least when the air is most charged with 
 (Page 26) clouds and vapours. It has been suggested that the difference in the air's 
 gravity proceeded from its being more or less charged with vapour. If this were the 
 cause of it there must be as much vapour in the air at a time as is equal to the weight of 
 3 inches of mercury ; for so much do we commonly find the mercury to rise and fall. 
 Consequently the vapours in the air at once will be equal to the weight of a column of 
 (Page 27) water 42 inches in height, which is not only incredible but exceeds a year's 
 
 M89 
 
AQUEOUS VAPOUR 
 
 1766. Saul. NOTES. 
 
 rainfall [in England]. The reason, then, why the air is heavier at one time than 
 another, cannot he from the quantity of vapour floating in it. When the air is heavy 
 (Page 29) the vapours rise with the greater ease, and continue supported in larger 
 quantities at a greater height from the surface of the earth. And this exhalation pro- 
 ceeds partly from a subterraneous heat streaming out from the centre of the earth raising 
 (Page 30) sometimes a sensible steam, but chiefly from the rays of the sun, which, 
 falling obliquely upon the surface of the water, and being, many of them, reflected back 
 with, minute aqueous particles adhering to them, or thin watery cases surrounding 
 them, are by that means supposed to raise copious and continual exhalations from 
 them. These vapours being rarefied to a great degree, and (as Dr. Halley and Mr. 
 Derham imagine) formed into real but imperceptible bubbles by the heat, and actuated 
 by the rays of the sun, grow specifically lighter than the air, and. consequently must 
 rise till they come to an air of the same specific gravity with themselves, where they 
 (Page 31) will rest. And thus in proportion to the weight of the air and the density 
 or rarefaction of the vapours themselves they will either float near the surface of the 
 earth under the appearance of mists or fogs, or else, mounting up out of sight they will 
 range themselves in higher or lower regions of the atmosphere, suitably to their specific 
 gravity, where they will rest. And if at any time during their suspension the state of 
 the atmosphere varies by any attenuation or compression in the regions above, the 
 situation of the vapours will in like manner range with it, either by a further ascent 
 upwards or depression downwards according as the weight of- the atmosphere is increased 
 or diminished. It is only of these steams, mists and vapours thus raised from the 
 surface of the earth and sea, thus carried up and supported at different heights, thus 
 floating in seemingly large compacted bodies, and those confusedly driven together and 
 accumulated by the winds, that the clouds are formed ; which are in reality no other 
 (Page 32) than exalted mists ranged above in higher or lower horizontal planes in 
 proportion to the comparative density or rarefaction of the vapours themselves with that 
 (Page 33) of the atmosphere wherein they are buoyed up. Such vapours as are raised 
 up by the declining sun or hang near the surface of the earth, being condensed by the 
 coldness of the nights, in the summer fall back as dews, and in the winter as hoary 
 (Page 34) frosts. In what we call a black frost either the rise of the vapours is quite 
 intercepted or rather they are raised too high to be reached and precipitated by the cold 
 (Page 36) belowv "When the wind turns the stream of clouds and vapours one way it 
 (Page 37) soon clears the hemisphere [ = atmosphere]. The dryness of Peru and Chili may 
 he ascribed to the accumulation of air there, the winds accumulating the air on the west 
 (Page 38) side of the Andes. It is to an extraordinary attenuation of the air that we 
 ascribe the sudden overcasting of the sky, when in a calm, sultry morning, without any 
 visible clouds arising from below the horizon, a clear hemisphere (by the descent of the 
 vapours into the lower regions of the air) unexpectedly becomes hazy, thick and cloudy, 
 (Page 42) and even sometimes misty and rainy. In misty or foggy weather (if it be 
 of any continuance) the glass is commonly observed to stand very high ; because the 
 air is then usually still and presses with its full perpendicular weight. Dr. Wallis is of 
 opinion that the mists and vapours hanging thus in the air add to its pressure, which no 
 (Page 43) doubt is true in general, because the collective body of the air and vapours 
 taken together must weigh more than the air alone. And upon this account n ot on. 
 in misty, but in dark settled calm weather (when the vapours are raised and supported 
 at a very great height ; and so equally and copiously dispersed that the sky appears 
 uniformly thick and hazy in all quarters ; without the least gleam of sunshine breaking 
 through or any cloud distinctly formed), in such a dense state of the atmosphere the 
 weight of -it is greatly increased, and the height of the mercury is usually near 30 
 inches. But as soon as this state of the atmosphere changes either by the wind rising, 
 the sun breaking out, or both together dispersing the hemisphere [canopy] of vapour, 
 and forming many of them into large clouds sailing above, the mercury will in a few 
 190 
 
AQUEOUS VAPOUR 1766. Saul. NOTES. 
 
 hours settle to 29% inches, and sometimes to 29 inches. Hence it is observable that the 
 general and equal distribution of the vapours, whether in mists below or in a hazy sky 
 above, acts with a greater degree of pressure than any partial or unequal distribution of 
 (Page 44) them in clouds, which, whether suspended in the air or moving horizontally v 
 interrupt and take off some part of the perpendicular pressure from the regions above. That 
 (Page 45) the clouds do lessen the weight of the air seems proved by the following 
 experiments by Boyle. A piece of sponge suspended in equilibrio in sunshine becomes- 
 heavier when a cloud passes over, but returns to equilibrium when the cloud has passed. 
 (Page 46) Boyle cites this as a proof of humidity, but it really indicates a decreased 
 (Page 47) heaviness in the air. Dr. Wallis accounts for the gradual sinking and low- 
 ness of the barometer in rainy weather by the air getting lighter in proportion to the 
 quantity of the falling rains. If this were strictly and generally true, it will seem to- 
 follow from thence that the glass should stand highest when the air is fullest of clouds- 
 and vapours, because it is then most burdened, and lowest when the rains are quite over,, 
 because the air is then most lightened. But by experience the mercury is usually low 
 in cloudy and rainy weather, because the air is then lighter, 'and may often be observed 
 to rise for several hours before the rains are over. I do not say Dr. Wallis' opinion is- 
 (Page 48) false, but only that is not absolutely true in all cases. When the regions- 
 above are calm, and at the same time crowded with clouds, discharging themselves in 
 heavy and plentiful rains, the quantity falling will, it is reasonable to imagine, in some 
 degree lessen the pressure of the atmosphere, because by the interposure of large and 
 bulky clouds the free influx of the circumambient air is in some measure, and for some 
 time, intercepted and excluded ; but when the communication is open and the clouds 
 broken or dissipated, the free and regular accession of new air will add more to the- 
 pressure upon the stagnant mercury than the falling rains detract from it. The highest 
 (Page 49) rise of the barometer must be ascribed to a concurrence of circumstances,, 
 including the suspension of the vapours in the air, as also (as suggested by Boyle) to the 
 (Page 71) escape of subterranean chinks during droughts. To what height the vapours- 
 ascend does in a great measure depend upon the degree of heat wherewith they are 
 actuated, and upon the lightness of the vapours themselves, upon the density of the air 
 wherein they are buoyed up, and even sometimes upon the strength and force of the 
 winds wherewith they are impelled. Some of them are so far attenuated and rise to so- 
 great a height as not to be distinctly visible, of which kind, in Sir Isaac Newton's 
 opinion, are those that form by refraction the blue colour of the sky. Other vapours of 
 a grosser kind being compacted into clouds, and keeping for some time a fixed station in 
 (Page 72) the regions above, have (as Boyle tells us) been ordinarily measured to the 
 height of one-fourth or one-third of a mile, and some to half-a-mile ; but that very few, 
 nnd those of the whitest and in appearance the loftiest clouds, were upon trial found to- 
 be above three-fourths of a mile in height. In France or Italy clouds have been 
 observed at 2000, 3000, or even 4000 geometrical paces high, but none have exceeded 
 5000 paces, or 5 miles in height. The same heights, or perhaps greater, might be some- 
 times discovered here if observations were made. Thus the day after the storm of 1703, 
 a cloud passed over Oxford which good mathematicians considered was at least five miles 
 (Page 73) in height, judging by sight only.. The cloud might have got such an impetus- 
 from the storm as to be carried in a straight line so as to rise higher above the earth. 
 Hence, it may be, the cause of rain coming on with a fall of wind is that such clouds 
 as have thus been carried on by an horizontal impulse, then fall, owing to their superior 
 ( Page 74) gravity, and pass into rain. The cloud noticed by Kicciolus as being higher 
 than the projected shadow of the earth, was probably a luminous cloud [=aurora]. 
 Dr. Halley calculates that the Mediterranean may yield 5280 millions of tons of vapour 
 iu a day, and that with a drying wind for two or three rainless days the quantity sup- 
 plied and kept in the air at once may be over 30,000 millions of tons of water. And 
 by this means it is possible for some parts of the atmosphere to be sometimes even 
 
 191 
 
AQUEOUS VAPOUR 1786. Oliver. NOTES. 
 
 saturated or overcharged with vapours, which, as they afterwards happen either to be 
 driven and dispersed or collected and accumulated by the winds, will accordingly pro- 
 (Page 78) duce moderate or plentiful supplies of rain upon some parts of the continent, 
 (Page 82) or excessive quantities in others. Sometimes we may discover two distinct 
 squadrons of clouds floating at different heights, in streams of air directly contrary ; 
 sometimes the clouds meet and mix and increase all of a sudden in bulk and quantity. 
 (Page 83) The common hygroscopes depend altogether upon the moisture or dryness of 
 the air near the surface of the earth. If we suppose, as it sometimes happens, the 
 (Page 84) lower region of the air to be moist when all above has a tendency to be fair 
 and dry, or the lower region to be dry when all above has a tendency to wet weather, it 
 is certain that no conjectures taken from part of the atmosphere can be so well grounded 
 as what is derived from the more general and prevailing quality of the whole [viz, 
 (Page 101) that shown by the barometer]. If in changeable or fair weather the surface 
 of the mercury appears to be concave the weather will in a few hours become cloudy, 
 and sometimes rainy or windy. 
 
 1786. 
 Franklin, Benjamin. (B. 1786, 2.) 
 
 (Page 51.) Hygrometers have been defective owing to their being themselves colder 
 (Page 52) or warmer than the air during sudden changes. Their sensitiveness is a 
 disadvantage, as means can only be obtained by making constant observations day and 
 night for long periods. A substance slow to acquire and part with moisture would be 
 (Page 56) the best to make an hygrometer of. Such would be a piece of mahogany 
 fitted with movable hands and a marked scale. If these instruments were kept in the 
 same place while making, and were graduated together, they would serve as comparable 
 hygrometers, which would give the mean dryness of different countries. 
 
 Oliver, A. (B. 1786, 3.) 
 
 (Page 88) Paper read January, 1774. Whatever the immediate cause of evaporation 
 may be, it is certain that the superficial moisture of all bodies is perpetually exhaling 
 in vapour, which ascends into the higher regions of the atmosphere where they gather 
 (Page 89) together into clouds and at length recondense as dew, mist, or rain. These 
 vapours are either detached in streams from the humid ground by the influence of the 
 sun, or thrown off by the perspiration of those infinite multitudes of animals and plants 
 which cover the face of the earth, or supplied by evaporation from the ocean or other 
 large collections of water. Considering the vast extent of the ocean and the comparatively 
 small degree of moisture of which the dry land is susceptible, we may conclude that a 
 very small proportion of the clouds which are formed in the atmosphere are exhaled 
 from the latter, and that the ocean is the grand source from whence they principally 
 (Page 90) derive their origin. Our natural senses convince us that sea air is always 
 replete with moist vapours. These vapours are at first generally invisible, but when the 
 weather is cold they are always visible, and appear like a steam arising from boiling 
 water. (This is always the appearance in a clear still morning when Fahr. marks or 
 (Page 100) lower.) If evaporation be performed independent of electricity should we 
 (Page 108) not be enveloped in everlasting fogs ? The water raised from the sea 
 beneath waterspouts is forced upwards in the finest globules by the intruding air into 
 (Page 109) the warm electrical air expelled from below, where it becomes converted 
 into vapour. These vapours will be greedily attacked by the craving particles of air, 
 now deficient of electrical matter and form a dense cloud, in like manner as thunder 
 clouds are formed over the land. This cloud will then be ready to discharge rain. 
 (Note. The water raised up by waterspouts is salt, but descends fresh, so that it must 
 have undergone a natural distillation.) .~ 
 192 
 
AQUEOUS VAPOUR 1786. Williams. NOTES. 
 
 Williams, Rev. Samuel. (B. 1786, 4.) 
 
 [His experiments on evaporation were made at Bradford in New England, but have 
 a general bearing.] 
 
 (Pago 118.) The experiments were made in 1771. I filled the vessel at the 
 beginning of each month. I observed that in the beginning of the month, when the tube 
 was nearly filled, it exhausted much faster than towards the latter end, when 1 or 2 
 inches of water were evaporated ; and that the quantity of evaporation measured this 
 way came out less than the quantity of rain that fell in the course of the year. In 1772 
 I examined the matter more carefully, and made the following experiments 
 
 Experiment 1. I procured two cylindrical vessels, 3 inches in diameter and 6 inches 
 deep, as much alike as could be made. One I filled with water once a month, as 1 had 
 done in 1771, the other with the same kind of water once a week, and placed them 
 about 6 inches apart, in such a manner as to be exposed to wind and sun, but covered 
 from the rain. The one filled once a week was exhausted about one-third more than 
 the other. In January and February the difference was a little less ; in March and 
 April a little more. In May the evaporation from the former was 6*35 inches; from 
 (Page 119) the other 4'1 inches. I was hence convinced that by neither of these 
 methods could the quantity of water that really evaporates from the sea, etc., be 
 correctly estimated. For in the one case, after about an inch has been exhausted the 
 surface is too much sheltered from the wind, while in the other the water has all the 
 advantage of the wind and is heated by the sun and atmosphere to a greater degree than 
 the water in seas, etc., and the quantity of evaporation comes out too much. 
 
 Experiment 2. To measure the quantity more accurately I tried to ascertain what it 
 really was from the surface of a river. I filled one of the vessels with river-water, and 
 placed it as before. The second I floated on a board in the middle of the Merrimack 
 Eiver, defending it from rain and dew by a disk of glass placed 8 inches above the tube, 
 the mouth of which was half an inch above the surface of the river. My efforts were 
 baffled by wind and waves ; but I succeeded in the week August 26 to September 2. 
 During that time there was little wind, still water, no rain, and no disturbances. The 
 tube was exhausted 1 15 inches. No water got in, as the surface of the board within 
 0> inches of the tube was dry every morning and evening. In the other tube the evapo- 
 ration was 1 5 inches, which gives a difference of '35 inch. All the Blatter evaporations 
 should be diminished in this proportion. 
 
 Experiment 3. I next tried what the evaporation was from the surface of the earth. 
 On September 14, two days after rain, I sank one of the vessels into the earth in a light 
 soil, so as to take up all the earth contained in a space equal to the contents of the 
 vessel. Having carefully weighed the vessel with the earth it contained, I fixed it in 
 the ground in a plain open field, where it was exposed to wind and sun, but defended 
 from rain and dew. At the end of seven days I took it up, and, weighing it again, found 
 it had lost 783 grains troy. The diameter of the vessel being 3 inches, its surface, 
 expressed in whole numbers, was 9 square inches ; this gives 87 grains per square inch, 
 or * 34 inch that passed off in evaporation, reckoning 254 grains to a cubic inch of 
 (Page 121) water. In the other vessel the evaporation was 1 inch. The conclusion is 
 that the evaporation from the earth is but little more than one-third of the evaporation 
 from water. 
 
 Experiment 4. I next tried what the evaporation was from plants and trees. On 
 August 20 I took up four different sorts of plants with as much of the earth adjoining 
 them as wholly covered their roots. Each plant, with the earth about it, being 6 inches 
 square, 1 put into a wooden box of the same size and form. The boxes were covered 
 with thin lead to prevent evaporation from them, and had two apertures at the top, one 
 for the stem of the plant and one for watering it, which was stopped when not in use. 
 Having taken the weight of each, I placed them on the ground. I added known 
 PABT II. No. 7. o 193 
 
AQUEOUS VAPOUR 1793. Dalton. NOTES 
 
 quantities of water, the amount being that presumed to be thrown off by them. At the 
 end of thirty days I re-weighed them. The results were as follows : 
 
 Water evaporated 
 
 Weight of Plant. in 30 days. 
 
 Apple tree .. .. '23 grains .. .. 1271 grains. 
 Alder tree .. .. 30 .. .. 2593 
 
 Spearmint .. .. 22 .. .. 5186 
 
 Clover ...... 43 .. .. 
 
 (Page 122) or 10,944 grains from the four, or about 43 cubic inches in 30 days. The 
 evaporation from the vessel suspended in air during the same time was 4 "25 inches in 
 depth. The quantity, therefore, thrown off by the plants was more than what the 
 evaporation would have been from a watery surface 10 inches square. The evaporation 
 from vegetation would therefore be greater than from water over equal areas. 
 
 1793. 
 Dalton, J. (B. 1793, 1.) 
 
 (Page ix.) De Luc's idea of vapour seems not unlike mine^ The hygrometer is an 
 (Page 31) instrument meant to show the disposition'of the air for attracting water, or for 
 depositing the water it has in solution with it. To ascertain the exact quantity of water 
 in a given quantity of air, and also the disposition of the air for imbibing or depositing 
 (Page 41) it is an object highly important to meteorology. The supposition of the 
 clouds rising or falling with the barometer or as the density of the air increases pr 
 diminishes is not countenanced by Crosthwaite's observations on the clouds of 
 Skiddaw. These observations also show that in very heavy and continued rains the 
 clouds are mostly below the summit of the mountain (1050 yards) ; but it frequently 
 (Page 98) rains when they are entirely above it. Prof. Musschenbroek ascribes the 
 (Page 99) barometric variations to five causes, the fifth being that the air is loaded with 
 (Page 100) or cleared of vapours and exhalations. As to the fifth cause it must be 
 allowed that water when changed into vapour constitutes a part of the atmosphere for a 
 time, and weighs with it accordingly ; also that when the vapour is precipitated in form 
 of rain the atmosphere loses the weight of it ; but it would be hasty to conclude 
 hence that where evaporation is going forward the barometer must rise, and where rain 
 is falling it must fall also ; because air loaded with vapour is found to be specifically 
 (Page 101) lighter than without it. Evaporation, therefore, increases the bulk and 
 weight of the atmosphere at large, though it will not increase the weight over any 
 particular country if it displaces an equal bulk of air specifically heavier than the 
 others ; and in like manner rain at any place may not diminish the weight of the air 
 there, because the place of the vapour may be occupied by a portion of air specifically 
 heavier. It should seem, therefore, that when the air over any country is cleared of 
 vapours, etc., the barometer ought to be higher than usual, and not lower. Clouds are 
 (Page 103) never observed to be above four or five miles high. The barometric 
 fluctuations are due mainly to changes in the density of the lower stratum of the air. 
 (Page 104.) The more vapour air has in it the less is its specific gravity. Saussure 
 found by experiment that a cubic foot of air at a certain temperature will imbibe 
 12 grains of water, and every grain of water dissolved in air becomes an elastic fluid 
 capable of supporting -^ in. of mercury, while its density to that of air is as 3 to 4. 
 Priestley finds that gases of different specific qualities diffuse equally into each other. 
 Sir B. Thomson found that moist air conducted heat better than dry air. A cubic foot 
 of dry air mixed with a cubic foot of moist air would form 2 cubic feet, and be of 
 equal elasticity with the simples. Hence, then, a fluctuation of the density of the air 
 may happen thus; if a current of warm and vapourised air flow into a body of 
 cold and dry air it will displace a part of the cold air and diffuse itself among the 
 rest, by which means the weight of the stratum will be diminished, whilst its bulk 
 194 
 
AQUEOUS VAPOUR 1793. Dalton. NOTES. 
 
 and spring remain the same ; and vice versa, if dry air flow into vapourised air. The 
 (Page 106) first fact [that the barometer varies little at the tropics] may be accounted 
 for thus ; the warmer any air is, the more water it will imbibe in similar circum- 
 stances ; hence the air over the torrid zone being the hottest will contain the 
 most vapour; and the air about the poles being the coldest will contain the least. 
 (Note. The terms moist air and vapourised air denote air containing a great quantity 
 of vapour irrespective of its humidity.) Moreover as the heat within the torrid zone 
 (Page 107) fluctuates little, the variation of the barometer will be little. As the air at 
 all times will endeavour to maintain a proportion of vapour suitable to its temperature, 
 it follows that the air in general in the higher latitudes will then be both cold and dry, 
 and in the lower latitudes both warm and moist, relatively speaking. The consequence 
 is obvious, that, as a current from one or the other hand prevails, the barometer will 
 rise or fall accordingly, and the rise or fall will be greater as the place is situate near to 
 the extremes of temperature, because the air will in that case suffer the least change in 
 its passage. In summer the heat all over the northern hemisphere is brought almost 
 to an equality at the different parallels ; the whole mass of air is heated, swelled, and 
 replenished with vapour ; the air over the northern regions is almost brought into the 
 same state as within the tropics, and the barometer, therefore, has almost as little 
 (Page 108) variation in that season here as there. As, independent of winds, heat and 
 moisture will always be diffusing themselves in every direction where there is a deficiency 
 of either, it seems impossible that the variations of the barometer should be local, though 
 the amount of each fluctuation will not be the same at places considerably distant. The 
 greater nearness of the mean height of the barometer to the higher extreme in winter 
 than in summer may be thus explained. Moist air conducts heat better than dry air, and 
 when the lowest extreme of the barometer happens, the air is moist, high winds generally 
 prevail, and the atmosphere is much ruffled by clouds and storms ; all these circumstances 
 tend to diffuse the heat and to diminish the rate of decrease of temperature with height. 
 (Page 110.) The mean weight of the column of air is thus lessened. The reason why 
 (Page 112) the low extreme at Kendal, in Jan. 1789, followed the high extreme, is as 
 follows. The extreme and long-continued cold preceding must have reduced the gross 
 part of the atmosphere unusually low, and condensed an extraordinary quantity of dry 
 air into the lower regions ; this air was succeeded by a warm and vapoury current coming 
 from the torrid zone before the higher regions, the mutations of which in temperature 
 and density are slow, had time to acquire the heat, quantity of matter, and elevation 
 consequent to such a change below ; these two circumstances meeting, namely, a low 
 atmosphere, and the greater part of it constituted of light vapoury air, occasioned the 
 pressure upon the earth's surface to be so much reduced. Hence, then, it should seem 
 we ought never to expect an extraordinary fall of the barometer unless when an extra- 
 (Page 114) ordinary rise has preceded, or, at least, a long and severe frost. It does not 
 appear that cold alone has a tendency to increase the mean weight over any place, if 
 so, it would be higher in winter than in summer contrary to experience ; if, therefore, 
 the mean state of the barometer be lower in the torrid zone than in the frigid zones, it 
 (Page 119) is most probably effected by the vapoury air. The evaporation from the 
 surfaces of living vegetables is much greater than from the same space of land uncovered 
 with vegetables. Evaporation and condensation of vapour are made subservient to the 
 more equal diffusion of heat over the different climates and places ; evaporation being 
 great in the torrid zone, a vast portion of heat is absorbed and rendered insensible, 
 till, being carried northward or southward, the vapour is condensed and gives out its 
 heat again, which, being diffused in ' the atmosphere, augments its temperature very 
 (Page 132) considerably. Evaporation is promoted by heat, dry air, and a decreased 
 weight or pressure of the atmosphere upon the evaporating surface. The first and 
 (Page 157) second are known to have that effect, the last is proved to have such an 
 effect by the air pump. Evaporation from land in general must be less chsin the rain 
 
 02 105 
 
AQUEOUS VAPOUR 1793. Dalton. NOTES. 
 
 that falls upon land, otherwise there could be no rivers. From a series of experiments 
 made in 1793, 1 found the mean daily quantity evaporated from a vessel of water in a 
 situation pretty well exposed to wind and sun for thirteen days of March to be '033 in. 
 depth, the greatest '064 in. ; for twenty-one days of April the mean daily quantity was 
 055 in., the greatest '1115 in. ; for twenty-six days of May the mean was '0755 in., 
 the greatest -1346 in. ; for fourteen days of June the mean was '063 in., the greatest 
 098 in. ; for eight days of July the mean was '122 in., the greatest 195 in. I never 
 found the evaporation from water any summer much to exceed *2 in. in 24 hours in the 
 hottest weather. From these experiments and other considerations it seems probable 
 that the evaporation both from land and water in the temperate and frigid zones is not 
 (Page 142) equal to the rain that falls there even in summer. When a precipitation of 
 vapour takes place, a multitude of exceedingly small drops form a cloud, mist, or fog ; 
 these drops, though 800 times denser than the air, first descend very slowly owing to 
 the resistance of the air, which produces a greater effect as the drops are smaller, as the 
 resistances are as the square of the diameters. From this it appears that clouds consist- 
 (Page 143) ing of very small drops may descend very slowly, which is agreeable to 
 observation ; if the drops in falling enter a stratum of air capable of imbibing vapour 
 they may be re-dissolved, and the clouds not descend at all ; and if the air's capacity 
 for vapour increase they may be all imbibed and the cloud entirely vanish. On the 
 other hand, if the precipitation goes forward, and the air below have its full quantity of 
 vapour, the small drops meeting one another will coalesce and form large ones, and 
 descend in the form of rain to the earth's surface. (Note. This account of the nature of 
 clouds and of the mode of their rising and falling was suggested by a friend.) From the 
 important observations on the height of the clouds [by Crosthwaite], we learn that they 
 are seldomer above the summit of Skiddaw in November, December, January, and Feb- 
 ruary than in the other months ; this clearly indicates the effect of cold in restraining the 
 ascent of vapour. Were the measurement extended above the summit of the mountains, 
 it is probable from the apparent law of the table that there could not be many observations 
 (Page 144) above 1300 yards in winter, nor above 2000 yards in summer. This, it must 
 be observed, relates only to the height of the tinder-surface of the gross clouds. The 
 small white streaks of condensed vapour which appear on the face of the sky in serene 
 weather I have, by several careful observations, found to be from throe to five miles above 
 earth's surface. When vapour is condensed into small drops upon the surface of bodies 
 on the ground it is called dew ; it differs from rain in being condensed on or near the solid 
 bodies receiving it, whereas rain is condensed in mid-air. At first sight it will 
 seem inconsistent that condensation of vapour should occur in the air resting on the 
 earth's surface, since it is generally supposed to be warmer than the air above ; but it 
 is a fact that after sunset and during the night in serene weather, the air is coldest at 
 (Page 145) the earth's surface. And accordingly we find that dew and hoarfrost are 
 more copious in valleys than in elevated situations. That dew depends upon this 
 circumstance can hardly be doubted, because, when clouds or winds prevent it, there is 
 (Page 151) little or no dew formed. When the barometer is very high, the air is 
 either very dry or cold, or both ; when very low it is very moist or warm, or both. 
 (Page 196) Very dark and dense clouds pass over without rain when the barometer is 
 high; whereas, when the barometer is low, it sometimes rains almost without any 
 (Page 202) appearance of clouds. The condensation of vapour exposed to the common 
 air does not in any manner depend upon the pressure of the air. The temperature of 
 the air bears a relation to the condensation of vapour. Though the pressure of the 
 air does not promote condensation, yet when the pressure is removed evaporation is 
 promoted. 
 
 196 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 Wells, W. C. (B. 1818, 1.) 
 
 (Page 122.) The second edition of ' An Essay on Dew,' published in 1815, differs 
 from the first chiefly in the form of several expressions, such as " repletion with 
 moisture," instead of " saturation with moisture," as my theory is inconsistent with the 
 idea of air being capable of dissolving water. In 1788, Patrick Wilson suggested that 
 (Page 123) hoarfrost was attended with the production of cold ; and in the same year 
 Six mentioned, in a paper communicated to the Royal Society, that on clear and dewy 
 nights the thermometer on the ground in a meadow was lower than one suspended six 
 feet above it. Six attributed the cold partly to the low temperature of the air through 
 (Page 124) which the dew had fallen, and partly to the evaporation of moisture from 
 the ground. An experiment, in the autumn of 1811, induced me to investigate the 
 subject. After giving some attention to it, I began to suspect that Wilson, Six, and 
 myself were in error in ascribing the cold to the formation of dew, and arrived at the 
 (Page 127) conclusions given in the present essay. Aristotle remarked that dew only 
 appears on calm and serene nights. Musschenbroek says that dew forms in Holland 
 while the surface is covered with a low mist ; but as he mentions at the same time that 
 it is deposited on all bodies indiscriminately, the moisture of which he speaks cannot 
 properly be called dew. Other writers have also regarded clearness of the air as not 
 being requisite for the production of dew, misled, probably, by observing on misty 
 (Page 128) mornings copious dews which had been produced during preceding clear 
 nights. I never knew dew to be abundant except in clear weather. In regard to the 
 necessity of the air being still, Prieur is the only author who rejects it, and he affirms 
 that a fresh wind is requisite for the production of dew. The remark of Aristotle, 
 however, is not to be received in its strictest sense, as I have frequently found a small 
 quantity of dew on grass, both on windy nights if the sky was clear, or nearly so, and 
 on cloudy nights, if there was no wind. If, indeed, the clouds were high and the 
 weather calm, I have sometimes seen on grass, though the sky was entirely hidden, no 
 very inconsiderable quantity of dew. Again, according to my observation, entire 
 stillness of atmosphere is so far from being necessary for the formation of this fluid that 
 its quantity has seemed to me to be increased by a very gentle motion in the air. Dew, 
 however, has never been seen by me on nights both cloudy and windy. If in the 
 (Page 129) course of the night the weather, from being calm and serene, should become 
 windy and cloudy, not only will dew cease to form, but that which has formed will 
 either disappear or diminish considerably. In calm weather, if the sky be partially 
 covered with clouds, more dew will appear than if it were entirely covered, but less than 
 if 'it were entirely cleared. Dew, probably, begins in this country [= England] to 
 appear upon grass, in places shaded from the sun during clear and calm weather, soon 
 after the heat of the atmosphere has declined. I have had few opportunities for making 
 such observations, but I have frequently felt grass moist, in dry weather, several hours 
 before sunset. On the other hand, I have scarcely ever known dew to be present in 
 such quantity upon grass as to exhibit visible drops before the sun was very near the 
 horizon, or to be very copious till some time after sunset. It also continues to form in 
 shaded places after sunrise ; but the interval between sunrise and its ceasing to form is, 
 according to my observation, which upon this point has not been extensive, considerably 
 shorter than that between its first appearance in the afternoon and sunset. Contrary, 
 (Page 130) however, to what happens at sunset, if the weather be favourable, more 
 dew forms a little before, and in shaded places a little after, sunrise than at any other 
 time. Musschenbroek, therefore, errs greatly when he says that dew does not form 
 after the sun has risen. The preceding observations on the early appearance of dew in 
 the afternoon, are to be restricted to what happens to grass or other substances highly 
 attractive of dew placed on the ground ; for it occurs much later on similar substances 
 
 197 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 which are elevated a few feet above the ground, though upon these it continues to form 
 as long after the rising of the sun as upon the others, if they be equally sheltered from 
 the rays of that body. The formation of dew, after it has once commenced, continues 
 during the whole night if the weather remains still and serene. Prieur, indeed, asserts 
 that dew forms only in the evening, and that any which occurs in the former season 
 always disappears in the course of the night. I can affirm, however, from long experi- 
 ence, that grass, after having been dewed in the evening, is never found dry till after 
 sunrise, unless the weather has in the meantime changed. Upon one serene and still 
 night I placed fresh parcels of wool upon grass every hour, and by weighing each 
 (Page 131) of them after exposure for an hour found that they had all attracted dew. 
 During nights that are equally clear and calm dew often appears in very unequal 
 quantities, even after allowance has been made for any difference in their lengths. One 
 great source of these differences is very obyious. For it being obvious that the more 
 replete the atmosphere is with moisture the more copious will the precipitation be when 
 the causes forming dew are in operation, and that all the circumstances which tend to 
 (Page 132) increase the quantity of moisture must likewise tend to increase the quantity 
 of dew. Thus dew, in equally calm and clear nights, is more abundant shortly after 
 rain than during a long tract of dry weather. It is more abundant also throughout 
 Europe, with perhaps a few exceptions, and in some parts of Asia and Africa, during 
 southerly and westerly winds, than during those which blow from the north and east. 
 Aristotle says that Pontus is the only country in which dew is more copious during 
 a northerly than during a southerly wind. But a similar fact occurs in Egypt. Both 
 cases, however, though contrary to the letter, are consonant with the spirit of the rule ; 
 since the north wind in the one country proceeds from the Euxine Sea, and in the other 
 from the Mediterranean. Another circumstance of the same kind with the blowing of 
 the wind from the south and west, as showing that the air contains much moisture, is 
 the lessening of the weight of the atmosphere. My experience, indeed, on this point 
 has not been great, as the falling of the barometer is very commonly attended with 
 (Page 133) wind or clouds, both unfavourable to the production of dew ; but stili 
 the greatest dews I have ever witnessed occurred while the barometer was sinking. A 
 corresponding observation was made by De Luc, who says that rain may be foretold 
 when dew is uncommonly abundant in relation to the season and climate. To the 
 greater or less quantity of moisture in the atmosphere, at the time of the action of the 
 immediate cause of dew, are to be referred several facts respecting its copiousness, the 
 explanation of which is, perhaps, not quite so apparent as in the preceding examples. 
 In the first place, dew is commonly more plentiful in spring and autumn than in 
 summer; the reason is, that a greater difference is generally found between the 
 temperatures of the day and night in the former seasons of the year than in the latter. 
 In spring, this circumstance is often prevented from having a considerable effect by the 
 opposite influence of northerly and easterly winds ; but during still and serene nights in 
 autumn dew is almost always highly abundant. In the second place, dew is always 
 very copious in those clear and calm nights which are followed by misty or foggy 
 (Page 134) mornings, the turbidness of the air in the morning showing that it must 
 have contained during the preceding night a considerable quantity of moisture. Thirdly, 
 I have observed dew to be unusually plentiful on clear mornings which had succeeded a 
 cloudy night; for the air, having in the course of the night lost little or no moisture, 
 was in the morning more charged with watery vapour than it would have been if the 
 night had also been clear. Fourthly, heat of the atmosphere, if other circumstances are 
 favourable which, according to my experience, they seldom are in this country 
 occasions a great formation of dew. For as the power of the air to retain watery vapour 
 in a pellucid state increases considerably faster while its temperature is rising in 
 proportion to the heat acquired, a decrease of heat, in any small given quantity during 
 the night, must bring it, if the temperature be high, much nearer to the point of 
 
 -1*70 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 repletion, before it be acted upon by the immediate cause of dew, than if the temperature 
 be low. We read, accordingly, in the writings of those who have travelled into hot 
 climates of a copiousness of dew frequently observed by them there, which very much 
 exceeds what occurs at any time in this country. But even here, dew, though for the 
 most part scanty in our hottest season, is sometimes very abundant during it; an 
 (Page 135) example of which occurred to me on the night common to the 29th and 
 30th of July, 1813; for on that night, notwithstanding its shortness, more dew appeared 
 than has ever been observed by me on any other. In the last place, I always found 
 when the clearness and stillness of the air were the same, that more dew was formed 
 between midnight and sunrise than between sunset and midnight, though the positive 
 quantity of moisture in the air must have been less in the former than in the latter 
 time, in consequence of a previous precipitation of part of it. The reason, no doubt, is 
 the cold of the atmosphere being greater in the latter than in the prior part of the night. 
 But there are many circumstances influencing the quantity of dew, though much more 
 open to accurate observation, are yet much less easy to be imderstood. In my first 
 attempts to compare the quantity of dew formed during different times or in different 
 situations, I attended only to the appearance which it made on bodies having smooth 
 surfaces. But quickly seeing this method to be very imperfect, I next employed wool 
 (Page 136) to collect dew from the atmosphere, and found it well adapted for my 
 purpose, as it readily admits amongst its fibres the moisture which forms on its outer 
 parts, and retains what it receives so firmly that I never but once had occasion to 
 suspect that it suffered any portion of what it had thus acquired to pass entirely 
 through it. The wool which I used was white, moderately fine, and already imbued 
 with a little moisture from having been long exposed to the air of a room in which no 
 fire was kept. I divided it into parcels of 10 grains each, and immediately before 
 exposure pulled the fibres of every parcel somewhat asunder, so as to give it the form of 
 a flattened sphere, the greatest diameter of which was about 2 inches. Tho parcels, 
 probably, differed a little in size, but not enough so to affect the accuracy of the 
 experiments, which were made in a garden in Surrey, about three miles from Blackfriars 
 (Page 137) Bridge, but not more than li mile from a densely-built part of the 
 suburbs on the south side of the Thames. The garden was level, and nearly half an acre 
 in extent. At one end was a dwelling-house, at the other a range of low buildings ; on 
 one side a row of high trees, on the other a low fence dividing it from another garden. 
 Towards one end there was a grass plat, in length 62 feet, and nearly 16 feet broad, the 
 herbnge of which was kept short by frequent mowing. The rest of the garden was 
 employed for the production of culinary vegetables. All of these circumstances, however 
 trifling they may appear, had an influence on my experiments, and most of them, as will 
 hereafter be seen, must have rendered the results less remarkable than they would have 
 been if they had occurred on a wide open plain considerably distant from a large city. I 
 now proceed to relate the influence which several differences in the situation, mechanical 
 state, and real nature of bodies, have upon the production of dew. One general fact 
 (Page 138) relative to situation is, that whatever diminishes the view of the sky, 
 as seen from the exposed body, occasions the quantity of dew which is formed upon it 
 to be less than would have occurred if the exposure to the sky had been complete. I 
 placed, on several clear and still nights, 10 grains of wool upon the middle of a painted 
 bo:ird 4 feet long, 2 feet wide, and 1 inch thick, elevated 4 feet above the grass-plat by 
 means of four slender props of equal height, and at the same time attached loosely 
 10 grains of wool to the middle part of its under side. The two parcels were conse- 
 quently only an inch asunder, and were equally exposed to the action of the air. Upon 
 one night, however, I found that the upper parcel had gained 14 grains in weight, but 
 the lower only 4. On a second night, the quantities of moisture acquired by like 
 parcels of wool in the same situations as in the first experiment were 19 grains and 
 6 grains ; on a third, 11 and 2 ; on a fourth, 20 and 4 ; the smaller quantity being 
 
 199 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 always gained by the wool attached to the lower side of the board. I bent a sheet 
 of pasteboard into the shape of a house-roof, making the angle of flexure 90, and leaving 
 both ends open. This was placed one evening, with its ridge uppermost, upon the 
 (Page 139) same grass-plat, in the direction of the wind, as well as this could be 
 ascertained. I then laid 10 grains of wool on the middle of that part of the grass 
 which was sheltered by the roof, and the same quantity on another part of the grass- 
 plat fully exposed to the sky. In the morning, the sheltered wool was found to 
 have increased in weight only 2 grains, but that which had been exposed to the sky 
 16 grains. In these experiments the view of the sky was almost entirely cut off from 
 the situations in which little dew was formed. In others, where it was less so, the 
 quantity gained was greater. Thus, 10 grains of wool, placed upon the spot of the 
 grass-plat which was directly under the middle of the raised board, and which enjoyed, 
 therefore, a considerable oblique view of the sky, acquired during one night 7, during 
 a second 9, and during a third 12 grains of moisture ; while the quantities gained 
 during the same time by equal parcels of wool laid upon another part of the grass-plat 
 which was entirely exposed to the heavens, were 10, 16, and 20 grains. As no moisture, 
 falling like rain from the atmosphere could, in a calm night, have reached the wool 
 in any of the situations where little dew was formed, it may be thought that the 
 (Page 146) substances under which the wool was placed prevented, mechanically, the 
 access of that fluid. But on this supposition it cannot be explained why some dew 
 was always found in the most sheltered places, and why a considerable quantity 
 occurred upon the grass under the middle of the raised board. A still stronger proof of 
 the want of justness in this supposition is afforded by the following experiment. I 
 placed upright on a grass-plat a hollow cylinder of baked clay, the height of which was 
 2z feet and diameter 1 foot. On the grass surrounded by the cylinder were laid 
 10 grains of wool, which in this situation, as there was not the least wind, would have 
 received as much rain as a like quantity of wool fully exposed to the sky. But the 
 quantity of moisture obtained by the wool surrounded by the cylinder was only a little 
 more than 2 grains, while that acquired by 10 grains of fully exposed wool was 16. 
 This occurred on the night during which the wool under the bent pasteboard gained 
 only 2 grains of moisture. Dew will, however, in consequence of other varieties of 
 situation, form in very different quantities upon substances of the same kind, although 
 these should be similarly exposed to the sky. In the first place, it is requisite for the 
 (Page 141) most abundant formation of dew that the substance attracting it should 
 rest on a stable horizontal body of some extent. Thus, upon one night, 10 grains of 
 wool laid upon the raised board increased 20 grains in weight ; an equal quantity 
 suspended in the open air 5 feet above the ground, increased only 11 grains, not- 
 withstanding that it presented a greater surface to the air than the other parcel. On 
 another night, 10 grains of wool gained on the raised board 19 grains, but the same 
 quantity suspended in the air on a level with the board only 13; and on a third, 
 10 grains of wool acquired on the same board 2 grains of weight during the time in 
 which other 10 grains hung in the air at the same height acquired only half a grain. 
 In the second place, the quantities of dew attracted by equal masses of wool, similarly 
 exposed to the sky and resting on equally stable and extended bodies, oftentimes vary 
 considerably in consequence of some difference in the other circumstances of these 
 bodies. Ten grains of wool, for instance, having been placed upon the grass-plat on 
 a dewy evening, 10 grains upon a gravel walk which bounded the grass-plat, and 
 10 grains upon a bed of bare garden mould immediately adjoining the gravel walk, in the 
 (Page 142) morning the wool on the grass was found to have increased 16 grains in 
 weight, but that on the gravel walk only 9, and that on the garden mould only 8. On 
 another night, during the time that 10 grains of wool laid upon grass acquired 2 grains 
 of moisture, the same quantity gained only half a grain upon the bed of garden mould ; 
 and a like quantity placed upon the gravel walk received no accession of weight what- 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 ever. Two objections will probably be made against the accuracy of these experi- 
 ments with wool. One is, that wool placed on grass may, by a kind of capillary 
 attraction, receive dew previously formed on the grass in addition to its own. To this 
 I answer, that wool in a china saucer, placed on the grass, acquired very nearly as much 
 weight as an equal parcel immediately touching the grass. The second objection is 
 that a part of the increased weight in the wool might arise from its imbibing moisture as 
 a hygroscopic substance. I do not deny that some weight was given to the wool in 
 this way ; but it may safely be affirmed that this quantity must have been very small. 
 For, on very cloudy nights, apparently the best fitted to increase the weight of 
 hygroscopic substances, wool upon the raised board would in the course of many hours 
 (Page 143) acquire little or no weight ; and in London I have never found 10 grains 
 of wool, exposed to the air on the outside of one of my chamber windows, to increase 
 during a whole night more than half a grain in weight. When this weight was gained 
 the weather was clear and still ; if the weather was cloudy and windy the wool received 
 either less or no weight. This window is so situated as to be in great measure deprived 
 of the aspect of the sky. It being shown that wool, though highly attractive of dew, 
 was prevented, by the mere vicinity of a gravel-walk, or a bed of garden mould, for 
 only a small part of it actually touched those bodies, from acquiring nearly as much 
 dew as an equal parcel laid upon grass, it may be readily inferred that little was 
 formed upon themselves. In confirmation of this conclusion I shall mention that I 
 never saw dew upon either of them. Another fact of the same kind is that, while 
 returning to London from the scene of my experiments, about sunrise, I never observed, 
 if the atmosphere was clear, the public road or any stone pavement on either side of it 
 to be moistened with dew, though grass within a few feet of it, and painted doors and 
 windows not far from it, were frequently very wet. If, indeed, there was a foggy 
 morning after a clear and calm night, even the streets of London would sometimes be 
 (Page 144) moist though they had been dry the day before, and no rain had in the 
 meanwhile fallen. This entire, or almost entire, freedom of certain situations from dew 
 depends, however, much more upon extraneous circumstances than upon the nature of 
 the substances found there ; for river sand, though of the same nature witlf gravel, when 
 placed upon the raised board, or upon grass, attracted dew copiously. A third differ- 
 ence, from situation, in the quantity of dew collected by similar bodies, similarly 
 exposed to the sky, depends upon their position with respect to the ground. Thus, a 
 substance placed several feet above the ground, though in this situation later dewed 
 than if it touched the earth, would, notwithstanding if it lay upon a stable body of 
 some extent, such as the raised board lately mentioned, acquire more dew during a 
 very still night than a similar substance lying on grass. A fourth difference of this 
 kind occurred among bodies placed on different parts of the raised board. For one that 
 was placed at the leeward end of it generally acquired more dew than a similar body 
 at the windward extremity. Differences in the mechanical state of bodies, though all 
 other circumstances be similar, has likewise an effect on the quantity of dew which 
 they attract. Thus, more dew is formed upon fine shavings of wood than upon a thick 
 (Page 145) piece of the same substance. It is chiefly for a similar reason, I believe, 
 that fine raw silk, fine unwrought cotton and flax were found by me to attract some- 
 what more dew than the wool I employed, the fibres of which were thicker than those 
 of the other substances just mentioned. Bright metals attract dew much less power- 
 fully than other bodies. Musschenbroek was the first who distinctly remarked this 
 peculiarity of metals, but Dufay, I believe, published it before him (1736), referring at 
 the same time the discovery to the proper author. Both Musschenbroek and Dufay, 
 however, made too large an inference from their experiments, for they asserted that 
 dew never appears on the upper surface of bright metals, whereas the contrary has since 
 been observed by many persons, and I have myself known dew to form on gold, silver, 
 (Page 146) copper, platina, iron, steel, zinc and lead. Dew, however, when it does 
 
 201 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 form upon metals commonly sullies only the lustre of their surface ; and, even when it is 
 sufficiently abundant to gather into drops, these are always small and distinct. Two 
 other facts of the same kind are ; first, that the dew which has formed upon metal will 
 often disappear, while other substances in their neighbourhood remain wet ; and 
 secondly, that a metal which has been purposely moistened will often become dry, 
 though similarly exposed with bodies which are attracting dew. This inaptitude to 
 attract dew in metals is communicated to bodies of a very different nature, which touch 
 or are near to them. For I have found that wool laid upon a metal will acquire much 
 less dew than an equal quantity laid upon grass in the immediate vicinity. A 
 large metallic plate laid upon grass resists the formation of dew more powerfully than 
 a very small one similarly situated. I conclude, from various collateral facts, that a con- 
 siderable difference in the thickness of two pieces of metal, exposing equal surfaces to 
 the sky, will be attended with a similar consequence wherever they be placed, though 
 I have no observation which proves this directly. If, however, a large and a very small 
 (Page 147) plate be suspended horizontally in the air at the same height, the small 
 plate will resist the formation of dew more powerfully than the large. If a metal be 
 closely attached to a substance of some thickness, which attracts dew powerfully, the 
 attraction of the metal itself for dew, instead of being increased from this circumstance, 
 becomes diminished, provided the metal covers the whole of the upper surface of the 
 other body. If only a part of this body be covered the production of dew on the metal 
 is forwarded by the conjunction, and this somewhat in proportion to the quantity of 
 surface in the body left uncovered. The justness of the first of these observations is 
 proved by the following experiment. I joined, in the form of a cross, two pieces of very 
 light wood, each 4 inches long, one-third of an inch broad, and one line thick. To one 
 side of the cross I fastened, by means of mucilage, a square piece of gilt paper, and then 
 exposed the instrument to the sky, with its metallic side uppermost, on a dewy night, in 
 a horizontal position, about 6 inches above the ground. A few hours after the 
 unattached part of the metalled paper was found covered with drops of dew, while those 
 parts which adhered to the cross were dry. A large metallic plate laid upon grass was 
 (Page 148) dewed with more difficulty on its upper surface than a similar plate elevated 
 a few inches above the grass by means of slender props which allowed the air to pass 
 freely under the metal. But the case with respect to small pieces was the reverse ; for 
 I have often seen covered with dew the metallic sheath of a small thermometer lying 
 upon grass, while the similar sheath of another thermometer suspended in the air 
 remained dry. Removing a metal several times in the course of the night from one part 
 of the grass-plat to another facilitated its being dewed. The same effect was produced 
 on gilt and silvered paper by first exposing them to the sky for some time with the 
 bare side uppermost, and then turning them. If a piece of glass, covered on one side 
 with a metal, be placed upon the ground with this side downward, the upper surface 
 will attract dew precisely as if no metal were attached to the lower surface. The upper 
 surfaces of metals are most readily and most copiously dewed on those nights and on 
 those parts of the night during which other substances are the most readily and the 
 most copiously dewed. If a metallic plate has been laid upon glass before dew began to 
 form anywhere, its lower side, notwithstanding, always became moist in the course of 
 (Page 149) the night ; and the same effect was almost always observed if the plate 
 had been placed horizontally in the air, a few inches above the grass. While the 
 undersides were thus moist the upper surfaces were very often dry. If, however, the 
 plate was elevated several feet in the air, the condition of both sides was always the 
 same, whether this was dry or moist. The remarks hitherto made on the relation of 
 metal to dew, apply to the class generally ; but it is now to be mentioned that they do 
 not all resist the formation of that fluid with the same force. I saw, for example, 
 platina one night distinctly dewed, while gold, silver, copper and tin, though similarly 
 situated, were entirely dry ; and I have also several times seen these four metals free 
 202 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 from dew, while iron, steel, zinc and lead were covered with it. I once supposed, in 
 consequence of the difficulty with which metals are dewed } that they might in a^ 
 circumstances resist, in a greater degree than other bodies, the condensation of watery 
 vapour upon their surface ; and I afterwards found that Le Eoi (1751) asserts this to 
 be the case. But having exposed at the same time to the steam of warm water 
 (Page 150) pieces of glass and of metal I did not see that moisture formed in 
 the least more readily upon the former than upon the latter. Saussure came to 
 the same conclusion. Le Roi said that dew is never deposited by the air of cities.. 
 With the view of testing this, I frequently exposed at night 10 grains of wool upon a 
 slight wooden frame, placed in such a manner between the two ridges of the top of my 
 house, which is situated in one of the most crowded districts of London, as to be 3- 
 feet distant from the nearest part of the roof. The event was that upon clear and calm 
 nights dew was always acquired by the wool, though never in any considerable 
 quantity ; probably, however, more from the wooden frame being nearly surrounded by 
 buildings much more elevated than itself, than from any particular condition of the 
 air in cities. The formation of dew, in this situation, proceeded much less 
 (Page 151) regularly than in the country. For upon one evening 10 grains of 
 wool gained in it 3 grains of moisture in one hour and eighteen minutes, though 
 I scarcely ever knew a greater quantity to be collected by a similar parcel of 
 wool in the same place during a whole night. Dew may be obtained every fine 
 evening upon grass in London. But as dew upon grass is said by Le Roi to proceed 
 from the ground and not from the atmosphere, the argument derived from its appearance- 
 there in cities against this assertion is thus eluded by him. From the time of Aristotle- 
 (Page 152) hoarfrost has justly been considered as frozen dew. Dew is often spoken of 
 as being cold by popular writers, as Cicero and Virgil. I have found the ground 
 (Page 153) colder than the air some feet above it several degrees on dewy nights, some- 
 (Page 154) times as much as 14. I did not speak in the preceding section of another 
 obscure state of the atmosphere, that occasioned by fog or mist, as the moisture deposited 
 attaches to all bodies indiscriminately, on which account I was unable to determine - 
 whether or not dew forms during its continuance. But with respect to the connexion, 
 of this condition of the atmosphere with cold, I have to remark that I have several 
 (Page 158) times on its appearance betwixt day-break and sunrise found the difference 
 between thermometers on grass and in the air, which had been considerable during the 
 night, to diminish considerably. I never, indeed, observed it to vanish. I have now, , 
 however, reason to doubt the justness of this conclusion ; for on the evening of Jan. 1, 
 1814, I found during a dense fog, while the weather was very calm, a thermometer 
 lying on grass thickly covered with hoarfrost 9 lower than another suspended in the 
 air 4 feet above the former. On the following evening, when the air was equally calm, . 
 but the fog sufficiently attenuated to allow me to see that the sky was almost covered 
 with clouds, the difference between two thermometers, similarly placed with the former, . 
 was only 1. On comparing the observations of these two evenings, I conclude that on 
 the first few or no clouds existed above the fog, and consequently that fogs, if there be 
 no clouds above them,'may in a very calm air admit of the appearance of a considerable 
 degree of cold at night upon the surface of the earth in addition to that of the atmosphere. . 
 He mentions several other observations shewing that the greater the number of 
 degrees the ground was colder than the air above, the more abundant was the dew.. 
 Dew, according to Aristotle, is a species of rain formed in the lower atmosphere in con- - 
 sequence of its moisture being condensed by the cold of the night into minute drops. 
 Gersten, who published his treatise on dew in 1733 [1732], proved these opinions to be 
 erroneous : for he found that bodies a little elevated in the air often become moist with 
 dew, while similar bodies lying on the ground remain dry, though necessarily from their 
 position as liable to be wetted by whatever falls from the heavens as the former. 
 Musschenbroek remarks that metals will be free from dew while other bodies attract it. 
 
 203 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 (Page 178) copiously. Dufay concluded from this that it might be an electrical pheno- 
 menon, since it leaves untouched the bodies which conduct electricity, while it appears 
 upon those which transmit that influence. If dew were to collect on the latter only, its 
 quantity would never be sufficiently great to admit its being distinctly seen ; for the non- 
 conductors, as soon as they became in the least moist, would be changed into conductors. 
 Charcoal, too, it is now known, though the best solid conductor of electricity after the 
 metals, attracts dew very powerfully, and in the last place dew frequently forms upon 
 metals themselves. Other authors have considered dew electrical for other reasons ; 
 but there are several considerations which seem to me to prove that no such opinion can 
 be just. 1. When dew is produced in a clear atmosphere the portion of air by which 
 it is deposited must necessarily be unable at that point to retain in a state of pellucid 
 vapour all the moisture which it had immediately before held in that form. But I 
 know of no experiment which shows that air by becoming positively electrical, which 
 is said to be its condition on the evenings during which dew is most abundant, is 
 (Page 179) rendered less able than it had previously been to contain watery vapour in 
 a state of transparency. 2. Bodies in similar circumstances, as far as electricity is con- 
 cerned, acquire very different quantities of dew. 3. Dew forms in different parts of the 
 night in quantities no way proportioned to the degrees of electricity found in the 
 atmosphere at the same times. Thus it is commonly more copious in the morning than 
 in the evening, notwithstanding that the air is observed to be in the latter season 
 more highly electrical than in the former. 4. I have several nights held a glass bottle, 
 upon which dew was forming, close to the top of a Bennett's electrometer which had 
 been previously kept in a dry place, but I never saw the slips of gold-leaf move in con- 
 sequence. It is very probable, however, that more refined experiments will show that 
 electrical appearances attend the production of dew. But the facts that have been stated 
 (Page 180) seem sufficient to establish that any such appearances which may be here- 
 after remarked during the formation of dew, must be considered as the effects and not 
 as the cause of the conversion of the watery vapour of a clear atmosphere into a fluid. A 
 remaining argument applies equally to all the theories which have hitherto been made 
 public on the cause of dew. This is that none of them include the important fact that its 
 production is attended with cold. Previous writers considered that the cold wasjcaused by 
 the dew [see under, 1793. Dalton, pages 144, 145]. I began to doubt its truth on finding 
 that bodies would sometimes become colder than the air without becoming dewed, and 
 that when dew was formed, if different times were compared its quantity and the degree 
 of cold which appeared with it were veiy far from being always in the same proportion 
 (Page 181) to each other. At last I was convinced that dew is the production of a 
 preceding cold in the substances upon which it appears. Wishing to obtain more 
 striking proofs I instituted experiments. I commenced these on the raised board as soon 
 as the sun ceased to shine on it. The first day, Aug. 19, 1813, was a favourable one. 
 There had been no rain for weeks, the wind was northerly, and the barometer 
 was rising; all which indicated that the atmosphere contained little moisture. The 
 air, too, was extremely still. The only appearance in the least unfavourable 
 was that the sky was not entirely free from clouds ; but these were few, 
 of small extent, thin and high. At 6 h. 25 m., immediately after the sun 
 had ceased to shine upon the spot where my experiments were to be carried 
 on, though the time of its setting was still 47 minutes distant, I placed upon the 
 raised board 10 grains of wool, and a small bag made of the skin of a swan's breast, 
 with the down adhering, and stuffed with wool, the whole weighing 5 drachms. 
 On each of these substances the naked bulb of a small but delicate thermometer was 
 laid. A similar thermometer, with its bulb also naked, was suspended in the air over 
 the grass-plat at the same height with the board. After an exposure of 20 minutes, 
 the wool was 7 colder than the air, but the swan-down bag only 6, no doubt in 
 consequence of its greater quantity of matter. Neither, however, had gained the least 
 204 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 weight according to the scales, which would turn to the one-sixteenth of a grain. 
 These observations were repeated several times during the hour, at none of which, 
 except the last, was either the wool or swan-down found in the least heavier than when 
 (Page 183) first placed on the board. At this last observation the wool, though 
 9| colder than the air, was still without any increase in weight ; but the swan-down 
 which was 1 colder than the wool, had gained half a grain. I again examined the 
 thermometer at 8h. 45m. The wool, which was still 9J colder than the air, had 
 gained somewhat less than half a grain, and the swan-down, which was now 11 colder 
 (Page 185) than the air, had gained 2 grains. I shall next apply the facts observed 
 to the explanation of several atmospherical appearances. The variety in the quantities 
 of dew which was found by me upon bodies of the same kind exposed to the air during 
 the same time of the night, but in different situations, is now seen to have been 
 occasioned by the diversity of temperature which existed among them. The cold 
 connected with dew is not proportional to tho quantity of it. The same degree of cold 
 (Page 186) may be attended with much, with little, or with no dew, according to 
 the existing state of the atmosphere in regard to moisture. The formation of dew 
 produces heat. I infer this partly because very little dew appeared upon the two* 
 nights of the greatest cold I have ever observed upon the surface of the earth rela- 
 tively to the temperature af the air, both of them having occurred after a long tract 
 of dry weather, and partly from the most dewy night I have ever seen having been 
 attended during the greater part of it with no considerable degree of cold. On this- 
 night the difference between the temperature of grass and of air was at first 7, the 
 dew being then not very abundant. But after the dew had become very abundant, the 
 difference of these temperatures never exceeded 4, and was frequently only 3. The 
 (Page 188) less difference commonly observed between the temperature of grass and of 
 air in the morning, than what occurs in the evening is likewise to be in part attributed 
 to a greater quantity of dew appearing in the former than in the latter season. In 
 (Page 189) very calm nights a portion of air, which comes in contact with cold grass, 
 will not, when the surface is level, immediately quit it, more especially as this air has 
 become specifically heavier than the higher, from a diminution of its heat, but will 
 proceed horizontally, and be applied successively to different parts of the same sur- 
 face. The air, therefore, which makes this progress must at length have no moisture 
 to be precipitated, unless the cold of the grass which it touches should increase. Hence, 
 in great measure, is to be explained why in such nights as have been just mentioned, 
 more dew was acquired by substances placed on the raised board than by others of the 
 same kind on the grass, though it began to form much sooner in the latter than in the 
 former situation, those on the raised board having received air which had deposited less 
 of its moisture. A reason is now also afforded why a slight agitation of the atmo- 
 sphere, when very pregnant with moisture, should increase the quantity of dew, since 
 fresh parcels of air will hence be more frequently brought into contact with the cold 
 surface of the earth than if the atmosphere were entirely calm. Dew can never be 
 (Page 190) formed in temperate climates upon the the naked parts of a living and 
 healthy human body during the night ; since their heat is never less in this season, 
 in such climates, than that of the atmosphere. I have, in fact, never perceived dew on 
 any part of my own body at night. On the other hand, in very hot countries the 
 uncovered parts of a human body may sometimes, from being considerably colder than 
 the air, condense the watery vapour of the atmosphere, and hence be covered with a 
 real dew, even in the daytime. 
 
 (To Is continued.) 
 
 205 
 
SCIENTIFIC UNION. 
 
 SCIENTIFIC UNION. 
 
 The rapid progress of science now going on is, in part, the result of the 
 great increase in the number of workers. This is accompanied by a larger 
 :and larger host of scientific serials. The consequence is that the student 
 finds an increasing difficulty in ascertaining what has been done, or is in 
 process of being accomplished, not only in his own special line of study, but 
 also, and more particularly, in such as do not immediately interest him. 
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 upon his special studies. The state of literature is such that he is frequently 
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 a great deal of time unnecessarily wasted. The remedy for this is the foca- 
 lisation of knowledge round a series of centres. The two main steps in the 
 process are, first, collection, and, next, classification. It is, with this ulterior 
 object in view, that all persons interested in meteorology are earnestly asked 
 to forward their names and addresses, particulars as to the work they have done 
 in meteorological and other sciences, their present lines of study, ways in 
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 The first list will be published in November, 1883 ; but correspondents are 
 requested to send in answers soon, in order to allow of ample time for 
 their classification, and for their utilisation in private correspondence in the 
 interests of correspondents. 
 
 In order to prevent any misconception, it may be stated that the Con- 
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 suggested, from time to time, for the students in other branches of science. 
 
 Newspapers and scientific journals of all countries, willing to help in 
 this matter, are asked to make the above requests known to their readers. 
 
 Address, Conductor, "Scientific Roll" office, 7 Ked Lion Court, Fleet 
 Street, London, E.G. 
 
 206 
 
THE SCIENTIFIC ENQUIRER. 
 
 THE SCIENTIFIC ENQUIRER. 
 
 Correspondence is invited on scientific subjects of all Jcinds. In all cases 
 names and addresses should be given ; but these will not be published if the 
 writers prefer noms de plume. The Conductor will not be responsible for the 
 opinions expressed by correspondents. All communications should be addressed to 
 the Conductor of the " Scientific Eoll" 1 Bed Lion Court, Fleet Street, London, 
 E.G. 
 
 Replies to questions should be numbered in accordance with the questions to which 
 they refer. The contractions following the questions and answers indicate the class of notes 
 to which they will ultimately be assigned, and the place where full references will be given 
 to the details bearing upon them. 
 
 M. Mammalia; R. Reptilia; L. Lepidoptera; 0. Orthoptera. 
 
 MIMETIC RESEMBLANCES AND MIMICRY IN ANIMALS. (Tiger, Leopard, Viverra, Crocodiles, 
 
 Moths, and Mantis.) 
 
 Some sketches, illustrative of a remarkable case of a caterpillar belonging to a species of 
 moth the name of which we have not been able to ascertain, have been sent to us by S. E. 
 Peal, of Aideo, in Asam. The caterpillar has a striking resemblance to a species of Viverra 
 inhabiting the same district. We are also indebted to the same correspondent for the 
 following note. 
 
 " The most general and interesting law, as far as I see, in the mimicry of inanimate 
 things by animals, or insects, is the remaining quite still till the last possible moment. I 
 often pin moths ere they move, and catch butterflies with my fingers. The range that this 
 quality takes is also much wider than is usually supposed ; not only is it for protection, as 
 in ' protective resemblance ' (as when a caterpillar exactly resembles the buds it feeds on 
 and lives among) ; but also as a means of luring insects, as in the Mantis that resembles a 
 blossom. Again, the tiger imitates the whistle of the large Sambur deer here (to call it) so 
 closely that only a trained ear can tell the difference. The leopard also imitates the smaller 
 deer. It is a common custom of all hunters to call deer by whistling with a leaf, and I have 
 done it myself. Occasionally, as might be expected, a tiger, and not a deer, turns up at 
 close quarters, when the astonishment is mutual. The crocodile's eye and nose floating on 
 our muddy waters also exactly resembles the lumps of dirty foam so common here, and I 
 have often, in my Rob Roy canoe, passed close to one and knew he would not move. There 
 is a Viverra in these hills, so far unknown to me, but it catches hawks by hiding its body 
 under a bare and very conspicuous branch of a tree, as in these hill-clearings, while it turns 
 its tail over on top and keeps jerking it ; any hawk within range at once takes it for a 
 squirrel, and, acting accordingly, gets caught." 
 
 The statements respecting the Viverra depend upon the testimony of individuals 
 belonging to the Naga tribe. 
 
 The following questions are suggested by the above : 
 
 1. Are any other cases known of lepidopterous caterpillars resembling species of 
 Mammalia? (L.I.) 
 
 207 
 
ANNOUNCEMENTS. 
 
 2. Would readers supply instances of caterpillars resembling species belonging to other 
 classes of animals than the Mammalian? (L. 2.) 
 
 3. What mimetic resemblances are there between caterpillars and the various parts 
 of plants, as twigs, buds, etc. ? (L. 3.) 
 
 4. What instances are there of mimetic resemblances in Mantis and other genera of the 
 same family to the leaves, stems, blossoms and other parts of plants ? The names of the 
 animals and plants should be given, and such particulars as regards habits, etc., as seems to 
 afford some explanation of the phenomena. (O. 1.) 
 
 5. What instances are there of the Carnivora imitating the call of their prey for the 
 purpose of luring them ? (M. 1.) 
 
 6. What instances are there amongst the reptiles of mimetic resemblance to inanimate 
 objects ? (R. 1.) 
 
 7. What instances are there amongst the species of Viverra of cunning displayed for the 
 purpose of inducing the near approach of prey ? (M. 2.) 
 
 We shall be glad to have any other questions and notes on the subject. 
 
 ANNOUNCEMENTS. 
 
 Part III. of the " Scientific Roll" will be commenced, if life and health and support be 
 granted to the Conductor, in 1883. In order that the bibliography may be as full as 
 possible, authors and publishers are respectfully solicited to send copies of, or references to, 
 all their publications dealing with the barometrical condition of the air. 
 
 As soon as 200 persons have expressed a wish to subscribe for any of the subjects men- 
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 amount of matter in hand, so that the subscription price for each cannot be fixed at present, 
 but will be settled when the publication of each part is commenced. The following is a 
 list of the principal subjects : 
 
 Atmosphere, Water, Ocean, Rivers, Lakes, Glaciers, Land, Elevation and Subsidence 
 of Land and Sea Bottom, Denudation, Orography, Earthquakes, Volcanoes, Marshes, 
 Minerals, Stratigraphy, Rocks, Plants generally and in classified groups ; Animals gene- 
 rally; Protozoa, Actinozoa, Hydrozoa, Echinodermata, Crustacea, Scolecida, Annelida, 
 Mollusca, Myriapoda, Arachnida, Rhynchota, Orthoptera, Diptera, Coleoptera, Lepidoptera, 
 Neuroptera, Hymenoptera, Pisces, Amphibia, Reptilia, Aves, Mammalia, and Man. 
 
 Subscribers' names only are asked for now. The sending of these will not involve any 
 pecuniary liability, but will simply be taken as implying that the senders take an interest 
 in the work, and will probably undertake to subscribe when asked to do so. 
 
 208 
 
AQUEOUS YAPOUR: NOTES. 
 
 1818. 
 
 Wells, W. C. Concluded from page 205 (B. 1818, 1). 
 
 (Page 190) Hygrometers formed of animal or vegetable substances, when exposed 
 to a clear sky at night, will become colder than the atmosphere, and hence, by 
 attracting dew, or, according to an observation by Saussure, by . merely cooling the 
 air contiguous to them, mark a degree of moisture beyond what the atmosphere 
 actually* contains. [See under 1786. Franklin (Page 51).] This serves to explain 
 an observation made by De Luc, that in serene and calm weather the humidity 
 (Page 191) of the air, as determined by the hygrometer, increases about and after 
 sunset with a greater rapidity than can be attributed to a diminution of the general 
 (Page 202) heat of the atmosphere. Dew appears chiefly where it is most wanted, on 
 herbage and low plants, avoiding in great measure rocks, bare earth, and considerable 
 masses of water. (Note. I have no direct observation for this assertion concerning 
 considerable masses of water. But I hold it, notwithstanding, to be just ; because as 
 soon as the surface of the water is in the least cooled by radiation, the particles com- 
 posing it must fall downwards from their increased gravity, and be replaced by others 
 that are warmer. The whole mass, therefore, can never, in the course of a single night, 
 be sufficiently cooled to condense into dew any great quantity of the watery vapour of 
 the atmosphere. Besides, I have found that even a small mass of water sometimes 
 acquires no weight from the reception of dew in the space of a whole night favourable 
 (Page 203) to the formation of that fluid.) Its production, too, tends to prevent the 
 injury that might arise from its own cause, since the precipitation of water upon the 
 tender parts of plants must lessen the cold on them which occasions it. The appearance 
 of dew is not confined to any one part of the night, but occurs during its whole course, 
 from means the most simple and efficacious ; for after one part of the air has deposited 
 its moisture on the colder surface' of the earth, it is removed in consequence of that 
 agitation in the air which exists during its stillest states, and gives place to another 
 having its quantity of water undiminished ; and again, as the night proceeds, a portion 
 of air, which had before deposited all the moisture which circumstances at that 
 time permitted, is rendered fit, by the general increase of the cold of the atmo- 
 sphere, to give out a fresh parcel when it comes anew into contact with the ground. 
 (Page 210.) The water deposited upon the earth during a fog at night may sometimes 
 be derived from two different sources, one of which is a precipitation of moisture from 
 a considerable part of the atmosphere in consequence of its general cold ; the other, a 
 real formation of dew, from the condensation, by means of the superficial cold of the 
 ground, of the moisture of that part of the air which comes in contact with it. In such 
 a state of things all bodies will become moist, but those especially which most readily 
 attract dew in clear weather. (Note. The moisture observed at night by Musschen- 
 broek in Holland, and called by him dew, appears to me to have been of this nature.) 
 (Page 212) Wilson (1780) observed the prominent parts of various bodies to be crusted 
 (Page 214) with hoar frost, while their more retired and massy parts were free from it. 
 The more hurtful effects of cold in hollow places may be in part due to the air being re- 
 tained there ; and consequently, as less dew is deposited, less heat will be extricated during 
 PART II. No. 8. p 209 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 (Page 215) its formation. Eictet ascribed the greater cold upon plains than upon 
 neighbouring hills to the evaporation of moisture from the ground. To show that this 
 is not so, it need only be mentioned that the appearance never occurs in any considerable 
 (Page 216) degree except upon such nights as are attended with some dew, and that its 
 great degrees are commonly attended with a copious formation of that fluid; since it 
 cannot be thought that the same stratum of air will deposit moisture upon the ground 
 from an insufficiency of heat at the very time it is receiving moisture from the ground 
 in the state of pellucid vapour, as this supposes that it is not yet replete with water. 
 (Page 226) Aristotle and Plutarch observed that dew is much less copious upon hills 
 than upon plains. This may be explained thus. For allowing at first the surface of 
 the ground to be in both positions equally colder than the air which is near to it, still, as 
 the production of dew must be in proportion to the whole depression of the temperature 
 (Page 227) of the air which furnishes it, below what its heat had been in the preceding 
 day; and as one part of this depression, the general cooling of the atmosphere, is 
 much more considerable on the plain than on the hill, moisture must necessarily be 
 deposited more copiously in the former than in the latter place. If the greater agitation 
 of the atmosphere, and the less quantity of moisture during clear weather in its higher 
 region than in the lower, be added, it may readily be inferred that dew shall sometimes 
 be altogether wanting upon a hill, though abundant on a plain at its foot, agreeably to 
 what has been actually observed by Mr. Jefferson. The leaves of trees often remain 
 dry throughout the night, while those of grass are covered with dew. As this is a 
 similar fact to the smallness of dew on hills, I shall, in accounting for it, do little more 
 than enumerate the circumstances on which it depends. The atmosphere is several 
 degrees warmer near the upper parts of trees on dewy nights than close to the ground. 
 The air in the higher situation is more agitated than that in the lower. The air at a 
 little distance from the ground, from being nearer to one of its sources of moisture, will 
 on a calm evening contain more of it than that which surrounds the leaves of elevated 
 (Page 228) trees. Only the leaves of the very tops of trees are fully exposed to the 
 sky. The declension of the leaves from a horizontal position will occasion the air 
 which has been cooled by them to slide quickly away and be succeeded by warmer 
 parcels. The length of the branches of the trees, the tenderness of their twigs, and 
 the pliancy of the footstalks of their leaves, will cause in the leaves an almost 
 perpetual motion, even in states of the air that may be denominated calm. I have 
 hence frequently heard, during the stillness of night, a rustling noise in the trees which 
 formed one of the boundaries of the ordinary place of my observations, while the air 
 below seemed without motion. Nearly in the same manner is to be explained why 
 shrubs and bushes also receive dew more readily than lofty trees. Bright metals exposed 
 to a clear sky in a calm night will be less dewed on their upper surface than other 
 solid bodies, since of all bodies they will in such a situation lose the smallest quantity 
 of heat by radiation to the heavens, at the same time that they are capable of receiving 
 by conduction at least as much heat as any others from the atmosphere, and more 
 than any others from the warmer solid substances which they happen to touch. If the 
 (Page 229) exposed pieces of metal be not very small, another reason will contribute 
 somewhat to their being later and less dewed than other solid substances. For, in 
 consequence of their greater conducting power, dew cannot form upon them unless 
 their whole mass be sufficiently cooled to condense the watery vapour of the atmo- 
 sphere ; while the same fluid will appear on a bad conductor of heat, though the parts 
 a very little beneath the surface are warmer than the air. (Note. I hence think it 
 probable that dew will sometimes form on the bulb of a thermometer before the 
 mercury in it is cooled below the temperature of the air. It seems certain to me also 
 that dew may appear upon substances which, from the thinness of the layer of matter 
 their cold is confined to, will produce little or no sensible effect upon a thermometer that 
 is applied to them.) From the same ready passage of heat from one part of a metal 
 210 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 plate to another, a metallic plate suspended horizontally in the air several feet above the 
 ground, will be found dewed on its lower side if the upper surface has become so, while 
 the lower surface of other bodies, more attractive of dew, but worse conductors of heat, 
 are without dew in a similar situation. A metal placed at night in the air near to the 
 ground is for the most part sufficiently cold to condense on its under side the vapour 
 (Page 230) which arises from the warmer earth, while the upper surface may be dry 
 from possessing the same or almost the same temperature as the atmosphere near to it. 
 As the temperature of metals is never much below that of the neighbouring air, a 
 slight diminution of their cold from radiation will often enable them to evaporate the 
 dew which they had previously acquired, though other substances which had been more 
 cooled by radiation are still attracting dew. For a like reason, a metal which has been 
 purposely wetted will often become dry at night, while other substances are becoming 
 moist. A substance, highly attractive of dew, will derive heat from it, and will 
 therefore acquire less dew than an equal portion of the same substance laid upon grass. 
 A large metallic plate will be less readily dewed while lying on grass than if it were 
 placed in the air, though only a few inches above the grass, because in the former 
 situation it receives freely, by means of its great conducting power, heat from the earth, 
 whereas when placed in the air it powerfully resists, by another property possessed in a 
 great degree by bright metals, the entrance of heat radiated towards it by the grass 
 (Page 231) beneath. Besides, the grass under the metal now has less heat than when 
 in contact with it, partly from having a small oblique aspect of the sky, and partly 
 from receiving air which has been cooled by passing over other grass fully exposed to 
 the heavens. When a piece of metal, having closely applied to its under surface a 
 substance of some thickness which attracts dew powerfully, and therefore imbibes 
 readily heat that is radiant to it, is exposed to the sky at night, the heat supplied by 
 the attached substance, both from its own original store and from what it has acquired 
 through the radiation of the ground to it during the exposure, will enable this piece to 
 resist longer than a bare piece, the formation of dew, or even than another piece which 
 has only a thin coat of matter considerably attractive of dew, attached to its underside. 
 A very small metallic plate suspended in the air is less easily dewed than a large one 
 similarly situated, as it receives, in proportion to its size, more heat from the atmosphere. 
 On the other hand, a very small plate laid upon grass rendered cold by radiation will 
 be sooner dewed than a larger one in the same situation, from presenting a greater 
 (Page 232) proportional circumference to the surrounding grass, and, therefore, losing 
 more quickly its heat by conduction. It will be also sooner dewed than another very 
 small one suspended in the air, since the latter, like other small bodies similarly 
 placed, must be continually acquiring more heat than the former. A piece of metal 
 applied to different portions of cold grass in succession will sooner become cold itself 
 than another piece which is suffered to remain constantly upon one portion of the same 
 grass, and will in consequence be sooner dewed. If the bare side of a piece of metalled 
 paper be exposed to a clear and calm sky at night it will become cold by radiation, and 
 receive by conduction the heat of the inferior metallic surface ; whence, if this surface 
 be afterwards made the upper one, it will sooner acquire dew than a similar metallic 
 surface which has been exposed to the sky during the whole of the experiment. When 
 a metal covers in part only the upper surface of a piece of glass, the uncovered portion 
 of the glass generally becomes cold by radiation on exposure to a serene sky in a still 
 night, and then, by deriving [? drawing] to itself a part of the heat of the metal, 
 occasions this body to be more readily dewed than if the whole of the exposed surface 
 (Page 233) had been metallic. In this experiment the outer edge of the metallic 
 surface, from being nearest to the colder glass, will be the first and most dewed, while 
 the parts of the uncovered glass which are contiguous to the warmer metal will be the 
 last and the least dewed, of their respective substances. A piece of glass covered on one 
 side with a metal being placed on the grass with this side down, its upper surface 
 
 V 2 211 
 
AQUEOUS VAPOUR 1818. Wells. NOTES, 
 
 attracts dew as readily as if no metal were attached to it, since the metal in this 
 situation has no power to lessen the radiation of heat from the upper surface of the glass. 
 I conclude, from general principles, that if the same piece of glass, having its metallic side 
 still undermost, were raised in the air a little above the grass, it would be more readily 
 dewed on its upper surface than if it had been without a metallic coating on the lower, 
 as this coating must resist the introduction of heat radiated by the warmer grass, and 
 thus preserve nearly undiminished the cold acquired from radiation of heat to the sky 
 by the bare upper surface. The preceding remarks apply to the whole class of metals ; 
 but the discoveries of Mr. Leslie, respecting the difference in the capacities of these 
 bodies to radiate heat, furnish an explanation among themselves in regard to attraction 
 (Page 234) for dew, which was noted in a former part of this essay ; gold, silver, copper 
 and tin are there said to resist the formation of dew more strongly than other sub- 
 stances of the same kind ; but these substances, according to Leslie, radiate heat the 
 most sparingly. On the other hand, lead, iron and steel, which, according to the same 
 author, radiate heat more copiously than the former metals, were found by me to 
 acquire dew more readily. I do not know the radiating force of platina; but as its con- 
 ducting power is small, its radiation must be great ; and I have, accordingly, observed 
 it to be dewed, while the four first mentioned metals were dry. (Note. All the 
 (Page 235) observations on dew made by Prevost may be accounted for by the two follow- 
 ing circumstances : that substances become colder, by radiation, than the air before they 
 attract dew; and that bright metals, when exposed to a clear sky at night, become 
 colder than the air much less readily than other bodies.) Thinking it probable that 
 black bodies might radiate more heat to the sky at night than white, I placed upon 
 grass, on five different evenings, equal parcels of black and white wool. On four of 
 the succeeding mornings the black wool was found to have acquired a little more dew 
 than the white ; whence I inferred that it had, in consequence of its colour, radiated 
 a little more heat. But I afterwards remarked that the white wool was somewhat 
 (Page 236) coarser than the black, which circumstance alone was sufficient to occasion 
 a difference in their quantities of moisture. Another night I laid on the raised board 
 a piece of pasteboard covered with white paper, and close to this a second piece, similar 
 to the former in every respect, except that it was covered with paper blackened with 
 ink. At daylight I saw hoar-frost on both pieces, but the black seemed to have a 
 greater quantity than the white. A doubt, however, afterwards arose upon the 
 accuracy of this experiment likewise ; for as the light was faint when I viewed the two 
 surfaces, the quantity of hoar-frost, though equal on both, might have appeared greater 
 on the black than on the white, from the contrast of its colour with that of the former 
 surface. But trials of this kind, as Leslie has observed, never afford firm conclusions ; 
 since a black body must always differ from a white in one or more chemical properties, 
 and this difference may cause a diversity with respect to radiant heat. I have 
 (Page 237J regarded dew as altogether derived from watery vapour previously diffused 
 through the atmosphere. The establishment of a contrary opinion will not affect my 
 conclusions. Other writers, however, have regarded dew as being entirely the product 
 of the vapour emitted during the night by the earth and plants upon it. According to 
 this theory dew is said to rise. The first traces I have found of the opinion that 
 dew rises from the earth at night, occurs in the * History of the Academy of Sciences ' 
 [of Paris] for 1687. It is mentioned there briefly and obscurely. Gersten in 1733 
 [1 732] advanced it as new, and considered himself to be the author of it. Musscheiibroek 
 embraced it, but soon admitted that dew sometimes falls. The only argument used 
 (Page 238) by the French academicians is, that as much dew is observed under an 
 inverted bell-glass as in any other situation. But admitting, for a moment, this to be 
 true, they could not thus prove that the ground is the only source of that fluid. 
 Gersten was led to think that dew rises from the earth by often finding grass and low 
 shrubs moistened with it, while trees were dry. But his chief argument is derived from 
 212 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 the fact that a plate of metal laid upon bare earth, on a dewy night, will remain dry on 
 its upper surface while it becomes moist on the lower. I have otherwise explained 
 this. (Note. I have observed, on a cloudy night, a piece of glass laid over an earthen 
 pan containing water and placed upon the ground, to be wet on its lower side, while 
 the upper was dry, the glass being, in this situation, sufficiently cold to condense the 
 vapour of water heated by the earth, but not enough so to condense the watery 
 vapour of the atmosphere.) Gersten, moreover, describes several appearances him- 
 self which refute his opinion. He maintains, for example, that the higher parts 
 of shrubs are more dewed than the lower ; that metallic plates placed horizontally in 
 the air are as much dewed on their superior as on their inferior surfaces ; and that 
 convex and cylindrical bodies suspended in the air, the latter having a position parallel 
 to the horizon, are dewed only on their upper parts. The principal reason given \)y 
 Dufay for the rising of dew is, that it appears more early on bodies near to the earth 
 (Paye 241) than on those which are at a greater height. This also I have accounted 
 for otherwise. Dew often occurs when the rising of Vcipour from the earth at night 
 can have little or no operation. It appears from Hasselquist and Bruce that, in Egypt 
 shortly before the rising of the Nile, and consequently when the ground there is in its 
 driest state, dew becomes exceedingly plentiful, though little or none had appeared 
 before, while the earth was somewhat less dry. The cause evidently is the moisture 
 brought from the Mediterranean by the north wind which then prevails. Webster, 
 speaking of hoar-frost, candidly says : " This frost appears when the surface of the 
 earth is sealed with frost, and, of course, the vapour of which it is formed cannot, at 
 the time, perspire from the earth." I have myself, at all seasons of the year, frequently 
 observed wool upon the middle of the raised board, and therefore out of the way of 
 vapour rising from the ground, to acquire more dew than wool laid upon the grass-plat. 
 The bodies that condense the rising vapour must necessarily be colder than it ; but, as 
 they are likewise, according to the opinion under view, of the same temperature with 
 the air surrounding them, this also should condense the rising vapour. Dew, therefore, 
 should never appear in any considerable quantity without being accompanied with fog 
 or mist. Now, I can assert that the formation of the most abundant dew is consistent 
 {Page 242) with a pellucid state of the atmosphere. Still, it must be admitted that 
 some of the moisture which forms, during clear and still weather, on bodies situated 
 upon or near its surface, is in most cases to be attributed to this source ; since, in my 
 experiments, substances on the raised board became much later moist than others on 
 the ground, though equally cold with them. The quantity from this cause, however, 
 can never be great. For, in the first place, until the air be cooled by the substances 
 attractive of dew with which it comes in contact, below its point of repletion with 
 moisture, it will be always in a condition to take up that which has been deposited on 
 the grass or other low bodies by warm vapour emitted from the earth ; just as the 
 moisture formed upon a mirror by our breath is, in temperate weather, almost imme- 
 diately carried away by the surrounding air. Accordingly, I have sometimes, in 
 serene and still weather, observed dew to appear sparingly upon grass, in the shade, 
 several hours before sunset, when it would increase considerably at the time that the 
 same fluid began to show itself on the raised board. In the second place, though bodies 
 situated on the ground, after they have been made sufficiently cold by radiation to 
 condense the vapour of the atmosphere, will be able to retain the moisture which they 
 {Page 243) acquire by condensing the vapour of the earth : yet before this happens the 
 rising vapour must have been greatly diminished by the surface of the ground having 
 become much colder. These considerations, added to the fact that substances on the 
 raised board attracted rather more dew throughout the night than similar substances 
 lying on the grass, warrant me to conclude that, on nights favourable to the produc- 
 tion of dew, only a very small part of what occurs is owing to vapour rising from the 
 earth : though I am acquainted with no means of determining the proportion of this 
 
 213 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 part to the whole. On the other hand, however, in a cloudy night, all the dew that 
 appears upon grass may sometimes be attributed to a condensation of the earth's 
 vapour, since I have several times, in such nights, remarked the raised board to be 
 dry while the grass was moist. These nights were calm, and evaporation from grass, 
 consequently, not copious. When evaporation, on cloudy nights, was assisted by wind, 
 dew has never been anywhere observed by me. (Note. The interval between the first 
 appearance of dew in the afternoon on grass, in shaded places, and sunset, was formerly 
 said by me, on the authority, however, only of a few observations, to be considerably 
 (Page 244) greater than that between sunrise and the ceasing of the formation of dew 
 upon grass in the morning. These observations were made on spots exposed during 
 the greater part of the day to the sun. In such places the heat acquired from the sun 
 by the uppermost layer of earth will be longer retained than that acquired by the grass, 
 which will, therefore, be sufficiently cool soon after the heat of the day has declined, 
 to condense a part of the vapour then copiously rising from the earth ; whereas in the 
 morning both less vapour will rise, the surface of the earth having now lost a great 
 part of its heat, and a less proportion of that which does rise will be condensed by the 
 grass, as the temperature of this body now more nearly approaches that of the ground, 
 from first receiving the heat of the sun, reflected from the atmosphere and other 
 substances.) Agreeably to another opinion, the dew found upon growing vegetables is 
 the condensed vapour of the very plants on which it appears. But this also seems to 
 me erroneous, for several reasons. Dew forms as copiously upon dead as upon living 
 vegetable substances. The transpired humours of plants will be carried away by the 
 wind which passes over them, when they are not sufficiently cold to condense the 
 vapour contained in it, unless, which is almost never the case if mist dees not already 
 exist, the general mass of the atmosphere be incapable of receiving moisture in a 
 pellucid form. Accordingly, on cloudy nights, when the air, consequently, can never 
 be cooled more than a little below the point of repletion with moisture by bodies in 
 (Page 245) contact with it, dew is never observed upon any plants that are elevated a 
 few feet above the ground. If a plant has become, by radiating its heat to the heavens, 
 so cold as to be enabled to bring the air in contact with it below the point of repletion 
 with moisture, that which forms upon it from its own transpiration will not then, indeed, 
 evaporate. But other moisture will, at the same time, be communicated by the 
 atmosphere ; and when the difference in the copiousness of these two sources is con- 
 sidered, it may, I think, be safely concluded that almost the whole of the dew which 
 will afterwards form on the plant must be derived from the air, more especially when 
 the coldness of a clear night, and the general inactivity of plants in the absence of light, 
 both lessening their transpiration, are taken into account. An experiment, however, 
 has been appealed to in proof that the dew of plants actually does originate from fluid 
 transpired by them ; that, namely, in which a plant, shut up in an air-tight case, becomes 
 covered with moisture. But this experiment, if attentively examined, will be found to 
 have little weight. First, the enclosed plant being exempt from the cold, which its own 
 radiation would have produced in its natural situation, in a dewy night will transpire 
 (Page 246) a greater quantity of fluid than a similar plant exposed at the same time in 
 the open air. Again, the small quantity of air contained in the case must soon be 
 replete with the moisture, after which the whole of what is further emitted by the plant 
 will necessarily assume the form of a fluid, whatever may be the condition of the 
 external atmosphere ; whereas during the clearest night only a part of the smaller 
 quantity of moisture emitted by the exposed plant will be condensed on its surface. In 
 the last place, notwithstanding the circumstances which favour the appearance of 
 moisture upon enclosed plants from their transpiration, still the quantity observed on 
 them is said to be much less considerable than what is seen upon plants of the same 
 kind exposed to the air for the same time during a calm and serene night. De Luc 
 (Page 259) remarks that clouds frequently disappear soon after sunset. I have also 
 
AQUEOUS VAPOUR 1818. Wells. NOTES. 
 
 noticed that the air is then calmer ; and that this calmness very commonly, if not always, 
 precedes the dissipation of the clouds. 
 
 i Thomson, Annals of Philosophy. (B. 1818, 2.) 
 Pliilo-chemicus Oxoniensis. 
 
 (Page 102) De Luc's and Howard's explanations of the suspension of clouds are 
 (Page 103) not satisfactory. The quantity of moisture which the air is capable of 
 dissolving must depend partly on the temperature and partly on the density of that 
 fluid. Near the earth's surface the higher temperature of the air causes it to preserve a 
 larger portion of aqueous vapour in an elastic form. In the most elevated regions, 
 owing to the extreme rarity of the air, atmospheric pressure scarcely opposes any check 
 to the natural tendency of water to assume an aeriform state, so that it remains in 
 the form of vapour, independent, perhaps, of any chemical solution. Hence, as we 
 ascend in the atmosphere, the quantity of moisture held, by it in solution must go on 
 diminishing, until we arrive at that point beyond which the effect of the diminished 
 pressure predominates over that of its chilliness ; so that from this point upwards the 
 quantity of aqueous vapour goes on increasing. The medium point is the region of the 
 clouds, which are known to occupy a certain height in the atmosphere, above which 
 (Page 105) they rarely extend. Let us then suppose an ascending portion of air to 
 have arrived at such a height that its diminished temperature no longer allows of its 
 retaining the whole of the moisture it had dissolved when near the surface ; the conse- 
 quence will be that a portion of water is disengaged in the state of what is termed 
 vesicular vapour, that is, holding intermixed with it a portion of atmospheric air. 
 Now, as the air is considerably rarer at the height of two or three miles (the usual 
 elevation of the clouds) than nearer the surface, it may easily happen that the watery 
 vesicles, in the progress of their descent, meet at length with a stratum of such density as 
 to be just equivalent to the weight of the vesicular vapour joined with that of the air 
 intermixed with it ; they will remain suspended until the air within becoming of 
 nearly equal density with the atmosphere without, or the particles coalescing into 
 larger drops, the whole becomes too heavy for the atmosphere to support. The presence 
 of intermixed air seems confirmed by the hollow found in the centre of hailstones ; and 
 the flakes of snow, which fall so slowly through the air, owe their low specific gravity 
 to the same cause. Cirri seem to be formed immediately from the disengagement of 
 the vesicular vapour, and therefore to occupy that line of elevation at which the quantity 
 (Page 106) of moisture held in an aeriform state is .at its minimum ; hence we see the 
 reason why they continue for so long a time without having their density increased. 
 Evaporation goes on from the upper surface, while the ascending portions of the air are 
 adding to its bulk on the inferior ; and unless the latter exceeds the former the cloud 
 will remain stationary. But when the quantity of vapour disengaged exceeds what is 
 carried off from it by evaporation, the vesicular vapour gravitates slowly downwards, 
 and, increasing in bulk as it descends, constitutes the cumulus. It would appear, then, 
 that the cumulus usually occupies that line of elevation at which the atmosphere is 
 exactly equivalent to the weight of the vesicular vapour joined with that of the air 
 intermixed with it. 
 
 [This is an amplification of ideas expressed at a much earlier date. See Notes, 1766. 
 Saul, pp. 30, 31.] 
 
 1819. 
 Dalton, John. (B. 1819, 1.) 
 
 (Page 8.) From observations made at Manchester by myself, by Hutchinson at 
 (Page 9) Liverpool, and by the Royal Society in London, it appears that from March 
 (Page 10) to September the weight of the air is heavier than from September to March. 
 
 215 
 
AQUEOUS VAPOUR 
 
 1819. Dalton. NOTES. 
 
 (Page 11.) This seems to depend on the declination of the sun. The means^by which 
 the effect is produced, I conceive, are these : the sun's action is constantly increasing 
 the mass of aqueous vapour in the atmosphere during the period from the vernal to the 
 autumnal equinox. That is, the whole mass of vapour existing in the air is daily 
 increasing, notwithstanding the quantity precipitated. This fact is verified by the 
 constant rise of the vapour-point till September, after which it commonly declines 
 pretty rapidly. Now it is obvious that the addition of aqueous vapour to the atmo- 
 sphere must add to the weight of the atmosphere, and this is, I imagine, the cause of 
 the increase of its weight in that season. An opposite conclusion may be deduced 
 from these premises, on the ground that, as aqueous vapour is specifically lighter than 
 air, the more there is of it the less is the weight in any given volume of air of given 
 elasticity. But the aqueous vapour at most constitutes but one-fiftieth part of the 
 atmosphere, and any excess of this which may prevail in any one place cannot be 
 supposed powerful enough to move the rest of the atmosphere towards any 
 place where the vapour is deficient. Now we have no reason to believe that much 
 intercourse takes place between the atmosphere of the northern and southern 
 hemispheres. The great and unceasing currents of the air are between the 
 equator and the polar regions, but that any large volumes of air cross the equator 
 from one hemisphere to the other does not appear from any phenomena we are acquainted 
 with. And if the air does not cross the equator, the vapour cannot, being so intimately 
 blended with the air. Thus although there may be a constant pressure or tendency of 
 (Page 13) the atmosphere in the northern hemisphere to invade that of the southern 
 during our summer, or vice versa in winter ; yet I conceive it never can be so effectual 
 as to restore a perfect equilibrium during the season, but will leave an excess of vapour 
 in one hemisphere unbalanced either by air or vapour of the opposite hemisphere. The 
 (Page 24) condensation of vapour by cold will not explain the phenomena of rain. Dr. 
 Button maintained that the quantity of vapour capable of entering into the air increases 
 in a greater ratio than the temperature ; and hence he infers that whenever two volumes 
 of air of different temperatures are mixed together, each being previously saturated with 
 vapour, a precipitation of a portion of vapour must ensue in consequence of the mean 
 (Page 25) temperature not being able to support the mean quantity of vapour. In 
 1793 I missed the distinguishing feature of his theory. My opinion that the vapour 
 was not in chemical union with the air, but was mechanically wafted along by its 
 currents, was founded in part on Saussure's experiments showing that a cubic foot of dry 
 air at 66 would imbibe 12 grains of water for its saturation. Now from experiments I 
 was persuaded that this was nearly what would fill a cubic foot of empty space at 66, 
 and hence I concluded that the same quantity of vapour was required to saturate a 
 given space whether it contained air or not. In 1801 I experimentally proved the 
 (Page 27) truth of this inference. I also proved that the temperature increasing in an 
 arithmetical ratio, the force of steam increased in a geometrical one. Hence Hutton's 
 (Page 28) theory is no doubt the true one. The whole quantity of water in the atmos- 
 phere in January is usually about 3 inches, as appears from the dewpoint which is then 
 about 32. The force of vapour at that temperature is '2 inch of mercury, i.e. 2 -8 or 
 3 inches of water. The dewpoint in July is usiially about 58 or 59, corresponding 
 to -5 inch of mercury or 7 inches of water ; the difference is 4 inches of water. Hence 
 with the same amount of intermixture of currents the rain should be 4 inches less than 
 the average in the former, and 4 inches above it in the latter period. In these estima- 
 tions I assume that the atmosphere of steam is blended with the general atmosphere 
 (Page 29) throughout in the same verhial [vertical] column, and subject to the com- 
 mon law of rarefaction in ascending. 
 
 21G 
 
AQUEOUS VAPOUR 1823. Daniell. ^^_^^ MOTHS. 
 
 1323. 
 
 Daniell, J. F. Meteorological Essays and Observations. SV^pn^on. 1823. (fvp.) 
 (Page 49.) I now consider an atmosphere of unmixed aqueous vapour on a sphere of 
 uniform temperature (32 F.) covered with water. Dalton has estimated the elastic 
 (Page 51) force of steam at different temperatures. The density of the vapours must 
 decrease in a geometrical progression for equal perpendicular distances, and the tempera- 
 ture will decline with it, but in a different ratio. At 10,000 feet it would be '157 in., 
 (Page 52) and the constituent temperature [dewpoint] 25. The following shows the 
 elasticity, density and temperature of the vapours at different elevations. 
 
 Height. 
 
 Elasticity. 
 
 Density. 
 
 Temperatur 
 
 Feet. 
 
 Inches. 
 
 
 ol Vapour. 
 
 
 
 .2 
 
 1.0 
 
 32.0 
 
 5,000 
 
 .177 
 
 .89 
 
 28.5 
 
 10,000 
 
 .157 
 
 .79 
 
 25.0 
 
 15,000 
 
 .140 
 
 .708 
 
 22.0 
 
 20,000 
 
 .124 
 
 .636 
 
 19.0 
 
 25,000 
 
 .110 
 
 .577 
 
 16.0 
 
 30,000 
 
 .100 
 
 .518 
 
 13.0 
 
 With such an arrangement there would be perfect equilibrium, and consequently per- 
 fect rest all over the sphere. No precipitation or evaporation would take place, and the 
 atmosphere would remain transparent. Such also would be the state to which an 
 atmosphere would strive to attain, notwithstanding any obstacles which might be 
 opposed to it. Hence we may also infer that if condensation were to take place in any 
 part of such an atmosphere, evaporation must follow in other parts to maintain the 
 balance of forces ; and conversely that evaporation must be accompanied by precipita- 
 tion. Should the temperature of the sphere rise gradually and equally over all its 
 surface, the elasticity of the steam would increase with it, without disturbance ; and 
 following its own law of decrease for its different elevations, would remain perfectly 
 {Page 53) transparent. In considering the second modification of circumstances, that, 
 namely, of the temperature of the sphere, increasing from the poles to the equator, we 
 must first observe that a pure unmixed atmosphere could not follow such a gradation. 
 The elasticity of the whole would be determined by that of the lowest point ; and the 
 water would distil from the hottest point to the coldest with such a rapidity as to 
 occasion strong ebullition at the former. The condensation of vapour may be affected, 
 not only by decrease of temperature, but by increase of pressure ; it is not necessary, 
 therefore, that it should pass from the hottest to the coldest point to be precipitated, 
 which would be a gradual process; but the elastic force arising from an increase of 
 density at one extremity would instantly be felt at the other. For our present purpose 
 we must imagine the passage of the vapour from one point to another to be so mechani- 
 cally retarded as to enable it to assume the gradations due to the heat of the sphere. 
 We may estimate the relative force and pressure of two of the perpendicular columns at 
 different stations. The following table represents the state of the vapour at the equator, 
 supposing the temperature 80 as before : 
 (Page 54.) 
 
 Feet. 
 
 Elasticity. 
 
 Density. 
 
 Temperature . 
 
 
 
 1.000 
 
 4.571 
 
 80.0 
 
 5,000 
 
 .897 
 
 4.115 
 
 76.5 
 
 10,000 
 
 .804 
 
 3.682 
 
 73.0 
 
 15,000 
 
 .722 
 
 3.356 
 
 70.0 
 
 20,000 
 
 .648 
 
 3.026 
 
 67.0 
 
 25,000 
 
 .581 
 
 2.723 
 
 63.0 
 
 30,000 
 
 .521 
 
 2.487 
 
 60.0 
 
 Comparing this with the last table, we observe that both the density and elasticity 
 increase greatly with the temperature, and the consequence must be that the equatorial 
 columns must press upon the polar throughout their length. The vapour will flow in 
 a mass from the equator to the poles, and being necessarily condensed in its course will 
 
 217 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 return from the poles to the equator in the form of water. Great evaporation will con- 
 stantly he goincr on at the latter stations and condensation at every other, so that the 
 atmosphere, excepting at the equator, would be rendered turbid by perpetual clouds and 
 rain. The temperature of the sphere would by this process soon become equalised, did 
 (Page 55) not our hypothesis provide for its permanency ; the equatorial parts would be 
 quickly cooled by evaporation, and the polar warmed by the heat evolved during the 
 condensation. It is worthy of attention that the elasticity of vapour increasing nearly 
 in a geometrical proportion for equal increments of heat, the decrease of temperature in 
 ascending in this atmosphere will be in arithmetical proportion only. The diminution 
 is very nearly three degrees for every 5000 feet. Upon the hypothesis of the gradation 
 of temperature before assumed, the following table will represent the corresponding 
 elasticity and density of the vapour at the surface of the sphere for every ten degrees of 
 
 latitude : 
 
 Poles 80 70 
 
 Elasticity. Density. Temp. Elasticity. Density. Temp Elas " c l ty ' ^fl' o^o' 
 
 064 34 .072 .38 3.2 .089 .466 9.6 
 
 60 50 40 
 
 Elasticity. Density. Temp. Elasticity. Density. Temp. Elasticity. Density. Temp. 
 
 .125 .611 19.2 .2 1.0 32 .351 1.7 48 
 
 3QO ' OQO 10 Equator. 
 
 ED T & D T. E. D. T. E. D. T. 
 
 .539 2.547 60.8 .731 3.403 70.4 .9 4.133 76.8 1.000 4.571 80 
 
 (Page 56.) Under these circumstances the equatorial regions will remain perfectly 
 transparent, while rains will continue to fall in every other situation in proportion to the 
 densities of the respective places and the decrease of temperature, and the supply of 
 vapour will be entirely kept up by the evaporation at the equator. The height of the 
 barometer decreases rapidly towards the poles from 1 in. to .064 in., and the quantity of 
 condensation is definite for each latitude ; for the resistance to the passage of the vapour 
 is supposed to be constant and equal. Let us now imagine that the temperature is 
 raised to the level of that which adjoins ; then condensation will cease at that particular 
 place, evaporation will commence, and the atmosphere will become transparent. The 
 quantity of water precipitated will be proportionally increased on the other side. If, on 
 the contrary, the temperature be lowered to the standard of the latitude next above, the 
 precipitation will be increased and the higher latitude will be cleared. The following 
 table represents lat. 30 under these two conditions. 
 
 40 30 20 
 
 Cloudy. Clear. Cloudy. 
 
 Elasticity. Density. Temp. Elasticity. Density. Temp. Elasticity. Density. Temp. 
 
 .351 1.7 48 .731 3.403 70.4 .731 3.403 70.4 
 
 Clear. Cloudy. Cloudy. 
 
 .351 1.7 .351 1.7 .731 3.403 70.4 
 
 (Page 57.) Again, if the mechanical retardation of the flowing vapour which we 
 imagined were subject to variation, the quantity of evaporation and precipitation would 
 be proportionate to the velocity of its passage ; thus, supposing the evaporation from a 
 given surface at a given temperature and under a certain resistance to be three grains 
 per minute, it would be increased to six grains with half the resistance. The changes 
 at the surface affect the whole of the superincumbent columns equally and the tempera- 
 ture of the vapour follows its own law of decrease. But what will be the consequence 
 if the vapour should be forced to adapt itself to a progression different from that of its 
 own, and if, from some cause or other, the heat of the upper regions should diminish at a 
 greater rate than is due to the natural gradation ? Let us, for instance, suppose that the 
 heat of the water upon the sphere is 80, but that at the height of 5000 feet above the 
 surface a temperature exists of 64.4, which from that point follows the former decreasing 
 scale. The water will have a tendency to throw off vapour of the same constituent 
 heat as its own temperature, but the pressure above being rendered too little by the 
 influence of the forced degree of cold to preserve the necessary elasticity below, the 
 218 
 
Elasticity. 
 
 Constant 
 
 Sensible 
 
 State of 
 
 
 Temperature. 
 
 Temperature. 
 
 Atmosphere. 
 
 [*].673 
 [*1.606 
 
 [*]67.9 
 
 [*]64.4 
 
 80 
 [*]64.4 
 
 Clear. 
 Cloudy. 
 
 " .542 
 
 61.0 
 
 61.0 
 
 Clear. 
 
 .490 
 
 58.0 
 
 58.0 
 
 do. 
 
 .443 
 
 55.0 
 
 55.0 
 
 do. 
 
 .401 
 
 52.0 
 
 52.0 
 
 do. 
 
 .363 
 
 49.0 
 
 49.0 
 
 do. 
 
 AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 atmosphere will only possess the tension due to the lower degree, that is to say, the con- 
 (Page 58) stituent temperature will be only 67'9. Evaporation must, therefore, ensue 
 below, and its concomitant precipitation will take place above. The calculation of these 
 effects has furnished the following tabular representation of their connection. 
 
 Height. 
 k Feet. 
 
 
 
 5,000 
 10,000 
 15,000 
 20,000 
 25,000 
 30,000 
 
 [The [*] indicate asterisks added in the 1845 ed.] 
 
 The consequence of this situation of things will be that a cloud will be formed at the 
 height named, for the atmosphere will be forced upward by the nascent [" spring 
 of the" is an addition in 1845 ed.] vapour, and will be condensed at this point. 
 The cloud, however, supposing the process to be sufficiently gradual, would 
 not extend very far downwards, for the water during its precipitation would be 
 redissolved [changed to " re-evaporated " in 1845 ed.] by the excess of heat in the 
 lower regions, so that they might remain transparent and undisturbed. The ultimate 
 effect would be that the temperature would be slowly equalised, and the balance offeree 
 restored. The water in its circulation backwards and forwards would act as a carrier of 
 the heat which it would abstract from the lower part by its evaporation, and give out to 
 the upper by its condensation. The atmosphere would thus gradually recover its state 
 of equilibrium and repose. The upper regions, upon this supposition, remain clear, for 
 (Page 61) there the regular gradation is undisturbed. We have already proposed the 
 simple case of a sudden decrease of heat at one stage of its height by which condensa- 
 tion was produced ; the elasticity was thereby reduced to the degree appropriate to that 
 temperature at that elevation, and evaporation commenced from the surface. This 
 evaporation was proportionate to the difference between the elasticity of the temperature 
 of the sphere and the elasticity of the superincumbent mass. We will now suppose 
 that the rapid decrease of temperature continues throughout the column, and that at the 
 (Page 62) following heights it is forced to adapt itself to the annexed progression. 
 
 Height. Temperature. 
 
 80 
 
 5,000 64.4 
 
 10,000 48.4 
 
 15,000 31.4 
 
 20,000 12.8 
 
 25,000 7.6 
 
 30,000 30.7 
 
 The elasticity could not then exceed .043 inch upon the surface; the evaporation 
 would consequently be excessive and its force would almost amount to explosive violence ; 
 while the condensation above would be proportionate, and the precipitation would 
 resemble a waterspout in its effects. 
 
 (To be continued.) 
 
 211) 
 
SCIENTIFIC UNION. 
 
 Srimtific 8tni0it. 
 
 The rapid progress of science now going on is, in part, the result of the 
 great increase in the number of workers. This is accompanied by a larger 
 and larger host of scientific serials. The consequence is that the student 
 finds an increasing difficulty in ascertaining what has been done, or is in 
 process of being accomplished, not only in his own special line of study, but 
 also, and more particularly, in such as do not immediately interest him. 
 Every student finds, from time to time, that he has a desire for full informa- 
 tion on subjects in these outlying sciences, for the purpose of throwing light 
 upon his special studies. The state of literature is such that he is frequently 
 daunted by the difficulties attending his research, or, if he perseveres, he finds 
 a great deal of time unnecessarily wasted. The remedy for this is the foca- 
 lisation of knowledge round a series of centres. The two main steps in the 
 process are, first, collection, and, next, classification. It is with this ulterior 
 object in view, that all persons interested in meteorology are earnestly asked 
 to forward their names and addresses, particulars as to the work they have done 
 in meteorological and other sciences, their present lines of study, ways in 
 which help is desired, and any other items that may occur to them. These 
 details will be classified, and, when the opportunity offers, selections from 
 them will be published. The Conductor will exercise careful discretion in 
 the selection, as also in the use he may make of the more private details. 
 The first list will be published in November, 1883 ; but correspondents are 
 requested to send in answers soon, in order to allow of ample time for 
 their classification, and for their utilisation in private correspondence in the 
 interests of correspondents. 
 
 In order to prevent any misconception, it may be stated that the Con- 
 ductor's object is solely to promote scientific union, and is no way intended 
 to be of a charitable nature in any pecuniary sense. If there is a sufficient 
 response to these requests, the same line of proceeding will hereafter be 
 suggested, from time to time, for the students in other branches of science. 
 
 Newspapers and scientific journals of all countries, willing to help in 
 this matter, are asked to make the above requests known to their readers. 
 
 Address, Conductor, "Scientific Boll" office, 7 Eed Lion Court, Fleet 
 Street, London, E.G. 
 
 In the hopes of promoting Scientific union, attention is asked to the circulars issued 
 by the Conference of Delegates of Scientific Societies reprinted below, as also to the sets of 
 questions asked by Sergeant J. P. Finley, of the United States Signal Service, which 
 are reprinted farther on, under ' The Scientific Enquirer.' The observations and tables 
 in the circulars of the Conference are intended to apply only to the British Isles, and 
 220 
 
SCIENTIFIC UNION. 
 
 Sergeant Finley's questions apply strictly to the United States. As it is desirable that 
 the results obtained by the workers in these areas should be comparable with those 
 obtained in other regions, a special request is made for modifications of these lists and 
 sets of questions, adapting them for each special district, as also for the lists, circulars, 
 and methods of procedure which have been adopted and acted upon in all parts of 
 the world. Any local Scientific Society which has not received the circular of the 
 Conference is requested to communicate with Mr. Fordham, or with the Conductor 
 of the "Scientific Roll." 
 
 CONFERENCE OF DELEGATES FROM SCIENTIFIC SOCIETIES. 
 
 Held Annually during the Meeting of the British Association. 
 
 To the Secretary of the 
 SIR, 
 
 I enclose a copy of the Minutes of the Proceedings' of the Conference held at 
 York, on September 6th, 1881. 
 
 You will see that a Committee was then appointed, with instructions (1) to " take 
 steps to have the Conference of Delegates recognised by the Council of the British 
 Association," and (2) " to send out a circular to the various local Scientific Societies, 
 pointing out the work undertaken by the Committees of the British Association, and 
 the valuable aid which maybe given by;these Societies in that and other scientific work." 
 
 The Committee have prepared and now enclose a circular drawn up in accordance 
 with their instructions, and you are requested to bring it and the other enclosures 
 under the notice of your Society. 
 
 There are only three Committees of the British Association whose investigations 
 seem likely to benefit through the assistance of local Scientific Societies, but the 
 Committee have selected some other subjects which may usefully engage the attention 
 of such Societies. 
 
 The Committee will be glad to have any criticisms or remarks on the subject- 
 matter of the circular, and they will be obliged if you will inform them should your 
 Society set on foot any regular system of recording observations on any of the points 
 referred to. 
 
 The Third Conference of Delegates will be held during the Meeting of the British 
 Association at Southampton, in August. The names of Delegates representing your 
 Society may be sent to me, and notice of the time and place of the Conference will be 
 left for them at the post office, in the reception room, as soon as possible after the 
 commencement of the Meeting. 
 
 It is necessary, if your Society desires to avail itself of the privilege conferred by 
 the Rule of the British Association given below,* and in order that your Delegates 
 should have the right to sit on the General Committee, and that their names should 
 appear in the Journal, that you should make a formal claim to the Assistant Secretary, 
 22, Albemarle Street, London, W., some little time before the date fixed for the 
 meeting. 
 
 Yours faithfully, 
 
 H. GEORGE FORDHAM, 
 
 ODSEY GRANGE, ROYSTON, GAMES., 
 
 2th April, 1882. Hon. Sec. to the Committee. 
 
 * " General Committee Class B. Temporary Members." "1. The President for the 
 time being of any Scientific Society publishing Transactions, or, in his absence, a delegate 
 representing him ; and the Secretary of such Society. Claims under this rule to be sent to 
 the Assistant Secretary before the opening of the Meeting." NOTE. Ihe Delegate must 
 be a Member (not Associate) of the British Association. 
 
 221 
 
SCIENTIFIC UNIOX. 
 
 CIRCULAR REFERRING TO SUBJECTS RECOMMENDED FOR INVESTIGATION 
 BY LOCAL SCIENTIFIC SOCIETIES, 
 
 I. COMMITTEES OF THE BRITISH ASSOCIATION. 
 
 The work of the three following Committees is of a character to receive valuable 
 help from local Scientific Societies. It will be seen that a large number of observers, 
 spread over the whole country, is necessary for carrying on the investigations for which 
 the Committees are appointed. 
 
 Attention is therefore called to the objects which these Committees have in view ; 
 but, as the limits of this circular do not permit of the insertion of full particulars of the 
 methods of observation employed by the Committees, Societies or individuals willing 
 to assist them should communicate with the Secretaries (whose names and addresses 
 are given), and to whom Eeports should be sent. 
 
 1. UNDERGROUND WATERS COMMITTEE. 
 SEC. : C. E. DE RANGE, F.G.S., 28, Jermyn Street, London, S.W. 
 
 OBJECT. To investigate the circulation of the Underground Waters in England and 
 Wales, and the quantity and character of the waters supplied to various towns and 
 
 districts. 
 
 Records of the heights of the water in wells, with particulars of the variations of 
 level at different periods, are required, as well as notes on the character of the water, 
 and particulars of the formations from which it is derived. 
 
 2. ERRATIC BLOCK COMMITTEE. 
 SEC. : REV. H. W. CROSSKEY, F.G.S., 28, George Road, Birmingham. 
 
 OBJECT. To record the position, height above the sea, lithological characters, size, 
 and origin of the Erratic Blocks of England, Wales, and Ireland, to report other 
 matters of interest connected with the same, and to take measures for their 
 preservation. 
 
 It is obvious that to obtain a record of the boulders of Great Britain and Ireland at 
 all approaching completeness, a large amount of local assistance must be relied on. 
 And as, at the same time, the value of the deductions to be made from the information 
 collected by the Committee depends almost entirely on their investigations covering the 
 whole area under consideration, the Committee are obliged to appeal to local Societies 
 and local observers for help. 
 
 Boulders are scattered over large districts of the country, particulars concerning 
 them can easily be noted, and as they are continually being destroyed, or removed from 
 their original sites, it is very desirable that records should be obtained as early as 
 possible. By the accumulation of information from all parts of the country, and by 
 its careful arrangement and examination, the Committee hope to arrive at data which 
 will be of material assistance in the study of the history of the Glacial Period. 
 
 The investigations of this Committee do not extend to Scotland ; the Royal Society 
 of Edinburgh having appointed a " Boulder Committee " for that country. Of the 
 Scotch Committee, Mr. D. Milne Home, M.A., F.R.S.E., F.G.S., 10, York Place, Edin- 
 burgh, is the Convener. 
 2-22 
 
SCIENTIFIC UNION. 
 
 3. UNDERGROUND TEMPERATURE COMMITTEE. 
 SEC. : PROF. J. D. EVERETT, M.A., D.C.L., F.R.S., Rushmere, Malone Road, Belfast. 
 
 OBJECT. To investigate the rate of increase of Underground Temperature downwards 
 in various localities of dry land and under water. 
 
 The Committee undertake the determination of temperature at great depths below 
 the earth's surface, in mines, deep wells, artesian borings, etc. Special thermometers 
 are lent by the Committee to observers. 
 
 II. INVESTIGATIONS CONDUCTED BY INDIVIDUAL OBSERVERS OR 
 
 SOCIETIES. 
 
 Information relating to the following subjects is collected by the observers or 
 Societies referred to, and further particulars as to the method of observation, etc., will 
 be furnished, on application, by them. The subjects mentioned are all very suitable 
 for investigation by local Scientific Societies. 
 
 1. RAINFALL. 
 G. J. Symons, F.R.S., 62, Camden Square, London, N.W. 
 
 The pamphlet sent herewith (Enclosure 1) sufficiently explains the nature and value 
 of the work undertaken by Mr. Symons. The more widely the knowledge of that 
 work and of its importance is spread, the greater will be the increase in the 
 number of observers, and the value of the ultimate results will be correspondingly 
 enhanced. 
 
 The Committee would recommend the publication, locally, of observations extended 
 over a limited area (such as a county), and at frequent intervals, as being very effective 
 in arousing local interest in the subject. A copy of the table published monthly in 
 Hertfordshire, in most of the local newspapers, is enclosed (Enclosure 2), as a specimen 
 of what may be done without much trouble or expense. In this table the various 
 stations are grouped in the river-basins of the county, and the average rainfall of each 
 of these areas is inserted. The Hertfordshire Natural History Society and Field Club 
 publishes also annually in its ' Transactions ' a considerable amount of information on 
 the Rainfall, and has obtained a substantial increase in the number of observers in the 
 county. It is suggested that other local Societies should take similar steps for the 
 encouragement of rainfall observation. 
 
 (Enclosure 1.) 
 
 ARRANGEMENTS FOR THE SYSTEMATIC OBSERVATION AND RECORD OF THE 
 RAINFALL OF THE BRITISH ISLES. 
 
 Introductory and Historical. I cannot help this section appearing to be egotistical ; the 
 rainfall organisation being entirely my own creation, it is impossible for it to be otherwise. 
 
 In the early part of the year 1859 I began collecting copies of records of the fall of rain, 
 and early in 1861 wrote to all the observers of whom I was then aware, and asked them to send 
 me all the records for the year 1860 that they could. I received 168 returns, and printed a 
 table showing the total fall of all those places, being a larger number than had ever been classed 
 together before. This publication gave a stimulus to observers, and from that time onwards 
 their number has steadily increased .until it now exceeds 2000. 
 
 The amount of information published has increased even more, for whereas at first I printed 
 only the total annual fall, I now publish essays on various branches of rainfall enquiry, and full 
 abstracts of the most remarkable falls in short periods (ten minutes, half-an-hour, and so on), 
 the heaviest falls in one day, tables of the monthly fall at several hundred stations, and, in 
 short, give all the information which I can collect and which it seems expedient to print. 
 
 From the foregoing it will be evident that the compilation of the present annual volume (of 
 which the short title is " British Rainfall, 1877," &c.) is a very serious labour. The mere 
 checking of two thousand returns takes a long time, and so does the due arrangement of the 
 
 223 
 
SCIENTIFIC UNION. 
 
 various facts reported, and by no means the least onerous matter is ensuring the accuracy of the 
 printing of the whole. . 
 
 During the first few years I not only gave my own time gratuitously to the work, but also 
 bore all the cost of postages and of printing. It soon, however, became far too costly for me to 
 bear it all and my correspondents most kindly offered to share it with me. In 1865 the price oi 
 the annual volume was fixed at five shillings, and, although the size and cost of the volume have 
 since largely increased, no rise has been made in the price There are two reasons for this: 
 (I) Because if the book could not be compiled without the help of observers, they ought to be 
 allowed to have it as cheaply as possible ; (2) Because a small number of the observers (about 
 300, whose subscriptions are duly published) contribute annual sums varying from one to ten 
 guineas towards the general expenses of the work. 
 
 ' The existing state of matters is, therefore, shortly as follows. There are about 2000 persons, 
 well spread over England and Wales, Scotland and Ireland, each of whom is, I hope, strictly 
 obeying the rules on page 5. To each of them I send on December 31st each year, blank forms 
 for them to return to me filled with the facts observed by them. At the same time I send a list 
 of the various publications, and invite such pecuniary aid as it may be agreeable to them to send. 
 I ought, perhaps, to say what becomes of the subscriptions. I will mention some of the 
 outlets. (1) There are nearly a thousand observers whose returns have to be collected, examined, 
 discussed, and printed, who do not contribute sixpence towards the cost thereof. (2) In some 
 localities it is impossible to obtain volunteer observers, and there the observers receive regular 
 salaries. (3) The mass of office work, correspondence, &c., is far beyond what I can myself 
 accomplish ; two regular assistants are, therefore, employed, and besides that, considerable sums 
 
 are paid for extra assistance at times of pressure. 
 (4) The expenditure for printing and postages is 
 very large. 
 
 In addition to the annual volume, I publish a 
 monthly periodical, Symons's Monthly Meteoro- 
 logical Magazine, giving, in addition to a full 
 chronicle of the progress of meteorology, details 
 of rainfall at about 100 stations. This is sent 
 free to subscribers. 
 
 It may, perhaps, be added that it always 
 affords me pleasure to reciprocate, as far as 
 possible, the assistance which the observers 
 render to me, either by affording them meteoro- 
 logical information, data as to the height of their 
 stations above sea level, or advice as to the 
 purchase of instruments. 
 
 In short, the state of the case is this : I have 
 given myself up to the collection of statistics of 
 rainfall old ones and current ones ; I invite 
 everybody to help 'me, both with observations 
 and funds, and I promise, in return, to render 
 to all my correspondents all the help that is in 
 my power. 
 
 Patterns of Rain Gauges, and where to buy 
 them. This is not a pleasant section to write, 
 for there is considerable jealousy among the 
 manufacturers, and I am almost certain to be 
 accused of favouritism by some one. However, 
 I have never patented any pattern of rain gauge, and, therefore, leave the field open to all. 
 
 Upon one point it is necessary to be despotic, viz., that amateurs never try to make their own 
 gauges ; they are almost certain to go wrong in some respect, and nothing is more vexing, both 
 to the observers and to myself, than for it to be discovered, after observations have been recorded 
 for a long time, that the labour of years is vitiated by an inaccurate instrument. 
 
 For use in ordinary localities I think the annexed is the best pattern ; it is known as the 
 Snowdon gauge, it is five inches in diameter, is easily fixed by four stakes as shown ; the glass- 
 jar when filled up to the top division holds 0.50 in., or half an inch, the bottle holds about three 
 inches of rain, and, of course, in the very rare case of the fall exceeding that, the excess is saved 
 by the can, and must be carefully measured. If made in japanned tin these cost from 16s. 
 to 20s., but they are much stronger, and more durable, if made in copper, when they cost from 
 21s. to 30s. Negretti's have just brought out a very stout pattern, in galvanized iron, at a still 
 lower price. Where cost is no object, it is, by some, thought better to have a rather larger 
 gauge, viz., eight inches diameter, costing from 2 to 3, but I do not advise it. 
 
 Snowdon pattern rain gauges can, no doubt, be obtained from any optician, but it may bo 
 convenient to give, in alphabetical order, the names and addresses of a few of the principal 
 makers : 
 
 CASELLA, L., 147, Holborn Bars, E.G. 
 HICKS, J. J., Hatton Garden. E.C. 
 221 
 
SCIENTIFIC UNION. 
 
 NEGRETTI & ZAMBRA, Holborn Viaduct and Cornhill, E.G. 
 PASTORELLI, F., 10, New Bond Street. 
 
 Testing. Wherever, and of whomsoever, rain gauges maybe bought, it is very desirable 
 that the purchaser should insist upon having certificates of their accuracy. Ram gauges are 
 examined, and certificates issued, by Kew Observatory, and by myself, the charge in each case 
 is the same, namely, 2s. 6d. 
 
 Blank Forms. All blank forms required for returns to myself, and additional ones wherever 
 desired, are supplied gratuitously, and even those sold are charged at little more than their 
 actual cost. 
 
 Change of Residence. Each observer is requested to decide upon a specific name for his 
 station, and to notify immediately any change in the position of the gauge or the discontinuance 
 of his record. 
 
 SUGGESTIONS FOR SECURING UNIFORMITY OF PRACTICE AMONG RAINFALL 
 
 OBSERVERS. 
 
 I. SITE. A rain gauge should not be set on a slope or terrace, but on a level piece of 
 ground, at a distance from shrubs, trees, walls, and buildings ; at the very least, as many feet 
 from their base as they are in height. Tall-growing flowers, vegetables, and bushes must be 
 kept away from the" gauge. If a thoroughly clear site cannot be obtained, shelter is most 
 endurable from N.W., N., and E., less so from S., S.E., and W., and not at all from S.W. or N.E. 
 
 II. OLD GAUGES. Old established gauges should not be moved, nor their registration 
 discontinued, until at least two years after a new one has been in operation, otherwise 
 the continuity of the register will be irreparably destroyed. Both the old and the new ones 
 must be registered at the same time, and the results recorded for comparison. 
 
 III. LEVEL AND FIXING. The funnel of a rain gauge must be set quite level, and so firmly 
 fixed, that it will remain so in spite of any gale of wind or ordinary circumstance. Its 
 correctness in this respect should be tested from time to time. 
 
 IV. HEIGHT. The funnel of gauges newly placed should be 1 ft. above grass. Information 
 respecting height above sea level may be obtained from the editor. 
 
 V. RUST. If the funnel of a japanned gauge becomes so oxidised as to retain the rain in 
 its pores, or threatens to become rusty, it should have a coat of gas tar, or japan black, or a 
 fresh funnel of zinc or copper should be provided. 
 
 VI. FLOAT GAUGES. If the measuring rod is detached from the float, it should never be 
 left in the gauge. If it is attached to the float, it should be pegged or tied down, and only 
 allowed to rise to its proper position at the time of reading. To allow for the weight of the 
 float and rod. these gauges are generally so constructed as to show only when a small amount 
 of water is left in them. Care must always be taken to set the rod to the zero or 0. 
 
 VII. CAN AND BOTTLE GAUGES. The measuring glass should always be held upright ; the 
 reading is to be taken midway between the two apparent surfaces of the water. 
 
 VIII. TIME OF READING. Nine a.m. daily; if taken only monthly, then 9 a.m. on the 1st. 
 
 IX. DATE OF ENTRY. The amount measured at 9 a.m. on any day is to be set against the 
 previous one ; because the amount registered at 9 a.m. of, say, 17th, contains the fall during 15 
 hours of the 16th and only 9 hours of the 17th. (2Vs rule has been approved by the Meteorolo- 
 gical Societies of England and Scotland, cannot be altered, and is particularly commended to the 
 notice of observers.") 
 
 X. MODE OF ENTRY. If less than one-tenth (-10) has fallen, the cypher must always be 
 prefixed ; thus, if the measure is full up to the seventh line, it must be entered as '07, that is, 
 no inches, no tenths, and seven hundredths. For the sake of clearness, it has been found neces- 
 sary to lay down an invariable rule that there shall always be two figures to the right of the 
 decimal point. If there be only one figure, as in the case of one-tenth of an inch (usually 
 written -1) a cypher must be added, making it -10. Neglect of this rule causes much incon- 
 venience. All columns should be cast twice once up and once down, so as to avoid the same 
 error being made twice. When there is no rain, a line should be drawn rather than cyphers 
 inserted. 
 
 XI. CAUTION. The amount should always be written down before the water is thrown 
 away. 
 
 XII. SMALL QUANTITIES. The unit of measurement being -01, observers whose gauges are 
 sufficiently delicate to show less than that, are, if the amount is under -005, to throw it away ; if 
 it is '005 to '010 inclusive, they are to enter it as '01. 
 
 XIII. ABSENCE. Every observer should train some one as an assistant ; but where this is 
 not possible, instructions should be given that the gauge should be emptied at 9 a.m. on the 1st 
 of the month, and the water bottled, labelled, and tightly corked, to await the observer's return. 
 XIV. HEAVY RAINS. When very heavy rains occur, it is desirable to measure immediately 
 on their termination, and it will be found a safe plan after measuring to return the water to the 
 irauge, so that the morning registration will not be interfered with. Of course if there is the 
 ^lightest doubt as to the gauge holding all that falls, it must be emptied, the amount being 
 previously written down. 
 
 PAKTIL No. 8. Q 225 " 
 
SCIENTIFIC UNION. 
 
 XV. SNOW. In snow three methods may be adopted ; it is well to try them all. (1) Melt 
 what is caught in the funnel by adding to the snow a previously ascertained quantity of warm 
 water, and then deducting this quantity from the total measurement, enter the residue as rain. 
 (2) Select a place where the snow has not drifted, invert the funnel, and turning it round, lift and 
 melt what is enclosed. (3) Measure with a rule the average depth of snow, and take one-twelfth 
 as the equivalent of water. This being a very rough method, is not to be adopted if it can be 
 avoided. Some observers use in snowy weather a cylinder of the same diameter as the rain 
 gauge, and of considerable depth. If the wind is at all rough, all the snow is blown out of a flat- 
 funnelled rain gauge. Snowdon pattern gauges are much the best. 
 
 XVI. OVERFLOW. It would seem needless to caution observers on this head, but as a recent 
 foreign table contains six instances on one day in which gauges were allowed to run over, it is 
 evidently necessary that British observers should be on the alert. It is not desirable to purchase 
 any new gauge of which the capacity is less than four inches. 
 
 XVII. SECOND GAUGES. It is desirable that observers should have two gauges, and that 
 one of them should be capable of holding eight inches of rain. One of the gauges should be 
 registered daily, the other weekly or monthly as preferred, but always on the 1st of each month. 
 By this means a thorough check is kept on accidental errors in the entries, which is not the case 
 if both are read daily. 
 
 XVIII. DEW AND FOG. Small amounts of water are at times deposited in rain gauges by 
 fog and dew; they should be added to the amount of rainfall, because (1) they " tend to water 
 the earth and nourish the streams ; " and not for that reason only, but (2) " because in many cases 
 the rain gauges can only be visited monthly, and it would then obviously be impossible to 
 separate the yield of snow, rain, &c. ; therefore, for the sake of uniformity, all must be taken 
 together." 
 
 XIX. DOUBTFUL ENTRIES. Whenever there is the least doubt respecting the accuracy of 
 any observation, the entry should be marked with a ?, and the reason stated for its being placed 
 there. 
 
 XX. BREAKAGE. The Editor has no desire to supply rain gauges or glasses, or in any way 
 to undertake, or interfere with, that which is the business of opticians ; but the continuity and 
 permanent accuracy of the records of his correspondents is to him of such importance, that he 
 deems it advisable to announce that any assistance in his power is always at their service. 
 
 62, Camden Square, London, N. W. G. J. SYMONS. 
 
 [For Rainfall in Herts (Enclosure 2), see next page.] 
 
 2. PERIODICAL NATURAL PHENOMENA. 
 
 ASSISTANT SECRETARY, Meteorological Society, 30, Great George Street, London, S.W. 
 REV. T. A. PRESTON, M.A., F.L.S., The Green, Marlborough, Wilts. 
 
 The appended list of 60 species recommeDded for observation (p. 229) is a selection 
 from the 100 species of which the list of the Meteorological Society consists, of which a 
 copy is enclosed (Enclosure 3). The phenomena to be observed are given in the pro- 
 bable order of occurrence as deduced from the mean of six years' observations (1876-81) 
 by members of the Hertfordshire Natural History Society. Observers may, if they pre- 
 fer to do so, adopt the more extensive list of the Meteorological Society, or they may 
 confine their attention to the 25 species of which the English names are here printed in 
 capitals. 
 
 There are at present over 40 observers, who record facts coming under this heading, 
 and it is very desirable that the number should be greatly extended, so that ultimately 
 no part of the county may be without observers. 
 
 Observers are referred for further information to the following : 
 
 ' Instructions for the Observation of Phenological Phenomena.' London : Williams 
 and Strahan. 1875. Price Qd. (Also to be had at the office of the Meteorological 
 Society.) 
 
 "On the Observation of Periodical Natural Phenomena," by John Hopkinson. 
 F.L.S. ; with notes on the Plants to be observed, by the Kev. W. M. Hind, LL.D. ; on the 
 Insects, by Arthur Cottam; and on the Birds, by J. E. Harting, F.L.S., in 'Trans. 
 Watford Nat. Hist. Soc.,' vol. i., part 2. London : David Bogue. 1875. Price Is. 
 226 
 
SCIENTIFIC UNION. 
 
 (Enclosure 2.) 
 RAINFALL IN HERTS. For the month of March, 1882. 
 
 Rainfall in River Districts. 
 
 Station. 
 
 Above Sea 
 Level. 1 
 
 Depth of Rain. 
 
 Diffnce. from 
 Mean 1870-79. 
 
 [Greatest fall 
 in 24 hours. 
 
 l 
 
 t 
 
 t 
 
 i 
 
 7 
 
 9 
 15 
 13 
 10 
 14 
 14 
 
 14 
 14 
 12 
 14 
 
 12 
 14 
 8 
 13 
 11 
 11 
 8 
 11 
 8 
 8 
 14 
 7 
 17 
 12" 
 9 
 13 
 13 
 11 
 
 /THAME 1-50 
 COLNE 1-52 
 BRENT 
 
 LEA 1-32 .' 
 
 ' 
 
 \ 
 j IVEL 1-20 
 
 1 CAM 1-19 
 
 Upper Thame 1-50 
 Upper Colne 
 
 Aylesbury (Bucks) 
 
 280 
 
 600 
 402 
 345 
 370 
 426 
 237 
 
 240 
 225 
 480 
 340 
 
 250 
 230 
 357 
 391 
 500? 
 484 
 220 
 235 
 240 
 273 
 147 
 82 
 240 
 238 
 422 
 220 
 264 
 269 
 
 fl'50 
 
 1-33 
 1-57 
 1-70 
 1-60 
 1-35 
 1-66 
 
 2-42? 
 1-59 
 1-39 
 1-50 
 
 1-39 
 97 
 1-17 
 1-57 
 1-20 
 1-12 
 1-32 
 1-38 
 tl'52 
 tl-23 
 1-47 
 tl'35 
 1-44 
 1-15 
 1-29 
 tl'17 
 1-15 
 1-23 
 
 -21 
 
 -42 
 -18 
 -05 
 -15 
 
 -40 
 -09 
 
 + -67 
 -16 
 -36 
 -25 
 
 -23 
 -65 
 -45 
 -05 
 -42 
 -50 
 -30 
 -24 
 -10 
 -39 
 15 
 
 60 
 
 46 
 63 
 50 
 65 
 61 
 68 
 
 81 
 65 
 61 
 72 
 
 71 
 20 
 62 
 73 
 50 
 56 
 77 
 65 
 71 
 62 
 91 
 73 
 65 
 57 
 58 
 51 
 56 
 62 
 
 25th 
 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 
 25th 
 25th 
 25th 
 25th 
 
 25th 
 1st 
 28th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 25th 
 
 Eensworth 
 
 Ver 1-45 j 
 
 Harpenden, Rothamsted . . . 
 
 Gade and Bui- 
 borne 1*58 ... 
 
 Chess 
 
 Berkhampstead . 
 
 Gt Gaddesden 
 
 Nash Mills 
 
 Watford, Watford House 
 Wans ford House 
 Bushey Heath 
 
 Lower Colne 1-49 | 
 
 ( 
 
 Upper Brent. 
 /Upper Lea 1-39 ... 
 
 Mimram 1'07 ... 
 Beane 1'57 
 Rib 1-16 ^ 
 
 Rickmansworth, Moor Park 
 Bayfordbur \i 
 
 Welwyn 
 
 Datchworth 
 
 Knebworth 
 
 Ther field ... 
 
 Throcking 
 
 Ash 1-35 f 
 
 Much Hadham . 
 
 Ware, Fanham's Hall 
 
 Stort 1-37 | 
 
 Stansted (Essex) . 
 
 Harlow, Moor Hall (Essex) 
 Hoddesdon 
 
 Lower Lea 1*42 
 
 \ 
 
 JHiz 1-22 | 
 
 Waltham Abbey (Essex)... 
 Southgate 
 
 -27 
 -18 
 -33 
 
 1 Q 
 
 Hitchin 
 
 
 I Upper Ivel 1-17 .. 
 Rheel-19 | 
 
 Stotfold (Beds ) 
 
 -31 
 -27 
 -19 
 
 Odsey (Cambs.) 
 
 Royston 
 
 
 Mean for the Countv 
 
 
 
 1-37 
 
 -29 ! 
 
 
 11 
 
 } Not taken into consideration in determining the County Mean Fall. + signifies above, below the mean. 
 N.B. One inch of rain represents 101 tons of water per acre. A wet day is one on which O'Ol in. or more falls. 
 
 Mean Rainfall (1870-79) for the month in River Districts, Thame 1-71 ; Colne 1-75 ; Brent [no observation] ; Lea 1-62 ; 
 
 Ivel 1-48; Cam 1-42. 
 
 C. W. HARVEY, F.M.S., Throcking Rectory, Buntingford, Herts. 
 [Reprinted from The Herts, and Catrtis. Reporter, 21st April.] 
 
 3. INJURIOUS INSECTS. 
 Miss E. A. ORMEROD, F.M.S., Dunster Lodge, Spring Grove, Isleworth, Middlesex. 
 
 The appearance of any of the Insects in the appended list (p. 228) in unusual numbers, 
 any injuries done by them, and the degree of success which has attended any methods 
 of prevention which have been tried, may be recorded and communicated to Miss 
 Ormerod, by whom this list has been compiled, and who will forward on application 
 forms on which to record observations. 
 
 Observers are referred for full information, instructions, and illustrations of the 
 insects, to the following : 
 
 * A Manual of Injurious Insects,' by Eleanor A. Ormerod. London : W. Swan 
 Sonnenschein and Co. 1881. Price 3s. 
 
 Q 2 
 
 227 
 
SCIENTIFIC UNION. 
 
 " Notes for Observations of Injurious Insects," by the same, in ' Trans. Watford 
 Nat. Hist. Soc.,' vol. ii., part 2. London : David Bogue. 1878. Price Is. Gd. 
 
 Report of Observations of Injurious Insects during the year 1881,' by the same. 
 London: W. Swan Sonnenschein and Co. 1882. Price Is. Qd. Previous Reports have 
 been published under the title of * Notes of Observations of Injurious Insects.' 1878-81. 
 
 Selected List of Periodical Natural Phenomena, in the probable Order of Occurrence. 
 
 JANUARY. 
 
 Son-j-thrush (Turdus musicus) sg. SNOWDROP (Galanthus nivalis) fi. 
 
 Skylark (Alauda arvensis) sg. " Honey-bee (Apis mellifica) ap. 
 
 FEBRUABY. 
 
 ROOK (Corvus fntgilegus) builds. COLTSFOOT ( Tussilago farfara) fi. 
 
 Sweet Violet (Viola odorata) fl. Dog's Mercury (Mercurialis perennis) fl. 
 
 MARCH. 
 
 PILEWORT (Ranunculus ficaria) fl. COWSLIP (Primula verts) fl. 
 
 Wych-elm (Ulmus montana) fl. MARSH-MARIGOLD (Caltha palustris) fl. 
 
 DAFFODIL (Narcissus pseudo-narcissus)-^. BLACKTHORN (Prunus spinosa] fl. 
 Barren Strawberry (Potentilla frag&lastruifi} Small white Butterfly (Pieris rapes) ap. 
 
 fl. Ground-ivy (Nepeta glechoma) fl. 
 
 Common Frog (Rani temporaria) spawns. GREATER STITCHWORT (Stellaria holostea) fl. 
 WOOD- ANEMONE (Anemone nemorosa) fl. 
 
 APRIL. 
 
 Wild Chervil (Anthriscus syhestris) fl. Large white Butterfly (Pieris brassiest) ap. 
 
 SWALLOW (Hirundo rustica) first seen; last Ribwort-plantain (Plantago lanceolata)fi. 
 
 seen (October). Upright Crowfoot (Ranunculus acris) fl. 
 
 Cuckoo-flower (Cardamine pratensis) fl. Germander-speedwell (Veronica cham&drys) fl. 
 
 NIGHTINGALE (Daulias luscinia) sg. HERB -ROBERT (Geranium robertianum) fl. 
 
 CUCKOO (Cuculus canorus) first heard. Bush-vetch (Vicia sepium) fl. 
 BLUE-BELL (Enjymion nutans) fl. 
 
 MAY. 
 
 Creeping Bugle (Ajuga reptans) fl. Mouse-ear (Hieradum pilosella) fl. 
 
 MILKWORT (Pdygala vulgaris) fl. OX-EYE (Chrysanthemum leucanthemum) fl. 
 SWIFT (Cypselus apus) first seen ; last seen Flycatcher (Muscicapa grisola) first seen ; last 
 
 (August). seen (August). 
 
 Cleavers (Galium aparine) fl. Bird's-foot Trefoil (Lotus corniculatus) fl. 
 
 Silver-weed (Potentilla anserina) fl. RED POPPY (Papaver rhceas) fl. 
 
 DUTCH-CLOVER (Trifolium repens) fl. Ragged Robin (Lychnis flos-cuculi) fl. 
 
 JUNE. 
 
 YELLOW IRIS (Tris pseudacorus) fl. Wild Thyme (Thymus serpyllum) fl. 
 
 Meadow-vetchling (Lathyrus pratensis) fl. Broad Willow-herb (Epilobium montanum) fl. 
 
 Spotted Orchis (Orchis maculata) fl. Field-thistle (Carduus arvensis) fl. 
 
 Dog-rose (Rosa canind) fl. Meadow-sweet (Spircea tilmaria) fl. 
 
 COMMON MALLOW (Malva sylvestris~) fl. BLACK KNAPWEED (Centnurea nigra) fl. 
 
 Hedge-woundwort (Stachys syhatica) fl. MILFOIL (AcMllea millefolium) fl. 
 
 JULY. 
 
 Tufted Vetch (Vicia cracca) fl. Ragwort (Senecio jacolxxa) fl. 
 
 Yellow Bedstraw (Galium verum) fl. HAIR-BELL (Campanula rotundifolia') fl. 
 
 ap. first appears ; fl. flowers open ; sg. song first heard. 
 
 List of Injurious Insects, observations of which are specially desired. 
 
 INJURIOUS TO FIELD AND GARDEN CROPS. 
 
 1. Silver Y Moth (Plusia gamma). 6. Spotted Crane Fly (Tipula masulosa). 
 
 2. Black Weevil (Otiorhynchus sulcatus~). 7. Onion Fly (Anthomyia ceparwn). 
 
 3. Pea Weevil (Sitcnes lineatus). 8. Celery Fly (Tephritis onopordinis) 
 
 4. Wire-worm Beetle (Agriotes lineatus), 9. Carrot Fly (Psila rosce). 
 
 5. Crane Fly (Tipula oleracca). 10. Bean Aphis, Collier (Aphis rumicis). 
 
 228 
 
SCIENTIFIC UNION. 
 
 21. 
 22. 
 23! 
 
 24. 
 
 20. 
 30. 
 
 To Cabbages and Turnips. 
 
 Cabbage Butterfly (Pieri* brassicce). 14. Turnip Fly (Phyllotreta undulata). 
 
 Cabbage Moth (Marnestra brassica). 15. Turnip Sawfly (Athalia spinjirum}. 
 
 Turnip "Moth (Agrotis seyeturri). 16. Turnip Aphis (Aphis rapes). 
 
 To Corn. 
 
 Corn Sawfly (Ccphus pygmccus). 
 Wheat Midge (Cecidomyia tritici). 
 
 .19. Corn Fly (Chlorops tceniopus). 
 20. Wheat Aphis (Aphis granaria). 
 
 INJURIOUS TO TIMBER TREES AND FRUIT. 
 
 Goat Moth (Cossus ligniperda). 
 
 Leopard Moth (Zeuzera cesculi). 
 
 Lackey Moth (Kombyx neustria). 
 
 Small Ermine Moth ( Yponomeuta padellus). 
 
 25. Magpie Moth (Abraxas grossularMta). 
 
 26. Apple Weevil (Anthonomus pomorurn). 
 
 27. Pear-tree Slug (Erioc'impa adumbrata). 
 
 28. Gooseberry Sawfly (Nematis ribesti). 
 
 To Pine Trees. 
 
 Giant Sirex (Sirex gigas). 31. Fir Weevil (ffylobius dbietls). 
 
 Pine-bud Tortrix (Retinia turionam) 32. Pine Beetle (ffylurgus pi 
 
 Observations of any other Insects are also desirable. 
 
 (Enclosure 3.) 
 THE METEOROLOGICAL SOCIETY. 
 
 Phonological Observations taken at 
 
 PLANTS. 
 
 during 
 
 188 
 
 
 Firsf Flower. 
 
 Full Flower. 
 
 
 First Flower. 
 
 Full_Flower. 
 
 1 ANEMONE NEMOROSA (Wood 
 
 
 
 19 Vicia cracca (Tufted Vetch) 
 
 
 
 Anemone) 
 
 
 
 20 septum (Bush Vetch) 
 
 
 
 2 RANUNCULUS FICARIA (Pile- 
 
 
 
 21 Lathyrus pratensis (Meadow 
 
 
 
 wort Lesser Celandine) 
 
 
 
 Vetchling) 
 
 
 
 3 Ranunculus acris (Upright 
 
 
 
 22 PRUNUS SPINOSA (Sloe 
 
 
 
 Crowfoot) 
 
 
 
 Black-thoru) 
 
 
 
 4 CALTHA PALUSTRIS (Marsh 
 
 
 
 23 Spircea ulmaria (Meadow- 
 
 
 
 Marigold) 
 
 
 
 sweet) 
 
 
 
 5 Papaver rhceas (Red Poppy) 
 
 
 
 24 Potentilla anserina (Silver- 
 
 
 
 6 Cardamine hirsuta (Hairy 
 
 
 
 weed) 
 
 
 
 Bitter-Cress) 
 
 
 
 25 Potentilla fragariastrum 
 
 
 
 7 Cardamine pratensis(C\ickoo- 
 
 
 
 (Barren Strawberry) 
 
 
 
 flower Lady's Smock) 
 
 
 
 26 Rosa canina (Dog Rose) 
 
 
 
 8 Draba verna (Whitlow-Grass) 
 
 
 
 27 Epilobium hirsut'im (Great 
 
 
 
 9 Viola odorata (Sweet Violet) 
 
 
 
 Hairy Willow-herb) 
 
 
 
 10 Polygala t'w/(7am(Milkwort) 
 
 
 
 28 Epilobium montanum (Broad 
 
 
 
 11 Lychnis flos-cuculi (Ragged 
 
 
 
 Willow-herb) 
 
 
 
 Robin) 
 
 
 
 29 Angelica s;/lvestris (Wild 
 
 
 
 12 Stellaria holostea (Greater 
 
 
 
 Angelica) 
 
 
 
 Stitchwort) 
 
 
 
 30 Anthriscus sylcestris (Cow 
 
 
 
 13 MALVA SYLVESTRIS (Com- 
 
 
 
 Chervil) 
 
 
 
 mon Mallow) 
 
 
 
 31 HEDERA HELIX (Ivy) 
 
 
 
 14 Ilypericum tetraptcruni 
 
 
 
 32 Galium aparine (Cleavers) 
 
 
 
 (Square St. John's Wort) 
 
 
 
 33 verum (Vellow Bed- 
 
 
 
 15 Ilypericum pulchrum (Up- 
 
 
 
 straw) 
 
 
 
 right St. John's Wort) 
 
 
 
 34 Dipsacus sylvestns (Teasel) 
 
 
 
 16 GERANIUM ROBERTIANUM 
 
 
 
 35 Scabiosa succisa (Devil's-bit) 
 
 
 
 (Herb Robert) 
 
 
 
 36 Pctasites UM/(/an'6(Butter-bur) 
 
 
 
 17 TRIFOLIUM REPENS (Dutch 
 
 
 
 37 TUSSILAGO FARFARA (Colts- 
 
 
 
 Clover) 
 
 
 
 foot) 
 
 
 
 18 Lotus corniculatus (Bir.l's 
 
 
 
 38 ACHILLEA MlLLEFOLIUM 
 
 
 
 Foot Trefoil) 
 
 
 
 (Milfoil ; Yarrow) 
 
 
 
 229 
 
SCIENTIFIC UNION. 
 
 PLANTS (continued). 
 
 39 Chrysanthemum leucanthe- 
 
 mum (Oxeye) 
 
 40 Artemisia vulgaris (Mug- 
 
 wort) 
 
 41 Senecio jacobcsa (Rag-wort) 
 
 42 CENTAUREA NIGRA (Black 
 
 Knap-weed) 
 
 43 Carduus lanceolatus (Spear- 
 
 Thistle) 
 
 44 Carduus arvensis (Field- 
 
 Thistle) 
 
 45 Sonchus arvensis (Corn 
 
 Sow-Thistle) 
 
 46 ffieracium pilosella (Mouse- 
 
 ear Hawkweed) 
 
 47 CAMPANULA ROTUNDI- 
 
 FOLIA (Hair-bell) 
 
 48 Gentiana campestris (Field 
 
 Gentian) 
 
 49 CONVOLVULUS SEPIUM 
 
 (Greater Bindweed) 
 
 50 Symphytum officinale (Com- 
 
 frey) 
 
 51 Pedicularis syhatica (Red 
 
 Rattle) 
 
 52 Veronica chamcedrys (Ger- 
 
 mander Speedwell) 
 
 53 Veronica hederifolia (Ivy- 
 
 leaved Speedwell) 
 
 72 Melolontha vulgaris (Cock- 
 
 Chafer or May-bug) 
 
 73 Rhizotrogussolstitialis(ei'i\- 
 
 Chafer) 
 
 74 Apis mellifica (Honey-Bee) 
 
 75 Pirn's brassica? (Large White 
 
 Cabbage Butterfly) 
 
 54 Mentha aquatica (Water- 
 
 Mint) 
 
 55 Thymus serpyllum (Wild 
 
 thyme) 
 
 56 Prunella vulgaris (Self-heal) 
 
 57 Nepeta glechoma (Ground 
 Ivy) 
 
 58 Galeopsis tetrahit (Hemp- 
 
 nettle) 
 
 59 Stachys sylvatica (Hedge 
 
 Woundwort) 
 
 60 Ajuga reptans (Bugle) 
 
 61 PRIMULA VERIS (Cowslip) 
 
 62 Plantago lanceolata (Rib- 
 
 wort Plantain) 
 
 63 Mercurialis perennis (Dog's 
 
 Mercury) 
 
 64 Ulmus montana (Wych Elm) 
 
 65 Salix caprea (Great Sallow) 
 
 66 Coryius avellana (Hazel) 
 
 67 Orchis maculata (Spotted 
 
 Orchis) 
 
 68 Iris pseudacorus (Yellow 
 
 Iris) 
 
 69 Narcissus pseudo-narcissus 
 
 (Daffodil) 
 
 70 Galanthus nivalis (Snow- 
 
 drop) 
 
 71 Scilla nutans (Blue-bell) 
 
 INSECTS. 
 
 76 Pieris rapes (Small White 
 
 Cabbage-Butterfly) 
 
 77 Epinephilejanira (Meadow- 
 
 brown butterfly) 
 
 78 ibiomarci(St. Mark's-fly) 
 
 79 Trichocera hiemalis (Win- 
 
 ter Gnat) 
 
 80 Strix aluco (Brown Owl) 
 
 81 Muscicapa grisola (Fly- 
 
 catcher) 
 
 82 Turdus musicus (Song 
 
 Thrush) 
 
 83 Turdus pilaris (Fieldfare) 
 
 84 Daulias luscinia (Nightin- 
 
 gale) 
 
 85 Saxkola ananthe (Wheat- 
 
 ear) 
 
 86 Phylloscopus trochilus (Wil- 
 
 low Wren) 
 
 87 Phylloscopus collybita (Chift- 
 
 chaff) 
 
 88 Alauda arvensis (Sky-lark) 
 
 89 Fringilla ccelebs (Chaffinch) 
 
 90 Corvus frugilegus (Rook) 
 
 91 Cuculus canorus (Cuckoo) 
 
 BIRDS. 
 (MIGRATION, SONG, NESTING, FIRST EGGS, &c. &c.) 
 
 VZaffirundo rustica (Swallow) 
 92bffirundo urbica (House 
 
 Martin) 
 
 93a Cypselus apus (Swift) 
 93b Caprimulgus europoeus 
 (Goatsucker or Fern- 
 Owl) 
 
 94 Columba turtur (Turtle- 
 
 dove) 
 
 95 Perdix cinerea (Partridge) 
 
 96 Scolopax rusticola (Wood- 
 
 cock) 
 
 97 Crex pratensis (Corncrake 
 
 or Land-Rail) 
 
 98 Frog Spawn, 
 pearance of. 
 
 First 
 
 ap- 
 
 Signed 
 
 Summary of these observations is published each year 
 Meteorological Society. 
 
 Observer. 
 in t.'ie Quarterly Journal of the 
 
THE SCIENTIFIC ENQUIRER. 
 
 Scientific inquirer. 
 
 Correspondence is invited on scientific subjects of all kinds. In all cases 
 names and addresses should be given ; but these will not be published if the 
 writers prefer noms de ~plume. The Conductor will not be responsible for the 
 opinions expressed by correspondents. All communications should be addressed to 
 the Conductor of the " Scientific Boll" 7 Red Lion Court, Fleet Street, London, 
 E.G. 
 
 Keplies to questions should be numbered in accordance with the questions to which 
 they refer. The contractions following the questions and answers indicate the class of 
 notes to which they will ultimately be assigned, and the place where full references will 
 be given to the details bearing upon them. 
 
 C. Climate. 
 
 The following questions by Sergt. John P. Finley are reprinted here with his per- 
 mission, partly because they have a reference to clouds, and partly because it is hoped 
 individuals will favour us with similar sets of questions on subjects they are interested 
 in, and about which they desire to collect observations. The numbers in curved 
 brackets are those given by the author, those which precede them are the numbers 
 adopted for the " Scientific Roll " for the purpose of reference. 
 
 TORNADO STUDIES FOR 1882. 
 
 Without speaking too positively about the future, but unreservedly concerning the past, I 
 can venture to say that the year before us will probably be a remarkable one in the chronology 
 of its tornado season. Already and unusually early has the dreaded work commenced, and 
 evidences are rife of unexampled fury coupled with those unmistakable signs which characterise 
 the manifestations of the funnel-shaped cloud, never to be forgotten when once experienced. 
 
 Michigan was visited on the 6th day of April by remarkably violent tornadoes, especially 
 the one which passed across the southern portion of the state, giving evidence of its wonderful 
 power in Van Buren, Allegan, Kalamazoo, Barry, Eaton, Ingham, Livingston, and Oakland 
 counties. This unfortunate and disastrous visitation upon the people of the Peninsula State was 
 in part, but to a less degree, realised throughout portions of Iowa, Kansas, Missouri, and Illinois, 
 on the same day and during the same afternoon. 
 
 Within the extensive barometric trough which consummated its energy on that fatal day, 
 whose major axis extended southwestward from the Upper Lake region to northern Texas, and 
 its minor axis from the Mississippi and Ohio rivers northwestward to central Minnesota and 
 southern Dakota, there appeared three points of local atmospheric intensity, viz., central 
 Kansas, northeastern Missouri, and the Lower Peninsula of Michigan. At the places here 
 indicated the violence of atmospheric changes resulted in the formation of tornadoes. 
 
 The work of investigation in Michigan has to a certain extent been completed, at least so far 
 so that it has been possible for me to accomplish the removal of my headquarters to Kansas 
 city, Mo., where, under special instructions from the Chief Signal Officer, I shall prosecute the 
 work of investigation in the Lower Missouri Valley. 
 
 This region of country embraces the states of Kansas, Nebraska, Missouri and Iowa, and can 
 literally be termed the battle ground of tornadoes. It is here that this class of violent wind 
 storms occurs with the greatest frequency, the most unexampled violence, the most marked 
 regularity, and with the most complete manifestation of their peculiar characteristics. Con- 
 
 231 
 
THE SCIENTIFIC ENQUIRER. 
 
 tinuing my labours until the expiration of the tornado season, I shall, aside from the examination 
 of any particular tornado, with a view to gain new and important truths, give special attention 
 to the following important features of this class of violent wind storms ; viz., more definite 
 information concerning the conditions precedent and favourable to the formation of tornadoes in 
 general ; the phenomena and laws of cloud development ; the velocity and power of centripetal 
 currents within the cloud vortex ; additional statistics respecting the tornadoes of former 
 years ; the arrangement and perfection of an acceptable scheme whereby reliable warnings can 
 be sent to certain communities in advance of the tornado, announcing that conditions are 
 favourable to its formation ; and lastly, to prepare and disseminate such information as will 
 direct people how to act in defence of their lives, and to a certain extent of their property, 
 during the approach and passage of a tornado. In the accomplishment of these momentous 
 results, or in bringing to light new points of value, I am desirous to enlist the active support of 
 every intelligent person throughout the Lower Missouri Valley or elsewhere. There are not a 
 few ways in which even the humblest can assist. If you cannot give any facts concerning a 
 tornado of recent date, write me what you know about one or more whose dates of occurrence 
 number many years past. In every description of the tornado conform as nearly as possible to the 
 character of the questions propounded in the accompanying circulars. Perhaps you can send me 
 some article or publication bearing upon the climatology or meteorology of your state, or some 
 portion of it. Photographs, sketches or printed cuts of the effects of the violence of any par- 
 titular tornado, no matter what date, would be very valuable, and thankfully received. 
 
 As it will probably be impossible (owing to press of other work) for me to visit and conduct 
 a personal examination in the case of every tornado that may occur in the Lower Missouri 
 Valley or in adjoining states during the year, I will deem it a great favour, and it will certainly 
 be a matter of most valuable service, if some one in the vicinity of a tornado's path will kindly 
 undertake to furnish me (at his earliest convenience after the tornado's occurrence) with a 
 complete history of its entire track. In performing this task, be careful to state as accurately 
 as possible the place of beginning. This location is not necessarily where the tornado cloud 
 first descended to the earth, although it may be, but more truly and hence more accurately, it is 
 that particular spot or portion of country over which (perhaps at a great height above the 
 earth) the funnel-shaped cloud was first seen to form. 
 
 Upon determining the place of commencement, carefully ascertain all the preliminary 
 conditions of atmospheric changes existing prior to the development of the tornado cloud. In 
 conducting the examination along the track and on both sides of it, make use of the questions 
 and remarks contained in the respective circulars, according as one or the other is required. In 
 determining the exact locality of final disappearance, exercise no inconsiderable vigilance, for 
 you may most easily be deceived. It is a characteristic feature of the tornado cloud to rise 
 suddenly from the earth, and, continuing its northeastward course in the lower regions of the 
 atmosphere, again reach terra firma after an interval of several miles. You may find a number 
 of these gaps along the tornado track you are examining, but do not mistake them for points of 
 termination ; rather look upon their existence as indubitable evidences of tornado (latent) 
 activity, a sign of reappearance rather than disappearance. If these gaps occur in consecutive 
 order as to time and place, pursuing, when taken together, a northeastward trend, and the 
 difference in time of disappearance and reappearance at each interval, accounting for the passage 
 of that interval, there can be no doubt of their forming disconnected parts of one and the same 
 tornado track. The invariable accompaniment of the tornado, the hailstorm, precedes the first 
 appearance of its terrible companion and succeeds its final disappearance. This characteristic 
 should be carefully watched for and any peculiarity minutely recorded. If any in the prosecu- 
 tion of this particular work should need a quantity of circulars,'the same will be mailed to them 
 immediately, upon my receiving word as to how many of each kind they desire. 
 
 In the fulfilment of my mission I have no pet theories to advance or support, neither have I 
 the time to speculate much or discuss the respective merits of uncertain or untenable positions ; 
 but I am prepared for the reception of facts, without measure. With regard to suggestions, I 
 shall be a most willing recipient, and I trust that no one, feeling a desire in this direction, will 
 hesitate to communicate with me at his earliest convenience. This is emphatically a public 
 enterprise, and not the effort or exclusive pride of an individual. 
 
 It is absolutely necessary and most invaluable, when a variety of people are called upon to 
 contribute iu aid of a work like this, that they should know precisely what information is most 
 desired. 
 
 With a view to cultivate familiarity respecting the character of the data required, 1 append 
 herewith the following list of questions and remarks : Circular No. I contains a list of inquiries 
 which are to be referred in all cases to persons who, on the day of the storm, were situated 
 without the tornado's path (to the N. or S. of it), on its immediate edge, or from one to ten miles 
 distant. In brief, this is a circular for outsiders only. 
 
 Circular No. II contains a list of inquiries which are to be referred in all cases to persons 
 situated within the tornado's path. In brief, this is a circular for insiders only. 
 
 Circular No. Ill contains a list of inquiries which are to be referred in all cases to persons 
 situated without the tornado's path (to the N. or S. of it), from 10 to 100 miles. Its scope is more 
 general, and seeks for information concerning surrounding atmospheric conditions. 
 
THE SCIENTIFIC ENQUIRES. 
 
 The information called for in each circular is in the main entirely distinct, but nevertheless 
 equally important in conducting a careful analysis of the phenomena of this class of violent 
 wind storms. I urgently solicit replies, on every hand and from every quarter, concerning the 
 matter hereinafter set forth : 
 
 CIRCULAR NO. I. QUESTIONS AND REMARKS. 
 
 8. (1.) How far and in what direction are you situated from the centre of the path of 
 destruction? (C. 1.) 
 
 9. (2.) The time of day that the tornado cloud passed. (C. 2.) 
 
 10. (3.) The direction of the wind while the tornado cloud was approaching. (C. 3.) - 
 
 11. (4.) The direction of the wind while the tornado cloud was passing. (C. 4.) 
 
 12. (5.) The direction of the wind after the tornado cloud passed. (C. 5.) 
 
 13. (6.) The direction of the wind during the fore part of the day and up to the time of the 
 first threatening appearance in the heavens. (C. 6.) 
 
 14. (7.) The prevailing direction of the wind at this season of the year. (C. 7.) 
 
 15. (8.) Any hail, and did it fall before or after (how long) the tornado cloud passed ? 
 (C. 8.) 
 
 16. (9.) Were the hailstones large or small, of peculiar shape, and few or many in number? 
 (C. 9.) 
 
 17. (10.) Did you examine the interior of any of the hailstones, and if so, how were they 
 formed and what did they contain? (C. 10.) 
 
 18. (11.) If hail fell at intervals through the day, state the times of beginning and ending 
 of each precipitation separately. (C. 11.) 
 
 19. (12.) Any rain, and did it fall before or after (how long) the tornado cloud passed? 
 (C. 12.) 
 
 20. (13.) Any peculiarity in the size or shape of the raindrops, or in the quantity which fell ? 
 (C. 13.) 
 
 21. (14.) The direction of the wind at the time of the hail, and also at the time of the rain. 
 (C. 14.) 
 
 22. (15.) If rain fell at intervals through the day, state the times of beginning and ending 
 of each precipitation separately. (C. 15.) 
 
 23. (16.) What time of day did threatening appearances commence, in what portion of the 
 horizon, and at what time were they the most decided? (C. 16.) 
 
 24. (17.) Describe the character and motion of the surrounding clouds before, during, and 
 after the tornado cloud passed. (C. 17.) 
 
 25. (18.) Give the time of day at which the light or dark irregular clouds surrounding the 
 tornado cloud were in the greatest confusion, and describe the scene. (C. 18.) 
 
 26. (19.) If you saw the tornado cloud, describe or sketch it, and note particularly any 
 change in motion or the successive stages of development during the time of observation. 
 (C. 19.) 
 
 27. (20.) Give the direction of the whirl of the tornado cloud, as against or with the hands 
 of a watch. (C. 20.) 
 
 28. (21.) Give all the motions of the tornado cloud which you observed, or which you heard 
 that others had witnessed ; as for example : rising and falling, swaying from side to side, or 
 whirling about a central axis, etc., etc. (C. 21.) 
 
 29. (22.) Thunder or lightning, in what portion of the horizon, at what time of the day and 
 whether violent or otherwise. (C. 22.) 
 
 30. (23.) Was lightning seen in the funnel-shaped tornado cloud, or in the dark, heavy 
 clouds surrounding it to the N. and W. ? (C. 23.) 
 
 31. (24.) Was the day unusually warm and sultry? Give the maximum temperature if 
 possible, and state the hour at which it was observed, together with the direction of the wind and 
 the state of the sky existing at the time. (C. 24.) 
 
 32. (25.) Condition of the temperature after the tornado cloud passed. Did the air 
 suddenly or gradually grow colder ? (C. 25.) 
 
 33. (26.) What had been about the average daily temperature, together with the accompany- 
 ing direction of the wind, for eight or ten days previous to the occurrence of the tornado ? (C. 26.) 
 
 34. (27.) Give the direction of the course pursued by the tornado cloud along its path of 
 destruction in your locality ; as for example, N 70 E ; E 30 N or E 20 S ; etc., etc. (C. 27.) 
 
 35. (28.) Give the maximum and minimum width, in yards or rods, of the path of destruc- 
 tion in your vicinity ; and state, if you can, whether, in examining that path, it was found that 
 on the S. side of the centre the sweep of destruction was broader and more regular than on the 
 N. side, or if any other difference existed between the two sides. (C. 28.) 
 
 36. (29.) If you, or any of your neighbours, have meteorological instruments, give the 
 readings of the thermometer and barometer, direction of the wind and the hour of observation, 
 for two days before, on the day of the storm, and for two days thereafter ; viz. on the 
 
 (C. 29.) 
 
 37. (30.) If you recall the occurrence, in times past, of any other tornado in your state, 
 give year, month, day of month, hour of day, the direction of the course of the path of destruc- 
 
 233 
 
THE SCIENTIFIC ENQUIRER. 
 
 tion as pursued by the tornado cloud, its length in miles, average width of destructive path in 
 yards or rods, maximum width, minimum width, and, if possible, the hour of beginning and hour 
 of disappearing of the tornado cloud. (C. 30.) 
 
 When I ask for direction of wind, I mean direction of motion of the surrounding air 
 currents, independent of the course or motion of the tornado cloud. 
 
 When time of day is asked, give the same in hours and minutes, and state whether it is local 
 or railroad time, and by what standard, viz., Chicago, Detroit, Columbus, St. Louis, etc., etc. 
 
 In giving your distance from the centre of the path of destruction, indicate the same in 
 miles and parts of miles or rods, stating the amount in northing and easting, northing and 
 westing, southing and easting, or southing and westing, estimated along section or township 
 lines. 
 
 If not individually prepared to answer any or all of the above questions, please call to your 
 aid such persons as may, in your judgment, be able to render you assistance. 
 
 If possible, try to represent the tornado cloud by a rough sketch, as also the dark and 
 irregular clouds surrounding it. 
 
 In describing the path of destruction, be careful to note where the tornado cloud left the 
 ground, where it again descended, the length of the interval and the topography of the earth at 
 the points of ascension and descension. 
 
 Send any newspaper article concerning the storm which you may have or can obtain without 
 inconvenience. 
 
 Give name and address of any one in your state who is in the habit of keeping a meteoro- 
 logical record. 
 
 If possible, try and secure the co-operation of some intelligent person, who, at the time of its 
 occurrence, was situated either in the path of the tornado or on the outer edge of it, and who 
 will be willing to furnish me a narrative of the result of his observations. 
 
 In all descriptions of the tornado's path, in giving any particular destruction in it, or in 
 detailing your experience while the tornado cloud was passing, be careful to state on \rhich side 
 of the centre (to the N. or to the S. and how far) the damage occurred or you were situated while 
 a witness of the scene. 
 
 CIRCULAR NO. II. QUESTIONS AND REMARKS. 
 
 38. (1.) What day of the month and at what time of the day did the tornado cloud pass ? 
 Take great care in giving the exact time. Perhaps you watched your clock or noted the approach 
 or passage of a railroad train. (C. 31.) 
 
 39. (2.) Give the position of your house with respect to the nearest post office, indicating 
 the same in miles and parts of miles or rods ; state the distance in northing and easting, northing 
 and westing, southing and easting, and southing and westing, estimated along section and town- 
 ship lines. (C. 32.) 
 
 40. (3.) How far and in what direction is your house situated from the centre of the path 
 of destruction ? (C. 33.) 
 
 41. (4.) Give the direction and distance from your house to your various farm buildings, if 
 possible drawing a plan of the same and indicating the points of the compass. This plan need 
 only be a rough sketch. (C. 34.) 
 
 42. (5.) Give the dimensions of your buildings and state the character of each as to whether 
 they are log, frame, stone, or brick, and weak or strong. (C. 35.) 
 
 43. (6.) In drawing a plan of your buildings, indicate the position of the tornado's path 
 with respect to each of them and the direction in which the tornado cloud moved. (C. 36.) 
 
 44. (7.) State in detail and separately the damage to each building; what portion or 
 portions were taken away or injured ; how far and in what direction were they moved bodily ; 
 what portion of each was first struck by the wind, and how far and in what direction were the 
 debris carried? Be very careful to give the exact position and peculiarities of structure 
 of buildings which were not damaged although standing near those which were destroyed. 
 (C. 37.) 
 
 45. (8.) In the damage or destruction of each or any building, state particularly how 
 far and in what direction any portion of them was carried a considerable distance. (C. 38.) 
 
 46. (9.) If any object has been carried a long distance by the force of the wind, state 
 where and what it came from ; its dimensions ; its shape ; probable height to which 
 transported in the air ; whether driven into the ground or not, how far and into what kind of 
 earth. (C. 39.) 
 
 47. (10.) State whether articles of clothing, fowls, or animals were carried into the air, to 
 what height, to what horizontal distance, and in what direction. (C. 40.) 
 
 48. (11.) Give detailed destruction of furniture contained in the house and of farming 
 implements in or about the barns. (C. 41.) 
 
 49. (12.) State the number, kind, and in what manner stock were killed or injured, and 
 whether at the time of the storm they were in or without buildings. Also narrate any miracu- 
 lous escapes of life. (C. 42.) 
 
 50. (13.) With respect to your family, give the whereabouts and condition of each person 
 on the approach of the tornado, and also after the tornado cloud passed. Give age and sex of 
 
 234 
 
THE SCIENTIFIC ENQUIRER. 
 
 each person, and particularise the character and extent of injuries to each. State very carefully 
 the distance and direction in which any of the persons were carried, and also narrate any 
 miraculous escapes of life. (C. 43.) 
 
 51. (14.) Be particular to note any evidence of the wind's extreme violence, as in the lifting 
 of heavy objects; the twisting of trees or heavy pieces of timber; pulling up of fence posts; 
 removing heavy stones, etc., etc. (0. 44.) 
 
 52. (15.) In describing the injury to any person, animal, or object, never fail to give the 
 distance and direction of such person, animal or object from the centre of the path of destruction 
 at the time the tornado cloud passed. (C. 45.) 
 
 53. (16.) With regard to destruction in orchards, among shade trees, and in forests, be 
 particular to give the direction in which the trees lie ; how theyTle en the two sides with regard 
 to each other and to the centre of the path of destruction ; any special acts of violence in the 
 twisting, uprooting, or breaking off of heavy timber ; give circumference of large trees, height 
 above ground where broken off, and dimensions of earth and roots where notably large trees were 
 overthrown. (C. 46.) 
 
 54. (17.) In general, when giving the position of any person or thing with regard to the 
 centre of the path of destruction, state the distance in feet or rods, and the direction, as 
 N. or S. (C. 47.) 
 
 55. (18.) Give the maximum and minimum width, in yards or rods, of the path of 
 destruction in your locality. (C. 48.) 
 
 56. (19.) How many funnel-shaped clouds did you see ? Describe each, giving their relative 
 sizes, shapes, and positions, and if possible a rough sketch of each. (C. 49.) 
 
 57. (20.) Did you hear a roaring noise on the approach of the storm, and if so, state the 
 intensity, or any accompanying peculiarity. (C. 50.) 
 
 58. (21.) Did you notice any peculiarity with the manner in which small objects were 
 suddenly removed from around about buildings as if sucked in by the advancing cloud? (C. 51.) 
 
 59. (22.) Did you notice any peculiarity in the falling of trees as the tornado cloud 
 advanced upon them ? Were they whipped about and bent to and fro as in a heavy wind, or 
 were they drawn steadily inward toward the centre on both sides, as if by some mysterious but 
 irresistible force ? (C. 52.) 
 
 60. (23.) How many rods of fencing (stating kind) did you have blown down ; in what 
 direction were the N. and S. fences carried ; what was the direction in which the E. and W. 
 fences were carried ? (C. 53.) 
 
 61. (24.) Give an estimate in money value of the loss to your property occasioned by the 
 tornado, the number of acres of timber you had destroyed, and the number of fruit trees you had 
 uprooted or broken off. (C. 54.) 
 
 62. (25.) Be particular to give the exact position, also the dimensions and probable strength 
 and weight of small objects which were not moved from about large buildings, although the 
 latter were entirely destroyed. (C. 55.) 
 
 63. (26.) Give the direction of the wind while the tornado cloud was approaching, while 
 the tornado cloud was passing, and after the tornado cloud passed. (C. 56.) 
 
 64. (27.) The direction of the wind during the fore part of the day and up to the time of 
 the first threatening appearance in the heavens. (C. 57.) 
 
 65. (28.) The prevailing direction of the wind at this season of the year. (C. 58.) 
 
 (29.) In asking for the direction of wind, I mean direction of motion from the surrounding 
 air currents, independent of the course or motion of the tornado cloud. 
 
 66. (30.) Any hail, and did it fall before or after (how long) the tornado cloud passed ? 
 (C. 59.) 
 
 67. (31.) Were the hailstones large or small, of peculiar shape, and few or many in number? 
 Give exact size and weight of the largest. (C. 60.) 
 
 68. (32.) On which side of the tornado's path (to the N. or to the S.) did the hailstones 
 appear to fall in the greatest quantity? (C. 61.) 
 
 69. (33.) Did you examine the interior of any of the hailstones, and if so, how were they 
 formed and what did they contain ? (C. 62.) 
 
 70. (34.) If hail fell at intervals through the day, state the times of beginning and ending 
 of each precipitation separately, together with the direction of the wind at each occurrence. 
 (C. 63.) 
 
 71. (35.) Any rain, and did it fall before or after (how long) the tornado cloud passed? 
 (C. 64.) 
 
 72. (36.) On which side of the tornado's path (to the N. or to the S.) was the rainfall the 
 heaviest ? (C. 65.) 
 
 73. (37.) Any peculiarity in the size or shape of the rain-drops, or in the quantity which 
 fell ? (C. 66.) 
 
 74. (38.) If rain fell at intervals through the day, state the times of beginning and ending 
 of each precipitation separately, together with the direction of the wind at each occurrence. 
 (C. 67.) 
 
 75. (39.) What time of day did threatening appearances commence, and in what portion of 
 the horizon, and at what time, were they the most decided? (C. 68.) 
 
 235 
 
THE SCIENTIFIC ENQUIBER. 
 
 76. (40.) Describe the character and motion of the surrounding clouds before, during, and 
 after the tornado cloud passed. (C. 69.) 
 
 77. (41.) Give the general atmospheric conditions of temperature, wind direction, humidity, 
 and clouds, for from ten to fifteen days previous to the occurrence of the tornado and from three 
 to five days thereafter. (C. 70.) 
 
 78. (42.) Give the time of day at which the light or dark irregular clouds surrounding the 
 tornado cloud were in the greatest confusion, and describe the scene. (C. 71.) 
 
 79. (43.) Describe any particular change or motion in the tornado cloud and the successive 
 stages of development during the time of observation. (C. 72.) 
 
 80. (44.) Give the direction of the whirl of the tornado cloud, as against or with the hands 
 of a watch. (C. 73.) 
 
 81. (45.) Describe minutely the manner in which objects were carried inward, upward, and 
 about in the whirling vortex of the tornado cloud ; how thrown outward and from what portion 
 of the cloud. (C. 74.) 
 
 82. (46.) Describe the colour of the tornado cloud ; its density ; how and when changes in 
 colour and density occur; the colour and density of the bottom of the cloud as compared 
 with the top; the existence of light and peculiar fleecy clouds over and about the upper 
 portion. (C. 75.) 
 
 83. (47.) Give the comparative size of top and bottom of tornado cloud; note particularly 
 and describe minutely any change in form when the bottom or tail reached the surface of the 
 ground. (C. 76.) 
 
 84. (48.) Did the tornado cloud remain in a vertical position as it travelled forward, or 
 was the tail of it inclined ; in what direction and how many degrees from the perpendicular ? 
 (C. 77.) 
 
 85. (49.) Give all the motions of the tornado cloud which you observed, or which you 
 heard that others had witnessed ; as for example, rising and falling, swaying from side to side, 
 or whirling about a central axis, etc., etc. (C. 78.) 
 
 86. (50.) In examining the path of destruction, did you find any difference between the 
 N. and S. sides of it ? Which side was the widest ; which the cleanest cut ; which the most 
 irregular and jagged along its outer edge ; on which side were narrow paths of destruction cut 
 inward toward the centre ? (C. 79.) 
 
 87. (51.) Thunder or lightning, in what portion of the horizon, at what time of the day, 
 and whether violent or otherwise. (C. 80.) 
 
 88. (52.) Was lightning or any other manifestation of electricity witnessed in the funnel- 
 shaped tornado cloud as it approached or passed ? If so, describe the appearance minutely. 
 (C. 81.) 
 
 89. (53.) Was lightning seen in the dark heavy clouds surrounding the tornado cloud to 
 the N. and W. ? (C. 82.) 
 
 90. (54.) Was the day unusually warm and sultry ? Give the maximum temperature if 
 possible, and state the hour at which it was observed, together with the direction of the wind 
 and the state of the sky existing at the time. (C. 83.) 
 
 91. (55.) What was the condition of the temperature after the tornado cloud passed? Did 
 the air suddenly or gradually grow colder ? Give the minimum temperature for that afternoon 
 and evening, and during the" night, with direction of the wind. (C. 84.) 
 
 92. (56.) What had been about the average daily temperature, also the maximum and 
 minimum, together with the accompanying direction of the wind, for eight or ten days previous 
 to the occurrence of the tornado and for three days succeeding its appearance ? (C. 85.) 
 
 93. (57.) Give the direction, in degrees, of the course pursued by the tornado cloud along 
 its path of destruction in your locality ; as for example, N. 70 E. ; E. 30 N., etc., etc. (C. 86.) 
 
 94. (58.) If you, or any of your neighbours, have meteorological instruments, give the 
 readings of the thermometer and barometer, direction of the wind and the hour of observation, 
 for two days before the day of the storm, and for two days thereafter, viz., on the 
 
 (C. 87.) 
 
 When the time of day is asked, give the same in hours and minutes, and state whether it 
 is local or railroad time, and by what standard, viz., Chicago, Detroit, Columbus, St. Louis, 
 etc., etc. 
 
 If possible, try to represent the tornado cloud by a rough sketch, as also the dark and 
 irregular clouds surrounding it. 
 
 95. (61.) In describing the path of destruction, be careful to note where the tornado cloud 
 left the ground, where it again descended, the length of the interval,- and the topography of the 
 earth at the points of ascension and descension. Also state whether the hail and rain con- 
 tinued to fall after the tornado cloud rose from the earth and disappeared in the overhanging 
 clouds. (C. 88.) 
 
 Send any newspaper article concerning the storm which you may have, or can obtain 
 without inconvenience. 
 
 Give name and address of any one in your state who is in the habit of keeping a meteoro- 
 logical record, or who desires to keep one and would like instructions. 
 
 If possible, try and secure the co-operation of some intelligent person, who, at the time of the 
 
THE SCIENTIFIC ENQUIRER. 
 
 occurrence, was situated either in the path of the tornado or on the outer edge of it, and who 
 will be willing to furnish me a narrative of the result of his observations. 
 
 In all descriptions of the tornado's path, in giving any particular destruction in it, or 
 in detailing your experience while the tornado cloud was passing, be careful to state on which 
 side of the centre (to the N. or S. and how far) the damage occurred or you were situated while 
 a witness of the scene. 
 
 96. (66.) Give an estimate of what you consider the progressive velocity of the tornado 
 cloud ; how many miles per hour. Give the data upon which you make the estimate, and why 
 you believe your estimate to be reliable. (C. 89.) 
 
 97. (67.) What evidence can you give of the existence of upward and whirling currents of 
 air within the central portion of the tornado cloud ? (C. 90.) 
 
 98. (68.) Estimate the time in minutes or seconds during which the tornado cloud 
 was committing the destruction at your buildings or in passing them at a safe distance. 
 (C. 91.) 
 
 99. (69.) As the tornado cloud approached, from what direction came the wind you first 
 experienced, whether against your body or against the building within which you were situated 
 at the time ? (C. 92.) 
 
 100. (70.) Did you notice any peculiar odour in the atmosphere during the passage of the 
 tornado cloud, and what was it like ? (C. 93.) 
 
 101. (71.) Do you know of any one who made observations on the presence of ozone in the 
 atmosphere on the day of the storm ? If so, send me his address or give the result of the 
 observations. (C. 94.) 
 
 102. (72.) Do you know of any one who made observations with the galvanometer or 
 compass concerning the deflection of the needle during the day of the storm, especially while 
 the tornado cloud was passing a given point ? If so, send me his address or give the result of 
 the observations. (C. 95.) 
 
 103. (73.) Try and give an estimate of what you consider the wind's velocity within the 
 central whirl of the tornado cloud, and also the data upon which you base this estimate. 
 (C. 96.) 
 
 104. (74.) In the destruction of your buildings, did you notice anything in the disposition 
 of the debris after the tornado cloud passed that would indicatelhe effect of an explosion; as, for 
 example, the sides and the ends of a building being thrown outward and the roof carried off or 
 let down upon the floor ? (C. 97.) 
 
 105. (75.) In the passage of the tornado cloud over a pond, lake, or river, carefully 
 describe every particular in the disturbance of the water ; how high into the air any portion 
 of it was carried ; if any fish, shells, stones or the like were carried out and in what direction. 
 Also state the exact position of the person or persons who witnessed the scene. (C. 98.) 
 
 106. (76.) Was mud, bits of leaves, straw, grass or the like thrown against your buildings ? 
 If so, state on what particular portion or portions, and whether apparently thrown thereon 
 with great force. If thrown upon the bodies of persons or animals, carefully state the circum- 
 stances. (C. 99.) 
 
 107. (77.) Where trees were overturned and wrenched or twisted by the force of the 
 wind, describe minutely how and in what direction the twist nms ; that is, its direction, as with 
 or against the hands of a watch. Perhaps you can compare it with the bit of an auger or 
 indicate the same by a rough pencil sketch. Also state what portion or portions of the tree 
 were twisted, and what the kind of timber. (C. 100.) 
 
 108. (78.) Observe carefully where the tornado cloud passed through forests, and state on 
 which side of the tornado's path (to the N. or S.) he trees were broken off at a considerable 
 height above the ground ; the maximum and minimum height ; general size of trees so affected ; 
 kind of timber, and whether broken square off or twisted. Try and illustrate the path through 
 the timber by a pencil sketch showing the various directions of the prostrated trees. Indicate 
 the points of compass. (C. 101.) 
 
 109. (79.) Did you notice any distinct peculiarity in the approaching or overhanging 
 clouds from which the hail itself fell ? Did the hailstones appear to drop from the funnel- 
 shaped cloud, or from surrounding clouds? (C. 102.) 
 
 110. (80.) Sketches of clouds, of peculiar destructive effects, of hailstones, of anything 
 that will illustrate any distinguishing feature of the storm's violence are very desirable. 
 (C. 103.) 
 
 111. (81.) If you recall the occurrence, in times past, of any violent hailstorm in your 
 state, give the place, year, month, day of month, hour of day, direction of the storm, maximum 
 and minimum width of path in rods or miles, size and shape of hailstones, and a narration of 
 the destructive effects. (C. 104.) 
 
 37. (82.) If you recall the occurrence, in times past, of any other tornado in your state, 
 give year, month, day of mouth, hour of day, the direction of the course of the path of destruc- 
 tion as pursued by the tornado cloud, its length in miles, average width of destructive path in 
 yards or rods, maximum width, minimum width, and, if possible, the hour of beginning and hour 
 of disappearing of the tornado cloud. (C. 30.) 
 
 237 
 
THE SCIENTIFIC ENQU1EEK. 
 
 CIRCULAR NO. III. QUESTIONS AND REMARKS. 
 
 112. (1.) Did you have a storm on this day ? (C. 105.) 
 ! 113. (2.) What was the nature of it ? (C. 106.) 
 | 114. (3.) From what point, or points, of the compass did it approach ? (C. 107.) 
 
 115. (4.) What was the hour of the day when it finally broke upon you ? (C. 108.) 
 
 116. (5.) What was the highest velocity of the wind in miles per hour, and the direction 
 from which it came ? Approximate the velocity if you can do no better. (C. 109.) 
 
 117. (6.) What was the time of day when the maximum velocity occurred ? (C. 110.) 
 
 118. (7.) Can you give the temperature at the time the highest wind velocity occurred? 
 If not, say whether it was warm or cold. (C. 111.) 
 
 119. (8.) If a hail-storm, state whether the hailstones were large or small, of peculiar 
 shape, and few or many in number. Give exact size and weight of some of the largest. 
 (C. 112.) 
 
 120. (9.) What was the direction of the wind with the hail ? (C. 113.) 
 
 121. (10.) Was there any peculiar condition of the clouds at the time of the hail ? If any 
 strange feature was noticed, give details. (C. 114.) . 
 
 122. (11.) If hail fell at intervals through the day, state the times of beginning and ending 
 of each precipitation separately, together with the direction of the wind at each occurrence. 
 (C. 115.) 
 
 123. (12.) If any rain fell during the hail-storm, be careful to state whether it fell before, 
 at the time of, or after the hail ceased. In case of the two extremes give the interval in 
 minutes. (C. 116.) 
 
 124. (13.) If rain fell at intervals through the day, state the times of beginning and ending 
 of each precipitation separately, together with the direction of the wind at each occurrence. 
 (C. 117.) 
 
 125. (14.) What time of the day did the first threatening appearances commence, and in 
 what portion of the heavens ? (C. 118.) 
 
 126. (15.) How did the day open? (C. 119.) 
 
 127. (16.) What was the direction and force of the wind when you first noticed the 
 weather in the early morning ? Give the hour of observation. (C. 120.) 
 
 128. (17.) What was the condition of the sky when you made your first observation in the 
 morning? Was it cloudy; three-fourths cloudy; one-half cloudy; one-fourth cloudy, or 
 entirely clear ? (C. 121.) 
 
 129. (18.) What was the direction, or directions, in which the clouds were moving at the 
 time of your first observation ? (C. 122.) 
 
 130. (19.) In the event of any storm whatever, give the direction and force of the wind 
 while the storm was approaching, while the storm was passing, and after the storm passed. 
 If a number of storms occurred on this day, give particulars of each, in accordance with the terms 
 of questions Nos. 1 to 7, inclusive. (C. 123.) 
 
 131. (20.) What time of the day did it commence to cloud up, and in what quarter of the 
 heavens? (C. 124.) 
 
 132. (21.) At what time, or times, of the day did you notice any freshening of the wind, 
 and what was the direction at each occurrence ? (C. 125.) 
 
 133. (22.) Describe the character of the clouds when the first threatening appearances 
 began. (C. 126.) 
 
 134. (23.) Give the time of day, the quarter of the heavens, and the character of each 
 formation, if there were frequent and sudden changes in the development or eroupin? of the 
 clouds. (C. 127.) 
 
 135. (24.) How many days previous did you notice any indications of an approaching storm, 
 and what were those indications? (C. 128.) 
 
 136. (25.) Did you observe that form of cloud commonly called " mare's tails " (cirrus) ; 
 in what portion of the heavens and how many days previous? "(C. 129.) 
 
 137. (26.) In what quarter of the heavens did the passing storm seem to be the heaviest ? 
 (C. 130.) 
 
 138. (27.) Could you distinguish any roaring noise with the storm ; what was it like, and 
 in what direction was it heard? (C. 131.) 
 
 139. (28.) Any damage to buildings, fences, or trees by the force of the wind or by 
 lightning ? If so, give the particulars. (C. 132.) 
 
 140. (29.) Did the clouds gradually thicken on this day, or was there a sudden and por- 
 tentous bankmg-up of them in the W. during the afternoon ? (C. 133.) 
 
 141. (30.) Did the clouds appear to gather near the earth and extend in irregular forms to 
 foTdownin theVT 6 ** 7 *"* maSS ' with com P ar atively regular outlines, hanging 
 
 !i 4 r S L) J What 1 time durin S the da 7> and in what portion of the heavens did you notice 
 small light or dark clouds, if any, driven swiftly by the wind? Tell how they moved, from 
 what direction or directions they came, and where they seemed to concentrate. (C. 135.) 
 
 3- (6*,) In describing clouds, especially where they are peculiar or portentous in appear- 
 238 
 
THE SCIENTIFIC ENQUIRER. 
 
 ance, aside from carefully indicating character of formation, give the most striking colours and 
 state how they blended with each other. (C. 136.) 
 
 (33.) What is the prevailing direction of the wind at this season of the year, in your 
 locality ? (C. 7.) 
 
 144. (34.) In the event of the occurrence of any storm, state whether it passed your 
 location by either the N. or S. point or directly overhead. (C. 137.) 
 
 145. (35.) Was the night of the day in question cold or frosty ? Can you give its minimum 
 temperature and the general direction of the wind ? (C. 138.) 
 
 146. (36.) What time of the day did you notice any decided change in the temperature, and 
 what was the extent of that change ? (C. 139.) 
 
 147. (37.) Did thunder or lightning accompany the storm or storms on this day ? If so, 
 state in what quarter of the heavens it was the heaviest or most violent. (C. 140.) 
 
 (38.) In making a statement concerning any feature of the weather during the day, be 
 careful to give the hour at which the condition referred to was observed. 
 
 (39.) Send me any newspaper article which you can obtain concerning the storm or 
 storms. 
 
 (40.) Give name and address of any one in your state who is in the habit of keeping a 
 meteorological record, or who desires to take observations and would like instructions. 
 
 148. (41.) What was the direction of the wind during the forepart of the day and up to 
 the time of the first threatening appearance in the heavens ? (C. 141.) 
 
 149. (42.) Give the general atmospheric conditions of temperature, wind direction, humidity 
 and clouds, for from ten to fifteen days previous to this date, and from three to five days there- 
 after. (C. 142.) 
 
 150. (43.) Was the day unusually warm and sultry ? Give the maximum temperature if 
 possible, and state the hour at which it was observed, together with the direction of the wind 
 and the state of the sky existing at the time. (C. 143.) 
 
 (44.) In any effort to indicate the force of the wind, use the following scale, employing the 
 words or figures as you can best express the condition : 
 
 Calm. 
 
 1 to 2 miles per hour Light wind. 
 
 3 to 5 miles per hour . Gentle wind. 
 
 6 to 14 miles per hour Fresh wind. 
 
 15 to 24 miles per hour Brisk wind. 
 
 25 to 39 miles per hour High wind. 
 
 40 to 59 miles per hour ....... Gale. 
 
 60 to 79 miles per hour . . Storm. 
 
 80 miles per hour and above Hurricane. 
 
 (45.) Let me advise you to carefully observe and record the daily changes of the weather 
 (if nothing more than miscellaneous phenomena) in your locality, if not throughout the year, at 
 least from the 1st of April to the 1st of September. The Weather Bureau will probably need 
 some facts from you each year, particularly such information as is herein set forth. 
 
 (46.) Can you not send me photographs, sketches, or printed cuts of the effects of the 
 violence of any particular tornado, no matter what date ? They will be very desirable. If you 
 cannot furnish them, perhaps you know of some one who can. I am particularly anxious to 
 obtain sketches of clouds, however rough and imperfect. If in any way you can roughly depict 
 upon paper the unroofing, overturning, or crushing of a building, the destruction of an orchard, 
 uprooted or twisted trees, or the falling or twisting of timber as the tornado cloud swept through 
 the forest, it will 'BTmost valuable. Perhaps you know of some one who witnessed these scenes, 
 or part of them, and who would be willing to illustrate them. Do not fail to send me some- 
 thing on this subject, if possible. 
 
 111. (47.) If you recall the occurrence in times past of any violent hail-storm in your 
 state, give the place, year, month, day of month, hour of day, direction of the storm, maximum 
 and minimum width of path in rods or miles, size and shape of hailstones, and a narration of 
 the destructive effects. (C. 104.) 
 
 37. (48.) If you recall the occurrence, in times past, of any tornado in your state, give year, 
 month, day of month, hour of day, the direction of the course of the path of destruction as 
 pursued by the tornado cloud, its length in miles, average width of destructive path in yards or 
 rods, maximum width, minimum width, and, if possible, the hour of beginning and hour of 
 disappearing of the tornado cloud. (C. 30.) 
 
ANNOUNCEMENTS. 
 
 ANNOUNCEMENTS. 
 
 Part III. of the " Scientific Roll " will be commenced, if life and health and support be 
 granted to the Conductor, in 1883. In order that the bibliography may be as full as 
 possible, authors and publishers are respectfully solicited to send copies of, or references to, 
 all their publications dealing with the barometrical condition of the air. 
 
 As soon as 200 persons have expressed a wish to subscribe for any one of the subjects 
 mentioned below, the publication of that section of the " Scientific Roll " will be forthwith 
 commenced. The subscription price will be 7s. 6d. and 10s. for each volume, according as 
 the residence of the subscriber is at home or abroad. Each volume will comprise from 
 400 to 500 pages ; and each volume will, in most cases, contain two or more parts, each of 
 which may be subscribed for separately. The extent of these parts will depend upon the 
 amount of matter in hand, so that the subscription price for each cannot be fixed at present, 
 but will be settled when the publication of each part is commenced. The following is a 
 list of the principal subjects : 
 
 Atmosphere, Water, Ocean, Rivers, Lakes, Springs, Glaciers, Land, Elevation and Sub- 
 sidence of Land and Sea-Bottom, Denudation. Orography, Earthquakes, Volcanoes, Marshes, 
 Minerals, Stratigraphy, Rocks, Plants generally and in classified groups ; Animals gene- 
 rally; Protozoa, Actinozoa, Hydrozoa, Echinodermata, Crustacea, Scolecida, Annelida, 
 Mollusca, Myriapoda, Arachnida, Rhynchota, Orthoptera, Diptera, Coleoptera,Lepidoptern, 
 Neuroptera, Hymenoptera, Pisces, Amphibia, Reptilia, Aves, Mammalia, and Man. 
 
 Subscribers' names only are asked for now. The sending of these will not involve any 
 pecuniary liability, but will simply be taken as implying that the senders take an interest 
 in the work, and will probably undertake to subscribe when asked to do so. 
 
AQUEOUS VAPOUE: NOTES. 
 
 1823. 
 
 Daniell, J. F. Concluded from page 219. 
 
 {Page 62) We must now provide.soine obstacle by which the course of the vapour may 
 be retarded in its ascent ; then may the condensation take place gradually and at 
 different heights. The relative distances of these points of precipitation will depend 
 upon the force of the vapour, and the greater or less facility with which it overcomes 
 the mechanical obstruction. For the scale of temperature laid down, the following 
 table would represent an adequate balance of evaporation and condensation with the 
 appropriate degrees of elasticity between the points : 
 
 Height. 
 Feet. 
 
 Sensible 
 Temp. 
 
 Constituent Temp, 
 of Vapour. 
 
 Elasticity. 
 
 " State of 
 Atmosphere. 
 
 Force of 
 Evaporation. 
 
 
 
 80 
 
 67.9 
 
 .673 
 
 Clear. 
 
 327 
 
 5,000 
 
 64.4 
 
 [*]64.4 
 
 *.606 
 
 Cloudy. 
 
 467 
 
 10,000 
 
 48.4 
 
 19.0 
 
 .124 
 
 Clear. 
 
 
 15,000 
 
 31.4 
 
 16.0 
 
 .112 
 
 do. 
 
 
 20,000 
 
 12.8 
 
 [*]12.8 
 
 *.100 
 
 Cloudy. 
 
 80 
 
 25,000 
 
 -7.6 
 
 -20.7 
 
 .027 
 
 Clear. 
 
 
 30,000 -30.7 [*]-30.7 *.020 Hazy. 
 
 [*] are asterisks added in the 1845 Ed. 
 
 The last column gives the relative force of evaporation at the different points, 
 supposing the total effect, if unopposed and sudden, to be 1000, and the same 
 numbers will represent the comparative amount of precipitation at the several 
 intervals of condensation, or the relative densities of the three clouds. Iii this 
 manner the struggle between the elasticity of the stream [corrected to steam in 
 1845 Ed.] and the condensing power of the cold is divided and moderated, and the whole 
 process becomes so gentle as quietly to restore the balance of force and temperature, 
 provided the counteracting cause be not of a permanent nature. The moisture fallin^ 
 gradually back into the excess of heat below is converted into vapour of higher force, 
 which pressing more upon the inferior strata proportionably raises their densities. From 
 {Page 64) these considerations it would appear that, in any single column considered 
 by itself, clouds of greater or less densities, and evaporation of greater or less force must 
 be the consequence of a temperature decreasing in a more rapid progression than is due 
 to the law of aqueous vapour. While the atmosphere is in the state represented in the 
 last table, let us now contemplate the effects of a general reduction of sensible tempera- 
 ture upon the constituent temperature and the different points of precipitation. We 
 will suppose the fall to take place gradually, and to amount to 18. In the first place, 
 the elastic force upon the surface will be diminished, but will approach the point of pre- 
 cipitation within 3. A plane of condensation will be established between the surface 
 and the height of 5000 feet. So likewise the vapour from 9000 to 14,000 feet will not 
 be disturbed, but the second plane of condensation will descend from 18,500 feet to an 
 intermediate position between that elevation and 14,000 feet. The shifting of these 
 planes would not be sensible at the surface for the light precipitations which would 
 PART II. No. 9. B 241 
 
AQUEOUS VAPOUR 1823. Daniell. 
 
 NOTES. 
 
 
 
 10 Lat, 
 
 
 ; Height. 
 
 Sensible 
 
 Const. 
 
 Elasticity. 
 
 Feet. 
 
 Temp. 
 
 Temp. 
 
 
 
 
 76.8 
 
 51.0 
 
 .388 
 
 5,000 
 
 61.1 
 
 - 48.0 
 
 .351 
 
 10,000 
 
 [*]44.9 
 
 45.0 
 
 .316 
 
 15,000 
 
 27.7 
 
 12.0 
 
 .096 
 
 20,000 
 
 9.3 
 
 9.3 
 
 .087 
 
 25,000 
 
 -11.6 
 
 -32.0 
 
 .019 
 
 30,000 
 
 -35.0 
 
 -35.0 
 
 .016 
 
 
 Lat. 
 
 
 
 Sensible 
 
 Const. 
 
 Elasticity. 
 
 State of 
 
 Temp. 
 
 Temp. 
 
 
 Sky. 
 
 80 
 
 67.9 
 
 .673 
 
 Clear. 
 
 64.4 
 
 [*]64.4 
 
 .606 
 
 do. 
 
 48.4 
 
 19.0 
 
 .124 
 
 do. 
 
 31.4 
 
 16.0 
 
 .112 
 
 do. 
 
 12.8 
 
 12.8 
 
 .100 
 
 do. 
 
 -7.6 
 
 -27.0 
 
 .027 
 
 do. 
 
 -30.7 
 
 -30.7 
 
 .020 
 
 do. 
 
 accompany their slow subsidence would be expended in equalising the temperature. 
 We must next contemplate these various phenomena, hitherto considered as confined to 
 a single column, in connection with adjacent sections. Let us take, as an illustration, 
 the equatorial column of 80 in the state in which we have just considered it, and the 
 adjoining one of 76 8. The flow of the lateral currents may be determined by the 
 following table : 
 
 10 Lat. 
 
 State of 
 
 Sky. 
 
 Clear. 
 
 do. 
 
 Cloudy. 
 Clear. 
 Cloudy. 
 Hazy, 
 do. 
 [The asterisks [*J are additions made in the 1845 Ed.] 
 
 (Page 66) In this table the first point of condensation above in the equatorial 
 division is supposed to take place at the height of 5000 feet ; while at latitude 10 it is 
 fixed at 10,000 feet ; and it will be seen that up to the former elevation the vapour of 
 the first column is of much greater elasticity and density than that of the latter ; it will 
 consequently flow towards it with considerable force. No cloud will be formed, at the 
 point of condensation, for the supply arising from the evaporation at the surface will be 
 carried off in a. lateral direction ; or, if previously formed, would soon be dissipated by 
 the same action. Nor would the transparency of latitude 10 be affected up to this 
 height ; for the current which it would receive would in constituent temperature still 
 be below what its sensible heat would maintain. But above this line a dense cloud 
 would be precipitated. A counter flow of small extent towards the equator will be 
 established at 10,000 feet ; and above this again the pressure will return to the first 
 direction. The constituent temperature of the returning current being below the 
 temperature of the elevation, the transparency of the equatorial column will be preserved 
 throughout. These lateral currents are supposed to take place under the same mechanical 
 retardation as the ascending vapour. Enough has been done to show generally that the 
 necessary condition of transparency in any vertical section of an atmosphere of pure 
 (Page 67) vapour, in which, from some extraneous cause the temperature diminishes 
 faster than the natural progression, is that the quantity generated from the evaporation, 
 necessarily accompanying such circumstances, should be carried off to adjoining regions. 
 Let us now suppose that water is only partially diffused, and that the uncovered 
 portions are absolutely dry. Vapour out of contact of water expands -^^ part of its 
 volume for each Fahr. If a current, therefore, were to pass over a dry space, heated 
 to a degree higher than itself, the same changes in its constitution would take place in 
 miniature as in dry atmosphere. The density would diminish, while its elasticity would 
 (Page 68) remain the same upon the surface, and be increased at higher stations. The 
 following table shows the effects of expansion upon vapour heated beyond the dew 
 point: 
 
 Height. 
 Feet. 
 
 
 
 5,000 
 10,000 
 15,000 
 20,000 
 25,000 
 30,000 
 
 Elasticity. 
 
 1.0 
 
 .899 
 .808 
 .727 
 .653 
 .587 
 .527 
 
 Const. 
 Temp. 
 
 80.0 
 76.5 
 73.0 
 70.0 
 67.0 
 63.0 
 60.0 
 
 Sensible 
 Temp. 
 
 90.0 
 86.5 
 83.0 
 80.0 
 77.0 
 73.0 
 70.0 
 
 Such modifications would necessarily ensue in the cases which have already been con- 
 sidered of the constituent temperature falling below the sensible heat ; but, by comparing 
 
AQUEOUS VAPOUR 1823. Daniell. 
 
 NOTES. 
 
 this table with that on p. 54, it will be seen that the total effect at the greatest extreme 
 does not exceed '007 in. and it will be unnecessary in the general view we are 
 taking of the subject to introduce a correction to such a small amount. In the case of 
 vapour becoming heated in this manner out of contact with water, it may reach its point 
 of deposition at a higher elevation without producing any sensible clouds ; for although 
 it would be instantly restored to the elastic form by the excess of heat in the inferior 
 strata ; and no accumulation could be formed for want of supply from the dry surface 
 below a slight haziness might be the result. Let us now imagine a stream of vapour 
 (Page 69) of known density filtering its way laterally through the resisting obstacle 
 which we have supposed, from one part of the sphere which is covered with water of a 
 certain temperature to another which is perfectly dry, and of equal or superior tempera- 
 ture. As it arrives at the latter point it will diffuse itself rapidly over the dry space, 
 and its elasticity being no longer confined by an incumbent atmosphere of like density 
 will be reduced, and it will assume that force which its own diffusion will enable it to 
 maintain. Or a stream of vapour, of high elasticity, flowing into a space where there 
 already exists an atmosphere of inferior force, will be reduced in density to that of the 
 general mean. In the next table [xxxii.] are represented two contiguous columns of 
 vapour, the first incumbent upon water of the temperature of 70, and the second upon 
 dry land of the temperature of 80. It is obvious that the former will flow into the 
 latter, but will no longer be distinguished by its constituent temperature of 60, but will 
 be reduced to the standard of the second column of 32. The elasticity of this column 
 will rise with the difference of the first : 
 
 Gen. Temp. 
 70 
 
 Const. Temp. 
 60 
 
 Elasticity. 
 .524 
 
 Gen. Temp. 
 80 
 
 Const. Temp. 
 32 
 
 Elasticity. 
 .200 
 
 But the supporting surface may be neither water nor yet perfectly free from it, but we 
 (Page 70) will imagine it to be earth differently imbued with moisture, and variously 
 heated ; then a partial supply, varying in quantity in different places, but of the same 
 degree of density would take place, and clouds of more or less opacity would be formed 
 at corresponding situations in the planes of deposition above. The following table will 
 tend to illustrate these different positions : 
 
 Height. 
 Feet. 
 
 General 
 Temp. 
 
 Const. 
 Temp. 
 
 Water 60 . 8 
 Atmos. Force of 
 
 Moist Earth 70 
 Atmos. Force of 
 
 Dry Earth 80 
 Atmos. Force of 
 
 
 
 
 
 Evap. 
 
 
 Evap. 
 
 
 Evap. 
 
 
 
 60.8 
 
 34 
 
 Clear. 
 
 368 
 
 Clear. 
 
 507 
 
 Clear. 
 
 786 
 
 5,000 
 
 44.6 
 
 31 
 
 do. 
 
 Density. 
 
 do. 
 
 Density. 
 
 do. 
 
 
 10,000 
 
 27.9 
 
 28 
 
 Cloudy. 
 
 .368 
 
 Cloudy. 
 
 092 
 
 Hazy. 
 
 
 15,000 
 
 10.0 
 
 -6.4 
 
 Clear. 
 
 
 Clear. 
 
 
 Clear. 
 
 
 20,000 
 
 -9.4 
 
 -9.4 
 
 Cloudy 
 
 .126 
 
 Hazy. 
 
 .021 
 
 do. 
 
 
 25,000 
 
 -31.2 
 
 -31.2 
 
 Hazy. 
 
 .020 
 
 Clear. 
 
 
 do. 
 
 
 30,000 
 
 -55.9 
 
 -55.9 
 
 Clear. 
 
 
 do. 
 
 
 do. 
 
 
 (Page 71) The same general temperature is here supposed to prevail momentarily 
 in every part of an atmosphere of equal force, resting upon a surface covered with 
 water in one part, with moist earth in another, and dry in a third, and varying more- 
 over in heat in the three situations. The first point of precipitation is placed at 
 10,000 feet. The water upon which the first part of the column rests is of the same 
 degree of heat as the general temperature at the surface, the force of evaporation is 
 368, and as the supply is equal to the force, the density of the cloud is 368. The 
 moist earth, upon which the second portion rests, is of the temperature of 70, which 
 makes the force of evaporation 507 ; but less steam being given off from the earth 
 than from the water, the quantity of the precipitation is proportionally diminished. 
 The dry surface which supports the third portion is heated to 80, and yields no 
 vapour ; the evaporating force, which is equal to 786, is wholly unsupplied, and no 
 cloud can therefore be maintained. The higher points are subject to the same modifica- 
 
 R 2 243 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 tions. The temperature of the evaporating surface regulates the quantity of water 
 raised in vapour, the tension of the pre-existing atmosphere determines its elasticity. 
 (Page 72) In the operations of the aqueous steam a power is developed fully adequate 
 to produce the disturbances of temperature hypothetically proposed in the examination 
 (Page 73) of the permanently elastic fluid. We may now investigate the compound 
 qualities of a mixture of dry air and aqueous vapour, and their mutual relations so 
 combined. The properties, which each possessed in its separate state, will be retained 
 in this connection unchanged, and the two fluids will exercise no further action upon 
 each other than a mechanical opposition when in motion. The particles of steam, in 
 penetrating the interstices of the permanently elastic fluid, experience the same species 
 of retardation as exists in their flowing through the pores of sand or cotton. When a 
 state of equilibrium is attained, this mutual action ceases, and the particles of each 
 press only upon those of their own kind. There are, therefore, two principal points of 
 view under which such a mixture may be regarded one in which the particles are in a 
 state of equipoise amongst themselves, and the other where they are seeking an 
 (Page 74) equilibrium by means of intestine motion. The first may be regarded 
 as a homogeneous fluid. We will now inquire what will be the natural state of such 
 an atmosphere surrounding a sphere of uniform temperature throughout. But we 
 must first consider the effects of mixing known measures of the gases with vapour of 
 different degrees of force. The first effect is increase of bulk under equal pressure in 
 the permanently elastic fluid, not in proportion to the measure of vapour in it, but in 
 proportion to its elasticity. Thus if we mix a cubic foot of dry air of the temperature 
 of 212 and of the elasticity of 30 inches with as much steam as would rise in the 
 space of a cubic foot of the same temperature, and consequently of the force of 30 inches, 
 the mixture would occupy the space of two cubic feet. So if we mix a like measure of 
 air of the temperature of 32 and of the elasticity of 30 inches with as much vapour as 
 would form in the same space at the temperature of 32, and consequently of the force 
 (Page 75) of only -2 inches, the bulk of the gas will only be increased '00666 of a 
 cubic foot. The second result is that the specific gravity of the gas is decreased, but 
 not exactly in proportion to its expansion ; for, while the vapour dilates its parts, it 
 adds its own weight to the mixture. But this weight, though increasing with the 
 elasticity, being, in all cases, less than that of an equal bulk of common air, decrease of 
 density must follow. [See under 1793, Dalton, p. 101.] The diminution becomes 
 greater with every increment of temperature. Let us imagine a homogeneous atmo- 
 sphere of air of the temperature of 77 and 30 inches pressure ; its specific gravity 
 compared to air at 32 would be '90626. Let us suppose this to be mixed with an 
 atmosphere of vapour of the same temperature and '91 inch force ; the specific gravity 
 of the mixture under equal pressure would be .89312 ; its total pressure would be 
 30-91 in., and its height would be increased from 28,775 feet to 30,260 feet. But as 
 the temperature of a homogeneous atmosphere must fall on assuming that gradation 
 of density which is essential to its natural state, the quantity of vapour must therefore 
 (Page 7 Q) suffer a proportionate reduction. The next table (xxxiv.) shows the small 
 quantity of vapour which could exist with the atmosphere of air, supposing it saturated 
 throughout. 
 
 Height 
 Fe t / Temp. Elasticity. 
 
 77.0 .910 
 
 5,000 61.0 .542 
 
 10,000 45.0 .316 
 
 15,000 27.5 .171 
 
 20,000 9.3 088 
 
 25,000 -11.0 .042 
 
 30,000 -35.0 .016 
 
 The average quantity [elasticity in 1845 Ed.], therefore, of vapour to this height could 
 not exceed '297 in. We must further consider that the altitude to which we have 
 244 
 
AQUEOUS VAPOUR 1823. Daniell. 
 
 followed our speculations has comprised but two-thirds ofto<^tjal height of jiur 
 atmosphere ; the remaining third may, without any risk of errors-he. considered, from 
 the lowness of its temperature, to be totally free from vapour. The mean pressure of 
 the steam would thus be reduced to '198 in. ; and, supposing such a state of circum- 
 stances to be possible, the barometer would only rise from 30 in. to 30'198 in. in the 
 atmosphere surrounding a sphere of the temperature of 70 by a change from absolute 
 dryness to perfect moisture. Nor would such a state of saturation constitute by any 
 (Page 77) means a natural condition of such an atmosphere as we are contemplating. 
 Even if a general mixture could be effected, in the proportions which we have above 
 imagined, the elasticity of the steam at the bottom of the column would be greater 
 than the weight which the upper strata would confine ; so that being urged upwards 
 it would be condensed by the temperature of the air, which decreases faster than the 
 progression due to the vapour, and the barometer would not rise to the height just stated. 
 A state of complete mixture, in which all the particles would be at rest amongst them- 
 selves, cannot, therefore, exist in the natural ['compound', in 1845 Ed.] atmosphere; 
 and it can only, consequently, be regarded in the second point of view distinguished 
 above, namely, as in a state of intestine motion. To place these particulars in a clearer 
 light let us trace the progress of vapour just beginning to form in a perfectly dry 
 atmosphere. For this purpose we will imagine the temperature of the sphere to be 77. 
 Let us now imagine water suddenly to overflow the surface, and evaporation will 
 instantly commence. No atmosphere of vapour exists to impede its progress ; the 
 nascent steam will, therefore, merely assume the degree of tension necessary to over- 
 come the vis inertia of the air which obstructs its motion. What this force may be 
 we have not, perhaps, sufficient data to determine. We must, for the present, fix it 
 arbitrarily and assume that at the temperature of 77 and pressure of 30 in., it amounts 
 (Page 78) to '200. The constituent heat of vapour of this elasticity is 32, so that 
 at the height of about 13,500 feet it would meet with its point of condensation. An 
 aqueous atmosphere of such a degree of force being now established, fresh resistance 
 to this amount is made to the progress of evaporation ; and the elasticity of the rising 
 steam must be doubled. Its constituent temperature is thus raised to 52, and it cannot 
 therefore pass the height of 7500 feet without decomposition. [The 1845 Ed. has 
 ' deposition.'] The resistance upon the surface now amounts to '601 in., to overcome 
 which vapour at 65 must be emitted. The first point of precipitation in ascending 
 from the surface would thus be fixed at about 3600 feet. We may now further remark 
 that the diffusion of vapour does not cease at the height of 3500 feet [corrected to 
 13,500 in 1845 Ed.] ; but the mechanical obstruction is proportionately reduced, and it 
 is carried by successive stages to more lofty regions, where its tenuity is so much 
 increased that it speedily eludes all observation. 
 
 With regard to the various points of condensation it is probable that no cloud would be 
 formed in any of them. The process of evaporation would be so gentle under these 
 circumstances that little above 6 grains of water would be raised per minute from the 
 surface of a square foot ; so that as the gradual precipitation of this quantity took place 
 between the different stages it would instantly be redissolved by the excess of heat into 
 which it would naturally incline to fall. The circulation thus becomes a process of equali- 
 (Page 79) sation by which the temperature of the upper regions is raised, the heat which 
 is abstracted below by evaporation is evolved by condensation, the pressure of the vapour 
 is increased, and all the changes tend to that distribution of heat which we formerly 
 contemplated as the natural state of an unmixed atmosphere of steam. The average 
 quantity of vapour which would exist upon the hypothesis which we have just assumed, 
 while the atmosphere maintained its proper progression of temperature, may be roughly 
 approximated as follows : A stratum of the force of '616 in. extends to the height of 
 3600 feet ; another of the force of '401 in. reaches 3900 feet farther ; a third of only 
 200 in. stretches almost as far as both the former together; making a total of 
 
 245 
 
AQUEOUS VAPOUR 1823. Daniell. 
 
 NOTES. 
 
 13,500 feet. The mean, therefore, to this point is nearly '354 in. For the farther 
 distance of 17,500 feet we cannot greatly err in taking '064 in. as the mean pressure, 
 making the average to the height of 31,000 feet *209 in. One-third of the atmo- 
 sphere beyond this being considered free from vapour reduces the mean to '139 in. 
 The following diagram may possibly tend to elucidate the effects of an unequal addition 
 of matter or of unequal expansion in various parts of the same column of fluid. 
 {Page 80.) Let A B represent the Column whose height and weight we will call 40. 
 Its four sections, A B C I) are each equal to 10. Let us suppose an addition of matter 
 to take place in B ef equal to 4 ; in D g li equal to 3 ; in C i k equal to 2 ; and in A I m 
 equal to 1. The total increase of weight and pressure at the 
 bottom will be 10, the same as if the total amount had been equally 
 distributed throughout the mass or added at once to the top of the 
 column on n o. Again, if in the same column an unequal expansion 
 were to take place in the four different sections, e/=4 ; gh=3; 
 ik=2 ; and Zm=l, the total increase of bulk n o would be the same 
 as if the expansion had everywhere been equal, and the weight at the 
 base remaining the same, that of the sections would be altered from 
 [0 added in 1845 Ed.] 10, 20, 30, 40, to 8, 16, 24, 32 and 40. In 
 the case of the atmosphere which we are considering, both these 
 changes are combined, the barometer rises at the surface of the 
 sphere, and the weight of the several strata is still further changed. 
 The following table exhibits the state of the barometer at equal 
 altitudes before and after the admission of vapour in an atmosphere 
 surrounding a sphere of the uniform heat of 77, together with the 
 temperature appropriate to the elevation and the dew point. 
 
 1G 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 n 
 
 A 
 
 
 m 
 
 I 
 
 C 
 
 
 i 
 
 i 
 
 D 
 
 
 h 
 
 
 
 B 
 
 e 
 
 10 
 
 Barometer. 
 
 Atmosphere 
 
 Temp. 
 
 without vapour. 
 
 with vapour. 
 
 Dew Point. 
 
 76.8 
 
 30.000 
 
 30.139 
 
 65 
 
 61.1 
 
 25.214 
 
 25.348 
 
 52 
 
 44.9 
 
 21.193 
 
 21.318 
 
 32 
 
 27.7 
 
 17.812 
 
 17.928 
 
 9 
 
 9.3 
 
 14.970 
 
 15.079 
 
 
 
 11.6 
 
 12.583 
 
 12.682 
 
 -35 
 
 35.0 
 
 10.578 
 
 10.667 
 
 -35 
 
 24 |-I 1 20 Height. 
 
 Feet. 
 
 
 
 5,000 
 10,000 
 15,000 
 20,000 
 30 25,000 
 30,000 
 
 Such, then, would be the new state of things from the admission 
 of water to the surface of the sphere ; a state, however, which, 
 notwithstanding the equality of the superficial heat, could not be 
 40 one of permanent rest. A perpetual struggle would ensue between 
 the temperature due to the density of the air and the constituent 
 temperature of the vapour, accompanied by perpetual evaporation below and simultaneous 
 condensation above. No winds or lateral currents would be established, but an increasing 
 (Page 82) circulation in a vertical direction. It will be observed that the total alteration 
 of pressure is but small, even in the almost extreme case which has been selected, and 
 the changes of density still less ; it is in the unequal distribution and its consequent 
 effects that we must seek for the principal influence of vapour in the mixed atmosphere. 
 Changing now our hypothesis of the sphere of equal temperature for that of the sphere 
 of unequal temperature, increasing from the poles to the equator, we will again assume 
 that the barometer stands everywhere at the same height upon the surface, which height 
 we will suppose to be 30 inches. The state of the vapour in the different columns of 
 the mixed atmosphere is to be imagined to be in the same proportion as in the atmo- 
 sphere which we have just been considering, that is to say, its constituent temperature 
 at the surface of the sphere is to be within 11 of the temperature of the several zones. 
 The arrangement is thus represented (Table opp. p. 82). 
 246 
 
AQUEOUS VAPOUR 
 
 1823. Daniell. 
 
 NOTES. 
 
 
 
 POLES. 
 
 
 
 
 Height. 
 
 Total 
 
 Pressure of 
 
 
 
 
 Feet. 
 
 Pressure. 
 
 Vapour. 
 
 Sp.gr. 
 
 Temp. 
 
 Dew Point. 
 
 
 
 30. 000 in. 
 
 .044 
 
 1.06666 
 
 
 
 -11 
 
 5,000 
 
 23.597 
 
 
 .86935 
 
 -18 
 
 
 10,000 
 
 18.587 
 
 
 .70856 
 
 -37 
 
 
 15,000 
 
 14.591 
 
 
 .57752 
 
 -58 
 
 
 20,000 
 
 11.411 
 
 
 .47071 
 
 -82 
 
 
 25,000 
 
 8.900 
 
 
 .38365 
 
 -109 
 
 
 30,000 
 
 6.906 
 
 
 .31270 
 
 -140 
 
 
 
 
 80. 
 
 
 
 
 
 
 30.000 
 
 .047 
 
 1.06038 
 
 3 
 
 -8 
 
 5,000 
 
 23.652 
 
 
 .86542 
 
 -15 
 
 
 10,000 
 
 18.630 
 
 
 .70637 
 
 -34 
 
 
 15,000 
 
 14.642 
 
 
 .57654 
 
 -55 
 
 
 20,000 
 
 11.484 
 
 
 .47057 
 
 -78 
 
 
 25,000 
 
 8.965 
 
 
 .38408 
 
 -104 
 
 
 30,000 
 
 6.978 
 
 
 .31352 
 
 -135 
 
 
 
 
 70. 
 
 
 
 
 
 
 30.000 
 
 .057 
 
 1.04685 
 
 9 
 
 -2 
 
 5,000 
 
 23,707 
 
 .033 
 
 .85684 
 
 -8 
 
 -17 
 
 10,000 
 
 18.724 
 
 
 .70140 
 
 -27 
 
 
 15,000 
 
 14.775 
 
 
 .57407 
 
 -47 
 
 
 20,000 
 
 11.617 
 
 
 .46991 
 
 -70 
 
 
 25,000 
 
 9.102 
 
 
 .38463 
 
 -96 
 
 
 30,000 
 
 7.100 
 
 
 .31483 
 
 -126 
 
 
 
 
 60. 
 
 
 
 
 
 
 30.000 
 
 .085 
 
 1.02607 
 
 19 
 
 8 
 
 5,000 
 
 23.793 
 
 .047 
 
 .84427 
 
 1 
 
 -8 
 
 10,000 
 
 18.893 
 
 
 .69405 
 
 -17 
 
 
 15,000 
 
 14.969 
 
 
 .57061 
 
 -36 
 
 
 20,000 
 
 11.827 
 
 
 .46904 
 
 -58 
 
 
 25,000 
 
 9.314 
 
 
 .38558 
 
 -83 
 
 
 30,000 
 
 7.302 
 
 
 .31699 
 
 -112 
 
 
 
 
 50. 
 
 
 
 
 
 
 30.000 
 
 .134 
 
 .99835 
 
 32 
 
 21 
 
 5,000 
 
 23.949 
 
 .079 
 
 .82563 
 
 14 
 
 6 
 
 10,000 
 
 19.106 
 
 .045 
 
 .68321 
 
 -3 
 
 -9 
 
 15,000 
 
 15.229 
 
 
 .56472 
 
 -22 
 
 
 20,000 
 
 12.044 
 
 
 .46677 
 
 43 
 
 
 25,000 
 
 9.579 
 
 
 .38582 
 
 -67 
 
 
 30,000 
 
 7.566 
 
 
 .31890 
 
 -95 
 
 
 
 
 40. 
 
 
 
 
 
 
 30.000 
 
 .237 
 
 .96358 
 
 48 
 
 37 
 
 5000 
 
 24.072 
 
 .139 
 
 .80230 
 
 31 
 
 22 
 
 10,000 
 
 19.338 
 
 .068 
 
 .66800 
 
 14 
 
 2 
 
 15,000 
 
 15.525 
 
 .037 
 
 .55629 
 
 4 
 
 - 14 
 
 20,000 
 
 12.409 
 
 
 .46273 
 
 -24 
 
 
 25,000 
 
 9.915 
 
 
 .38489 
 
 -47 
 
 
 30,000 
 
 7.852 
 
 
 .32016 
 
 -62 
 
 
 
 
 30. 
 
 
 
 
 
 
 30.000 
 
 .375 
 
 .93463 
 
 61 
 
 50 
 
 5000 
 
 24.215 
 
 .221 
 
 .78245 
 
 44 
 
 35 
 
 10,000 
 
 19.531 
 
 .112 
 
 .65503 
 
 28 
 
 16 
 
 15,000 
 
 15.739 
 
 .046 
 
 .54855 
 
 10 
 
 - 8 
 
 20,000 
 
 12.673 
 
 .034 
 
 .45856 
 
 - 9 
 
 -17 
 
 25,000 
 
 10.162 
 
 
 .38327 
 
 -31 
 
 
 30,000 
 
 8.135 
 
 
 .32035 
 
 -56 
 
 
 247 
 
AQUEOUS VAPOUR 1823. Daniell. 
 
 NOTES. 
 
 Height. 
 Feet. 
 
 Total 
 Pressure. 
 
 Pressure of 
 Vapour. 
 
 Sp. gr. 
 
 Temp. 
 
 Dew Point. 
 
 
 
 20. 
 
 
 
 
 o 
 
 30.000 in. 
 
 .507 
 
 .91278 
 
 70 
 
 59 
 
 5000 
 10,000 
 15,000 
 20,000 
 25,000 
 30,000 
 
 24.279 
 19.675 
 15.898 
 12.811 
 10.342 
 8.313 
 
 .328 
 .162 
 .068 
 .046 
 
 .76703 
 .64489 
 .54180 
 .45500 
 .38166 
 .32010 
 
 54 
 38 
 20 
 1 
 -19 
 -43 
 
 46 
 
 26 
 2 
 - 8 
 
 10. 
 
 
 
 5000 
 10,000 
 15,000 
 20,000 
 25,000 
 30,000 
 
 
 
 5000 
 10,000 
 15,000 
 20,000 
 25,000 
 30,000 
 
 30.000 
 24.319 
 19.738 
 16.012 
 12.974 
 10.467 
 8.424 
 
 30.000 
 24.342 
 19.779 
 16.060 
 13.043 
 10.521 
 8.483 
 
 .616 
 .401 
 .200 
 .087 
 .064 
 .015 
 
 Equator. 
 
 ,443 
 .229 
 .100 
 ,071 
 ,032 
 
 .89764 
 .75621 
 .63762 
 .53703 
 .45147 
 .38010 
 .31948 
 
 .89018 
 .75133 
 .63436 
 .53520 
 .45068 
 .37980 
 .31980 
 
 77 
 61 
 45 
 27 
 9 
 
 -11 
 -35 
 
 80 
 
 64 
 
 48 
 
 31 
 
 12 
 
 - 7 
 
 -30 
 
 65 
 
 52 
 
 32 
 
 9 
 
 
 
 -35 
 
 69 
 
 55 
 
 36 
 
 13 
 
 3 
 
 -16 
 
 (Page 83) The specific gravity and elasticity of the air is but very slightly affected 
 by this intermixture of aqueous vapour. It will also be remarked that while the great 
 aerial ocean is divided into two distinct strata flowing in opposite directions from N. to s. 
 and from s. to N., the aqueous part, which is nearly confined to the lower current, presses 
 in a contrary direction. The adjustment of these particulars remaining as now sup- 
 posed, the compensating winds flow on and the balance remains undisturbed. The 
 admixture of vapour which we have hitherto considered, has not yet affected the grada- 
 tion of temperature resulting from the decreasing density of the atmosphere in its upper 
 parts ; the process of evaporation, however, which has been described must, in time, neces- 
 sarily induce such an alteration. The stream [steam in 1845 Ed.], as it reaches its point 
 of condensation, must give out its latent heat, and during its precipitation, combining with 
 a fresh proportion, it again ascends and again evolves it in the middle regions. It may 
 thus be considered as carrying caloric from the surface of the sphere to higher strata ; 
 and it is obvious how a considerable section of any one column may thus have its 
 temperature equalised and fully saturated with aqueous particles. The currents 
 (Paye 84) thus become affected both by the expansive powers of the vapour and of the 
 extricated heat ; causes, the influence of which so applied must be partial and cannot 
 reach the higher regions. The unequal action must produce a fall in the barometer. 
 As upon the one hand this effect upon the barometer is produced by the augmentation 
 of the aqueous vapour, so on the other, a rapid increase of the latter may be produced 
 by a fall in the former. The mechanical resistance of the air must of course be 
 increased by its motion in opposition. When this is stopped, as it soon is, by a trifling 
 fall of the mercurial column, the vapour will rush forward with its whole force, retarded 
 only by its filtration through the quiescent air ; and, the temperature of the higher 
 latitude being unable to support its elasticity, precipitation must follow. From the 
 operation of these causes the temperature of the latitude is partially affected, the 
 density of the air is still further reduced, and the aerial current is reversed. The course 
 of the vapour is thus greatly accelerated, and abundant precipitation will follow. [An 
 addition comes in here at page 114 of 1845 Ed.] When first formed in the higher 
 elevations cloud would probably assume a light cirriform appearance ; in lower regions 
 218 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 the precipitation would become denser, and the attraction of aggregation stronger ; the 
 (Page 85) mass would subside gently to a lower station, where the density of the air would 
 oppose a greater resistance to its descent. Here, in a higher temperature, the cloud 
 would again begin to be dissolved, and would assume a rounded and compact form ; 
 and thus the equalization of the temperature and the diffusion of the vapour would be 
 carried on from several points at once. The different beds obey the impulse of the 
 winds, and as they sail along enlarge the circumference of their action, till at length, 
 the natural equilibrium of the atmosphere can be no further curbed. The precipitation 
 increases, the strata of the clouds inosculate, and the air no longer buoys up their load. 
 It will be convenient here to subjoin a synoptic view of the force of the aerial currents, 
 and the counter-pressure of the vapour in a mixed atmosphere surrounding a sphere 
 unequally heated in the manner already set forth. 
 
 (Page 86) Table XXXVII. showing the force of the different currents in a mixed 
 atmosphere of air and vapour between the poles and the equator. W=wind. 
 V= vapour. 
 
 Lat. 90 and 80. 80 and 70. 70 and 60. 
 
 W. V. W. V. W. V. 
 
 + .178 --003 +.387 -.010 +.575 -.028 
 
 + .057 +.191 +.281 -.014 
 
 + .019 +.048 +.045 
 
 -.023 -.063 -.093 
 
 -.069 .112 -.185 
 
 -.078 -.152 -.240 
 
 -.095 .-.161 -.264 
 
 60 and 50. 50 and 40. 40 and 30. 
 
 W. V. W. V. W. V. 
 
 + .810 -.049 +1.034 -.103 +.854 -.138 
 
 + .375 -.032 + .570 -.060 +.454 -.082 
 
 + .112 + .217 .023 +.215 .044 
 
 -.084 .035 +.031 .009 
 
 -.149 .239 -.131 
 
 -.272 - .307 -.196 
 
 -.321 - .322 -.291 
 
 30 and 20. 20 and 10. 10 and 0. 
 
 \V. V. W. V. W. V. 
 
 + .648 -.132 +.447 -.109 +.208 -.082 
 
 + .392 -.107 +.282 -.073 +.118 -.042 
 
 + .165 .050 +.159 .038 +.0. ; '3 .029 
 
 + .038 -.022 +.036 -.019 +.008 -.013 
 
 -.024 -.012 -.068 -.018 -.045 -.007 
 
 -.128 -.074 -.054 
 
 -.170 -.090 -.070 
 
 (Page 87) The resistance which air opposes to the passage of vapour in motion may 
 be regarded as twofold : first, in connection with the permanently elastic fluid at rest ; 
 and, secondly, with it in motion. With regard to the state of rest, the opposition with, 
 which vapour passes through air is in proportion to its density. De Saussure concluded 
 from his experiments that a diminution in the density of one-third doubled the rate of 
 evaporation. JkVith regard to the state of motion, a breeze in opposition to the stream of 
 vapour mus^fetard its progress as much as one in the same direction favours it. Much 
 obscurity envelopes this inquiry from the vagueness of the terms employed in denoting 
 the velocity of the air. Dalton has determined that the rate of evaporation, in a perfect 
 calm, being denoted by 120, that of a brisk wind is 154, and of a high wind 189. The 
 retardation of opposing currents of the same respective forces may therefore be in pro- 
 portion. Some important conclusions follow from these propositions, however wanting 
 in precision. Thus, taking latitude 30, the current which blows in the direction of 
 (Page 88) lat. 40 may be deemed high, and retards the motion of the vapour towards 
 lat. 20 accordingly. At the height of 10,000 feet the density of the air is reduced one- 
 
 249 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 third and the velocity is consequently doubled; to which we must also add, that the 
 opposin" current, at the same elevation, declines in strength, whereby the force is again 
 increased in the proportion of 189 to 154. More vapour, therefore, would probably pass 
 at this elevation than at the surface, although its excess of elasticity is only .044 m. at 
 the former station and .138 in. at the latter. Whenever a deep stratum of air has had 
 its temperature and vapour equalized, it is easy to conceive that the aqueous atmosphere 
 may travel in its upper part with considerable velocity in a course directly opposed to 
 the wind at its lower. The approximation may be carried a little further, perhaps, as 
 follows. The effect of a brisk wind in accelerating evaporation is equal to an increase of 
 about three-tenths of the elasticity ; that of a high wind, six-tenths. The retarding 
 influence of the polar current, in its regular state, may therefore be apportioned to the 
 different latitudes thus. From the poles to 80 = & of the elasticity ; to lat. 70, ^ ; lat. 
 60, T % ; lat. 50, -5% ; lat. 40, & ; lat. 30, -& ; lat. 20, & ; lat. 10, T % ; and from 
 lat. 10 to the equator, ^. Tne following table then represents the efficient force of the 
 vapour in a lateral direction calculated for the surface of the sphere and for the altitude 
 of one-third the density. 
 
 (Page 89) 
 
 Feet. Height. Balance of Effects of wind 
 
 Feet. force. and density. 
 
 90 and 80 -.003 -.002 
 
 10,000 -.001 -.002 
 
 80 70 -.010 -.008 
 
 10,000 -.004 -.008 
 
 70 60 -.028 -.017 
 
 10,000 -.008 -.017 
 
 60 50 -.049 -.025 
 
 10,000 - .012 - .026 
 
 50 40 -.103 -.042 
 
 10,000 -.023 -.043 
 
 40 30 -.138 -.069 
 
 10,000 -.044 -.072 
 
 30 20 -.132 -.093 
 
 10,000 -.050 -.090 
 
 20 10 -.109 -.088 
 
 10,000 -.038 -.070 
 
 10 -.082 -.074 
 
 10,000 - .029 - .058 
 
 (Page 90) These tables are simply rough tentative approximations. The last table 
 will give some idea of the retardation of force in the vapour occasioned by the wind at 
 the surface of the sphere ; and also of the increase of velocity occasioned by dissimilar 
 pressure in the upper regions. The permanency of the barometric pressure on the 
 surface of the sphere is dependent upon the equal balance of the aerial currents, and its 
 fluctuations are due to the destruction of the equipoise by unequal and local expansions 
 and condensations. One of the chief causes of these latter, there can be no doubt, is the 
 increase and decrease of the aqueous vapour counteracting the natural progression of 
 temperature by the caloric evolved in its condensation ; but there is another which must 
 necessarily be powerful in this operation. It has hitherto been supposed, for the sake of 
 simplifying the subject, that the source of heat has been in the sphere itself, and that all 
 the regular changes of temperature have emanated from its surface. In a transparent 
 state the sun's rays pass through the air without materially affecting it, and expend 
 (Page 91) their energy upon the surface of the globe. But if the atmosphere becomes 
 cloudy and opaque, the rays of heat emanating from an external source are in great part 
 absorbed before they reach the surface, and an increase of temperature and elastic vapour 
 must take place in the middle regions. To this we may also add the property which the 
 clouds possess of preventing the radiation of heat from the surface beneath them, and 
 the greater conducting power of damp than of dry air. Amongst the literally number- 
 less modifications of circumstances to which an atmosphere of the nature we have been 
 250 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 considering is liable, there are yet two or three to which it will be necessary shortly to 
 refer. The surface of the sphere has hitherto been chiefly considered as perfectly plain, 
 and either thoroughly dry or everywhere covered with water. We will now contem- 
 plate it as covered with water to the extent of three-fourths of its superficies, uneven 
 and intersected by eminences. This intermixture of land and water at once introduces 
 inequalities of temperature of a different character from those that have been hitherto 
 considered. They chiefly arise from the greater rapidity both of heating and cooling, 
 on the dry surface, dependent upon the peculiar constitution of the watery element. 
 As the processes by which their impressions are communicated to the superincumbent air 
 are slow and gradual, they mostly affect the different columns in an equable manner, so 
 that their influence upon the currents resolves itself into the cases which have been 
 already proposed of total and regular expansion. With respect to the vapour the case 
 is different. It is evident that the parts of the air which are immediately over the dry 
 spaces will not remain free from its admixture, for the elasticity of the surrounding 
 mediums will soon supply the vacuum. The rapidity of this equalization will depend 
 upon the mechanical obstruction of the air being increased or diminished by an adverse 
 or favourable wind. When once diffused over the land it would be more subject to 
 condensation ; and the amount of precipitation must be restored from the expanse of 
 waters. The average quantity of vapour in the atmosphere decreases from below 
 {Page 100) upwards, and from the equator to the poles. This is derivable from the 
 (Page 101) laws of temperature, and is, moreover, amply confirmed by experiment. The 
 condensation of elastic vapour into cloud raises the temperature of the air. This 
 is confirmed by De Luc's observations. While reflecting on the sudden appearance of 
 clouds, I observed a small bank of vapour towards the northward some 300 or 400 feet 
 below me. I carefully watched it, and I then noticed that its volume was sensibly 
 increasing without my being able to see from whence came the increase. Then I saw 
 that instead of descending as it increased in size it became denser and higher. The wind 
 blew it towards me. It at length reached me, and enveloped me so as to shut the view 
 both of sky and plain. I bethought me at the moment of registering a thermometer 
 which had been suspended in the air exposed to the sun, and which I had before seen 
 at 4 (42 F.). I presumed that the action of the sun being intercepted by the cloud, 
 it would sink, but I was surprised to see it at 5 (45 F.). The cloud, which was 
 obliquely rising towards the south, soon passed the place where I was, and the sun 
 re-appeared, but nevertheless the thermometer again sank (III. p. 251). 
 
 (Page 104) The western coasts of the extra-tropical continents have a much higher 
 mean temperature than the eastern coasts. This difference is extremely striking between 
 (Page 105) the western coasts of North America and the opposite eastern coast of Asia. 
 It is explained by the heat evolved in the condensation of vapour swept from the surface 
 of the ocean by the western winds. This general current, in its passage over the land, 
 deposits more and more of its aqueous particles, and by the time that it arrives upon the 
 eastern coasts it is extremely dry ; as it moves onwards it bears before it the humid 
 atmosphere of the intermediate seas, and arrives upon the opposite shores in a state of 
 saturation. Great part of the vapour is there at once precipitated, and the temperature 
 of the climate raised by the evolution of its latent heat. 
 
 (Page 107) Eain seldom occurs in the constant trade wind, and constantly in the adjoin- 
 ing latitudes. Between the tropics the elasticity of the vapour reaches its maximum 
 amount ; and within these limits only, rises to any extent into the upper current of the 
 atmosphere. Its own force, therefore, is assisted by the equatorial wind, and it flows to 
 the north and south as fast as it rises within the zone. No accumulation can therefore 
 be formed, and the temperature being remarkably steady precipitation can but seldom 
 occur. The continental parts of the same regions being liable to greater vicissitudes of 
 heat, are subject to rainy seasons, which are periodical, like the monsoons of the same 
 climates, and are governed as they are by the progress of the sun in declination. The 
 
 251 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 condensation while it lasts is in proportion to the density of the vapour, and is violent 
 beyond anything that is known in temperate climates. The alternate seasons of fine 
 weather are distinguished by cloudless skies and perfect serenity. The extra-tropical 
 (Page 108) latitudes, on the contrary, beyond the bounds of the trade winds are at all 
 times subject to great precipitations. The vapour in its course is subjected to a rapidly 
 decreasing temperature, and the condensation is fed by a constant supply. Between 
 the tropics the fluctuations of the barometer do not much exceed i inch, while 
 beyond this space they reach to 3 inches. Variations of temperature alone do not affect 
 the mercurial column ; and it is in the aqueous condensation we shall probably find the 
 cause of barometrical changes. The vapour passing north and south from the equatorial 
 parts and reaching the extra-tropical regions is precipitated. The effect of this precipita- 
 tion must be to destroy the progression of temperature in the vertical columns by 
 equalizing the heat of the strata exposed to its influence. But as the process is carried 
 {Page 109) on chiefly in the lower current and cannot from its very nature equally affect 
 the column, the total weight will be reduced by the consequent irregular expansion. In 
 the temperate climates the rains and the winds are variable. The rain must depend very 
 much upon the changes of the wind, and the retardation or acceleration which they offer 
 to the progress of the vapour. But another cause arises from the unequal supply which 
 the process of evaporation receives from the irregular surface of the globe. This cannot 
 be placed in a stronger light than by the following considerations. The Caspian Sea, 
 which is placed in the centre of the largest continent of the world, receives the precipi- 
 tations of an immense tract of the atmosphere by means of the rivers which flow into it, 
 and drain the neighbouring countries. The whole of this supply is again returned by 
 evaporation and its waters have no other means of escape. The lakes of North America, 
 situated in nearly the same parallel of latitude and at the same altitude, receive the 
 drains of a much less space ; but annually roll an immense volume of water to the 
 ocean. We are thus furnished with an hygrometer upon a large scale by which we may 
 (Page 110) judge of the state of saturation of the two atmospheres. The difference can 
 arise from no other cause than the proximity of the surrounding seas in the latter situa- 
 tion which furnish an inexhaustible source of vapour which is deficient in the other. It 
 is for the same reason that less vapour is contained in the atmosphere above a continent 
 than above the ocean, although more rain falls in the former situation than in the latter 
 under the same latitudes owing to the greater vicissitudes of temperature. Much of the 
 aqueous atmosphere which is formed from the great deeps is thus drawn off towards the 
 continents, where a scarcity of water occasions an inadequate pressure of the vapour 
 (Page 111). In the extra-tropical climates a fall in the barometer always precedes a 
 period of rain, and indicates an acceleration or change of the aerial currents. As the 
 proximate cause of the fall of the barometer is an accumulation of aqueous vapour, and 
 a consequent unequal expansion of the atmospheric columns, it is obvious that this alone 
 would increase the probability of a proportionate precipitation ; but it is not the only 
 reason of the effect. The fall of the barometer indicates a decrease of density in the 
 aerial currents, and, consequently, a decrease of the resistance to the passage of the 
 vapour. A constant stream will thus rush in with increasing force, augmenting by 
 (Page 112) its condensation the cause of its velocity, till a current sets in from some 
 other quarter and restores the equilibrium. Northerly winds almost invariably raise 
 (Page 115) the barometer; while southerly winds as constantly depress it. The 
 (Page 116) northerly current is the natural course of the air. Coming from the frozen 
 arctic regions it speedily reduces the accumulation of vapour, stops the supply, and 
 dissipates the concomitant heat, from which originated the depression ; and if it flow 
 with a velocity beyond its regular rate, causes a reduction of temperature below the due 
 progression, and augments the total weight ; the southerly wind on the contrary facilitates 
 the passage of vapour which by its unremitting condensation unceasingly increases the 
 cause of depression. The supply of vapour which occasions rain may be traced to two 
 252 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 sources. One is the evaporation of the latitude itself, where it is precipitated ; and the 
 other, the stream which is perpetually struggling to advance from the equatorial zone. 
 These causes sometimes act conjointly and sometimes separately. Eain from the first 
 is derived from sudden falls of temperature produced by cold currents or the changes 
 of the seasons, and assumes chiefly the form of showers of greater or less continuance. 
 The expenditure of vapour is but slowly supplied, and the precipitation occurs at inter- 
 vals. Kain from this source is always accompanied by a declining temperature. When 
 on the contrary, in consequence of diminished pressure, the tropical current reaches in 
 succession the colder parallels, the supply continues in a perpetual flow, the temperature 
 (Page 117) is raised, the depression of the barometer increases, and rain descends with 
 little intermission. Many persons have supposed that the fluctuations of the barometer 
 are owing to the greater or less weight of the aqueous particles contained in the atmo- 
 sphere at one time than at another. If, however, our theory be correct, the difference of 
 pressure between a perfectly dry atmosphere and one saturated with moisture cannot 
 much exceed .15 inch ; the difference of the seasons must therefore be even less than 
 this amount. But small as it is, it may nevertheless be detected by the system of 
 averages. The subject of atmospheric vapour has hitherto been less studied than its 
 importance would seem to require. A few general conclusions based on three years' 
 (Page 118) observations by myself and an experiment by Captain Sabine, will add 
 weight to our synthetic deductions. The elasticity of the aqueous vapour does not decrease 
 gradually as we ascend in the atmosphere in proportion to the gradual decrease of the 
 temperature and density of the air ; but the dew point remains stationary to great heights 
 and then suddenly falls to a large amount. I have been able to confirm this by direct 
 experiment. [An addition is made here in the 1845 edition at p. 161.] The first experi- 
 ments I shall refer to are by Green, who ascended in a balloon from Portsea on September 
 6, 1821, taking two of my hygrometers. At about 9840 [9890 in 1845 edition, page 162] 
 (Page 119) feet he found the dew point to be 64, or the same as I saw it to be on the 
 earth's surface. At 11,060 feet it had fallen to 32, making a difference of 32 in little 
 more than 1100 feet. Here, then, we have presumptive evidence of an immense bed of 
 circumambient medium, unaffected by decrease of density or temperature till checked 
 by its point of precipitation ; and of an incumbent bed of not much more than one-third 
 the density, regulated, no doubt, as the last, by its own point of deposition in loftier 
 regions. Captain [Colonel in 1845 edition] Sabine established the same fact at Sierra 
 Leone. The dew point at sea level was 70 ; and it was the same at the same hour on 
 the summit of the Sugar Loaf Mountain, 2520 feet above. At the Isle of Ascension the 
 readings were at 17 feet above the sea, 30.165 in. barometer, 83 temperature of the air, 
 and 68 dew point. On the summit of the mountain they were 27.95 inches, 70 tem- 
 perature, and 66.5 dew point ; so that in a height of 2220 feet the temperature of the 
 (Page 120) air fell 13, and the constituent temperature of the vapour 1.5. At Trinidad 
 the temperature of the air at the sea level was 82 and the dew point 77 ; 1060 feet 
 above they were both 76.5, and precipitation was going on. At Jamaica by the sea- 
 side the temperature of the air was 80, and the point of deposition 73, while on the 
 mountains at a height of 4080 feet they were both 68.5. At a station not 500 feet 
 higher, the point of deposition was found to be 49, and the temperature of the air 65. 
 These results are against the chemical solution idea, and favour the theory of mechanical 
 mixture. Sabine's experiments furnish also some evidence of that slight diminution of 
 density in the upper parts of the beds of vapour which would arise from the decrease 
 of their own pressure. At Jamaica the dew point fell about 4.5 in 4080 feet. I have 
 calculated this diminution to be 3.5 for 5000 feet for an atmosphere of much less 
 density. 
 
 (Page 122) The tension of vapour given off in the process of evaporation is deter- 
 mined, not by the temperature of the evaporating surface, but by the elasticity of the 
 aqueous atmosphere already existing. I have often endeavoured by means of the 
 
 253 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 hygrometer to detect, within a limited circle, a difference in the elastic force of the vapour 
 incumbent on different surfaces of various temperatures, but without success ; the rising 
 vapour was always of the same quality, whether from water, vegetation, or ploughed 
 land, in sunshine or in shade. For the same reason the dew point is but little affected 
 by the increase of daily temperature from morning to afternoon, or by its subsequent 
 declension at night. But one of the most remarkable confirmations of the fact was 
 ascertained by Sabine upon the coast of Africa. While the sea breeze was blowing 
 upon that station the hygrometer denoted the dew point to be about 60, but when the 
 wind blew strong from the land it approached in its character to a harmattan ; and the 
 point of precipitation was not higher than 37.5, the temperature of the air being 66. 
 Notwithstanding the heat of the evaporating surfaces in the interior of that continent 
 (Page 123), the burning sands of its desert yield so little vapour that it becomes atten- 
 uated by its diffusion, and there can be little doubt that the aqueous vapour incumbent 
 upon it, and which when wafted to the coast constitutes the true harmattan, is not of 
 greater force than that which rests upon the polar seas ; and that while the heat of the 
 air sometimes approaches to 90, the constituent temperature of the vapour is below 32. 
 The apparent permanency and stationary aspect of a cloud is often an optical deception 
 arising from the solution of moisture on one side of a given point as it is precipitated on 
 the other. No phenomenon is more common amongst mountains or upon hills by the 
 seaside than clouds upon the summits which appear to be perfectly immovable, although 
 a strong wind is blowing upon them at the time. That this should be the real state 
 of the case is clearly impossible, as so attenuated a body as constitutes the substance of the 
 clouds must obey the impulse of the air. The real fact is that the vapour which is 
 wafted by the wind is precipitated by the cold contact of the mountain, and is urged 
 forward in its course till borne beyond the influence which caused its condensation, it is 
 again exhaled and disappears. Keasoning from analogy we may conclude that the 
 process which thus proceeds under our eyes upon the summits of the hills likewise takes 
 (Page 124) place on either side of the planes of precipitation in the heights of the atmo- 
 sphere ; the vapour is continually condensed, as continually redissolved in the act of 
 precipitation, and the cloud appears to be unchanged and stationary. The quantity 
 of vapour in the atmosphere [in temperate climates, 1845 edition] in the different seasons 
 of the year (measured on the surface of the earth and near the level of the sea) follows 
 the progress of the mean temperature. This result of observation might readily have 
 been anticipated, for the rate of evaporation and the quantity which the air can support 
 are both obviously dependent upon the same progression. But this connection is not 
 discoverable in short periods, and the changes of diurnal temperature do not much affect 
 the quantity of elastic vapour. The air at night generally reaches the point of deposi- 
 tion even at the surface of the sea, but in a very gradual manner ; and at the same time 
 the supply from evaporation ceases. The progress of the vapour in fine weather may 
 often be very satisfactorily traced by means of the clouds. During the heat of the day 
 it rises from the surface of the land and water, and reaches its point of condensation in 
 greater or less quantities at different altitudes. Partial clouds are formed in different 
 parallel planes, which always maintain their relative distances. The denser forms of the 
 lower strata, as they float along with the wind, shew the greater abundance of the pre- 
 cipitation at the first point of deposition, while the feathery shapes and lighter texture 
 of the upper attest a rarer atmosphere. These clouds do not increase beyond a certain 
 (Page 125) point, but often remain stationary in quantity and figure for many hours ; but 
 as the heat declines they gradually melt away, till at length when the sun has sunk 
 below the horizon the ether is unspotted and transparent. The stars shine through the 
 night with undiminished lustre, and the sun rises in the morning in its brightest splendour. 
 The clouds again begin to form, increase to a certain limit, and vanish with the evening 
 shades. This gradation of changes which we often see repeated in our finest seasons, 
 might at first appear to be contrary to our principles ; and that precipitation should occur 
 254 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 with the increase of temperature, and disappear with its decline, would seem at first sight 
 to be diametrically opposite to all our conclusions. But a little consideration will shew 
 that these facts confirm our theory. The vapour rises and is condensed ; but in its 
 precipitation falls into a warmer air, where it again assumes the elastic form ; and as the 
 quantity of evaporation below is exactly equal to supply this process above, the cloud 
 neither augments nor decreases. When the sun declines, the surface of the earth cools more 
 rapidly than the air, evaporation decreases, but the dissolution of the cloud continues. 
 The supply at length totally ceases and the concrete vapour melts completely away. 
 The morning sun revives the exhalations of the earth, and the process of nimbification 
 again commences and again undergoes the same series of changes. The fall of the tem- 
 perature shifts a little the planes of deposition, but scarcely affects the total pressure 
 (Page, 126) of the vapour. The deposition of dew slightly diminishes the quantity, 
 but the first touch of the sun's rays restores it to the " blue expanse." When, however, 
 the natural equilibrium has been disturbed, when the temperature of the air has become 
 equalized through various successive strata by the beds of vapour with which they are 
 embued, the decline of the day will often determine precipitation, and will increase its 
 amount if already established. The result of experiment has already shown that a greater 
 amount of rain falls while the sun is below than while it is above the horizon. The 
 pressure of the aqueous atmosphere separated from that of the aerial, generally exhibits 
 opposite changes to the latter. [This passage is modified in the 1845 edition, page 167.] 
 As the quantity of vapour increases it will mostly be found that the barometer falls, and 
 it rises with the decrease. This observation does not apply to the averages of the 
 different seasons, but to the daily fluctuations. This fact, so utterly irreconcilable to 
 the hypothesis which ascribes the rise and fall to the weight of the aqueous vapour, 
 confirms that which attributes them to the unequal expansion of balancing currents. 
 The prime source of this expansion we have supposed to be the elastic vapour, and this 
 experience confirms the theory. Great falls of the barometer are generally accompanied 
 by a temperature above the mean for the season, and great rises by one below the same. 
 This is a confirmation of the same nature as the last, and inseparably connected with it. 
 It is by the evolution of heat that the vapour principally acts. The mean temperature 
 which balances all irregularities must be the regular temperature of the climate, and, 
 cceteris paribus, that at which it must be most disposed to regularity ; variations on 
 either side of this point must produce corresponding retardations and accelerations ; and 
 these, if not general through the mass, annihilate the equipoise. The conclusions come 
 (Page 128) to may be briefly recapitulated thus. There are two distinct atmospheres, 
 mechanically mixed, surrounding the earth, whose relations to heat are different and 
 whose states of equilibrium, considering them as. enveloping a sphere of unequal 
 temperature, are incompatible with each other. The first is a permanently elastic fluid, 
 expansible in an arithmetical progression by equal increments of heat, decreasing in 
 density and temperature according to fixed ratios as it recedes from the surface, and 
 (Page 129) whose equipoise under such circumstances would be maintained by a re- 
 gular system of antagonistic currents. The second is an elastic fluid, condensable by 
 cold with evolution of caloric, increasing in force in geometrical progression with equal 
 augmentation of temperature ; permeating the former and moving in its interstices as a 
 spring of water flows through a sand rock. When in a state of motion this intestine 
 filtration is retarded by the inertia of the gaseous medium, but in a state of rest the 
 particles press only upon those of their own kind. The density and temperature of this 
 fluid have a tendency likewise to decrease as its distance from the surface augments, 
 but by a less rapid rate than that of the former. The equipoise would be maintained 
 by the adaptation of the upper parts of the medium in which it moves to the progression 
 of its temperature and by a current flowing from the hotter parts of the globe to the 
 colder. Constant evaporation on the line of greatest heat and increasing precipitation 
 at every other situation, would be the necessary accompaniment of this balance. Now 
 
 255 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 the conditions of these two states of equilibrium are essentially opposed to each other. 
 The vapour or condensable elastic fluid is forced to ascend in a fluid whose heat decreases 
 much more rapidly than its own natural rate ; and it is therefore condensed and preci- 
 pitated in the upper regions. Its latent caloric is evolved by the condensation and 
 communicated to the air, and it thus tends to equalize the temperature of the medium 
 in which it moves, and to constrain it to its own law. This process must evidently 
 (Page 130) disturb the equilibrium of the permanently elastic fluid by interfering with 
 that state of temperature and density which is essential to its maintenance. The system 
 of currents is unequally affected by the unequal expansion, and the irregularity is 
 extended by their influence, much beyond the sphere of the primary disturbance. The 
 decrease of this elasticity above is accompanied by an extremely important reaction upon 
 the body of vapour itself ; being forced to accommodate itself to the circumstances of 
 the medium in which it moves, its own law of density can only be maintained by a 
 corresponding decrease of force below the point of condensation ; so that the temperature 
 of the air at the surface of the globe is far from the term of saturation, and the current 
 of vapour, which moves from the hottest to the coldest points, penetrates from the 
 equator to the poles, without producing that condensation in mass which would other- 
 wise cloud the whole depth of the atmosphere with precipitating moisture. The clouds 
 are thereby confined to parallel horizontal planes with intermediate clear spaces, and 
 thus arranged are offered to the influence of the sun, which dissipates their accumulations 
 and greatly extends the expansive power of the elastic vapour. The power of each 
 fluid being in proportion to its elasticity, that of the vapour compared with the air can 
 never at most exceed 1 : 30 ; so that the general character of the mixed atmosphere is 
 derived from the latter, which, in its irresistible motion, must hurry the former along 
 (Page 131) with it. The influence however of the vapour upon the air, though slower 
 in its action, is sure in its effects ; and the gradual and silent processes of evaporation and 
 precipitation govern the boisterous powers of the winds. By the irresistible force of 
 expansion mechanically applied they give rise to undulations in the elastic fluid ; the 
 returning waves dissipate the local influences, and the accumulated effect is annihilated, 
 again to be reproduced. By an invisible but ever active agency the waters of the deep 
 are raised into the air, whence their distribution follows as it were by measure and 
 weight, in proportion to the beneficial effects which they are calculated to produce. By 
 gradual, but almost insensible, expansions the equipoised currents of the atmosphere are 
 disturbed, the stormy winds arise, and the waves of the sea are lifted up, and that 
 stagnation of air anc^ water is prevented which would be fatal to animal existence. But 
 the force which operates is calculated and proportioned ; the very agent which causes 
 the disturbance bears with it its own check, and the storm as it vents its own force, is 
 itself setting the bounds of its own fury. The complicated and beautiful contrivances by 
 which the waters are collected " above the firmament " and are at the same time derived 
 from the waters which are '* below the firmament," are inferior to none of those adapta- 
 (Page 132) tions of Infinite Wisdom which are perpetually striking the inquiring mind 
 in the animal and vegetable kingdoms. Had it not been for this nice adjustment of 
 conflicting elements, the clouds and concrete vapours of the sky would have reached from 
 the surface of the earth to the remotest heavens, and the vivifying rays of the sun 
 would never have been able to penetrate through the dense mists of perpetual precipi- 
 tation. Nor can I here refrain from pointing out a confirmation which incidentally 
 arises of the Mosaic account of the creation of the atmosphere. The question has 
 been asked, How is it that light is said to have been created on the first day, and day 
 and night to have succeeded each other, when the sun has been described as not having 
 been produced till the fourth day? This is apparently a contradiction. But Moses 
 records that God created on the first day the earth covered with waters, and did not till 
 its second revolution upon its axis call the firmament into existence. Now one result of 
 the previous inquiry has been that a sphere unequally heated and covered with water 
 256 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 must be enveloped in an atmosphere of steam, which would necessarily be turbid in its 
 whole depth with precipitating moisture. The exposure of such a sphere to the orb 
 of day would produce illumination upon it ; that dispersed and equal light which now 
 {Page 133) penetrates on a cloudy day, but the sun could not have been visible from its 
 surface. On the second day the permanently elastic firmament [= air] was produced, 
 and we have seen that the natural consequences of this mixture of gaseous matter and 
 vapour must have been that the waters would begin to collect above the firmament and 
 divide themselves from the waters which were below the firmament. [ u Waters " here 
 then is used in its most general sense, and in the case of those above the firmament may 
 be equivalent to clouds, hail, snow, or other atmospheric condition of the aqueous 
 element.] The clouds would thus be confined to plains [ = planes] of precipitation, and 
 exposed to the influence of the winds and still invisible sun. The gathering together of 
 the waters, and the appearance of dry land, would present a greater heating surface and 
 a less surface of evaporation, and the atmosphere during this revolution would let fall its 
 excess of condensed moisture ; and upon the fourth day it would appear probable, even 
 to our short-sighted philosophy, that the sun would be enabled to dissipate the still 
 remaining mists and burst forth with splendour. Granville Penn's * Estimate of the 
 Mineral and Mosaical Geologies ' gave me the first hint upon the subject. I had, how- 
 ever, already unconsciously proved the necessity of the turbid state of the atmosphere 
 previous to the creation of the firmament. 
 
 {Page 139) Nee non et in conviviis mensisque nostris vasa quibus esculentwn additur 
 sudorem repositoriis linquentia \liquentia in 1845 edition] diras tempestates prsenunti- 
 ant. C. Plin. Nat. Hist., lib. xviii. This passage has thus been translated into Eng- 
 lish : " And to conclude and make an end of this discourse ; whensoever you see at any 
 feast the dishes and platters whereon your meat is served up to the board sweat or stand 
 {Page 140) of a dew, and leaving that sweat which is resolved from them either upon 
 dresser, cupboard, or table, be assured that it is a token of terrible tempests approach- 
 ing." Philemon Holland, 1601. This indicates that the viands were colder than the 
 place they were brought into. I was induced to make experiments upon the deposition 
 {Page 141) of dew on cooled glasses and vessels of brass. The Academicians del Cimento 
 {Page 142) had previously experimented in the same way as regards principle. They 
 cooled conical glass vessels and regarded the frequency of the drops which fell from the 
 downwardly-placed point as a measure of the humidity of the air. Le Eoi measured 
 the temperature at which dew was formed, and judged of the humidity of the air by 
 the greater or less degree of depression necessary to produce precipitation. Dalton in 
 * Mem. Lit. and Phil. Soc. Manchester,' vol. v., also measured the dew point as indi- 
 cated by cooled vessels. Wollaston's cryophorus gave me the hint for making my 
 hygrometer. I found metal to be no better than glass, when the glass is black and 
 {Page 149) viewed by a reflected light. This hygrometer is simple ; its graduation is 
 not arbitrary ; and it is not liable to deterioration ; in proper hands it cannot give 
 erroneous results. The determinations are as strictly comparable one with another 
 under all circumstances 'as those of the barometer or thermometer. When consulted 
 with a view of predicting the greater or less probability of rain or other atmospheric 
 changes, two things are to be principally attended to the difference between the con- 
 stituent temperature of the vapour and the temperature of the air ; and the variation 
 of the dew point. In general the chances of rain or other precipitation of moisture 
 {Page 150) from the atmosphere may be regarded as in inverse proportion to the difference 
 between the two thermometers ; but in making this estimate regard must be had to 
 the time of day at which the observation is made. In settled weather the dryness of 
 the air increases with the diurnal heat and diminishes with its decline ; for the consti- 
 tuent temperature of the vapour remains nearly stationary. Consequently a less 
 difference in the morning or evening is equivalent to a greater in the middle of the day. 
 But to render the observation most completely prospective regard must be had to the 
 PART. II. No. 9. s 257 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 movement of the dew point. As the elasticity of the vapour increases or declines so 
 does the probability of the formation and continuation of rain. An increasing difference, 
 therefore, between the temperature of the air and the diiference of the point of condensa- 
 tion, accompanied by a fall of the latter, is a sure prognostication of fine weather ; 
 while diminished heat and a rising dew point infallibly portend a rainy season. In 
 winter when the range of the thermometer during the day is small, the indication of the 
 weather must be taken more from the actual rise and fall of the point of condensation 
 than from the difference between it and the temperature of the air. It must be 
 {Page 151) remembered that a state of saturation may exist and precipitation even take 
 place in fine weather, and under a cloudless sky ; but this is when the diurnal decline of 
 the temperature of the air near the surface of the earth falls below an unfluctuating term 
 of precipitation ; and it is probable that at some period or other of the twenty-four hours- 
 this term is always passed. The radiation of the earth, in the absence of the sun, cools 
 the stratum of air in contact with it ; and a light precipitation takes place, of so little 
 density as totally to escape the observation of the eye. At other times it becomes 
 visible and assumes the appearance of mist or fog. Under such circumstances the 
 hygrometer will sometimes exhibit a different kind of action. If it be brought from an 
 atmosphere of a higher temperature into one of a lower degree, in which condensed 
 aqueous particles are floating, the mist will begin to form at a temperature several 
 degrees higher than that of the air. The heat emanating from the ball of the instru- 
 ment dissolves the particles of water and forms an atmosphere around it of greater 
 elasticity than the surrounding medium ; so that when it is put in action the point of 
 deposition is proportionately raised. This action does not at all interfere with the 
 determination of the real force and quantity of vapour ; for in all such cases the full 
 saturation of the atmospheric temperature must take place, and consequently the tempe- 
 rature of the vapour must be coincident with that of the air. This kind of precipitation, 
 which may often be detected by the hygrometer when it would otherwise escape notice, 
 {Page 152) far from being indicative of rain, generally occurs in the most settled 
 weather. It is analogous to the formation of dew and is dependent upon the same 
 cause, the radiation of the earth which only takes place under an unclouded sky. A 
 sudden change in the dew point is generally accompanied by a change of wind ; but the 
 former sometimes precedes the latter by a short interval ; and the course of the aerial 
 currents may be anticipated before it affects the direction of the weathercock, or even 
 the passage of smoke. My own experience and the testimony of others assure me that 
 the hygrometer when applied is more to be depended upon than any instrument which 
 has yet been proposed. Even when its indications are contrary to those of the baro- 
 meter, reliance may be placed upon them ; but simultaneous observations of the two- 
 most usefully correct each other. The rise and fall of the mercurial column is, most 
 probably, primarily dependent upon the state of the upper regions of the atmosphere 
 with regard to heat and moisture. Local chemical [physical in 1845 edition] alterations 
 of its density, thus partially brought about, are mechanically adjusted, and the baro- 
 meter gives us notice of what is going on in inaccessible regions. A rise in the dew 
 point, accompanied by a fall of the barometer, is an infallible indication that the whole 
 mass of the atmosphere is becoming imbued with moisture, and a copious precipitation 
 may be looked for. If the fall of the barometer take place at the same time that the 
 point of precipitation is depressed, we may conclude that the expansion which occasions 
 (Page 153) the former has arisen upon some distant point, and wind, not rain, will be 
 the result. But when the air attains the point of precipitation with a high barometer, 
 we may infer that it is a transitory and superficial effect, produced by a local depression 
 of temperature. Thus does the .hygrometer mark with infallible precision the com- 
 parative degrees of moisture and dryness in the atmosphere. But it is of wider applica- 
 tion. By means of tables we can find with the utmost accuracy and ease the positive 
 weight of aqueous vapour diffused through any given portion of space, and its force or 
 258 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 elasticity is measured by the column of mercury which it is capable of supporting ; we 
 discover at once the proportion of moisture in any space to the quantity which would be 
 required to saturate it, or what has been called the true natural scale of the hygrometer ; 
 we can calculate with perfect ease the specific gravity of any mixture of air and aqueous 
 vapour ; and we can measure the force and quantity of evaporation. [He then gives 
 data upon which the tables are formed, which strictly belong to the physical properties 
 of aqueous vapour, not to climate ; but a few remarks are given here.] By two simple 
 (Page 161) observations and easy calculations we ascertain the following points of the 
 utmost interest in meteorology : 
 
 Temp, of air, 70. 
 
 Dew point, 55. 
 
 Degree of dryness on thermometric scale, 15. 
 
 Degree of moisture on hygrometric scale, 618. 
 
 Weight of vapour in a cubic foot, 5.175 grains. 
 
 (Page 162) The state of the weather assumed above would constitute fine weather ; 
 and one of two things, or a modification of both, must happen before any precipitation 
 of water could take place either the temperature of the air must fall below 55, or the 
 quantity of vapour must increase to 8.392 grains in the cubic foot, the maximum 
 quantity which could exist at 70; or the point of condensation may become inter- 
 mediate by a corresponding rise and fall of the two. In the first case the precipitation 
 would probably be only slight and transitory, such as mist or fog ; in the second case it 
 would assume the form of hard rain and storms ; while in the third, some conjecture 
 might be formed of its probable duration and quantity, according as one or other of its 
 causes prevailed. The hygrometer may also be applied to indicate the force and quantity 
 of evaporation. Dalton ascertained that the quantity of vapour evaporated in a given 
 time bore an exact proportion to the force of vapour at the same temperature. The 
 atmosphere obstructs its diffusion, which would otherwise be instantaneous as in vacuo, 
 but this obstruction is overcome with a celerity proportioned to the force of the vapour. 
 The retardation is caused by the vis inertiee of the particles of air, and is similar to that 
 which a stream of water meets with in descending among pebbles. In ascertaining this 
 point at ordinary atmospheric temperatures regard must be had to the force of vapour 
 already existing in the air. For instance, if water at 57 were the subject, the force of 
 vapour at that temperature is -^ of the force at 212 ; and one might expect the force of 
 evaporation to be -^ also ; but if it should happen that an aqueous vapour to that 
 amount does already exist, the evaporation would be nothing at all. On the other hand, 
 if the aqueous vapour were less than that, suppose half of it, then the effective force 
 would be y^oth of that from boiling water ; in short, the evaporative force must be univer- 
 sally equal to that of the temperature of the water diminished by that already existing 
 in the atmosphere. But the air, by its mechanical action, has another influence upon 
 the rate of evaporation. When calm and still it merely obstructs the process ; but 
 when in motion it increases its effect in direct proportion to its velocity by removing the 
 vapour as it forms. Dalton fixes the extremes that are likely to occur in ordinary 
 circumstances at 120 and 189 grains per minute from a vessel 6 in. in diameter at 212. 
 
 (Page 164) The following table shews the force of vapour and the full evaporating 
 force of every degree of temperature from 18 to 85, expressed in grains of water that 
 would be raised per minute from a vessel 6 in. in diameter, supposing there were no 
 vapour already in the atmosphere : 
 
 T. Force of vapour. Evaporative force in grains. 
 
 212 30. 000 iu. 120 154 189 
 
 18, .131 .52 .67 .82 
 
 19 .135 .54 .69 .85 
 
 20 .140 .56 .71 .88 
 
 21 .146 .58 .73 .91 
 
 22 .152 .60 .77 .94 
 
 s 2 253 
 
AQUEOUS VAPOUR 1823. Danioll. 
 
 NOTES. 
 
 T. 
 
 Force of vapour. 
 
 Evaporative force in grains. 
 
 23 
 
 .158 
 
 .62 
 
 .79 
 
 .97 
 
 
 24 
 
 .164 
 
 .65 
 
 .82 
 
 1.02 
 
 
 25 
 
 .170 
 
 .67 
 
 .86 
 
 1.05 
 
 
 26 
 
 .176 
 
 .70 
 
 .90 
 
 1.10 
 
 
 27 
 
 .182 
 
 .72 
 
 .93 
 
 1.13 
 
 
 28 
 
 .188 
 
 .74 
 
 .95 
 
 1.17 
 
 
 29 
 
 .194 
 
 .77 
 
 .99 
 
 1.21 
 
 
 30 
 
 .200 
 
 .80 
 
 1.03 
 
 1.26 
 
 
 31 
 
 .208 
 
 .83 
 
 1.07 
 
 1.30 
 
 
 32 
 
 .216 
 
 .86 
 
 1.11 
 
 1.35 
 
 
 33 
 
 .224 
 
 .90 
 
 1.14 
 
 1.39 
 
 
 34 
 
 .232 
 
 .92 
 
 1.18 
 
 1.45 
 
 
 35 
 
 .240 
 
 .95 
 
 1.22 
 
 1.49 
 
 
 36 
 
 .248 
 
 .98 
 
 1.26 
 
 1.54 
 
 
 37 
 
 .256 
 
 1.02 
 
 1.31 
 
 1.60 
 
 
 38 
 
 .264 
 
 1.05 
 
 .35 
 
 1.65 
 
 
 39 
 
 .272 
 
 1.09 
 
 .40 
 
 1.71 
 
 
 40 
 
 .280 
 
 1.13 
 
 .45 
 
 1.78 
 
 
 41 
 
 .292 
 
 1.18 
 
 .51 
 
 1.85 
 
 
 42 
 
 .304 
 
 1.22 
 
 .57 
 
 1.92 
 
 
 43 
 
 .316 
 
 1.26 
 
 .62 
 
 1.99 
 
 
 44 
 
 .328 
 
 1.31 
 
 .68 
 
 2.06 
 
 
 45 
 
 .340 
 
 1.36 
 
 .75 
 
 2.13 
 
 
 46 
 
 .352 
 
 1.40 
 
 1.80 
 
 2.20 
 
 
 47 
 
 .364 
 
 1.45 
 
 1.86 
 
 2.28 
 
 
 48 
 
 .376 
 
 1.50 
 
 1.92 
 
 2.36 
 
 
 49 
 
 .388 
 
 1.55 
 
 1.99 
 
 2.44 
 
 
 50 
 
 .400 
 
 1.60 
 
 2.06 
 
 2.51 
 
 /. 
 
 51 
 
 .414 
 
 1.66 
 
 2.13 
 
 2.61 
 
 
 52 
 
 .428 
 
 1.71 
 
 2.20 
 
 2.69 
 
 
 53 
 
 .444 
 
 1.77 
 
 2.28 
 
 2.78 
 
 
 54 
 
 .460 
 
 1.83 
 
 2.35 
 
 2.88 
 
 
 55 
 
 .476 
 
 1.90 
 
 2.43 
 
 2.98 
 
 
 56 
 
 .492 
 
 1.96 
 
 2.52 
 
 3.08 
 
 
 57 
 
 .508 
 
 2.03 
 
 2.61 
 
 3.19 
 
 
 , 58 
 
 ,526 
 
 2.10 
 
 2.70 
 
 3.30 
 
 
 59 
 
 .543 
 
 2.17 
 
 2.79 
 
 3.41 
 
 
 60 
 
 .560 
 
 2.24 
 
 2.88 
 
 3.52 
 
 
 61 
 
 .577 
 
 2.31 
 
 2.98 
 
 3.63 
 
 
 62 
 
 .594 
 
 2.39 
 
 3.07 
 
 3.76 
 
 
 63 
 
 .615 
 
 2.46 
 
 3.16 
 
 3 37 (3,87 in 1845 
 ( Edition. 
 
 64 
 
 .636 
 
 2.54 
 
 3.27 
 
 3.99 
 
 
 65 
 
 .657 
 
 2.62 
 
 3.37 
 
 4.12 
 
 
 66 
 
 .678 
 
 2.70 
 
 3.47 
 
 4.24 
 
 
 67 
 
 .699 
 
 2.79 
 
 3.59 
 
 4.38 
 
 
 68 
 
 .722 
 
 2.88 
 
 3.70 
 
 4.53 
 
 
 69 
 
 .745 
 
 2.98 
 
 3.83 
 
 4.68 
 
 
 70 
 
 .770 
 
 3.08 
 
 3.96 
 
 4.84 
 
 
 71 
 
 .796 
 
 3.18 
 
 4.09 
 
 5.00 
 
 
 72 
 
 .822 
 
 3.29 
 
 4.23 
 
 5.17 
 
 
 73 
 
 .849 
 
 3.40 
 
 4.37 
 
 5.34 
 
 
 74 
 
 .877 
 
 3.52 
 
 4.52 
 
 5.53 
 
 
 75 
 
 .906 
 
 3.65 
 
 4.68 
 
 5.72 
 
 
 76 
 
 .936 
 
 3.76 
 
 4.83 
 
 5.91 
 
 
 77 
 
 .966 
 
 3.88 
 
 4.99 
 
 6.10 
 
 
 78 
 
 .997 
 
 4.00 
 
 5.14 
 
 6.29 
 
 
 79 
 
 1.028 
 
 4.16 
 
 5.35 
 
 6.54 
 
 
 80 
 
 1.060 
 
 4.28 
 
 5.50 
 
 6.73 
 
 ~ 
 
 81 
 
 1.093 
 
 4.40 
 
 5.66 
 
 6.91 
 
 
 82 
 
 1.127 
 
 4.56 
 
 5.86 
 
 7.17 
 
 
 83 
 
 1.162 
 
 4.68 
 
 6.07 
 
 7.46 
 
 
 84 
 
 1.198 
 
 4.80 
 
 6.28 
 
 7.75 
 
 
 85 
 
 1.235 
 
 4.92 
 
 6.49 
 
 g 01 |8.04inl845 
 
 (Page 165) The first column contains the degree of temperature ; the second, the 
 UoO 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 corresponding force of vapour ; the third the amount of evaporation per minute from a 
 vessel of 6 in. in diameter in calm weather ; the fourth is the amount in a moderate 
 breeze ; and the fifth, in a high wind. The use of the table is this. Let it be required 
 to know the force of evaporation at the existing state of the atmosphere ; find the point 
 of condensation by the hygrometer ; subtract the grains opposite that temperature, 
 either in the third, fourth, or fifth column, according to the state of the wind, from the 
 grains opposite to the temperature of the air in the same column, and the remainder 
 will be the quantity evaporated in a minute from a vessel of 6 in. in diameter under the 
 given circumstances. For example, let the point of condensation be 55, the tempera- 
 ture of the air 70 with a moderate breeze. The number opposite to 55 in the fourth 
 column is 2.43 and that opposite to 70 is 3.96 ; the difference 1.53 grain is the evapo- 
 ration per minute. But it is perhaps simpler and more convenient in many cases to 
 estimate the depth of the water evaporated in a day, and Dr. Young has shewn how 
 this may be done from Dalton's data. It happens that the column of mercury equiva- 
 lent to the elasticity of vapour expresses accurately enough the mean evaporation in 
 twenty-four hours. Mr. Dalton's experiment gives 45 grains per minute from a disc of 
 3Hnches. Now 45 x 60 x 24 = 64,800 grains or 256.6 cubic inches, which would 
 {Page 166) make a cylinder 30.9 in. in height on a base 3in. in diameter ; and this 
 differs only -^ from the weight of the column of mercury. We may therefore assume 
 that the mean daily evaporation is equal to the tabular number expressing the elasticity 
 of the vapour, sometimes exceeding it or falling short of it about one-fourth ; and we 
 may readily allow for the effect of the moisture of the atmosphere by deducting the 
 number corresponding to the temperature of deposition. Thus supposing the mean 
 temperature of twenty-four hours to be 60 and that of the dew point 50, the evapora- 
 tion will be equal to .560 .400=. 16 in. It is evident that these estimates can be but 
 mere approximations ; for till we can obtain some accurate measure of the velocity of 
 the wind, they must be liable to great uncertainty. They are, however, as much to be 
 relied upon as the registers of the evaporating gauge in common use, whose only proper 
 application can be to furnish a rough estimate of the state of atmospheric saturation 
 and the point of deposition. The notion that they afford the absolute measure of the 
 quantity of vapour raised into the air is absurd, for the instrument can only give the 
 amount of evaporation from the shallow body of water in the place where it has been 
 fixed. The conditions which modify the process vary almost ad infinitum. They vary 
 on the land and on the water ; they vary in sunshine and in the shade ; they vary as 
 land is more or less clothed with vegetation, or as water is more or less deep. The 
 evaporating gauge, so far from representing the circumstances of those bodies which yield 
 (Page 167) the great body of water on the earth's surface, probably does not correspond in 
 all essential particulars with a dozen puddles in the course of the year. The results of 
 the hygrometer accommodate themselves more easily to the ever varying conditions of 
 the problem, and from these we can infer the effect of each combination of circum- 
 stances, and the capacity of the air for moisture modified by the velocity of the winds. 
 The expansion which vapour causes in air is not precisely similar to that occasioned 
 (Page 177) by heat; for while it dilates its parts it adds its own weight to the mixture. 
 Let it be required to know the specific gravity of air at 32 saturated with vapour com- 
 pared with dry air at the same temperature. Call the latter 1.00000 ; the quantity of 
 expansion will be .00720 ; which deducted from 1.00000 leaves .99280. Now, the 
 weight of a cubic foot of air under the conditions above-named is 558.131 grains, and 
 the weight of a cubic foot of vapour at 32 is 2.539 grains, which, the former being 
 1.00000, will be nearly .00455 ; and which, added to the .99280 before obtained, will 
 give .99735 for the specific gravity sought. Upon this principle I have constructed the 
 following table, by means of which the specific gravity of any mixture of atmospheric 
 air and aqueous vapour from to 90 may readily be found with sufficient precision. I 
 have made air under a pressure of 30 in. of mercury and at the temperature of 32 the 
 
 261 
 
AQUEOUS VAPOUR 
 
 1823. Daniell. 
 
 NOTES. 
 
 standard of comparison. The first column gives F. ; the second, the quantity due to 
 each degree of heat to be subtracted or added according as the temperature is above or 
 below the standard ; the third exhibits the expansion of volume occasioned by vapour 
 of the respective degrees of elasticity appropriate to the several degrees of heat, and is 
 always to be subtracted ; the fourth is the correction to be applied for the weight of the 
 vapour, and is constantly to be added; and the fifth is the correct specific gravity, sup- 
 posing the air saturated with moisture at the given temperature. 
 
 
 
 + .06666 
 
 1 
 
 + .06458 
 
 2 
 
 + .06249 
 
 3 
 
 + .06041 
 
 4 
 
 + .05833 
 
 5 
 
 + .05624 
 
 6 
 
 + .05416 
 
 7 
 
 + .05208 
 
 8 
 
 + .04999 
 
 9 
 
 + .04791 
 
 10 
 
 + .04583 
 
 11 
 
 + .04374 
 
 12 
 
 + .04166 
 
 13 
 
 + .03958 
 
 14 
 
 + .03749 
 
 15 
 
 + .03541 
 
 1G 
 
 + .03333 
 
 17 
 
 + .03124 
 
 18 
 
 + .02916 
 
 19 
 
 + .02708 
 
 20 
 
 + .02475 
 
 21 
 
 + .02291 
 
 22 
 
 + . 02083 
 
 23 
 
 + .01874 
 
 24 
 
 + .01666 
 
 25 
 
 + .01458 
 
 26 
 
 + .01249 
 
 27 
 
 + .01041 
 
 (Page 179) 
 
 
 28 
 
 + .00833 
 
 29 
 
 + .00624 
 
 30 
 
 + .00416 
 
 31 
 
 + .00208 
 
 32 
 
 . 0000 
 
 33 
 
 -.00208 
 
 34 
 
 -.00416 
 
 35 
 
 -.00624 
 
 36 
 
 -.00833 
 
 37 
 
 -.01041 
 
 38 
 
 -.01249 
 
 39 
 
 -.01458 
 
 40 
 
 -.01666 
 
 41 
 
 -.01874 
 
 42 
 
 -.02083 
 
 43 
 
 -.02291 
 
 44 
 
 -.02475 
 
 45 
 
 -.02708 
 
 46 
 
 -.02916 
 
 47 
 
 -.03124 
 
 48 
 
 -.03333 
 
 49 
 
 -.03541 
 
 50 
 
 -.03749 
 
 51 
 
 -.03958 
 
 52 
 
 -.04166 
 
 53 
 
 -.04374 
 
 54 
 
 -.04583 
 
 55 
 
 -.04791 
 
 56 
 
 -.04999 
 
 262 
 
 -.00226 
 
 + .00153 
 
 1.06593 
 
 -.00237 
 
 + .00159 
 
 1.06381 
 
 -.00247 
 
 + .00166 
 
 1.06168 
 
 -.00257 
 
 + .00172 
 
 1.05956 
 
 -.00267 
 
 + .00179 
 
 1.05745 
 
 -.00277 
 
 + .00185 
 
 1.05532 
 
 -.00287 
 
 + .00191 
 
 1.05320 
 
 -.00297 
 
 + .00197 
 
 1.05108 
 
 -.00307 
 
 + .00204 
 
 1.04896 
 
 -.00317 
 
 + .00210 
 
 1.04684 
 
 -.00327 
 
 + .00216 
 
 1.04472 
 
 -.00343 
 
 + .00224 
 
 1.04255 
 
 -.00357 
 
 + .00234 
 
 1.04043 
 
 -.00370 
 
 + .00243 
 
 1.03831 
 
 -.00384 
 
 + .00251 
 
 1.03616 
 
 -.00397 
 
 + .00260 
 
 1.03404 
 
 -.00410 
 
 + .00268 
 
 1.03191 
 
 -.00423 
 
 + .00276 
 
 1.02977 
 
 -.00437 
 
 + .00284 
 
 1.02763 
 
 -.00450 
 
 + .00292 
 
 1.02550 
 
 -.00467 
 
 + .00302 
 
 1.02310 
 
 -.00487 
 
 + .00314 
 
 1.02118 
 
 -.00507 
 
 + .00327 
 
 1.01903 
 
 -.00527 
 
 + .00339 
 
 1.01686 
 
 -.00547 
 
 + .00351 
 
 1.01470 
 
 -.00567 
 
 + .00363 
 
 1.01254 
 
 -.00587 
 
 + .00375 
 
 1.01037 
 
 -.00607 
 
 ; +.00387 
 
 1.00821 
 
 -.00627 
 
 + .00399 
 
 1.00605 
 
 -.00647 
 
 + .00411 
 
 1.00388 
 
 -.00667 
 
 + . 00423 
 
 1.00172 
 
 -.00694 
 
 + .00439 
 
 0.99953 
 
 -.00717 
 
 + .00454 
 
 0.99737 
 
 -.00747 
 
 + .00471 
 
 0.99516 
 
 -.00773 
 
 + .00486 
 
 0.99297 
 
 .00800 
 
 + .00502 
 
 0.99078 
 
 . 00827 
 
 + .00518 
 
 0.98858 
 
 -.00854 
 
 + .00533 
 
 0.98638 
 
 -.00880 
 
 + .00549 
 
 . 98420 
 
 -.00907 
 
 + .00564 
 
 0.98199 
 
 -.00934 
 
 + .00580 
 
 0.97980 
 
 .00974 
 
 + .00604 
 
 0.97756 
 
 .01014 
 
 + .00627 
 
 0.97530 
 
 .01054 
 
 + .00650 
 
 0.97305 
 
 .01094 
 
 + .00674 
 
 0.97105 
 
 .01134 
 
 + .00697 
 
 0.96855 
 
 .01174 
 
 + .00720 
 
 0.96630 
 
 .01214 
 
 + .00743 
 
 0.96405 
 
 .01254 
 
 + .00766 
 
 0.96179 
 
 .01294 
 
 + .00789 
 
 0.95954 
 
 .01334 
 
 + .00803 
 
 0.95720 
 
 .01380 
 
 + .00839 
 
 0.95501 
 
 .01426 
 
 + .00864 
 
 0.95272 
 
 .01480 
 
 + .00896 
 
 0.95042 
 
 .01534 
 
 + .00926 
 
 0.94809 
 
 .01586 
 
 + .00957 
 
 0.94580 
 
 .01640 
 
 + .00987 
 
 . 94348 
 
AQUEOUS VAPOUR 1823. Daniell. 
 
 NOTES. 
 
 57 
 58 
 59 
 
 180) 
 60 
 61 
 62 
 63 
 64 
 65 
 66 
 67 
 
 68 
 9 
 70 
 71 
 72 
 73 
 74 
 75 
 76 
 77 
 78 
 79 
 80 
 81 
 82 
 83 
 84 
 85 
 86 
 87 
 88 
 89 
 90 
 
 -.05208 
 -.05416 
 -.05624 
 
 .05833 
 .06041 
 .06249 
 .06458 
 .06666 
 .06874 
 .07083 
 .07291 
 .07499 
 .07708 
 .07916 
 .08124 
 .08333 
 .08541 
 08749 
 .08938 
 .09166 
 .09374 
 .09583 
 .09791 
 .09999 
 .10208 
 .10416 
 .10624 
 .10833 
 ,11041 
 ,11249 
 ,11458 
 ,11666 
 ,11874 
 12083 
 
 .01694 
 .01754 
 .01810 
 
 .01867 
 .01923 
 .01980 
 .02050 
 .02120 
 .02190 
 .02260 
 .02330 
 .02407 
 . 02484 
 .02567 
 .02654 
 .02740 
 .02830 
 .02923 
 . 03020 
 .03120 
 .03220 
 .03323 
 . 03427 
 .03533 
 .03643 
 .03756 
 . 03873 
 .03993 
 .04116 
 . 04243 
 . 04373 
 .04503 
 , 04633 
 ,04766 
 
 + .01017 
 + .01051 
 + .01083 
 
 + .01114 
 
 + .01146 
 + .01178 
 + .01217 
 
 ,01256 
 .01295 
 .01334 
 .01372 
 .01415 
 
 + .01457 
 + .01503 
 + .01551 
 + .01598 
 + .01648 
 + .01699 
 + .01752 
 + .01810 
 + .01861 
 + .01916 
 + .01973 
 + .02030 
 + .02090 
 + .02150 
 02213 
 02277 
 02343 
 02411 
 02486 
 02549 
 02618 
 
 + .02688 
 
 0.94115 
 0.93881 
 0.93649 
 
 0.93414 
 0.93182 
 0.92949 
 0.92709 
 0.92470 
 0.92231 
 0.91991 
 0.91751 
 0.91509 
 0.91265 
 0.91020 
 0.90773 
 0.90525 
 0.90277 
 0.90027 
 0.89794 
 0.89524 
 0.89267 
 0.89010 
 0.88755 
 0.88498 
 0.88239 
 0.87978 
 0.87716 
 0.87451 
 0.87186 
 0.86919 
 0.86655 
 0.86380 
 0.86111 
 0.85839 
 
 (Page 181) To find the specific gravity of any mixture of air and aqueous vapour, 
 proceed thus. Note the temperature and the point of condensation ; if they coincide, 
 that is to say, if the air be in a state of saturation, we shall find the specific gravity 
 required in the fifth column opposite to the proper degree of heat in the first column. 
 If the point of condensation be below the temperature we must look for the correction to 
 be applied separately for the heat in the second column. The quantity to be subtracted 
 for the vapour of the given degree must be sought for in the third column, and must be 
 applied minus the quantity due to its weight which stands beside it in the fourth. For 
 example, if we wish to know the specific gravity of a mixture of air and vapour of the 
 temperature of 60, and of which the dew point is 40, we find in the second column 
 opposite to 60 the number .05833, which deducted from 1.00000 leaves .94167. In the 
 third column opposite to 40, we have .00934, and beside it in the fourth .00580. Now, 
 .00934- .00580= .00354 ; which subtracted from .94167 leaves .93813 as the number 
 sought. It has been objected that time is occupied in making observations with my 
 (Page 187) hygrometer ; but then one good observation is worth a thousand approxi- 
 mations. I have not experienced any difficulty in making observations owing to the 
 time required. Moreover, by the ordinary instruments time is occupied in making 
 calculations, and these are uncertain. Bibl. Univ., April 1819, says : Saussure's hair 
 (Page 190) hygrometer changes in its degree of sensitiveness, so that the hair has to be 
 (Page 191) changed every two years. Humboldt says : Saussure's instrument is most 
 sensitive to the smallest changes of dryness, while De Luc's is most exact in very 
 moist air ; Saussure's instrument is liable to derangement in very high wind. Old 
 (Page 192) hygrometers, if not corrected, have a tendency to indicate too great dryness. 
 Leslie says hygroscopic substances are slow to receive their impressions, and hence 
 
 263 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 (Page 193) cannot be precise. All appear to lose tone. Saussure's hygrometer requires 
 (Page 194) excessive care in its formation; and it is difficult to make comparable 
 instruments. Moreover, the relations of its indications to the actual quantity of 
 (Page 195) vapour in the air has not been determined. It is to be added that errors 
 may arise from the disturbing influence of heat, the heat of the body being sufficient ; 
 (Page 196) the adhesion of dust, etc., the choking of the pivot of the wheel, and possibly 
 friction from the index. Saussure says, a perfect hygrometer should have a range suffi- 
 (Page 198) cient to indicate the smallest difference of humidity and dryness ; should 
 be sufficiently prompt in action to vary with the state of the air ; always read the same 
 under the same conditions ; be comparable with other hygrometers ; be affected only by 
 (Page 199) aqueous vapour ; all the degrees of the scale equal. Hutton suggested the 
 use of the dry and wet bulb thermometer for hygrometric purposes. Observations with 
 it may furnish data for solving the problem ; but abstruse calculations are necessary, and 
 many delicate and unsettled corrections. Leslie's form multiplies the source of error 
 (Page 200). The observation in its most simple form is by no means so easy to make 
 accurately as appears at first sight. It is almost impossible to prevent radiant heat 
 interfering with the result. The temperature of evaporation is no longer that constant 
 quantity which it is supposed to be, if dependent only upon the temperature of air, and 
 is liable to fluctuations with every change of place and every breath of wind. The 
 density of the air must also be taken into account, and it is allowed that the cold pro- 
 duced by evaporation from the moist bulb must depend in some measure upon the height 
 of the barometer. The formulas, corrections, etc., differ according to the authority, Leslie, 
 (Page 201) Anderson, Ivory and Gay-Lussac. [He then gives experiments shewing 
 (Page 202) the high degree of sensitiveness and accuracy of his hygrometer. In his 
 (Page 234) essay upon radiation of heat in the atmosphere, he has numerous observations 
 bearing upon aqueous vapour, but he does not describe any of the results as being due to 
 aqueous vapour. Those only are mentioned here in which aqueous vapour is referred 
 to; the others will be given under Temperature.] Scoresby in his * Journal/ p. 291, 
 says : In cloudy weather no freezing of the sea, I believe, ever occurs when the tempe- 
 rature is above 29 ; but in clear calm weather the sea, in the interstices of the ice, 
 generally freezes on the decline of the sun towards the meridian below the pole, though 
 the temperature be 32 or higher. In the instance now alluded to, the freezing com- 
 menced when the temperature was 36, being 73 or 8 above the freezing point of sea 
 water. Leslie found the effect on his differential thermometer to depend upon the 
 (Page 235) clearness of the atmosphere. [He has many observations in which he notices 
 the state of the sky, but he does not make any special reference to the influence of the 
 aqueous vapour. These observations belong to Temperature at London.] The oppres- 
 (Page 264) sive effe9t of close weather and sultry days may probably be accounted for 
 from the obstruction of the insensible perspiration of the body, which is prevented from 
 exhaling itself into the atmosphere, already surcharged with moisture ; while unimpeded 
 transpiration from the pores, when the air is more free from aqueous vapour, adds new 
 energy to all the vital functions. The mean quantity of vapour follows exactly the 
 (Page 269) changes of the mean monthly temperature, that is to say, the dew point 
 rises and falls with the increase and decrease of the heat. [This is based on observations 
 in London.] The force of radiation in May in London from the surface of the earth is 
 (Page 277) 13 ; in April it was 14. The reduction of this effect implies a rather more 
 (Page 279) clouded state of the atmosphere in May than in April. In July the increase 
 of the mean temperature appears to be wholly derived from the night. This must be 
 owing to the cooling power having been checked by a cloudy sky. In October, the 
 (Page '282) remaining heat of the earth is preserved from a needless expenditure, and 
 (Page 301) guarded from a dissipation by an increasing canopy of clouds. The curves 
 (Page 302) of monthly mean temperature and of the dew point [for London] shew how 
 closely the constituent temperature of the vapour follows the mean temperature of the 
 264 
 
AQUEOUS VAPOUR 1823. Daniell. NOTES. 
 
 air. It is more speedily diminished by the fall of the latter than it is increased by its 
 rise. Hence arises the contrast between the dryness of the spring and summer months 
 and the dampness of the autumn and winter. The force of the vapour appears to be 
 (Page 303) governed chiefly by the minima of temperature ; and a line connecting 
 together the points of greatest depression would not differ very essentially from the dew 
 point. A rise in the line is generally accompanied by a fall in the barometric curve 
 (Page 304). The variations of the aqueous atmosphere are greater for equal differences 
 at the upper than at the lower part of the thermometric scale. 
 
 2G5 
 
SCIENTIFIC UNION. 
 
 Srimtifir Simon. 
 
 The rapid progress of science now going on is, in part, the result of the 
 great increase in the number of workers. This is accompanied by a larger 
 and larger host of scientific serials. The consequence is that the student 
 finds an increasing difficulty in ascertaining what has been done, or is in 
 process of being accomplished, not only in his own special line of study, but 
 also, and more particularly, in such as do not immediately interest him. 
 Every student finds, from time to time, that he has a desire for full informa- 
 tion on subjects in these outlying sciences, for the purpose of throwing light 
 upon his special studies. The state of literature is such that he is frequently 
 daunted by the difficulties attending his research, or, if he perseveres, he finds 
 a great deal of time unnecessarily wasted. The remedy for this is the foca- 
 lisation of knowledge round a series of centres. The two main steps in the 
 process are, first, collection, and, next, classification. It is with this ulterior 
 object in view, that all persons interested in meteorology are earnestly asked 
 to forward their names and addresses, particulars as to the work they have 
 done in meteorological and other sciences, their present lines of study, ways 
 in which help is desired, and any other items that may occur to them. These 
 details will be classified, and, when the opportunity offers, selections from 
 them will be published. The Conductor will exercise careful discretion in 
 the selection, as also in the use he may make of the more private details. 
 The first list will be published in November, 1883 ; but correspondents are 
 requested to send in answers soon, in order to allow of ample time for their 
 classification, and for their utilisation in private correspondence in the 
 interests of correspondents. 
 
 In order to prevent any misconception, it may be stated that the Con- 
 ductor's object is solely to promote scientific union, and is no way intended 
 to be of a charitable nature in any pecuniary sense. If there is a sufficient 
 response to these requests, the same line of proceeding will hereafter be 
 suggested, from time to time, for the students in other branches of science. 
 
 Newspapers and scientific journals of all countries, willing to help in 
 this matter, are asked to make the above requests known to their readers. 
 
 Address, Conductor, " Scientific Eoll " office, 7 Bed Lion Court, Fleet 
 Street, London, E.C. 
 
 We are glad to find that some attention is being given to the subject of promoting 
 
 greater unanimity of action amongst our local Scientific Societies ; but up to the present 
 
 time the interest manifested has not been equal to what the importance of the movement 
 
 demands. In the course of the present session we hope the numerous committees of 
 
 266 
 
SCIENTIFIC UNION. 
 
 the local societies will consider the matter, and do what they can to help. The report 
 of the last Conference is given below ; and it is followed by extracts from a paper which 
 the author, Dr. Baker, has kindly allowed us to reprint, which enforce the great need 
 there is for combined systematic study of a subject which has hitherto been strangely 
 neglected. In early numbers of the " Scientific Boll," remarks will be offered upon the 
 systematic observations and plans of operation which have been made or adopted by 
 local societies. 
 
 CONFERENCE OF DELEGATES FROM SCIENTIFIC SOCIETIES, 
 
 Held Annually during the Meeting of the British Association. 
 
 Third Conference. 
 
 SOUTHAMPTON. 
 
 25th August, 1882. 
 
 MINUTES. 
 
 Society represented : 
 
 :l 
 
 . f Norwich Geological Society. 
 
 i^East Kent Natural History Society. 
 
 . Cardiff Naturalists' Society. 
 
 Leicester Literary and Philosophical Society. 
 
 Hertfordshire Natural History Society and 
 
 Field Club. 
 . Royal Cornwall Polytechnic Society. 
 . Geological Society of Glasgow. 
 . Yorkshire Naturalists' Union. 
 . Yorkshire Geological and Polytechnic Society. 
 . Belfast Naturalists' Field Club. 
 . Birmingham Natural History and Micro- 
 scopical Society. 
 
 Winchester College Natural History Society. 
 . > Epping Forest and County of Essex Natura- 
 . > lists' Field Club. 
 
 Natural History Society of Glasgow. 
 , Barnsley Naturalists' Society. 
 
 Present : 
 
 W. WHITAKER, B.A., F.G.S. 
 (In the Chair.) 
 
 PETER PRICE .... 
 F. T. MOTT, F.R.G.S. . 
 ALFRED T. BRETT, M.D. 
 H. GEORGE FORDHAM, F.G.S. 
 Rev. Canon ROGERS, M.A. . 
 D. CORSE GLEN, F.G.S. 
 CHAS. P. HOBKIRK, F.L.S. . 
 WM. CASH, F.G.S. 
 WILLIAM GRAY, M.R.I. A. . 
 CHARLES PUMPIIREY . 
 
 F. A. BATHER .... 
 RAPHAEL MELDOLA, F.R.A.S., F.C.S. 
 JOHN SPILLER, F.C.S. . 
 
 JOHN KIRSOP, F.S.A., Scot. . 
 THOMAS LISTER. 
 
 G. J. SYMONS, F.R.S 
 
 The Minutes of the Conference held at York, 6th September, 1881, were taken as 
 read, confirmed, and signed by the chairman. 
 
 Mr. Fordham read the following report of the committee appointed at the York 
 Conference: " Report of the committee, consisting of Sir Walter Elliot, Mr. G. J. 
 Symons, Mr. W. Whitaker, Mr. John Hopkinson, and Mr. H. G. Fordham, appointed 
 at the Conference of Delegates held at York, 6th September, 1881, (1) ' to take steps to 
 have the Conference of Delegates recognised by the Council of the British Association ' ; 
 and (2) ' to send out a circular to the various local scientific societies, pointing out 
 the work undertaken by the committees of the British Association, and the valuable 
 aid which may be given by these societies in that and other scientific work.' 
 
 "1. The General Committee of the British Association having referred to the 
 Council * to consider the number and position of delegates from scientific societies, and 
 the regulations which should be adopted for governing their relations to the Association,' 
 the committee have thought it better not to make the formal representation to the 
 Council contemplated in their instructions. Some communications on the subject have, 
 however, passed between individual members of the committee and the officers of the 
 Association. 
 
 267 
 
SCIENTIFIC UNION. 
 
 " The Council have appointed a committee to consider and report on the question 
 referred to them by the General Committee, and this committee having recommended to 
 the Council * that they be empowered to confer with delegates representing the societies, 
 to ascertain in what way the Association might be able to aid them in obtaining a 
 better organization and a more effective direction of their efforts in the cause of science,' 
 and the Council having adopted this recommendation, your committee was invited to 
 send one or two representatives to confer with the committee of the Council on the 
 subject. The meeting was held on March 28th, when Mr. Hopkinson and Mr. Fordham 
 attended on behalf of your committee, and the position and objects of the annual 
 Conference of Delegates were discussed at some length. The results of this discussion 
 are embodied in the report presented by the Council to the General Committee on 
 Wednesday.* 
 
 " 2. The committee have prepared and issued the circular to local scientific societies, 
 with a circular letter, drawing attention to the annual Conference, and to the rule of 
 the British Association under which delegates may become members of the General 
 Committee, asking for a discussion of the circular and enclosures, and giving information 
 as to the Conference to be held at Southampton. With this letter they sent a printed 
 copy of the minutes of the York Conference. 
 
 " The circular itself referred to the work of three committees of the British Associa- 
 tion (those on underground waters, erratic blocks, and underground temperatures), and 
 to investigations relating to the following subjects : Kainfall, periodical natural phe- 
 nomena, and the appearance of and damage done by injurious insects. The following 
 papers were enclosed with it : Mr. Symons' pamphlet on the * Arrangements for the 
 systematic observation and record of the rainfall of the British Isles,' a copy of the 
 table of monthly rainfall in Hertfordshire*and the form, with lists of plants, insects, 
 and birds recommended for observation, issued by the Meteorological Society. 
 A selected list of periodical natural phenomena (prepared by Mr. Hopkinson) and a list 
 of injurious insects (from Miss Ormerod's publications) were printed at the end of the 
 circular. 
 
 " The special thanks of the committee are due to Mr. Symons, and to the Meteoro- 
 logical Society, for copies of the pamphlet on rainfall, and of the phenological form, 
 and the committee have also to thank the editor of the * Scientific Eoll ' for reprinting 
 in his publication the minutes of the York Conference, and the papers issued by the 
 committee. About 200 copies of the circular, with the other papers enclosed, have 
 been sent out to local scientific societies. The committee regret that they have not 
 received many replies to their circular letter ; on the other hand, in some cases applica- 
 tions for copies of the papers have been received from societies whose existence was not 
 known to the committee, and no doubt a certain amount of interest has been aroused, 
 and some practical good has been achieved, by putting before a large number of local 
 scientific workers a definite proposal for systematic scientific work. The amount 
 received in 5s. subscriptions at the York Conference was 3 10s., and 1 has been since 
 received by the committee. The expenditure up to the York Conference for printing 
 and postage was 2 10s., and the expenditure since incurred in printing and issuing the 
 circular and other papers has been 4 14s., showing a deficiency of 2 14s. There will 
 also be some small additional expense in convening the present Conference." 
 
 The recommendations of the Council, which were adopted, after some discussion, by 
 the General Committee, were as follows :'(!) The omission in the rules (General Com- 
 mittee, Class B Temporary Members, 1) of the words " and the Secretary of such Society," 
 which follow the words, "or, in his absence, a delegate representing him." (2) The 
 appointment of a committee in order to draw up suggestions upon methods of more 
 systematic observation and plans of operation for local societies, together with a more 
 uniform mode of publication of the results of their work,' and also, ' that this committee 
 should draw up a list of local societies which publish their proceedings.' " 
 268 
 
SCIENTIFIC UNION. 
 
 The adoption of the report was moved by Mr. Mott, seconded by Mr. Price, and 
 unanimously agreed to. 
 
 The change made by the General Committee of the British Association in the rule of 
 the Association relating to the appointment of representatives of scientific societies on 
 that committee, by which the representation is now limited to the president of a 
 society, " or, in his absence, a delegate representing him," was discussed at some length. 
 It was pointed out that the presence of the president of a society at a meeting of the 
 Association, even if only for a single day, and without his taking any practical part in 
 the business of the General Committee, prevented his society being represented by a 
 delegate on the committee, and in order to obviate the inconvenience arising in this and 
 other ways from the wording of the rule, and to place in the hands of societies the 
 direct appointment of their representatives, it was moved by Mr. Price, seconded by 
 Mr. Glen, and unanimously resolved, that steps should be taken to amend the rule, so 
 that it should read, " A delegate appointed by any scientific society publishing trans- 
 actions." It was left to Mr. Fordham to bring this proposal before the Council and 
 General Committee at the earliest opportunity. 
 
 The chairman drew attention to the desirability of obtaining greater regularity and 
 method, and a nearer approach to uniformity of plan, in the publications of societies 
 having similar objects, and undertaking similar work. 
 
 After some discussion, Messrs. Meldola, Hopkinson, and Fordham were appointed a 
 committee for making the arrangements for the next Conference, to be held during the 
 Meeting of the British Association in 1883. 
 
 It was referred to the committee to obtain one or two papers on subjects of interest 
 to local scientific societies to be brought before the next Conference, in order to insure a 
 regular discussion of special questions, and several matters were suggested as being 
 suitable for consideration by the Conference. 
 
 Votes of thanks to the committee and to the chairman closed the proceedings. 
 
 THE SYSTEMATIC STUDY OF CAUSES OF SICKNESS 
 AND DEATHS. 
 
 BY HENRY B. BAKER, M.D., SECRETARY OF THE STATE BOARD OF HEALTH OF MICHIGAN. 
 
 \Eeprinted in part from the Annual Report of the Michigan State Board of Health for 1881.] 
 
 The first and most constant need of the sanitarian is accurate knowledge respecting 
 those most common of all occurrences sickness and deaths from diseases which 
 during years and series of years have afflicted mankind. If it seems strange that there 
 is so great lack of knowledge on such common subjects, it must be remembered that 
 sanitary science is one of the latest sciences, and that physicians, as such, have had no 
 need to record or to note many of those classes of facts which form the foundation of 
 sanitary science, though some have had occasion to contribute greatly thereto. The 
 prevention of sickness has not been their work, and the collection of facts respecting 
 vast numbers of cases of sickness or deaths involves labour and expense too great to be 
 borne by individuals, unless the knowledge gained thereby is such as will advance the 
 work in which they are engaged. It has not been apparent that sanitary science would 
 greatly advance the art of healing or the science of therapeutics, for which other classes 
 of facts are needed, and for which they have been diligently collected, in times past. 
 Though it is possible that the science of therapeutics might be fostered and advanced 
 
 269 
 
SCIENTIFIC UNION. 
 
 by crovernmental aid, there seems to be no especial need for such aid so long as it is for 
 the pecuniary advantage of individuals to perfect their knowledge of therapeutics in 
 order to lead in the practice or teaching of their profession. But with sanitary science 
 the case is very different, there never has been, and there is not now in this State, any 
 class of persons having such an income from any public-health service by the indi- 
 vidual citizen as will permit of any effort for the collection of those facts which are 
 essential to the beginning of sanitary science. In the statement just made I do not 
 forget that progress in sanitary science and improved health-service increases the 
 incomes of individuals generally throughout the State ; this is undoubtedly true, but it 
 does so by lessening expenditures and by increasing the ability to labour in ordinary 
 and extraordinary pursuits. It is plain, therefore, that we cannot expect much progress 
 in sanitary science without some such associated effort as that afforded by governments 
 -State, National, and local. The old saying that what is everybody's business is no- 
 body's business " is particularly applicable in this connection ; for though it is readily 
 granted by every one we meet that "health is wealth," that "public health is public 
 wealth," that " an ounce of prevention is worth a pound of cure," and that measures 
 for the promotion of health are of vital consequence to every person, yet, except the 
 government aids, there is now no person who can get a living by labouring for the 
 prevention of sickness. 
 
 HOW CAN A GOVERNMENT PROMOTE SANITARY SCIENCE? 
 
 The chief duty of a government is to do for the safety of a people whatever they 
 are unable singly or by practicable voluntary associations to do for themselves. If, as 
 is now known to be the case, people die or suffer in great numbers from lack of know- 
 ledge which only the government can collect and diffuse among them, evidently it is 
 one of the highest duties of the government to collect and diffuse that knowledge. 
 That hundreds of such deaths have occurred in this State in every year is now 
 established by good evidence. 
 
 WHAT KNOWLEDGE IS NEEDED FOR THE PREVENTION OF DEATHS. 
 
 Manifestly the first requisite for the prevention of deaths is a knowledge of the 
 causes of the deaths. This has long been recognized by intelligent legislators, and in 
 most civilized countries "vital statistics" have for many years been regularly and 
 systematically collected. The same is true in many of the States of this Union. The 
 history of progress in public-health movements shows that sooner or later the facts 
 thus collected usually lead to some organized work for the prevention of deaths ; thus 
 in England, Annual Keports by the Kegistrar General relative to vital statistics have 
 been published since the year 1838, while Eeports by the Medical Officer of the Privy 
 Council date from the year 1858, showing that after the beginning of vital statistics in 
 England, twenty years elapsed before a general Board of Health was established with 
 the view of attempting to systematize the public-health work, and make it more 
 effective. In this country, in Massachusetts, vital statistics have been collected since 
 1842, and in 1869 a State Board of Health was established for the prevention of those 
 deaths which the vital statistics showed to be most numerous. During the twenty- 
 seven years preceding the establishment of a State Board of Health in Massachusetts, 
 the statistics of deaths and their causes had been collected, published, and studied by 
 citizens of that State, and the evidence was conclusive that many deaths occurred from 
 causes known to be preventable, and many more occurred from diseases believed to be 
 preventable or avoidable. In Michigan, vital statistics have been collected since 1868, 
 and the State Board of Health was organized in 1873, following the first inquiry for 
 facts more speedily than in the older countries, partly because the vital statistics of 
 Michigan soon showed that in Michigan as in Massachusetts, there were many pre- 
 270 
 
SCIENTIFIC UNION. 
 
 ventable or avoidable causes of sickness and death, and suggested a similar agency for 
 communicating to the people the knowledge necessary to avoid or prevent deaths from 
 such causes, It must not be understood that the vital statistics alone are sufficient to 
 give this important knowledge. It is said that a single bone enabled Owen to construct 
 or reproduce the skeleton and form of an extinct species of animals, and subsequent 
 discoveries of fossil remains confirmed his hypothesis and heralded another of the grand 
 triumphs of mind over the difficult problems with which thinking minds everywhere 
 are engaged. But it was to Owen, the diligent student of anatomy, the close 
 observer of the many ways in which organ is correlated with function, and function 
 with function, the learned teacher of the fundamental laws of structure and of the 
 history and philosophy of structural development it was to the keen eye and mind of 
 such a man, and not to the mere delver in the earth by whose spade the bone was 
 brought to light, that the communicative fossil disclosed its secrets of the past, its 
 vision of the perfect form that should be revealed. 
 
 Thus it is not to the mere compiler of vital statistics that there is given a compre- 
 hensive view of the relations which the various classes of deaths bear to the varying 
 conditions of soil, climate, age, occupation, nationality, social custom, individual habit, 
 and pecuniary circumstances, by which the people of a State are surrounded, and of the 
 various means of prevention or avoidance, direct and indirect, by which it is possible to 
 lessen the death-rate of a State, diminish its burden of sickness, crime, and poverty, 
 prolong the lives of its inhabitants, and promote their comfort, welfare, and happiness. 
 
 The man or the body of men who, from its vital statistics, shall construct the public- 
 health service of a State must bring to the task the knowledge which can be acquired 
 only at the feet of the masters of the medical sciences, and in the every-day walks of the 
 physician ; the familiarity with the manifold forms and habits of minute organic bodies, 
 both animal and vegetable, which only the biologist has attained ; the command of the 
 inorganic substances and forces of nature which is bestowed only in the laboratory of the 
 chemist ; the knowledge of the formation and relative position of rocks and soils and of 
 the relations of these to drainage and water-supply which is the reward of the geologist ; 
 the knowledge of climate which is the heritage of the meteorologist ; the knowledge of 
 the principles of government and of the moral nature of man which characterizes the 
 lawyer ; the power of commanding the attention and addressing the conscience of the 
 people which is the glory of the orator and the preacher, these qualifications and more 
 are requisite not only to that study of vital statistics which shall discover the preventable 
 causes of deaths, and elaborate practicable means for their removal or control, but also 
 to that successful adaptation of means to ends by which the people shall be led to adopt 
 and enforce practicable measures for their own protection and safety, 
 
 USES OF VITAL STATISTICS. 
 
 To vital statistics we are indebted not only for evidence showing the necessity of 
 effort for the prevention of deaths, but such statistics are needed for constant reference in 
 studying methods by which the deaths may be prevented. Before we can act intelli- 
 gently for the prevention of deaths from any given disease or cause, we need to know 
 the time of year at which the danger is greatest, the ages at which a person is most in, 
 danger, to persons of which sex the danger is greatest, whether the danger is greater in 
 one part of the State or country than in another, and many other facts. Vital statistics, 
 accurately collected, compiled, and studied, for a period sufficiently long, will give us- 
 such information. 
 
 WHAT AEE " CONTRIBUTIONS TO SANITARY SCIENCE"? 
 
 It is, I think, just as important to " know a good thing when we see it" in public- 
 health work as in any other affair ; therefore it is well to bear in. mind that popular books- 
 
 271 
 
SCIENTIFIC UNION. 
 
 and articles are not usually "contributions to science," that papers (such, for instance, as 
 this one) read at public meetings are not usually " contributions to sanitary science," 
 and that really valuable " contributions to science " are not commonly easy and pleasant 
 reading, notwithstanding their high value in advancing existing knowledge. A science 
 is built'up by the accumulation of numerous facts, which, ultimately, are grouped so as 
 to exhibit general truths. When an individual or a government collects numerous facts, 
 and skilfully groups those facts so as to lead to new knowledge bearing upon the 
 problems with which public-health work deals, that individual or that government makes 
 an important contribution to sanitary science. However useful it is to have essays on 
 public-health work in all its various departments, and however much good may be done 
 because of the stimulus of such essays, which I consider essential to progress in sanita- 
 tion, yet it must not be forgotten that the real solid basis of all such work must be laid 
 in the patient, painstaking accumulation of facts (such as physicians are freely contri- 
 buting), their classification, comparison, collation, provisional grouping, and final 
 grouping so as to serve as bases of action. Thus the recognized basis of sanitary science 
 is statistics of deaths, of sickness, of meteorological and other surrounding conditions, 
 though very much more than such statistics is needed for an effective public-health 
 service. 
 
 USEFUL FACTS FROM THE VITAL STATISTICS OF MICHIGAN. 
 
 Facts illustrating the nature of some of the information gained by means of vital 
 statistics already collected in this State, may be given: It has been learned, for 
 instance, that in this State, during a long series of years, the danger from small-pox was 
 not as great as the danger of death from whooping-cough, there being twice as many 
 deaths from whooping-cough as from small-pox (though the proportion of children is 
 greatest among those who die from whooping-cough). It has been learned that diseases 
 of the lungs cause nearly one-fifth of all the deaths reported in this State, and that 
 nearly one-half of all the deaths are attributed to diseases of the lungs, the bowels, and 
 the brain ; and it is found that a large proportion of the deaths from each of these three 
 groups of diseases are reported to be caused by tubercular diseases, such as consump- 
 tion of the lungs, consumption of the bowels, tubercular disease of the brain and 
 coverings, etc., so that if, as now seems probable, sanitarians shall soon be able to class 
 consumption among the preventable diseases, and to teach people how to prevent a 
 considerable proportion of the deaths now charged thereto, it will be one of the grandest 
 achievements of the century ; for it will add more to the financial prosperity of the 
 people than can be easily computed, hundreds of thousands of dollars annually now 
 being lost to the people of this State by reason of sickness and deaths from consumption ; 
 and then the anguish of human hearts beyond any power of computation or expression ! 
 
 The deaths reported from consumption in Michigan will average over 1,400 annually, 
 and there is evidence that the number reported should be much increased in order to 
 equal the deaths which actually occur ; probably two thousand persons die in this State 
 in every year from consumption. And yet compared with many other States Michigan 
 is a very healthful State, and we are accustomed to regard these deaths as inevitable 
 indeed, as a rule, they seem to be when once consumption has been contracted ; and up to 
 this time no effort has been made to prevent the spread or occurrence of this disease. It 
 may serve to awaken the enthusiasm sufficient to start some effort for its study and 
 restriction, if we consider that consumption is now proved to be communicable from man 
 to lower animals ; that there is good evidence that the disease may be communi- 
 cated from animals affected with it to man as, for instance, to susceptible children 
 by means of milk of a tuberculous cow, to any susceptible person by means 
 of insufficiently cooked meat of a tuberculous animal; that there are hundreds of 
 tubercular cows and other animals ; and that consumption is probably spread among 
 people in un ventilated rooms by breathing air which has come from the lungs of persons 
 272 
 
SCIENTIFIC UNION. 
 
 suffering from, consumption. The evidence of this last proposition is twofold because 
 from statistical and other evidence some have been convinced of the truth of it, and 
 lately experiments have shown that dogs will contract the disease if caused to breathe 
 air in which tuberculous matter has been anatomized. Let us place these facts by the 
 side of those others which the vital statistics give us namely, that, counting all children 
 and grown people in this State, at least twelve per cent, die from consumption an average 
 equal to every eighth person you meet in this State ; and we may add that the death- 
 rate is reported about double this among persons over fifty years of age ; thus we begin 
 to see abundant reason for tremendous effort to learn the whole truth, and then, for 
 another effort for the prevention of this great waste of human life, which is going on 
 among us. 
 
 THE VALUE OF REPORTS OF SICKNESS. 
 
 Until recently sanitarians have been obliged to accept as their best guide in the 
 study of the causes of sickness the facts reported concerning the number, time, and 
 alleged causes of deaths ; but evidently there is much sickness which does not result in 
 death, but which, nevertheless, it is very desirable to prevent if possible, and there are 
 many deaths having a remote cause in sickness or other conditions quite different from 
 those immediately preceding the death, and likely to be reported as its cause ; so that 
 statistics concerning the sickness of a people are no less necessary than those concerning 
 deaths. Weekly reports of sickness also serve to announce to a State Board of Health, 
 outbreaks of communicable diseases, and thus enable the board to direct attention in 
 various parts of the State where such diseases occur, to necessary measures for the 
 restriction and extirpation of the disease. For such timely work by the State Board a 
 system of prompt and regular reports of sickness is essential. Yet it is only for a few 
 years that the attempt has been made to collect statistics of sickness ; and at this time 
 I know of no such systematic effort being made elsewhere for the collection of facts 
 respecting sickness as that by the Michigan State Board of Health. This Board receives 
 weekly reports of the sickness under the observation of many of the leading physicians 
 in this State, about one hundred of whom in nearly as many different parts of the State 
 promptly notify the Board of the outbreak of any communicable disease, and regularly 
 report concerning the relative prevalence of cases of each of the prominent diseases 
 under their observation. This makes it possible for the State Board of Health to send 
 promptly to each locality, documents bearing upon the restriction of any particular 
 disease which occurs, concerning the restriction of which the State Board has gained 
 useful information ; provided the State Board has the means to print and to distribute 
 documents in that manner ; and such distribution is desirable even if the document has 
 been generally distributed before, because, during an outbreak of a disease, many will 
 seek and gain information relating to that disease, who will not do so at other times. 
 But aside from keeping the State Board constantly informed concerning the health or 
 sickness of the people, the weekly reports of sickness have great value as contributions to 
 our exact knowledge on the subject ; because the facts thus reported can be systemati- 
 cally arranged, compiled, and joined with other facts similarly arranged respecting the 
 surroundings of people at different ages and at different seasons of the year, and know- 
 ledge may thereby be gained which will eventually enable the board to tell the people 
 the conditions under which sickness from each of the prominent diseases occur, and the 
 conditions under which it does not occur, knowledge which must be gained if we are 
 ever to be able to avoid or control those conditions which are now permitted to 
 cripple and to destroy so many prematurely. 
 
 METEOROLOGICAL AND OTHER CONDITIONS MUST BE KNOWN. 
 
 In order to build up a sanitary science which shall serve as a basis for the prevention 
 of sickness and deaths, it is essential, as has already been said, to have facts from more 
 PART II. No. 9. T 273 
 
SCIENTIFIC UNION. 
 
 sources than one. It is not enough to know that there are more deaths from inflamma- 
 tion of the lungs in winter, and more from diarrhoea in the summer, we need to know 
 to what condition of the air, what condition of the body, or of its surroundings, the 
 increase of deaths or of sickness is due, before we can consider the best methods for changing 
 or for avoiding those conditions. 
 
 Only by long- continued watching, recording, and studying the meteorological con- 
 ditions can we learn whether it is the cold, the absence of moisture, the excess of ozone, 
 or the action of the wind, which causes so many more deaths from diseases of the throat 
 and air-passages in winter than in summer, or whether all these are but indirectly 
 related to the subject and the real cause is as Dr. A. N. Bell has recently suggested 
 filth, which can easily be removed or avoided. Yet nothing is more certain than that if 
 systematic effort is made we can learn which of the conditions are invariably coincident 
 with the disease and which are only incidentally present ; for notwithstanding the fact 
 that in this State the air is generally cold, dry, windy, and contains an excess of ozone 
 in winter, these conditions do not prevail with absolute uniformity, but sometimes one 
 is absent and sometimes another, therefore sooner or later every one of these and other 
 conditions can be compared with the sickness and the deaths from each of the different 
 diseases which now afflict us, and the truth learned as to whether these relations severally 
 or collectively are those of cause and effect. If individual effort could readily achieve 
 this, I think it would have been done long ago ; but when the people of a State collect, 
 compile, and publish the material essential for such studies the work has begun, and in 
 this State such a beginning has been made. From the earliest times it has been known 
 that the weather has much to do with health, but at the time the first State report on 
 vital statistics in Michigan was published (for 1867) the compiler gave only a single 
 table of results of meteorological observations, at the Agricultural College, and regretted 
 his inability to secure results of any other observations in the State. It is only within 
 a few years that systematic observations have been taken for the public-health service 
 of the State, and even now no compensation is given for such important service ; but 
 philanthropic persons are now prompted to contribute their labours because the State will 
 compile and publish, and thus render their work available for use in sanitaiy science. 
 
 The State Board of Health now receives contributions of meteorological records from 
 about thirty observers in different pails of the State. Each observer makes records of 
 observations three times each day, namely, at 7 a.m., 2 p.m., and 9 p.m.; and he records 
 the facts relative to temperature, humidity, barometric pressure, clouds, winds, ozone, 
 rain, and snow. As these observers " work for nothing and board themselves," they 
 are not expected to add the figures in the several columns for the months ; such labours 
 and also computations of the absolute and the relative humidity, computations to learn 
 the actual pressure of the atmosphere, etc., are performed in the office of the State Board 
 at Lansing, where also tri-daily observations are taken. The reports of these thirty or 
 more observers, when added, computed, and averaged, are compiled in tables, showing 
 for each locality the average for each meteorological condition which is observed. These 
 tables may be used for purposes of study by any person. In order, however, to prepare 
 in the best manner possible the statements of the conditions of the air, so that they 
 may most easily be compared with statements of the sickness or deaths from each 
 disease, and an estimate made of the influence upon the disease by each meteorological 
 condition, it has been the custom to so perfect the data that it can be represented to 
 the eye on a diagram drawn accurately to scale. Such diagrams are as useful and as 
 essential to the sanitarian as are the profiles which the surveyor makes for " cuts " and 
 " fills" to the builders of railroads and streets, and their modes of construction and use 
 are similar. 
 
 SPECIAL INVESTIGATIONS. 
 
 Sanitarians must do more than utilize contributions from meteorology and from 
 274 
 
SCIENTIFIC UNION. 
 
 each of the other sciences ; they must make original investigations, such as will result in 
 the actual creation of knowledge never before attained ; this is the grand mission of 
 sanitary science in behalf of human welfare, and for this sanitarians must face up to 
 nature in ways never before attempted by human beings, and must bring back from 
 this search after revelations, portions of that eternal truth which will teach us the way 
 of life, the way of health, and the way of happiness. 
 
 What some of the points are concerning which special investigations are needed, it 
 may not be amiss to say a word here. With regard to small-pox, diphtheria, and scarlet 
 fever, three dreaded diseases which afflict our people, the State Board of Health, in 
 common with the leading men of the medical profession generally throughout the State, 
 already know enough to suppress these diseases if the people could be put in possession 
 of the knowledge and would act upon the information, which however is not likely to be 
 placed before them unless the State Board of Health can have the means for this 
 important service. In fact, small-pox is practically suppressed in Michigan to-day, and 
 diphtheria and scarlet fever have, in many instances in this State, been stamped out of 
 existence in localities where they have appeared. The way to control scarlet fever or 
 diphtheria is not, as seems to be the opinion of many intelligent people and some 
 physicians even, to wait till the disease has taken possession of an individual and then 
 do something to him to kill the disease, provided that the disease does not first kill him, 
 but to keep the disease out of him from the first, by keeping it away from him and him 
 away from it ; and to shut the disease into the closest possible quarters and then burn 
 i t out or smother it in its most secret lurking-places. This is possible, it is practicable 
 and when all our people join hands to do it, it will be as easy as it is now to keep the 
 wild bears of the forest from our homes ; but without efficient local boards of health, and 
 general cooperation by the people, no family can protect itself from either scarlet fever 
 or diphtheria. 
 
 With regard to diphtheria, however, there are questions which it would be of use to 
 have decided. We know that the living germs or the poisonous elements which cause 
 the disease are reproduced within the human body, and that in various ways, direct and 
 indirect, the disease is communicated from one person to another ; in other words, we 
 know that the disease is contagious ; whether it is also infectious, that is, whether the 
 invisible germs or elements of poison whose presence in the body causes the disease are 
 also sometimes reproduced in substances outside the body, how long they can live (or 
 continue efficient to cause disease) in substances outside the human body, and in what 
 substances they can live and retain their deadly power, are questions the correct and 
 unquestioned answers to which would be of great use in preventing the disease and in 
 destroying its cause. It would also be of service to know what it is that makes some 
 epidemics of diphtheria much more malignant than others, for thus we may be able to 
 substitute mild for malignant epidemics, in some such way as is done for small-pox. 
 
 We know that the typhoid-fever poison is communicated by water and by milk ; but 
 we need investigations to learn in what other ways it may be communicated, and how it 
 is propagated, whether always in the body or sometimes outside the body, and in what 
 lower animals. 
 
 There is much, too, that needs to be known concerning consumption, a disease of 
 which more is said in another part of this paper. 
 
 The question of the causation of intermittent fever, or fever and ague, as it is called, 
 which we now know to cause more sickness in Michigan than does any other disease, is 
 still an unsettled question ; and while much has been done towards preventing it, by 
 drainage, by cultivation of the soil, and by planting of trees, it would be a great boon to 
 the people of this State if we could know certainly what are the relations of intermittent 
 fever to marsh land, or what it is connected with overflowed land that so greatly favours 
 the disease, what are the conditions both subjective and objective under which ague is 
 certain to arise, what is the specific poison of the disease, if such there be. 
 
 275 
 
<c lU 35JJ8F5S 
 
 ANNOUNCEMENTS. 
 
 DISEASES MAY BE CONTROLLED OR AVOIDED. 
 
 With increasing -facilities for travel it may soon be practicable for human beings to 
 gain as much control over their climatic conditions as the wild geese have so long 
 enjoyed ; but before this can be realized we must know as much as the geese do, for 
 they seem to have gained that knowledge which mankind are so slow in gaining, and for 
 the attainment of which I am pleading, namely such knowledge as will enable any 
 person to know the special danger at each age and at each season of the year in each 
 habitable portion of the earth. But, because of the expenses of travel and the many 
 difficulties in the way of periodical movements of the population, I would not be content 
 to stop with the knowledge of a wild goose. There are animals which know enough to 
 take care of themselves in warm or in cold seasons of the year, particularly in climates 
 so favorable as that in Michigan ; and I see no reason why men may not eventually learn 
 to do as well, if only they will admit the feasibility of so doing, and will devote a neces- 
 sary part of their energies to this undertaking. In order to accomplish it, however, it 
 seems to me essential that there shall be organized effort, and especially that those whom 
 we elect to apportion the expenditures of the State, in the interest of the whole people 
 and not for the exclusive benefit of local or class interests, shall understand the aims 
 and purposes of the systematic study of the causes of sickness and deaths, and shall 
 recognize those purposes as high and noble. 
 
 I hope no one will infer that in this paper all the work of the State Board of Health 
 is mentioned ; in view of the many other labours by the Board, and by individual members 
 of the Board, it is my duty to say that this paper relates only to a small part of the 
 work of the Board, a part which less than many other parts has to do with its every-day 
 work at the present time, such, for instance as the dissemination of information already 
 gained ; yet it seems to me that it is work which it is absolutely essential to have done in 
 order that in the future progress in sanitary science and service may be possible ; and it 
 cannot be done except by thorough cooperation among several classes of people. The 
 purpose of this paper is, therefore, the hope of creating a greater interest in a subject 
 which I deem of vital importance to our fellow-men. 
 
 ANNOUNCEMENTS. 
 
 Part III. of the " Scientific Eoll " will be commenced, if life and health and support be 
 granted to the Conductor, in 1883. In order that the Bibliography may be as full as 
 possible, authors and publishers are respectfully solicited to send copies of, or references to, 
 all their publications dealing with the barometrical condition of the air. 
 
 As soon as 200 persons have expressed a wish to subscribe for any one of the subjects 
 mentioned below, the publication of that section of the "Scientific Eoll " will be forthwith 
 commenced. The subscription price will be Is. 6cZ. and 10s. for each volume, according as 
 the residence of the subscriber is at home or abroad. Each volume will comprise from 
 400 to 500 pages ; and each volume will, in most cases, contain two or more parts, each of 
 which may be subscribed for separately. The extent of these parts will depend upon the 
 amount of matter in hand, so that the subscription price for each cannot be fixed at present, 
 but will be settled when the publication of each part is commenced. The following is a 
 list of the principal subjects : 
 
 Atmosphere, Water, Ocean, Kivers, Lakes, Springs, Glaciers, Land, Elevation and Sub- 
 sidence of Land and Sea-Bottom, Denudation, Orography, Earthquakes, Volcanoes, Marshes, 
 Minerals, Stratigraphy, Kocks, Plants generally and in classified groups; Animals gene- 
 rally; Protozoa, Actinozoa, Hydrozoa, Echinodermata, Crustacea, Scolecida, Annelida, 
 Mollusca, Myriapoda, Arachnida, Ehynchota, Orthoptera, Diptera, Coleoptera, Lepidoptera, 
 Neuroptera, Hymenoptera, Pisces, Amphibia, Eeptilia, Aves, Mammalia, and Man. 
 
 Subscribers' names only are asked for now. The sending of these will not involve any 
 pecuniary liability, but will simply be taken as implying that the senders take an interest 
 in the work, and will probably undertake to subscribe when asked to do BO. 
 $76 
 
AQUEOUS VAPOUR: NOTES. 
 
 1824. 
 Dalton, John. Reprint from Mem. Phil Soo., Manchester: Read Feb. 9, 1821. (ra.) 
 
 (Page 2) In 1801 I first announced the notion of an aqueous vapour atmosphere 
 distinct from the general atmosphere. If this idea be true, there should be a decrease 
 in density in ascending in a geometrical progression to increments of height in arith- 
 metical progression. I have tested this idea on Helvellyn and other heights by measuring 
 (Page 5) the dew point by means of cold water poured into a glass tumbler, or where 
 water was wanting, by means of pounded nitre and sal-ammoniac, or by means of snow. 
 (Page 20) [He gives a large number of observations which are of local importance only.] 
 The conclusions are. 1. That the quantity and density of vapour is constantly (or with 
 very rare exceptions) less the higher we ascend. 2. That wherever a dense cloud or fog 
 exists there the temperature of the air and the dew point are the same. 3. That when 
 a mountain is wholly or in great part enveloped in fog there is little variation in ascending 
 either in the temperature of the air or in the dew point. 4. That on the average the dew 
 point sinks 1 for every 100 yards of ascent. 5. That the phenomena of aqueous 
 meteors, such as rain, fog, dew, etc., depend upon the known relations of heat and water. 
 Electricity appears to be a consequent rather than an agent in the formation and decom- 
 (Page 21) position of clouds. As the dew point and temperature of the air approximate 
 in proportion as we ascend, at some height they must become the same ; and hence the 
 cause why the upper regions of the atmosphere are so frequently clouded ; also why the 
 mossy summits of mountains are generally moist. The following represents the drying 
 power of the air according as its temperature is above that of the dew point. 
 
 D. P. 
 
 2 
 
 4 
 
 6 
 
 8 
 
 10 
 
 12 
 
 14 
 
 16 
 
 18 
 
 20 
 
 30 
 
 8 
 
 16 
 
 24 
 
 32 
 
 41 
 
 51 
 
 63 
 
 74 
 
 86 
 
 98 
 
 35 
 
 9 
 
 17 
 
 26 
 
 37 
 
 48 
 
 61 
 
 72 
 
 85 
 
 99 
 
 114 
 
 40 
 
 10 
 
 22 
 
 33 
 
 45 
 
 57 
 
 71 
 
 85 
 
 100 
 
 117 
 
 135 
 
 45 
 
 12 
 
 24 
 
 37 
 
 51 
 
 66 
 
 81 
 
 99 
 
 117 
 
 135 
 
 154 
 
 50 
 
 14 
 
 28 
 
 43 
 
 60 
 
 78 
 
 96 
 
 115 
 
 135 
 
 155 
 
 178 
 
 55 
 
 16 
 
 33 
 
 51 
 
 69 
 
 88 
 
 109 
 
 131 
 
 155 
 
 181 
 
 209 
 
 60 
 
 18 
 
 37 
 
 57 
 
 77 
 
 100 
 
 126 
 
 153 
 
 182 
 
 213 
 
 244 
 
 1827. 
 Daniell, J. F. (B. 1827, 1.) 
 
 (Page 119.) At about 9890 feet. [1st ed. has 9840.] 
 (Page 164.) .149 [in second col. is a misprint for .140]. 
 (Page 176.) .00725 [not .00720 as in 1st ed.]. 
 
 (Page 177.) [The table as given differs materially from that in 1st ed. in the way 
 indicated below, the differences only being given.] 
 
 PAKT II. No. 10. u 277 
 
AQUEOUS VAPOUR 1827. Daniell. 
 
 NOTES. 
 
 
 1st col. 
 
 2nd col. 3rd col. 4th col. 
 
 5th col. 
 
 
 
 
 [All - for + +.0227 [This col. 
 
 1.0703 
 
 
 1 
 
 down to 31.] [and + is is unaltered.] 
 
 1.0679 
 
 
 2 
 
 substituted for 
 
 1.0655 
 
 
 3 
 
 all down the 
 
 1.0631 
 
 
 4 
 
 column.] 
 
 1.0607 
 
 
 5 
 
 
 1.0583 
 
 
 6 
 
 
 1.0559 
 
 
 7 
 
 .00298 
 
 1.0536 
 
 
 8 
 
 .00308 
 
 1.0512 
 
 
 9 
 
 .00318 
 
 1 . 0489 
 
 
 10 
 
 .00328 
 
 1.0466 
 
 
 11 
 
 .00344 
 
 1.0442 
 
 
 12 
 
 .00358 
 
 1.0419 
 
 (Page 178.) 
 
 13 
 
 .00372 
 
 1.0396 
 
 
 14 
 
 .00385 
 
 1.0373 
 
 
 15 
 
 .00398 
 
 1.0350 
 
 
 16 
 
 .00412 
 
 1.0327 
 
 
 17 
 
 .00425 
 
 1.0304 
 
 
 18 
 
 .00439 
 
 1.0282 
 
 
 19 
 
 .00452 
 
 1.0260 
 
 
 20 
 
 .00469 
 
 1.0239 
 
 
 ' 21 
 
 .00489 
 
 1.0215 
 
 
 22 
 
 .00509 
 
 1.0194 
 
 
 23 
 
 .00529 
 
 1.0171 
 
 
 24 
 
 .00549 
 
 1.0148 
 
 
 25 
 
 .00570 
 
 1.0125 
 
 
 26 
 
 .00590 
 
 1.0104 
 
 
 27 
 
 .00610 
 
 1.0082 
 
 
 28 
 
 .00631 
 
 1.0061 
 
 
 29 
 
 .00651 
 
 1.0041 
 
 
 30 
 
 .00671 
 
 1.0017 
 
 
 31 
 
 .00698 
 
 .9995 
 
 
 32 
 
 .00725 
 
 .9973 
 
 
 33 
 
 [All + instead .00752 
 
 .9952 
 
 
 34 
 
 of from 33 .00779 
 
 .9927 
 
 
 35 
 
 to 90.] .00806 
 
 .9909 
 
 
 36 
 
 .00834 
 
 .9887 
 
 
 37 
 
 .00864 
 
 .9867 
 
 
 38 
 
 .00889 
 
 .9846 
 
 (Page 179.) 
 
 39 
 
 .00915 
 
 .9824 
 
 
 40 
 
 .00942 
 
 .9804 
 
 
 41 
 
 .00983 
 
 .9783 
 
 
 42 
 
 .01024 
 
 .9761 
 
 
 43 
 
 .01064 
 
 .9741 
 
 
 44 
 
 .02499 .01105 
 
 .9720 
 
 
 45 
 
 .01146 
 
 .9699 
 
 
 46 
 
 .01187 
 
 .9679 
 
 
 47 
 
 .01228 
 
 .9658 
 
 
 48 
 
 .01269 
 
 .9636 
 
 
 49 
 
 .01310 
 
 .9616 
 
 
 50 
 
 .01351 
 
 .9596 
 
 
 51 
 
 .01399 
 
 .9575 
 
 
 52 
 
 .01447 
 
 .9555 
 
 
 53 
 
 .01502 
 
 .9535 
 
 
 54 
 
 .01557 
 
 .9514 
 
 
 55 
 
 .01612 
 
 .9494 
 
 
 56 
 
 .01667 
 
 .9474 
 
 
 57 
 
 .01723 
 
 .9453 
 
 
 58 
 
 ,01784 
 
 .9433 
 
 
 59 
 
 .01843 
 
 .9414 
 
 
 60 
 
 .01902 
 
 .9394 
 
 
 61 
 
 .01961 
 
 .9374 
 
 
 62 
 
 .02020 
 
 .9354 
 
 
 63 
 
 .02093 
 
 .9334 
 
 (Page 180.) 
 
 64 
 65 
 
 .02166 
 .02239 
 
 - .9314 
 .9274 
 
 278 
 
 
 
 
AQUEOUS VAPOUR 
 
 1827. Daniell. 
 
 NOTES. 
 
 1st col. 2nd col. 
 
 3rd col. 4th col. 
 
 5th col. 
 
 
 66 
 
 .02312 
 
 .92 [Type 
 See 1845 ed., vol. 
 
 damaged, 
 ii. p. 43.] 
 
 67 
 
 .02386 
 
 .92 5 [type 
 
 damaged] 
 
 68 
 
 .02466 
 
 .9235 
 
 
 69 
 
 .02546 
 
 .9216 
 
 
 70 
 
 .02634 
 
 .9196 
 
 
 71 
 
 .02725 
 
 .9177 
 
 
 72 
 
 .02817 
 
 .9157 
 
 
 73 
 
 .02912 
 
 .9137 
 
 
 74 
 
 .03011 
 
 .9117 
 
 
 75 .08958 
 
 .03114 
 
 .9098 
 
 
 76 
 
 .03221 
 
 .9079 
 
 
 77 
 
 .03327 
 
 .9059 
 
 
 78 
 
 .03438 
 
 .9039 
 
 
 79 
 
 .03548 
 
 .9020 
 
 
 80 
 
 .03663 
 
 .9001 
 
 
 81 
 
 .03781 
 
 .8982 
 
 
 82 
 
 .03903 
 
 .8962 
 
 
 83 
 
 .04029 
 
 .8943 
 
 
 84 
 
 .04159 
 
 .8924 
 
 
 85 
 
 .04293 
 
 .8905 
 
 
 86 
 
 .04431 
 
 .8885 
 
 
 87 
 
 .04573 
 
 .8867 
 
 
 88 
 
 .04716 
 
 .8847 
 
 
 89 
 
 .04858 
 
 ,8828 
 
 
 90 
 
 .05005 
 
 .8809 
 
 
 (Page 181.) To find the specific gravity of any mixture of air and aqueous vapour by 
 means of this table, proceed thus. Note the temperature and the point of condensation 
 by the hygrometer ; if they coincide, that is to say, if the air be in a state of saturation, 
 we shall find the specific gravity required in the fifth column opposite to the proper 
 degree of heat in the first column. If the point of condensation be below the temperature, 
 we must look for the alteration of volume due to the heat in the second column, and for 
 the expansion due to the vapour in the third column. Add these together if they have 
 like signs ; or subtract one from the other if they have different signs. As the volume 
 corrected by this quantity is to the original volume, so is the standard specific gravity 
 to the specific gravity as affected by the expansion or contraction. To this must be 
 added the increase of weight due to the vapour in the fourth column, and the result will 
 be the correct specific gravity sought. For example, if you wish to know the specific 
 gravity of a mixture of air and vapour of the temperature of 60 and of which the dew 
 point is 40, we find in the second column opposite to 60 the number +.05833, and 
 in the third column opposite to 40 we have + .00942 ; the sum of which is + .06775 ; 
 therefore 1.06715 :!::!: .93659. In the fourth column opposite 40 we find + .00580, 
 and .93659 + .00580 =.94239 which is the correct specific gravity under the assumed 
 circumstances. Something appears to be still wanting to complete the investigations 
 (Page 489) of De Luc, De Saussure and Dalton, and to follow up the results to their 
 ultimate consequences. It is a well known fact that water under all circumstances is 
 (Page 490) endued with the power of emitting vapour of an elastic force proportioned 
 to its temperature. It is also well understood that the gaseous atmosphere of the earth 
 in some degree opposes the diffusion, and retards the formation of this vapour not by its 
 weight or pressure, but by its vis inertia. It may facilitate the comprehension of the 
 subject to distinguish three cases with regard to the evaporating fluid : the first, when 
 its temperature is at the boiling point; the second, when it is below the boiling 
 point but above that of the surrounding air; the third, when it is below that 
 of the atmosphere. The first does not bear upon the subject in hand. In the- 
 (Page 491) second case the exhalation is proportionate to the difference of tem- 
 perature. The gaseous fluid in contact with the surface becomes lighter by the 
 abstraction of portions of the excess of heat, and rising up carries with it in 
 
 u 2 279 
 
AQUEOUS VAPOUR 1827. Daniell. NOTES. 
 
 its ascent the entangled steam. This is precipitated, and in the form of cloud 
 is exposed to the third species of evaporation. This process is not only proportional 
 to the difference of temperature and the elasticity of the vapour, but is also governed by 
 the motion of the air. A current of wind tends to keep up that inequality of heat on 
 which it depends, and prevents that equalization which would gradually take place in a 
 stagnant air. Such is the evaporation which often takes place in this climate in autumn 
 from rivers, lakes, and seas, and which is indicated by the fogs and mists which hang 
 over their surfaces. It is, however, the third modification which is the most interesting 
 in the point of view which I have suggested. When the temperature of water is below 
 that of the atmosphere it still exhales steam from its surface, but in this case the 
 {Page 492) vapour, neither having the force necessary to displace the gaseous fluid, nor 
 heat enough to cause a circulation which would raise it in its course, is obliged to filter 
 its way slowly through its interstices, and the nature of the resistance it meets with is 
 the first object of investigation. The force of vapour at different temperatures has 
 been determined with great accuracy, and the amount of evaporation has been shown to 
 be, cceteris paribus, always in direct proportion to this force. The quantity is also 
 known to depend upon the atmospheric pressure, but I know of no experiments which 
 establish the exact relation between the two points. I attempted to elucidate the point 
 as follows, viz., by enclosing in a glass receiver upon the plate of the air pump a vessel 
 with sulphuric acid and another with water ; and by properly adjusting the surface of 
 the two it is easy to maintain, in the included atmosphere of permanently elastic fluid, 
 an atmosphere of vapour of any required force ; or in the usual way of expressing the 
 same fact, the air may be kept at any required degree of dryness. The density of air in 
 such an arrangement may of course be varied and measured at pleasure. Now there 
 are three ways of estimating the progress of evaporation in such an atmosphere : the 
 first and most direct is to weigh the loss sustained by the water in a given time ; the 
 second, to measure by a thermometer the depression of temperature of an evaporating 
 surface ; and the third, to ascertain the dew point by means of the hygrometer. 
 (Page 493) [Experiment 1 showed that water at 56 and 58 over sulphuric acid in an 
 air pump receiver could not maintain an atmosphere of vapour of elasticity .068 in., no 
 dew being deposited at 26 nor at 0. This degree of dryness is less than 129 ; sattira- 
 (Page 494) tion being 1000. The air was equally dry in the most highly rarefied air 
 obtained, as shown in experiment 2.] Experiment 3. With the temperature at 45 
 and the height of the barometer 30.4 in., the water lost by evaporation 1.24 grain in 
 (Page 495) half an hour. It was replaced and the air rarefied to 15.2 in. ; in half an 
 hour at 43, the loss was 2.72 grains. The loss from evaporation in equal intervals, 
 with a pressure constantly diminishing one half, was found to be as follows : 
 
 Pressure. Temperature at Loss in 
 
 Beg. End. grains. 
 
 30. 4 in. 45 45 1.24 
 
 15.2 45 43 2.87 
 
 7.6 45 43 5.49 
 
 3.8 45 43 8.80 
 
 1-9 45 41 14.80 
 
 95 44 37 24.16 
 
 47 45 31 39.40 
 
 When the exhaustion was pushed to the utmost the gauge stood at 0.07, and the 
 evaporation in the half-hour was 87.22 grains. Now, before we infer from these ex- 
 periments the state of evaporation from different degrees of atmospheric pressure, it is 
 necessary to apply a correction for the variation of temperature. The quantity of 
 evaporation having been determined to be in exact proportion to the elasticity of the 
 vapour, we must estimate the latter from the mean of the temperatures before and after 
 the experiments, and calculate the amount for any fixed temperature accordingly ; but 
 (Page 496) as the thermometer was in the water it would not give the correct tempera- 
 280 
 
AQUEOUS VAPOUR 1827. Daniell. NOTES. 
 
 ture of the surface. The following table presents us with the former results so corrected 
 for the temperature of 45 : 
 
 pressure. Grains. 
 
 30. 4 in. 1.24 
 
 15.2 2.97 
 
 7.6 5.68 
 
 3.8 9.12 
 
 1.9 15.92 
 .95 29.33 
 .47 50.74 
 .07 112.32 
 
 Notwithstanding the slight irregularity of the above series, we can, I think, run no 
 risk in drawing from it the conclusion that the amount of evaporation is, cceteris paribus, 
 in exact inverse proportion to the elasticity of the incumbent air ; and that De Saussure 
 was misled by his hygrometer when he inferred from its indications that a diminution 
 of one-third the density doubled the rate. There is an apparent discrepancy between 
 Dalton's results and mine under the full atmospheric pressure. He found it to be 
 1.26 grains per minute from a vessel 6 in. in diameter at 45 ; this would give 7.65 
 grains in half an hour from the glass of 2.7 in. diameter. Dalton's experiments were, 
 {Page 497) however, made at a temperature above that of the surrounding medium, 
 which caused a current in the latter which greatly accelerated the process. Dalton 
 found that a strong wind would double the evaporating effect. Experiment 4. This 
 was intended to determine whether the elasticity of the vapour varied with the pressure. 
 The sulphuric acid was placed in a vessel 2.8 in. in diameter. The temperature of the 
 water and air was 52, and the height of the barometer 29.8. The following table 
 shows the dew point which was obtained at intervals of half an hour at different degrees 
 of atmospheric pressure : 
 
 Bar. Temp, of water Dew point. 
 
 and air. 
 
 29. 8 in. 52 36 
 
 14.9 53 37 
 7.45 52 35 
 3.72 53 36 
 1.86 52 34 
 
 .93 52 36 
 
 .15 52 36 
 
 The differences are so small that we may regard them as errors of observation, and con- 
 clude that the elasticity of vapour given off by water of the same temperature is not 
 influenced by differences of atmospheric pressure. The equal surfaces of sulphuric acid 
 and water here made use of maintained at 52 a degree of saturation equal to 570. At 
 {Page 499) 61 the amount of saturation was 651 ; an increase evidently dependent 
 upon the force of the vapour, but not in exact proportion to its augmentation. Experi- 
 ment 5. I next tried in what degree the temperature of an evaporating surface would 
 be influenced by differences in the density of the air by means of the following 
 apparatus. To a brass wire sliding through a collar of leathers, in a ground-glass plate, 
 I attached a very delicate mercurial thermometer ; this was fixed air-tight upon the 
 top of a large glass receiver, which covered a surface of sulphuric acid of nearly equal 
 dimensions with its base. Upon a tripod of glass standing in the acid was placed a vessel 
 containing a little water into which the thermometer could be dipped and withdrawn by 
 means of the sliding wire. The bulb of the thermometer was covered with filtering 
 paper. At the commencement of the experiment the barometer was at 30.2 in., and 
 the temperature of the air at 50. Upon withdrawing the thermometer from the water 
 it began to fall very rapidly, and in a few minutes reached its maximum of depression. 
 The following table presents the results of the experiments for different degrees of the 
 air's density ; the intervals were each of twenty minutes : 
 
 281 
 
AQUEOUS VAPOUR 1827. Daniell. NOTES. 
 
 
 Bar. 
 
 Temperature of 
 Air. Wet therm. 
 
 Diff. 
 
 
 30.2 in. 
 
 50 
 
 41 
 
 9 
 
 
 15.1 
 
 49 
 
 37 
 
 12 
 
 
 7.5 
 
 49 
 
 34 
 
 15 
 
 
 3.7 
 
 49.5 
 
 31.5 
 
 18 
 
 (Page 500.) 
 
 1.8 
 .9 
 
 49.5 
 49 
 
 28.5 
 24.5 
 
 21 
 24.5 
 
 
 .4 
 
 49 
 
 23 
 
 26 
 
 In the case of the first the 9 was produced in ten minutes, and the water evaporated 
 from the thermometer not more than -^^ of a grain. The depression increased with 
 the rarefaction of the air in the proportion of an arithmetical progression to a geometrical 
 one. The increase is attributable, not to the augmented quantity of the evaporation, 
 but to the decreased heating power of the atmosphere. We may conclude that the 
 (Page 501) temperature of an evaporating surface is not affected by the mere quantity of 
 evaporation. These few simple facts appear to be intimately connected with the 
 solution of some very important atmospherical phenomena. The aqueous fluid is so 
 abundantly spread over the face of the earth that there can be no doubt that the 
 permanently elastic atmosphere which surrounds it would very speedily be saturated 
 with its steam, did not some cause, analogous to the sulphuric acid in the receiver, 
 prevent its universal diffusion. This never-failing cause is inequality of temperature. 
 As in the smaller experiment we found that the degree of dryness was proportional to 
 the energy of the absorbent mass, and that the existing vapour was equally diffused 
 between it and the exhaling surface, so, in the larger operation of nature, we shall find 
 that the state of saturation is dependent upon the point of precipitation, and that the 
 (Page 502) aqueous vapour is nearly uniform between it and the source of steam. 
 Now it is well understood that the temperature of the gaseous atmosphere in its 
 natural state must decrease with its density as we ascend to its upper parts ; so that a 
 great degree of cold is at all times to be found within a very moderate distance from 
 the surface of the waters. It is this low tension which determines the tension of the 
 aqueous vapour ; and it is evident that the evaporation which is thus caused at the 
 base of the aerial fluid, must be accompanied by a simultaneous and equal precipitation 
 above. What then becomes of the precipitated moisture ? Let us endeavour to trace 
 the order of this phenomenon. We will first suppose a calm state of the atmosphere, a 
 temperature of 80, and a barometer at 30 in. at the surface of the earth. By a calm 
 state of the atmosphere is here meant one that is free from any lateral wind, and in 
 which, the only currents being in an ascending and descending direction, evaporation 
 would proceed at the rate exhibited in the first column of Dalton's table. The dew 
 point at the surface of the earth is 64, and this is determined by the temperature at 
 the height of about 5000 feet, where the barometric column would maintain itself at 
 24 in. The degree of saturation would therefore be 600, and the amount of evaporation 
 1*74 grain per minute from a surface of 6 in. in diameter. This quantity we therefore 
 suppose condensed at the height above named. But the state of saturation in the 
 (Page 503) atmosphere above this point of precipitation is again diminished: for we 
 may suppose the force of the vapour to be determined by a temperature of 31 at a height 
 of 15,000 feet, where the barometer would stand at about 16 in. The force of evaporation 
 would therefore be 1'71 grain per minute at the full atmospheric pressure ; and this 
 amount increasing as the pressure diminishes would give 2-13 grains per minute : so 
 that the power of evaporation at this stage exceeds the supply of moisture, and no cloud 
 could possibly be formed. Above the second point of condensation let us now suppose 
 the force of vapour to be determined in still loftier regions by a temperature of 12. 
 The force of evaporation would then be 0.44 grain increased in the proportion of 
 16 in. to 30 in. or 0.82 grain. Here then the power of evaporation would be in- 
 ifBcient to diffuse in the upper regions the whole of the moisture supplied from the 
 surface of the earth, and a cloud, it might be supposed, must consequently result. 
 
 v 
 
AQUEOUS VAPOUR 1827. Daniell. NOTES. 
 
 But another modification of the process now ensues : the precipitated moisture has a 
 tendency to fall back into the warm air below it, and consequently would assume the 
 elastic form with a rapidity proportioned to the rarefaction of the stratum in which it is 
 diffused. There is I think no difficulty in supposing that no visible cloud, or one of 
 extreme tenuity, would be formed during this double process of evaporation. A very 
 important reaction, however, must take place upon the strata of vapour beneath ; the 
 elastic force being increased above enables the water below to maintain an atmosphere 
 {Page 504) of a higher degree, and the quantity of evaporation must decrease', as the 
 point of saturation rises. A different arrangement of the points of precipitation would 
 ensue in the progress of these effects. An important distinction must here be drawn 
 between the ultimate effects of the superior and inferior evaporation denoted above. 
 In the first the whole weight of water is condensed and simultaneously exhaled, 
 and although it constitutes steam of an inferior degree of force, there is little or no 
 difference in the quantity of its latent heat and no effect is produced upon the tempera- 
 ture of that portion of the atmosphere in which the change takes place. But in the 
 second the condensation happens at one spot and the vaporization at another inferior to 
 it; the latent heat is therefore evolved at the former and communicated to the air, 
 while at the latter this process is reversed and the air is cooled. The process 
 of this operation would therefore tend to Equalize the temperature. We will next 
 imagine that the surface of the earth is swept by a high wind, and that the atmosphere, 
 instead of resting calmly upon its base, moves laterally with great velocity. Under 
 these circumstances experience has shown that the amount of evaporation will be 
 nearly doubled ; but the force of evaporation is not altered in the upper regions. The 
 inferior, exhaling surface being immovable, the motion of the air perpetually changes 
 and renews the point of contact, and prevents accumulation at any one place ; but in 
 the heights of the atmosphere the exhaling surface of the clouds is borne upon the 
 wind and their relative situations never change. The progress of precipitations must, 
 {Page 505) therefore, necessarily, under the circumstances, outstrip that of evaporation, 
 and the disturbance of the atmospheric temperature will be greatly accelerated. There 
 is another cause which would also quicken evaporation below without equally increasing 
 its power of diffusion at any given height above ; and that is a decrease in the density 
 of the air at the surface of the earth. Under the circumstance of our first supposition, 
 imagine the barometer to fall to 28 in., the evaporation would be increased from 1.74 
 grain to 1.86 grain per minute ; but this decline of 2 in. at the surface would indicate 
 a contemporaneous fall of little more than 1 in. at the height of 15,000 feet, and the 
 rate of diffusion would vary accordingly. When it is considered that great falls of the 
 barometer are generally accompanied by high winds, and that this disparity is multi- 
 plied by the force of the current, it is easy to appreciate the influence of this local 
 increase of the power of evaporation. The facility of evaporation in the rarer regions of 
 the atmosphere will also go far to account for the state of saturation in which the air of 
 mountainous regions is generally found, and many minor meteorological phenomena 
 might probably meet with their explanation from variation of the same cause : such as 
 the fogs which frequently accompany a very high degree of atmospheric pressure, and 
 {Page 506) that peculiar transparency which often precedes rain, and is accompanied by 
 a falling barometer. These ideas are supported by De Luc's accurate observations. 
 At first sight we might ^regard mountain fogs as permanent ; that the evaporation has 
 reached its maximum owing to the air being saturated ; and that the vesicles of vapour 
 remain for weeks or months. But the real state of things is quite different : evaporation 
 still continues from the surface of water, the vaporous vesicles are constantly rising 
 {Page 507) and evaporation is reassumed on the surface of the fog. It is an interesting 
 and instructive sight to see such a surface below one in a valley, and in the distance the 
 brown slopes of a mountain. Such a valley, when lighted up by the sun, seems to be 
 filled with cotton drawn out into myriads of threads, protuberances appear everywhere, 
 
 283 
 
AQUEOUS VAPOUR 1827. Daniell. NOTES. 
 
 as though a spinner was drawing threads from the mass, and they disappear in succession 
 as they dissipate into the air. Occasionally these protuberances are elongated and 
 detached from the main mass as they rise ; we then see it like a film of gauze, which 
 gradually vanishes. Fogs then are constantly being formed on the ground and as 
 constantly being dispersed in the air, and yet there is no increase of humidity (Idees, xi. 
 p. 78). Since I have changed my opinions as to the cause of rain, I have constantly 
 watched the clouds, and readily perceived that they may enlarge, even while in process 
 of evaporation. If one gazes on their scooped edges, which present such a variety of 
 shapes against the clear blue sky, it often happens that the part on which we fix our 
 (Page 508) attention vanishes in situ ; often we see it extend while the cloud has 
 shown no apparent movement, nor decrease of size. Sometimes while we see one piece 
 disappear, others may be seen in process of formation, producing festoons, which increase 
 the size of the cloud ; at other times the cloud is lessened, and then all its festoons 
 vanish ; we perceive that at the same time the cloud thins and totally disappears. 
 Hence I am inclined to believe that there is in the air a general source of vapour ; that 
 these vapours are produced at the place where the cloud is formed ; that it is by 
 the persistency of this vapour production that clouds are sustained, and even grow in 
 size in spite of the continuance of evaporation, and that their disappearance is due to 
 the rate of evaporation exceeding that of supply (tome xi. p. 117). It has been said 
 that vapour condensation would supply but a trifling amount of heat, but the evolution 
 (Page 509) of caloric is by no means so small as supposed. The condensation of a 
 pound of steam would raise the temperature of 3567 cubic feet of air 10. The water 
 which falls represents only a portion of the condensation which occurs in the air. 
 Looking at this, we shall perhaps have a juster notion of the prodigious power of atmo- 
 spheric vapour. 
 
 [The following remarks down to p. 530 are from a paper read to the Hort. Soc. on 
 Aug. 17, 1824.] 
 
 (Page 513.) The changes of moisture extend from 1.000 [corrected to 1000 in the 
 1845 ed.] or saturation to 389. The amount of evaporation from the soil, and of exhala- 
 (Page 514) tion from the foliage of the vegetable kingdom, depends upon two circum- 
 stances : the saturation of the air with moisture, and the velocity of its motion. They 
 are in inverse proportion to the former and in direct proportion to the latter. The 
 horticulturist cannot control the saturation, but he has some command over the velocity. 
 He can break the force of the blast by screens, or may find natural shelter in situations 
 on hill-slopes. Excessive exhalation is very injurious to many of the processes of vegeta- 
 tion, and no small proportion of what is commonly called blight may be attributed to 
 this cause. Evaporation increases in a prodigiously rapid ratio with the velocity of 
 the wind, and anything which retards the motion of the latter is very efficacious in 
 diminishing the amount of the former, the same surface which in a calm state of the 
 air would exhale 100 parts of moisture would yield 125 in a moderate breeze, and 150 
 in a high wind. The dryness of the air in spring renders the effect most injurious 
 (Page 515) to the tender shoots of this season of the year, and the easterly winds 
 especially are most to be opposed in their course. The moisture of the air flowing from 
 any point between N.E. and S.E. inclusive, is to tkat of the air from the other quarters 
 of the compass in the proportion of 814 to 907 upon an average of the whole year, and 
 t is no uncommon thing in spring for the dew point to be more than 20 below the 
 temperature of the atmosphere in the shade, and I have even seen the difference amount 
 to 30. [His observations were in all probability made in England and near London.] 
 The effect of such a degree of dryness is parching in the extreme, and if accompanied 
 with wind is destructive to the blossoms of tender plants. Hence screens to the N. 
 E. are protective to plants. The south aspect of walls has an exalted temperature, 
 but the air is extremely dry. This would cause such an exhalation from the blossoms 
 tender fruit-trees as to be detrimental to them. Such plants should perhaps be 
 
AQUEOUS VAPOUR 1827. Daniell. NOTES. 
 
 (Page 516) partially shaded. In May I have seen the thermometer in sun at 101, 
 and the dew point at 34 ; this gives a dryness of 120. The shelter of a mat would 
 often suffice to prevent injury. Some of the present practices of gardening are founded 
 upon experience of similar effects ; and it is well known that cuttings of plants succeed 
 best in a border with a northern aspect protected from the wind ; or if otherwise situated 
 they require to be screened from the force of the noonday sun. If these precautions be 
 unattended to they speedily droop and die. For the same reason the autumn is selected 
 for placing them in the ground as well as for transplanting trees ; the atmosphere at 
 that season being saturated with moisture is not found to exhaust the plant before it 
 has become rooted in the soil. Over the absolute state of vapour in the air we are 
 wholly powerless ; and by no system of watering can we affect the dew point in the 
 free atmosphere. This is determined in the upper regions. It is well known to 
 (Page 519) gardeners that less dew is formed under a tree or hedge than in places which 
 are wholly exposed. To vegetation growing in the climates for which they were origi- 
 (Page 520) nally designed by nature, there can be no doubt that the action of radiation is 
 particularly beneficial from the deposition of moisture which it determines upon their 
 foliage. But to tender plants the extra cold may be highly prejudicial. It also appears 
 probable from observations that the intensity of the action increases with the distance 
 from the equator to the poles ; as the lowest depression of the thermometer which has 
 been registered between the tropics from this cause is 12, whereas in the latitude of 
 (Page 522) London it not unfrequently amounts to 17. In the hothouse the plants 
 (Page 524) are natives of torrid places having hot and very vaporous atmospheres. 
 Captain Sabine found it to be between about 730 and upwards. In hothouses the 
 (Page 530) degree of moisture often falls short of 500. The dry air often induces 
 (Page 561) excessive evaporation in plants, which injures them. That part of the Con- 
 tinent of Europe over which our observations [on the barometer] extend, lies about 
 midway in the course of the antagonist currents in the atmosphere ; which from the 
 distribution of the temperature of the globe must, in an undisturbed state of a gaseous 
 fluid, flow between the poles and the equator. The whole line of its northern extremity, 
 however, is bounded by the ocean, the evaporation from which must constantly disturb 
 that , regular progression of temperature upon which the balance of the two streams 
 depends. It is by the heat evolved from the condensation of the rising vapour in the 
 upper regions, and by the cold communicated by its rapid re-evaporation that such 
 inequalities are produced. The actions and consequent reactions produced by these 
 irregularities we find constantly communicated from the north, where they originate in a 
 (Page 562) decreasing degree, to the south. The northern ocean is exactly situated in 
 the best position with regard to the Continent of Europe for producing powerful effects ; 
 by its means the warm waters of the Atlantic are brought into contact with the cold 
 winds and ice of the Arctic regions. In such a combination of circumstances evapora- 
 tion and condensation must reach the most violent extremes, particularly in the spring 
 and autumn of the year. The precession of the western before the eastern curves [of 
 (Page 563) the barometric condition] may be explained by the situation of the immense 
 reservoir of vapour which is continually rising from the Atlantic Ocean ; this when 
 wafted by the currents to the northern shores of Europe can only progressively exert 
 its influence along the successive meridians. Captain Basil Hall has favoured me 
 (Page 593) with an illustration of the fact that the vapour of the atmosphere is 
 arranged in beds of equal density from observations made by him on the k peak of 
 Teneriffe. 
 
 (Page 596.) Elastic force of aqueous vapour calculated by Galbraith, 124 F. 
 
 285 
 
AQUEOUS VAPOUR 1832. 1835. Hilhouse. NOTES. 
 
 1832. 
 
 Hilhouse, William. (B. 1832, 2.) 
 
 (Page 241.) The evaporation in the neighbourhood of the line being supposed ten times 
 greater than near the poles, the rains are in proportion much more heavy and frequent. 
 * (Page 242.) Woody countries are always the most humid. 
 
 1833.' 
 Ainsworth, W. (B. 1833, 1.) 
 
 (Page 213.) During Captain Beechey's expedition observations f were made on the 
 humidity of the air in different parallels. 
 
 1834. 
 Ainsworth, William. (B. 1834, 1.) 
 
 (Page 71.) The diaphanous character of the air (Humboldt) at once increases the 
 radiation of the plains and the power of transmission of the radiated heat. Jacquemont 
 attributed the inequality in the height of the snow line on the two sides of the Himma- 
 layeh to the serenity of the plains of Ladauk and the foggy climate that reigns- 
 in the Hindoostan side. 
 
 Campbell. (5.1834,2.) 
 
 (Page 148.) At Melville Isle [off N. Australia], when the N.W. monsoon terminates in 
 April the sky becomes clear, the air dries, while the rain ceases. During the dry season 
 (Page 149) there are frequent heavy dews at night. 
 
 Jackson, J. R. (B. 1834, 3.) 
 
 (Page 84.) What is a fog, a haze> a thick atmosphere ? The transparency of the air 
 is relative till its measure be determined, and that in a manner not dependent on the 
 greater or less perfection of the observer's sight. In making observations of evaporation 
 (Page 235) the same hours should be kept in order that the reference may always be to 
 the same twenty-four hours. Particulars should be entered of the appearance of clouds. 
 (Page 237) In the case of evaporation the sum of the quantities should be given. 
 
 Parish, Woodbine. (B. 1834, 4.) 
 
 (Page 95.) In East Falkland Island fogs are frequent, especially in autumn and spring, 
 but they usually dissipate towards noon. 
 
 1835. 
 
 Committee of the S. African Lit. & Phil. Institution. Journ. Boy. Geog. Soe. 
 
 vol. v. (1835). (rvp.) 
 
 (Page 376.) The best measure of the momentary evaporative power of the air seems to 
 be the depression of the wetted thermometer below the dry one. But the actual evapora- 
 tion from a given surface is quite another thing, and a question may be raised how far 
 any useful approximation to a knowledge of the total evaporation from an extensive and 
 (Page 377) diversified surface unequally moistened and variously exposed to the sun, 
 defended by clouds or refreshed by dews, can be obtained by any small or local experi- 
 ments. In hot arid climates the effects of copious dews must be separated from that 
 of rain. Attention to the amount of dew is very necessary, not only because the 
 meteorological questions involved are of a high degree of interest generally, but because 
 286 
 
AQUEOUS VAPOUR 1836. 1837. Coulter. NOTES. 
 
 in arid climates the dews are of almost as much importance to the maintenance of 
 (Page, 378) vegetation as the rain. In connection with wind it is important to observe the 
 connection of cloudy weather with the quarter from which the wind blows, or has blown 
 for some time previous, and the usual character of the winds as to moisture or dryness. 
 In describing the state of the sky as to clouds, etc., the observer will bear in mind that it is 
 only in that region of the sky which is vertically above him that the true form and outlines 
 of the cloud are exhibited, and the area they cover, as well as the intervals between them, 
 distinctly seen. As they approach the horizon in any direction their extent is fore- 
 shortened by perspective, their apparent magnitude diminished by distance, and their 
 intervals covered in and hidden by their mutual interposition. In estimating, therefore, 
 the quantity of clouds in the sky, regard must be had to this, and our judgment should 
 rather be formed on a view of the region extending from the zenith every way half 
 down to the horizon than from the aspect of the heavens below that limit. It would be 
 better to notice both and to state separately the proportions in which each are covered, 
 and the quarter of the horizon towards which the chief masses in the lower region lie. 
 The general aspect of clouds should be noticed, and especially the height of the lower 
 surfaces, or the level of the vapour planes should be estimated. In a mountainous region 
 this is easy so long as the vapour plane is below or not far above the summits of the 
 hills ; and in such regions the formation and dissipation of clouds in the neighbourhood 
 of the mountain summits under the influence of certain winds forms an interesting 
 study. The formation of clouds at night under the influence of a gradually descending 
 temperature is a point worthy of attention. It frequently happens that without any 
 perceptible wind the sky will suddenly become hazy in some one point, and the haze 
 condensing and spreading in all directions without a wind, the whole heavens will 
 (Page 379) become overcast in a remarkably short time. The same thing will sometimes 
 occur nearly at the same hour for many nights in succession. The height and thickness 
 of the cloud-strata, their connection with cross or opposite currents of wind in the regions 
 where they subsist, and the laws of their formation and intermixture, deserve to be 
 studied with care ; and with reference to the hygrometric state of the air at the time 
 and place, and for several hours before and after. 
 
 Coulter, Dr. Journ. Boy. Geog. Soc. t vol. v. (1835.) (rvp.) 
 
 (Page 69.) The air about Aqua Sola, California, is excessively dry. The severe cold 
 felt in some places must be attributed to this extreme dryness. The great heat expe- 
 rienced at Aqua Sola, 140F., is in part to be explained by the excessively dry air. On 
 the table lands of Mexico the frequent occurrence of frosts is associated with a scarcity 
 of water. 
 
 1836. 
 Fitz Roy, R. Journ. Roy. Geog. Soc., vol. vi. (1836.) (rvp.) 
 
 (Page 331) Clouds are said to be attracted, if not partly caused, by land or by 
 trees. As the low islands of the Dangerous Archipelago have no hill or height of any 
 kind about which the clouds attracted by them can gather and discharge their contents, 
 whether electrical or fluid, perhaps those clouds wanting a conductor discharge them- 
 selves irregularly and in squalls. 
 
 1837. 
 Journ. Eoy. Geog. Soc., vol. vii. (1837.) (rvp.) 
 
 [There is nothing in it for these notes.] 
 
 287 
 
AQUEOUS VAPOUR 1838. 1842. Page. NOTES. 
 
 1838. 
 
 Page, E. L. Journ. Boy. Geog. Soc., vol. viii. : (1838.) (rvp.) 
 
 (Page 319.) At Gualan, June 1834, we were in the rainy season which lasts from. 
 April to November, and, although the mornings were fine, at 3 P.M. the clouds gathered 
 on the wooded hills around, lightnings flashed and torrents of rain poured down for about 
 three hours, when the sky cleared and all was bright and calm as a summer's evening in 
 England. 
 
 1839. 
 Kichardson, Dr. Journ. Roy. Geog. Soc., vol. ix. (1839.) (n?.) 
 
 (Page 364.) The amount of terrestrial radiation is greatly influenced by the clear- 
 ness of the sky, and it was often remarked at Fort Enterprise that a clear sky soon after 
 sunset was accompanied by a brilliant aurora borealis, and that this seldom continued 
 beyond midnight, or one in the morning, when it was superseded by fleecy clouds, 
 (Page 365) obscuring the blue sky. It often happened that shortly before sunrise the 
 sky again cleared, and it was almost always much colder to the sensations at that time 
 than at any other hour of the night. 
 
 Journ. Roy. Geog. Soc., vol. x. (1840.) (rv.) 
 [Nothing in it for these notes.] 
 
 1841. 
 
 Allen, Bird. Journ. Roy. Geog. Soc., vol. xi. (1841.) (rvp.) 
 (Page 87.) On the Belize the long dry season commences in February. 
 
 1842. 
 
 Bacon, Dr. P. Journ. Roy. Geog. Soc., vol. xii. (1842.) (rv.) 
 
 (Page 201.) About Cape Pal mas the dry season commonly includes less than three 
 months in December, January, and February, a state of things strikingly different from 
 the seven, eight or nine months' absolute drought so constant and regular in Senegambia 
 and the adjacent coast. The peculiarity of the seasons here [about Cape Palmas] 
 (Page 202) furnishing an abundance of moisture throughout the greater part of the year, 
 gives this country very eminent advantages for the production of rice ; which, as is well 
 known, in almost every other part of the world as in Carolina, India, China, etc. is 
 confined to low grounds, liable to regular inundation. This is also the case with the 
 northern part of the rice-growing region of W. Africa, from, the Gambia to Sierra Leone. 
 But on the Grain and Ivory Coasts, the long and abundant rains furnish a bountiful 
 supply of water to the whole surface, high and low. Along the Gold Coast the period 
 of the rainy season is about the same as that of the western region in the same latitude, 
 but the showers are light and short. This peculiarity of climate has its advantages for 
 maize, which can hardly be ripened in a wet climate. On the windward coast it is 
 plucked while green, as the wet season would seldom permit it to ripen. 
 
 Karaczay, Count. Journ. Roy. Geog. Soc., vol. xii. (1842.) (;.) 
 (Page 46.) The signs which in Albania usually foretell the approach of the N.E. 
 wind, called the Bora, are small dark clouds surrounding the summits of the mountains, 
 and moving in different directions ; sometimes white clouds of a round form hover over 
 the mountains, and the sea is very low. On the contrary, the scirocco, or scilocco, a 
 S.E. wind, causes the sea to run extremely high. Its approach is indicated by black 
 288 
 
AQUEOUS VAPOUR 1842. 1845. Sehomburgk. NOTES. 
 
 clouds covering the mountains, a higher rise of the sea, and an increased temperature. 
 The wind brings much rain. 
 
 Schomburgk, Robert H. Journ. Roy. Geog. Soc., vol. xii. (1842.) (rv.) 
 
 (Page 179.) It is well known to the agriculturists [of British Guiana] how 
 beneficially the blocks of ferruginous clay operate on the soil on which they lie, 
 contributing not only to the retention of moisture, which would otherwise evaporate, but 
 to the precipitation of atmospheric vapours. 
 
 1843. 
 Schomburgk, Robert H. Journ. Roy. Geog. Soc., vol. xiii. (1843.) (rop.) 
 
 (Page 25.) The mauritias grow only in moist soil or swamps, and when we failed 
 to procure water by digging at the foot of their trunks, we knew that our search would 
 prove hopeless anywhere else in the neighbourhood. In April, 1842, the wind near 
 (Page 29) Ilami-Kipang, in British Guiana, generally lulled towards sunset, but began 
 to blow hurricane-like from the northern quarter towards 8 o'clock. I observed a 
 black cloud rise about that time on the southern hemisphere [=horizon], which, when 
 it reached the altitude of about 25 degrees, expended [=expanded], and the strong breeze 
 set in. May 13, 1842. Near the sources of the Takutu and Eupununi. The savan- 
 (Page 68) nahs present ranges of hills, and the sight of mauritia palms gives hope of 
 water. In lieu of this, however, the ground under the mauritia is as dry as the 
 surrounding savannah. 
 
 1844. 
 Baily, J. Journ. Roy. Geog. Soc., vol. xiv. (1844.) (rv.) 
 
 (Page 129.) Evaporation, according to various calculations, amounts upon an 
 average to about 39 in. per annum in inter tropical climates. 
 
 Christopher, W. Journ. Roy. Geog. Soc., vol. xiv. (1844.) (m) 
 
 (Page 97.) On the Haines river, the driest season is in February and March. The 
 rains commence towards July. 
 
 1845. 
 Daniell, J. F. Elements of Meteorology. 2 vols. 1845. (rvp.) 
 
 ( Vol. I. Page xxxii.) Sir John Herschel, referring to Daniell's scientific labours, 
 says : " The continued generation of the aqueous atmosphere at the equator and its 
 destruction in high latitudes, furnishes a motive power in meteorology whose 
 modification and the mechanism through which it acts, have yet to be inquired 
 into." 
 
 (Page 26.) The spontaneous evaporation of water and the diffusion of steam through 
 the air take place doubtless by the same process, and the independence of the aqueous 
 atmosphere is in fact proved by the invariableness of the depression of temperature 
 produced by the evaporation from the surface of any moistened porous body in an 
 atmosphere of any given degree of dryness. The amount of this depression depends 
 solely upon the temperature and upon the dew point, and although the amount of 
 evaporation in a given time is greatly affected by the density and motion of the gaseous 
 medium, the temperature of the evaporating surface and the tension of the rising vapour 
 (Page 27) are governed entirely by the elastic force of the steam previously inter- 
 mingled with it. [In this edition * is placed opposite the figures in table xxvii. as 
 (Page 90) indicated in 1823 notes. 
 
 * .673 * 67.9 
 
 * .606 * 64.4 * 64.4 
 
AQUEOUS VAPOUR 1845. Daniel! NOTES. 
 
 ' Spring of the ' [are words added in this edition, at the passage indicated in notes 
 1823 edL, p. 58.] 
 
 * Ee-evaporated ' [in place cf re-dissolved, in 1823 edition, p. 58.] 
 
 (Page 95.) [Asterisks added to constituent temperature column of table on p. 62 
 of 1823 edition opposite 64'4, 12'8 and 30'7.] 
 
 ' Steam ' [for stream, 1823 edition, p. 64]. 
 
 (Page 97.) [* is added to 44.9 in sensible temperature column, and to 64.4 in con- 
 stituent temperature column. See notes, 1823 edition, p. 64.] 
 
 (Page 103.) [The decimal point is here prefixed to .368, .507 and .786, omitted in 
 1823 edition, p. 71.] 
 
 (Page 108.) ' Elasticity ' [substituted for quantity, in 1823 edition, p. 75.] 
 
 (Page 109.) * Elasticity of that' [instead of weight in 1823 edition, p. 77], and 
 compound [for natural, 1823 edition, p. 77.] 
 
 (Page 110.) * Deposition' [for decomposition in 1823 edition, p. 78], and 13500 
 [for 3500 on same page.] 
 
 (Page 113.) ' [added in place indicated in notes, 1823, p. 80.] 
 
 (Page 114.) [The following addition is made after ' mixed atmosphere.' See notes, 
 1823, p. 82.] 
 
 The elasticity of the vapour at the surface of the sphere is no guide to the mean 
 pressure of the total aqueous atmosphere ; nor by deducting the amount of that elastic 
 (Page 115) force from the total atmospheric pressure do we obtain, as has been supposed, 
 the simple pressure of the dry gas ; for it must be remembered that from the difference 
 of their specific gravities the principal effect of mixing vapour with an unconfined dry 
 gaseous atmosphere is the expansion of the latter, which, considered alone, like the 
 expansion of heat in a column of air, will cause a different distribution of weight among 
 its upper horizontal sections without proportionally distributing the total pressure at its 
 base. 
 
 [Table xxxvi. is referred to. In the copy consulted by me it is placed opposite 
 p. 115 of vol. ii.] . 
 
 (Page 116.) * Steam ' [for stream, in 1823 ed., p. 83]. 
 
 (Page 118.) [Addition to 1823 edition, p. 84. In S. E. notes p. 248, the page 114 
 was given by mistake for 118.] Neither must we here exclude from our consideration 
 that vertical circulation of the air to which we have before referred as resulting from 
 the ascent of the strata heated by the surface of the sphere and their descent after 
 cooling in the upper regions. It is obvious how the evaporation must be thus ac- 
 celerated and how the vapour formed in the hotter regions must be transported into the 
 upper current and precipitated from it upon the colder latitudes of the sphere. Indeed 
 there can be little doubt that the first admixture of the vapour itself with the lower 
 stratum will give it a mechanical tendency to rise which will greatly assist the act of 
 evaporation ; and there is reason to think that the amount of evaporation experi- 
 mentally determined by Dr. Dalton in calm weather greatly exceeds that which would 
 result in a confined atmosphere where this mechanical action would be impeded. 
 
 (Page 133.) [Addition to 1823 ed. p. 94.] The comparative levity of the atmo- 
 sphere of the southern hemisphere of our globe may probably be accounted for by the 
 permanent expansion produced in it by the -perpetual rise and precipitation of aqueous 
 vapour from a surface almost covered with sea, and differing in this respect so 
 materially from the corresponding dry latitudes of the northern hemisphere. 
 
 (Page 159.) [Addition to 1823 ed., p. 118.] If there be one point of more interest 
 and importance than another in meteorology it is certainly the perpetually varying 
 state of the great ocean of aqueous vapour which permeates the gaseous atmosphere ; 
 but it has hitherto been sadly neglected by observers, who, even in the few observations 
 which have been regularly made, have persevered in the use of imperfect instruments 
 when more perfect ones have been at command. We can nowhere find mean results 
 290 
 
AQUEOUS VAPOUR 1845. Daniell. NOTES. 
 
 for every part of the globe comparable with those which we possess for temperature 
 by which to test our theoretical conclusions ; but, still, experience as far as it has been 
 recorded, confirms that general distribution of vapour which seemed legitimately to 
 follow from our hypothesis. There cannot be a doubt that on the surface of the earth 
 at the level of the sea, the average elastic force and constituent temperature of the 
 vapour decreases with the mean temperature, and in the immediate neighbourhood of the 
 sea the dew point may be reckoned as two or three degrees below it. In the following 
 table will be found the results of the most authentic observations which have been 
 {Page 160) collected upon the subject. Table (xlv.) of the mean dew point and force of 
 vapour in different latitudes on the level of the sea. 
 
 Place. Observer. Dew point. Force. 
 
 Atlantic between Hon,, Capt. Spencer 72 .773 in. mercury. 
 24 25' S. and 27 50' N. 
 
 Do. Gulf of Guinea Maj. Sabine 74 to 80 .911 
 
 Do. St. Thomas Do. 71 to 74 .773 
 
 Indian Ocean. Bombay Sykes 73-76, .853 
 
 Atlantic. Madeira Heineker 59.4 .497 
 
 Do. London Daniell 44.5 .290 
 
 Polar Sea, 71 20' 73 48 Parry 27.6 .157 
 
 Mr. Neuber, of Apenrade in Denmark, made observations at Apenrade every two 
 hours for a year from 7 A.M. to 11 P.M. The mean is .346 for the tension of the vapour, 
 and for the several hours as follows (table xlvi.). 
 
 7a.m. .319 1 p.m. .374 9p.m. .321 
 
 9 .343 3 .372 11 .391 p. 319] 
 
 11 .363 5 .358 
 
 12 .360 7 .332 
 
 The means in table xlv. were based on observations for August and September, and 
 would be greatly above the true annual average. 
 
 (Page 161.) [Addition to 1823 ed., p. 118.] Saussure remarked that his hygro- 
 meter near the surface of the earth proved the air to be removed 30 or 40 degrees from 
 extreme saturation when the presence of clouds in the upper sky demonstrated the 
 perfect humidity of that region. That philosopher often observed this phenomenon 
 when he ascended a mountain whose summit was enveloped in a cloud. On the other 
 hand, he as frequently found that when mists covered the plains and a bright sun gilded 
 the summit of the mountain the limit of extreme humidity was below, and air far 
 removed from saturation above. Bands of clouds he sometimes found to swim between 
 masses of air less humid than themselves. 
 
 (Page 162.) Colonel Sabine [captain in 1823 ed., p. 119]. 
 
 (Page 167.) [Addition to 1823 ed., p. 126.] The obvious general stratification 
 of the clouds can be accounted for upon no other principle than that of the sudden 
 attainment of the dew point in the rise of different beds of vapour under the control of 
 the natural progression of temperature of the gaseous atmosphere in which they are 
 con6ned. Had it not been for this provident adaptation of the two elastic fluids to 
 each other, the atmosphere would necessarily have been at all times turbid throughout 
 its depth with precipitating moisture ; but as it is, the clouds are confined to definite 
 planes of precipitation. Nothing can be more interesting at times than to watch the 
 indications of those natural hygrometers of the heights above us, and to observe the 
 first precipitation of the moisture of the lower stratum of vapour carried by an almost 
 instant evaporation into vapour of a lower tension to still greater altitudes, again to be 
 precipitated, and again to be evaporated. When indeed the normal progression of tem- 
 perature becomes necessarily disturbed by the process which we are contemplating, then 
 the depths of air become turbid, the winds arise, and the rains descend, effect their bene- 
 ficial purpose, and in effecting it restore the more permanent order due to the gaseous 
 
 291 
 
AQUEOUS VAPOUR 
 
 1845. Daniell. NOTES. 
 
 law. Mr. Green hasjbund that the isothermal planes of the atmosphere are parallel, 
 or nearly so, to the' earth's surface; so that the aeronaut knows generally, even 
 though the earth may be intercepted by a cloud [he means view of the earth], when he 
 is crossing a chain of hills, because the upper surface of the clouds generally follows in a 
 great measure the configuration of the earth. The upper surface of the clouds, on 
 *(Page 168) occasions when they overspread the surface of the earth at a moderate 
 elevation, seems to accommodate itself to all the variations of form in the subjacent 
 
 soil 
 
 (Page 178.) It is clear that we must seek for the origin of the greater extra- 
 (Page 179) tropical oscillations of the barometer in the irregular convection of heat pro- 
 duced by the formation and condensation of aqueous vapour. The bodily rise of a large 
 (Page 199) column of heated air will tend to draw towards its base as to a centre the 
 air from all the surrounding districts ; and it will carry with it a sufficient cause for its 
 continual expansion and ascent in the vapour with which it is mixed, and which, by its 
 rapid precipitation, must give out its latent heat. During the blowing of a full harmat- 
 (Page 214) tan it has been found that salt of tartar (carbonate of potassa) which had 
 imbibed moisture so as to run upon a tile, became perfectly dry upon two or three 
 (Page 215) hours' exposure to the wind ; which fact indicates a dew point considerably 
 below the one just mentioned [which was 32]. Common experience has proved that in 
 all countries the winds which have blown over large tracts of land are much drier than 
 (Page 216) those which proceed from the sea. We have two natural hygrometers on a 
 large scale, clouds and rain. Dr. Button's explanation of rain is generally accepted. 
 He supposed it to result from the simple mingling together of great beds of air of 
 (Page 217) unequal temperatures differently stored with moisture. " A volume of air 
 of a given temperature can be charged with only a limited quantity of humidity, and so 
 long as the temperature remains unchanged the moisture cannot be augmented. As the 
 air cools it approaches to a state of saturation, and is disposed to part with some of its 
 humidity ; and on the contrary, when heat is gained at any time by it, the power of 
 receiving more moisture is at the same time obtained, while the union of two volumes 
 of unequal temperatures must chill the one and warm the other, the former will resign 
 some of its moisture and the latter will be disposed to receive it ; and had the order of 
 nature permitted these opposite conditions of humidity and temperature to be exactly 
 balanced, the united volume might have preserved its moisture unchanged, and no 
 portion of the vapour whatever have been rendered visible. The mingling of two 
 saturated volumes of air may result in a mean temperature, but a mean degree of 
 moisture cannot result, but some quantity will be found beyond what the mean tem- 
 perature requires. This quantity, sometimes more and sometimes less, according to 
 the temperature of the mingling volumes, must be discharged in the shape of rain, for 
 the moisture which the air cannot support ought of necessity to descend. If we mix 
 saturated air of 40 and 60, whose force of vapour would be .263 and .524 in. of 
 mercury, the mixture will have a mean temperature of 50. The mean elasticity is 
 .393 in., but the elasticity of saturated air at 50 is .375 in., the difference .018 in. is 
 the amount of moisture which must be precipitated." But upon close examination this 
 will appear to be by no means a satisfactory explanation of the process of nature. 
 Indeed, every one may have an opportunity of observing that when vapour of high 
 pressure is suddenly mixed with the atmosphere, it is very seldom precipitated in the 
 form of rain. A copious cloud is indeed formed which speedily evaporates and vanishes 
 into thin air. The fact is that one most important part of the process has been left 
 out of consideration : namely, the enormous quantity of latent heat which is instantly 
 disengaged by the condensation. The cloud is no sooner formed than it is again evapo- 
 (Page 219) rated ; the warmed air being prepared to support steam, not at once of the 
 full elastic force of the hottest volume of the mixture, but considerably higher than 
 that of the coldest. By slow degrees enormous tracts of the atmosphere have their 
 292 
 
AQUEOUS VAPOUR. 1845. Daniell. NOTES. 
 
 natural progression of temperature thus subverted and raised, and are made to support 
 vast beds of moisture far exceeding in amount what could exist in the normal state of 
 the permanent gases. Fresh stores pour in on every side ; the process goes on ; but the 
 counteraction of the air against this coercion increases in energy ; the precipitating pro- 
 cess prevails, while evaporation becomes more languid ; the clouds increase slowly, 
 approach the earth, the different strata inosculate with each other, and at length descend 
 in rain. The atmosphere gradually discharges its load as the natural progression is re- 
 stored. In such a saturated state of the atmosphere an artificial shower of rain may be 
 formed by the escape of steam into the air, and occasionally under such circumstances 
 the rushing vapour from steam vessels is partly returned in large drops upon the deck. 
 Mr. Monck Mason has remarked that " whenever from a sky completely overcast with 
 clouds rain is falling, a similar range of clouds invariably exists at a certain elevation 
 above ; and that, on the contrary, whenever, with the same apparent condition of the 
 {Page 220) sky below, rain is altogether or generally about, a clear expanse of firma- 
 ment with a sun unobstructed by clouds is the prevailing character of the space above." 
 The transport and mixture of the vapour is partly effected by 'the convection of the air, 
 and partly by its own diffusive energy. It is carried aloft by the horizontal winds from 
 the hot moist regions of the globe towards the colder dry regions, and it rises from the 
 evaporating surfaces in those rotatory vertical motions which we have noticed as affect- 
 ing the mixture of the hot and cold particles of the air. But besides these mechanical 
 processes, the process of diffusion by which it permeates the particles of air without dis- 
 turbing their relative positions is perpetually and energetically acting to spread it from 
 points of greatest to those of least tension, and thus tending to equalize its pressure. 
 The attentive and systematic study of the clouds as they form, dissolve away, and 
 reform in their great successive planes of precipitation, is one of extreme interest, and if 
 properly followed up would explain much that is at present obscure in the process of 
 nimbification. Their language is, however, very difficult to decipher from the difficulty 
 of understanding the perspective of the ever changing masses. They are never at rest ; 
 but as they float upon the wind they may be observed to have proper motions of their 
 own. Different portions of their masses will be found to circulate, as the air, heated 
 by the act of precipitation, rolls to mingle with the cooler masses with which it is in 
 contact. It is this rolling motion which gives the infinitely varied rounded contour to 
 (Page 221) the cumulated heaps which appear fixed in the distance, but which a near 
 examination proves to be in a state of perpetual change. The process of diffusion is 
 also distinctly marked by the fibrous streaks which may often be seen to shoot and 
 expand from different centres before they have time to accumulate into the larger 
 (Page 222) wreaths or denser rolling masses. The diffusive power of the vapour is 
 sometimes attested even against the force of a gentle wind, and the dense fogs which 
 infest the banks of Newfoundland are often observed to advance in a direction contrary 
 to the breeze. The following passages [p. 506-508 of the 1827 ed.] from De Luc's 
 works will afford a complete illustration of the preceding remarks. 
 
 (Page 224.) The theory of solution will not explain this [i.e. the phenomena 
 observed by De Luc as given in the 1827 ed., p. 506-508] ; but the Daltonian theory 
 of diffusion does. On the borders of the Orinoco, and during the rainy season, the 
 (Page 228) clouds at first form and the rain is discharged only during the hottest hours 
 of the day, and disappear at night. But as the season advances, and especially during 
 the time that the sun is in the zenith, both commence in the morning. Towards the end 
 of the wet season they are again confined to the afternoon. It would appear that these 
 violent rains, so evidently connected with the rising temperature, as well as those which 
 occur in the region of calms upon the broad oceans, depend upon the rising columns of 
 rarefied air, which carry up with them in their ascent the highly elastic vapour of the 
 hot latitudes. As they rise, the air assumes the equivalent temperature due to the 
 elevations to which it ascends, which, falling rapidly below the constituent temperature 
 PART II. No. 10. x 293 
 
AQUEOUS VAPOUR. 1845. Daniell. NOTES. 
 
 of the entangled steam, precipitates the excess in rain. The moisture is thus returned 
 nearly to thesurface from which it rises. The rain in extratropical regions gradually 
 loses its periodical character, and the maximum quantity no longer falls when the sun is 
 in the zenith, but rather in the winter months, when its influence is least, or on the 
 decline. It proceeds principally from the vapour transported by the horizontal currents 
 of the atmosphere, fed by the evaporation of the subjacent surface. In the temperate 
 {Page 229) climates, however, the quantity of vapour in the atmosphere in the different 
 seasons of the year (measured on the surface of the earth and near the level of the sea) 
 follows the progress of the mean temperature. The elasticity of the aqueous atmosphere 
 {Page 231) in the temperate zones, on the surface of the earth, separated from that of 
 the aerial, generally exhibits directly opposite changes to the latter. Whenever the 
 (Page 237) particles in the form of cloud, or fog, or condensing steam, are brought into 
 contact with one another with mechanical force, as when they are carried by the wind 
 (Page 238) against any obstacle, as a tree, a rock, or a building, they generally coalesce, 
 become too heavy to be buoyed up by the air, and commence a rapid descent in the 
 form of rain. This is an observation which any one may make who will attend to the 
 phenomena of those dripping fogs with which our climate is sometimes infested [Hobbes 
 in 1682 has somewhat the same idea]. Dove thus explains the cause of the horary oscil- 
 (Page 298) lations of the barometer. The pressure of the atmosphere on the barometer 
 being the sum of the pressure of the dry air and the vapour of water, the barometric 
 column is, so to speak, of two parts : one corresponding to the air, the other to the 
 vapour. Now when the temperature rises, the density of the air diminishes, but the 
 tension of the vapour increases ; and it is not easy to determine the relations which 
 exist between the diurnal variations of the barometer and thermometer by taking account 
 of each of these two influences. To obtain this, Dove analyzed the observations made 
 by Neuber at Apenracle. with one of DanielPs hygrometers, and having calculated the 
 tension of vapour for each hour of the day ^subtracted it from the barometric column. 
 (Page 299) He imagined that he thus obtained the pressure of the dry air alone, and of 
 which there was but one maximum and one minimum; the former occurring about 
 1 A.M., and the latter about 2 P.M. These he ascribes to the diurnal variations of tem- 
 perature with the maximum and minimum of which they are nearly coincident. This 
 single maximum and minimum are also augmented by the vapour of water that rises 
 during the day. In the morning, when the pressure of the dry air diminishes, not only 
 does the tension of the vapour compensate this effect, but it makes the column rise ; and 
 it attains its maximum when the pressure of the air begins to diminish. For the same 
 reason we find a minimum in the morning, because the diminution of the vapour 
 during the night is more rapid than the increase of the pressure of the dry air (Kamtz, 
 Martin's ^translation). Now [we have already shown that the total pressure of the 
 atmosphere of vapour upon the barometric column cannot be estimated by the tension 
 of the lower stratum, and that the deduction of its amount from the height of the 
 mercurial column will not afford us the amount of the dry air. The law of the progres- 
 sion of the elasticity of vapour mixed with an atmosphere of gas must be totally 
 different from that of the gas itself ; and we have shown there is reason to suppose that 
 it is interstratified in beds of different degrees of force, each of which, in the act of 
 diffusion, adds its different quota to the general pressure. Moreover, the results which 
 (Page 300) have been derived by Dove from one year's observations at Apenrade are 
 not confirmed by observations made at other stations, and indeed, are directly opposed 
 to them. Observations between the tropics, where the variations of the dew point are 
 the smallest, and the amplitude of the horary oscillations the greatest, are wholly 
 inconsistent with this view. 
 
 2D4 
 
AQUEOUS VAPOUR. 1845. Daniell. NOTES. 
 
 Vol. II. 1845. 
 
 (Page 1.) ' Liquentia ' [not linquentia as in 1823 edition, p. 139.] 
 (Page 15.) ' Physical ' [not chemical, as in 1823 edition, p. 152.] 
 (Page 28.) < 3.87 and 8.04 ' [in place of 3.37 and 8.01 in 1823 edition, p. 164.] 
 (Page 42.) [The table given at pp. 178-180, of the 1823 edition is modified in the 
 1827 edition, as shown in the notes under that year. In this edition, it is nearly the 
 same as in that of 1827 ; the alterations are indicated below. In col. 2, opposite 20 
 .02500 is given in place of .02475. 
 (Page 43.) In 5th column we have 
 
 65 .9295 
 
 66 .9275 
 
 67 .9255 
 
 for the readings in the place where the copy of the 1827 edition was defective.] 
 
 (Page 45.) The calculations on p. 181 of the 1823 and 1827 editions run thus in 
 this edition.] In the third column opposite to 40 we have .00942 ; and beside it in the 
 fourth, .00580. Now .00942 .00580 = .00362 ; which, subtracted from .94167 leaves 
 .93805 as the number sought. 
 
 (Page 92.) Mason's form of dry and wet bulb thermometer is the most convenient 
 kind of hygrometer. Dr. Apjohn gives the circumstances under which observations 
 (Page 93) should be made. When in the moist bulb hygrometer the stationary heat 
 is attained, the heat which vapourizes the water is assumed to be necessarily equal 
 to that which the air imparts in descending from the temperature of the atmosphere to 
 that of the moistened toilb. It is also assumed -that the air which has undergone this 
 reduction becomes saturated with moisture. In calculating from these assumptions 
 (Page 94) the weight of water which would be converted into vapour by the heat 
 which a given weight of air would evolve in cooling from the temperature of the air to 
 that of the moistened bulb, it is not only necessary to know the tension of vapour for 
 every degree of the thermometer within the atmospheric range, but the specific heat of 
 air must be taken into account as well as the latent heat of steam. In the formula the 
 latent heat of steam is assumed to be 1129, and the differences of the specific heats 
 under a constant volume are assumed to be proportional to the differences of pressure. 
 Allow that these are sufficient approximations, there still remains an objection. It 
 might be that when the stationary temperature has been reached, the quantities of heat 
 which it loses and gains in a given time, are perfectly equal, and that the heat lost is 
 entirely employed in converting the water into vapour, but the whole of the acquired 
 heat is not necessarily derived, though this is assumed to be the case, from the air 
 (Page 95) cooled by contact with the bulb of the instrument. In fact, the hygrometer 
 is in the predicament of a cool body placed in a warm medium, and it must consequently 
 receive from surrounding bodies a greater amount of heat than it imparts to them in 
 virtue of the same process, and this will even vary with the state and colour of its sur- 
 face. Dr. Apjohn acknowledges that this disregarded influence must be of sufficient 
 magnitude to exert an appreciable influence, and regrets his inability to assign any 
 means of determining its amount. The scale is too small ; the readings should be made 
 to one-tenths of a degree Fahr. The probable errors of observation bear a high propor- 
 tion to the required result, particularly about 32. An error in reading of at 32 
 would affect the observation with an error of g^th of the whole amount ; at 80 the 
 inaccuracy would amount to about j^ih. But there is a still more serious source of error, 
 if Peltier is to be trusted. He has shown that from a surface charged with resinous 
 (Page 96) electricity, the process of evaporation in the atmosphere is more rapid than 
 from the same surface in a neutral state. If this is the case, theu the hypothesis that 
 such process is wholly dependent upon calorific influence must lead to erroneous results ; 
 and it is not at all improbable that in some such unappreciated influence the explanation 
 
 x 2 295 
 
AQUEOUS VAPOUR. 1845. Daniell. 
 
 NOTES. 
 
 will be found of those negative results, in which the temperature of the wet ther- 
 mometer has been found above that of the dry, which occur in all long series of 
 observations, and which have been ascertained with the greatest care in the Greenwich 
 observations. The formula for the calculation of the elasticity of steam from the obser- 
 vation of the moist bulb thermometer, as finally corrected by Dr. Apjohn, is as 
 
 follows : /" = /'- fL x 2~ 
 88 30 
 
 wherein/' denotes the tension of steam at the dew point;/', the tension of steam at the 
 observed temperature of the air ; d = the depression of the moist surface ; 88 (or pos- 
 sibly 87) = a co-efficient dependent upon the specific heat of the air and the latent heat 
 of the vapour ; p = the existing pressure of the air ; 30 ==: the mean pressure of the 
 air. Dr. Apjohn has, moreover, calculated the subjoined table (Phil. Mag. 1835, vol. vu.) 
 (Page 97) by which the determination of the dew point from the formula is greatly 
 
 facilitated. It gives ^= ^ for every value of d between .1 and 10. In calculating 
 
 an observation this quotient, as is obvious from the formula, is to be multiplied by p 
 the existing pressure, and the product when deducted from/' will afford /". Should the 
 
 o= KT; may still be derived from the table by 
 
 o i X oU 
 
 = .00383 + .0014 = .00497. The following; 
 
 depression exceed 10 the value of 
 addition. Thus if d =s 13 
 
 87 x 30 
 
 is the table. The first column is d ; the second 
 
 X 
 
 .1 
 
 .2 
 
 .3 
 
 .4 
 
 .5 
 
 .6 
 
 .7 
 
 .8 
 
 .9 
 
 1.0 
 
 1.1 
 
 1.2 
 
 1.3 
 
 1.4 
 
 1.5 
 
 1.6 
 
 1.7 
 
 1.8 
 
 1.9 
 
 2.0 
 
 2.1 
 
 2. -2 
 
 2.3 
 
 2.4 
 
 2.5 
 
 2.6 
 
 2.7 
 
 2.8 
 
 2.9 
 
 3.0 
 
 3.1 
 
 3.2 
 
 3.3 
 
 3.4 
 
 .00003 
 .00007 
 .00011 
 .00015 
 .00019 
 .00022 
 .00026 
 .00030 
 .00034 
 .00038 
 .00042 
 .00045 
 .00049 
 .00053 
 .00057 
 .00061 
 .00065 
 .00068 
 .00072 
 .00076 
 .00080 
 .00084 
 .00087 
 .00091 
 .00095 
 .00099 
 .00103 
 .00107 
 .00111 
 .00114 
 .00118 
 .00122 
 .00126 
 .00130 
 
 3.5- 
 
 3.6 
 3.7 
 3.8 
 3.9 
 4.0 
 4.1 
 4.2 
 4.3 
 4.4 
 4.5 
 4.6 
 4.7 
 4.8 
 4.9 
 5.0 
 5.1 
 5.2 
 5.3 
 5.4 
 5.5 
 5.6 
 5.7 
 5.8 
 5.9 
 6.0 
 6.1 
 6.2 
 6.3 
 6.4 
 6.5 
 6.6 
 6.7 
 
 .00134 
 .00137 
 .00141 
 .00145 
 .00149 
 .00153 
 .00157 
 .00160 
 .00164 
 .00168 
 .00172 
 .00176 
 .00180 
 .00183 
 .00187 
 .00191 
 .00195 
 .00199 
 .00202 
 .00206 
 .00210 
 .00214 
 .00218 
 .00222 
 .00225 
 .00229 
 .00233 
 . 00237 
 .00241 
 .00245 
 .00248 
 .00252 
 . 00256 
 
 6.8 
 6.9 
 
 7.0 
 7.1 
 7.2 
 7.3 
 7.4 
 7.5 
 7.6 
 7.7 
 
 8.0 
 8.1 
 8.2 
 8.3 
 8.4 
 8.5 
 8.6 
 8.7 
 8.8 
 8.9 
 9.0 
 9.1 
 9.2 
 9.3 
 9.4 
 9.5 
 9.6 
 9.7 
 9.8 
 9.9 
 10.0 
 
 .00260 
 .00264 
 .00268 
 .00271 
 .00275 
 .00279 
 .00283 
 .00287 
 .00291 
 .00294 
 .00298 
 .00302 
 .00306 
 .00310 
 .00313 
 .00317 
 .00321 
 .00325 
 .00329 
 .00333 
 .00337 
 . 00340 
 .00344 
 .00348 
 .00352 
 .00356 
 .00360 
 .00363 
 .00367 
 .00371 
 .00375 
 .00379 
 .00383 
 
 (Page 98.) When the reading, however, of the wet thermometer is lower than 32 
 the formula becomes/" = / ^~ + JL because the latent heat of water as well as the 
 296 
 
AQUEOUS VAPOUR. 1845. Daniell. NOTES. 
 
 latent heat of steam must be taken into account, as the heat evolved has first to liquefy 
 ice and then to convert the water into vapour. These calculations are troublesome, and 
 some of the data are uncertain. It rarely happens that any one will make them for a 
 long series of observations. Without reduction no precise conclusions can be obtained. 
 (Page 99) Observations of the dew point by hygrometer has already led to most valuable 
 conclusions. The safest deductions from the differences between the dry and wet bulb 
 thermometers are those which may be derived from a long series of experimental com- 
 parisons with the differences between the dew point and the temperature of the air, 
 which, as bearing a fixed ratio to each other, may probably be depended upon, at least 
 in the locality in which the observations were made. The Astronomer Koyal has thus 
 constructed from the Greenwich observations a table of the values of the fraction : 
 
 Difference between dew point and temp, of air. 
 Dift'. between evaporation temp, and air temp. 
 
 The difference between the dry and wet thermometers multiplied by these factors 
 according to temperature and deducted from the temperature of the air, will give a 
 close approximation to the dew point. Suppose the observation to have been 
 
 Air. Evap. Diff. Factor. 
 
 51.5 - 46.7 = 4.8 4.8x2=9.6 
 
 51 . 5 - 9 . 6 = 41 . 9 dew point. 
 
 (Page 100.) Greenwich factors for finding dew point from temperature of evaporation. 
 
 Temp, of air Temp, of air 
 
 between between 
 
 20-25 9.0 55-60 1.7 
 
 25-30 5.2 60-65 1.7 
 
 30-32 4.1 65-70 1.6 
 
 32-35 2.8 70-75 1.5 
 
 35-40 2.5 75-80 1.5 
 
 40-45 2.2 80-85 1.6 
 
 50-55 2.0 85-90 1.7 
 
 From a comparison of two years' observations at Greenwich of the wet bulb hygro- 
 meter with those of the dew point hygrometer it appears that the extreme differences 
 are by Dr. Apjohn's formula 
 
 -3. 9 between 65 and 70 
 
 +3.6 75 80 
 
 whilst the extreme differences by the Greenwich factors are 
 
 -3.7 between 75 and 80 
 + 5.6 75 80 
 
 Thus an appeal must be made to the dew point hygrometer whilst we are seeking to 
 become acquainted with the almost infinitely varying circumstances by which the eva- 
 poration hygrometer is affected. [Table xxxvi is placed opposite p. 115 in the Meteor. 
 Soc. copy. It should be in vol. I. opp. p. 115.] 
 
 (Page 154.) [He gives directions for observing with actinometer. He says perfect 
 clearness of sky is indispensable, the slightest cloud or haze over the sun being at once 
 marked by a diminution of resulting radiation. To detect such haze or cirrus a brown 
 glass applied before the eye is useful. He gives Forbes's actinometric observations at 
 (Page 165) Brienz and Faulhorn ; these are local, but the following comments are 
 made which bear upon aqueous vapour.] With respect to the points of contrary flexure, 
 they probably arise from a twofold effect of the sun's radiation. The one is the increased 
 intensity as the sun is higher; the other is the transference of vapour from the lower to 
 the higher regions of the air by the heating of the lower strata producing incipient con- 
 densation at a certain elevation and slight clouds which often appear between 10 and 12 
 o'clock. As the sun's power diminishes and the vapours redescend into the less rarefied 
 and warmer regions, they are in some degree redissolved in the afternoon, and the increased 
 
 297 
 
AQUEOUS VAPOUR. 1845-1849. Norton, W. A. NOTES. 
 
 transparency of the atmosphere checks the downward progress of the curve due to the 
 increasing obliquity of the rays. The maximum of intensity is sooner attained above 
 than below because the sun shines with a disproportionate intensity in the morning on 
 the upper station owing to the mass of vapour being then in the valleys. Forbes asks 
 {Page 166) what becomes of the heat absorbed by the air. Is it radiated in rays of a 
 different order from the clouds V or is it rendered latent by the conversion of the latter 
 into vapour? 
 
 (Page 219.) 1000 [for 1.000 in 1827 edition, p. 513]. 
 
 (Page 385.) The periodical increase and decrease of intensity [of atmospheric electri- 
 city] is so regular as evidently to be connected with the position of the sun above or 
 below the horizon, and is probably directly dependent upon the ultimate tendencies to 
 precipitation and evaporation produced by the regular changes communicated to the air. 
 It should also be remembered that similar and contemporaneous changes seem to affect 
 the magnetic phenomena of the earth. With regard to the sources from whence the air 
 (Page 387) receives its electric charges, we are in a state of great ignorance. Up to 
 the time of the late experiments of Dr. Faraday upon the electricity of effluent steam, 
 little doubt was entertained that the processes of evaporation and condensation were the 
 most active in supply. 
 
 Hunt, Carew. Journ. Boy. Geog. Soc., vol. xv. (1845.) (TV.} 
 
 (Page 284.) On the Island of St. Michael the mean hygrometrical dew point of the 
 summer half-year has been 58 ; of the winter, 55 ; making the quantity of vapour in 
 a cubic foot of air 5.35 grains and 4.87 grains. Either in consequence of this humidity 
 or the conducting power of the mountains, heavy thunderstorms are unknown. The 
 (Page 285) evaporation of the summer months is 28 inches, and of the winter 17 inches. 
 
 1846. 
 
 Journ. Eoy. Geog. Soc., vol. xvi. (1S4G.) (rv.) 
 [Nothing in it for these notes.] 
 
 1847. 
 
 Jcurn. Eoy. Geog. Soc., vol. xvii. (1847.) (TV.) 
 [Nothing for these notes.] 
 
 1848. 
 
 Barker, Lieut. Journ. Eoy. Geog. Soc., vol. xviii. (1848.) (rv.} 
 (Page 132.) Along the E. coast of Africa, from Goobul Karab to Core Kurangwah, 
 October to April is the rainy season [and hence the dry season occurs during the other 
 part of the year]. 
 
 1849. 
 
 Cruttenden, C. J. Journ. Eoy. Geog. Soc., vol. xix. (1849.) (rvp.) 
 (Page 69.) [When high upon the Peak of Eyramid in the Somali country he refers to 
 the night being bitterly cold, 48, and the dew falling like soft rain.] 
 
 Norton, W. A. (B. 1849, 3.) 
 
 (Page 352.) [He attributes the decrease in the horizontal force of the magnetic needle 
 from 4 A.M. to 6 A.M. to evaporation, a supposition which implies that evaporation is 
 greatest at these hours. He says this is the case. For the dew deposited at ni^ht is 
 evaporated during the morning hours; and the greater part of the evaporation of the 
 ram that falls during the night and the latter part of the day will take place durino- the 
 forenoon of the following day, except when the ground is unusually moist, in which case 
 the evaporation will be most energetic during the warmest part of the day.] 
 298 
 
AQUEOUS VAPOUR. 1851-1853. Fitz Roy, R. NOTES. 
 
 1851. 
 Pitz Roy, R. Journ. Eoy. Geog. Soc., vol. xx. (1851.) (rvp.) 
 
 (Page 107.) In Central America hot and dry weather prevails in the summer season 
 when the sun is not so high at noon as in winter. In the northern parts of the Isthmus 
 the dry season lasts longer than about Darien and Choco. In the season called winter 
 the sun is seldom seen, so clouded is the sky. There is a short interval of fine weather 
 in the middle of the rainy season near the end of June, but the regular and continued 
 summer, a very dry and parching time in the northern parts of the Isthmus, lasts from 
 December to April or May. 
 
 Gutzlaff, Ch. Journ. Boy. Geog. Soc., vol. xx. (1851.) (rvp.) 
 (Page 200.) In Tibet from October to March the sky is clear, the atmosphere is arid, 
 and the vegetation is frequently scorched by dry winds. 
 
 Livingston, Dr. David. Journ. Eoy. Geog. Soc., vol. xx. (1851.) (rvpJ) 
 (Page 140.) The dry season on the Zouga extends from May to October. 
 
 Parkyns, Mansfield. Journ. Eoy. Geog. Soc., vol. xx. (1851.) 
 (Page 261.) In the region occupied by the Kubbabish Arabs between Kordofan and 
 Dongola there is a dry season before the rains (about April and May). 
 
 Wallin, GK A. Journ. Boy. Geog. Soc., vol. xx. (1851.) (rvp.) 
 (Page 299.) At Muweilah, and to some extent throughout the N.E. part of Arabia, 
 rain falls at intervals from October to April. During the remaining months the 
 weather is hot and dry. 
 
 Journ. Boy. Geog. Soc., vol. xxi. (1851.) (rv.) 
 [Nothing in it for these notes.] 
 
 1852. 
 
 Journ. Boy t Geog. Soc., vol. xxii. (1852.) (n>.) 
 [Nothing for these notes.] 
 
 1853. 
 Davis, Sir J. F. Journ. Boy. Geog. Soc., vol. xxiii. (1853.) (rvp.} 
 
 (Page 247.) The wet and dry seasons at Chusan and at Hongkong are reversed ; in 
 the south the winter is dry, and the flooding rains fall during summer. 
 
 Findlay, A. G. Journ. Boy. Geog. Soc., vol. xxiii. (1853.) (rvp.) 
 
 (Page 237.) Beyond the tropics the warm wind descends and blows towards the 
 poles, parting with its heat and moisture ; till at last reaching the pole quite dried, and 
 at a minimum temperature, it by its accumulation rises and returns to the tropics. If 
 the earth's surface were uniform, these belts of calms and winds would be symmetrical 
 on either side of the equator. But the proportion of land to water in the northern 
 hemisphere is 100 to 154 ; while in the southern hemisphere it is 100 to 628, according 
 to Prof. Eenouard. Yet all the countries in S. latitude are remarkable for the dryness 
 of their climate, and it can be demonstrated that the evaporation of the southern is 
 deposited, in the northern hemisphere. From this unequal distribution of land and its 
 (Page 238) effects we have the phenomenon of that line of junction of the trade winds 
 to the north of the equator (in a mean between 8 and 2 N. lat.) varying with the 
 progress of the sun in the ecliptic, but always characterized in its axis by an enormouy 
 deposition of rain. 
 
 299 
 
EXPLANATORY REMARKS. II. 
 
 Strachey, H. Journ. Eoy. Geog. Soc., vol. xxiii. (1853.) (rvp. 
 (Page 64.) In the high Tibetan regions, as elsewhere, wind and moisture seem to 
 be connected with low barometer. Winter is the season of clouds at Ladak, the number 
 (Page 65) of cloudy days exceeding the fine ones ; in spring they are nearly equal ; in 
 summer the sunny weather greatly exceeds the cloudy ; and in autumn the sunshine 
 still predominates in a less degree. The snow line of a country may be regarded as 
 (Page 68) an index of its joint thermometric and hygrometric status and their mutual 
 reaction. The hygrometric element has often been too much overlooked. 
 
 Sykes, W. H. Journ. Boy. Geog. Soc., vol. xxiii. (1853.) (rvp.) 
 (Page 111.) At Zanzibar, from observations made by Lieut. Fergusson in 1850, the mean 
 depression was 22 [ = 2.2], and the mean dew-point temperature by Glaisher's factors 
 76.6 ; by Apjohn's formula 76.85. The lowest dew point was 72.9, and the highest 
 (Page 113) 79.3 in April. The sky seems ever clouded. The place is remarkable for 
 the extraordinarily continuous amount of humidity and the consequent very high tension 
 of vapour, humidity so great that in the driest month, February, it amounted to 87 ; 
 while in every other month of the year it was never less than 91 per cent. Nothing 
 approaching to these facts occurs on the shores of India ; even during the monsoons. 
 At Bombay the highest percentage of humidity was 88 in July, and the mean of the 
 year 66 in 1844. At Madras in the same year 83 per cent, in December (a monsoon 
 month), and the mean of the year 74 per cent. At Calcutta in 1844 in August the 
 percentage was 94, and the r mean of the year 84. At Aden in Arabia in 1848 the 
 highest percentage was 77, and the mean of the year 71 per cent. In the tablelands of 
 India the mean annual percentage of humidity ranges from 55 to 60. In India the only 
 approach to the humidity of Zanzibar is met with in the cloud-capped summit of 
 Dodabetta, at 8640 feet above the sea; in Oct. 1847 (a monsoon month) it amounted to 
 97 per cent., and the mean of the year was 90 per cent. From various short observa- 
 (Page 114) tions made by Capt. Elliott, the atmosphere of Zanzibar would seem to be 
 more continuously loaded with vapour than any place to the eastward. It does not 
 necessarily follow that the highest temperature of the air and the highest temperature 
 of evaporation give the highest dew point and consequent tension of vapour. Witness 
 Batavia and Moulmein ; at the former the temperature of the air and evaporation was 
 85.8 and 79.4, and at the latter 100.9 and 83'3, yet the tension of vapour and dew 
 point were identical at both places, viz. .909, and dew point 76.95, while at neither place 
 (Page 115) was the degree of humidity equal to that of Zanzibar. 
 
 EXPLANATORY REMARKS. II. 
 
 IT is no part of the plan of the ' Scientific Roll ' to correct and comment upon the views 
 and statements of the various authors. If such a course were adopted the spirit 
 of impartiality which it is hoped will be adhered to in the " Notes " would not be main- 
 tained. Each author is allowed to state his own views, and each reader must judge for 
 himself which views are the more correct by a careful comparison of one with the other. 
 In many cases the errors of one writer are pointed out by subsequent writers. More- 
 over, if comments were made upon the ' 4 Notes " whenever they seemed to be called for, 
 the work would be extended to a most inconvenient size, as the comments would be 
 more voluminous than the " Notes " themselves. Hence it is necessary for the reader to 
 thoroughly criticize all the notes before accepting their strict accuracy as matters of 
 ict. The Conductor does not claim to write with any high authority, but is simply 
 endeavouring to carry out what he conceives to be a useful plan to the best of his 
 power. In order to ascertain what writers mean, and how far they agree or disagree, it 
 is necessary to make comments, which are kept with the Notes" in the manuscript 
 300 
 
EXPLANATORY EEMAKKS. II. 
 
 state, but are not intended for publication. As a sample of these we give those referring 
 to the Rev. Edward Saul's Notes under the year 1766. 
 
 Saul clearly perceives that vapour adds to the weight of the air, but he does not 
 see that owing to its unequal diffusion the specific gravity of the air is least in the 
 place where there is most vapour. He believes that as the variation in the barometer 
 indicates a greater variation of weight than is consistent with the addition and with- 
 drawal of the probable amount of vapour in the air, therefore such variation cannot be 
 due to vapour. His mistake lies partly in overlooking the question of specific gravity, 
 and partly in ignoring that the vapour may have some influence on the result. 
 Suppose the pressure over all the earth to be 30 in., then the uniform addition of vapour 
 corresponding to .025 in. of mercury would increase the pressure to 30.025 in. 
 Suppose, however, that the addition is confined to one hemisphere, then the air in the 
 moister hemisphere would expand, and cause a compression of the air in the drier 
 hemisphere to such an extent that the mean pressure of the two hemispheres would be 
 30.0125. If, then, the effect was to lower the pressure in the moist hemisphere to a 
 mean of 29.990 in., it would raise that in the other to a mean of 30.035 in. In fact, 
 the increased pressure would manifest itself in the dry regions, not in the moist. 
 Therefore the diffusion of vapour will cause variation of pressure, increasing it in the 
 dry regions just as much as it decreases it in the moist. The mean pressure will vary 
 with the quantity of vapour, and the mean variation also will vary with the quantity 
 of vapour. The difference of pressure in contiguous areas will increase with the 
 quantity of vapour. The precise extent of the influence of vapour requires to be 
 accurately gauged. It is only one of several causes which influence pressure. It is not 
 (Page, 16) quite clear what Saul intends to impute to Boyle. The meaning which the 
 passage bears implies that the cloudiest days are always those on which the barometer 
 is lowest. If this were strictly true, then the range of the barometer below a certain 
 maximum would be a gauge of the degree of cloudiness. Is this so ? Again, it 
 .also implies that the barometer is lowest on days which have the most vapour in the 
 .air, quite irrespective of cloudiness. In this case the barometer should rise and fall 
 inversely with the dew point, being highest when it is lowest ; and axiomatically the 
 height of the barometer should be correlative with the dew point. The latter idea is in 
 effect rejected by him (on Page 26), because the range of the barometer indicates a 
 greater quantity of vapour in the air than is credible, viz. 42 in. of water for England. 
 By parity of reason, the barometric range of the equator would imply a far less 
 amount, which is not consistent with well-established facts. The case of high 
 barometer in fogs is in opposition to Boyle's idea ; and the fall of the barometer at 
 times with rise of fogs, also seems to be against it. Boyle's view may be right in the 
 sense that the pressure is relatively least where most vapour is. The meaning implied 
 by Saul seems, however, to be absolutely least. 
 
 Boyle's idea of the connection between cloudiness and low barometer may be tested 
 by arranging cloudiness, the pressure of vapour, and the humidity, according to 
 quantity, and setting against them the contemporaneous barometric height. Then the 
 barometric heights may be arranged in the order of height, and the cloudiness set 
 against them. The observations made by Professor Kedzie at Lansing, in Michigan, 
 will be used for the purpose of testing this point. 
 
 First, then, take cloudiness. 
 
 Date, 
 
 1878. 
 
 Observation 
 hour. 
 
 Percentage of sky 
 covered. 
 
 Height of barometer, 
 inches. 
 
 Jan. 1. 
 
 7 a.m. 
 
 100 cum.-stratus. 
 
 28.963 
 
 
 2 p.m. 
 
 do. 
 
 28.890 
 
 
 9 p.m. 
 
 do. 
 
 28.912 
 
 2. 
 
 7 a.m. 
 
 100 nimbus. 
 
 29.123 
 
 4. 
 
 7 a.m. 
 
 do. 
 
 28.839 
 
 
 2 p.m. 
 
 do. 
 
 28.863 
 
 301 
 
EXPLANATOKY KEMAKKS. II. 
 
 Date, 
 
 1878. 
 
 Observation 
 hour. 
 
 Percentage of sky Height of barometer, 
 covered. inches. 
 
 Jan. 5. 
 
 7 a.m. 
 2 p.m. 
 
 100 stratus. 
 100 nimbus. 
 
 29.196 
 29.055 
 
 _ 
 
 a |j.jij 
 
 7 a.m. 
 
 100 stratus. 
 
 29.511 
 
 ?> ' 
 
 O n m 
 
 do. 
 
 29.513 
 
 8 
 
 & p. in* 
 9 p.m. 
 7 a.m. 
 
 do. 
 100 nimbus. 
 
 29.454 
 29.286 
 
 ,, 0. 
 
 2 p.m. 
 
 100 stratus. 
 
 29.215 
 
 9 
 
 9 p.m. 
 7 a.m. 
 
 do. 
 do. 
 
 29.237 
 29.193 
 
 3> P< 
 
 2 p.m. 
 9 p.m. 
 
 do. 
 do. 
 
 29.056 
 28.955 
 
 9 
 
 ' 
 
 , 3. 
 
 9 p.m. 
 7 a.m. 
 
 No cloud, 
 do. 
 
 29.259 
 29.267 
 
 ?J 
 
 5. 
 
 9 p.m. 
 
 do. 
 
 29.015 
 
 
 6. 
 23. 
 
 9 p.m. 
 7 a.m. 
 
 do. 
 do. 
 
 29.356 
 29.431 
 
 Feb. 10. 
 
 9 p.m. 
 
 do. 
 
 28.912 
 
 Next take the pressure of vapour. 
 
 The first group are 
 
 observations with high- 
 
 vapour pressure ; the second those with 
 
 low-vapour pressure. 
 
 
 Date. 
 
 Observation 
 
 Vapour 
 
 Height of 
 
 
 hour. 
 
 pressure. 
 
 barometer. 
 
 Jan. 10. 
 
 9 p.m. 
 
 .188 in. 
 
 28.807 in. 
 
 16. 
 
 7 a.m. 
 
 .188 
 
 28.895 
 
 17. 
 
 2 p.m. 
 
 .212 
 
 28.987 
 
 20. 
 
 7 a.m. 
 
 .229 
 
 28.936 
 
 
 2 p.m. 
 
 .241 
 
 28.882 
 
 
 9 p.m. 
 
 .204 
 
 28.929 
 
 21. 
 
 7 a.m. 
 
 .188 
 
 28.950 
 
 
 2 p.m. 
 
 .204 
 
 28.925 
 
 25. 
 
 9 p.m. 
 
 .199 
 
 28.950 
 
 2 
 
 7 a.m. 
 
 .098 
 
 29.123 
 
 
 9 p.m. 
 
 .065 
 
 29.259 
 
 3. 
 
 7 a.m. 
 
 .071 
 
 29.267 
 
 
 2 p.m. 
 
 .066 
 
 29.013 
 
 ., 4. 
 
 9 p.m. 
 
 .086 
 
 28.980 
 
 5. 
 
 7 a.m. 
 
 .065 
 
 29.196 
 
 
 2 p.m. 
 
 .075 
 
 29.055 
 
 
 9 p.m. 
 
 .048 
 
 29.015 
 
 6. 
 
 7 a.m. 
 
 .050 
 
 29.138 
 
 
 2 p.m. 
 
 .086 
 
 29.189 * - 
 
 
 9 p.m. 
 
 .055 
 
 29.356 
 
 7. 
 
 7 a.m. 
 
 .062 
 
 29.511 
 
 
 2 p.m. 
 
 .055 
 
 29.513 
 
 
 9 p.m. 
 
 .051 
 
 29.454 
 
 8. 
 
 7 a.m. 
 
 .060 
 
 29.286 
 
 
 2 p.m. 
 
 .087 
 
 29.215 
 
 23. 
 
 7 a.m. 
 
 .065 
 
 29.431 
 
 
 2 p.m. 
 
 .084 
 
 29.410 
 
 
 9 p.m. 
 
 .082 
 
 29.443 
 
 28. 
 
 7 a.m. 
 
 .082 
 
 29.137 
 
 
 2 p.m. 
 
 .087 
 
 29.177 
 
 
 9 a.m. 
 
 .071 
 
 29.237 
 
 29. 
 
 7 a.m. 
 
 .057 
 
 29.343 
 
 There seems to be an inverse relationship here. Now test this quantitatively. On 
 Jan. 10 and 16 the vapour pressure was .188 in. ; on the former date the barometer was 
 28.807 in., and on the latter, 28.895. Although the vapour pressure is the same, the 
 barometer has risen .088 in. What caused this difference? The humidity was the 
 same on both occasions, or 100 ; the temperature was the same ; and the cloudiness 
 was the same, that is, 100. The wind on the 10th at 9 p.m. was N.W. 4, and on the 
 302 
 
EXPLANATORY - , , 
 
 16th, at 7 a.m., S.W. 2. Would the wind cause it ? or is itSE{&K.t^ yap. pur observa- 
 tions are too local and rough? On the 21st, at 7 a.m., the vapour pressure was .188, 
 and the barometer was 28.950 in.; the temperature was the same as before; the 
 humidity 100 ; and the cloudiness 100. The wind was N.E. 4. On the 25th, at 9 p.m., 
 the vapour pressure was .199 in., and the barometer 28.950 in. ; that is, with more 
 vapour the barometer was at the same height. On the 21st, at 2 p.m., the vapour 
 pressure is .204 in., and the barometer 28.925. The vapour is .005 more, and the 
 barometer is .025 less; this gives an inverse ratio of 1 : 5. On the 17th, at 2 p.m., 
 the vapour is .008 in. more, and the barometer .058 in. higher, which gives a direct 
 ratio of 1 to 7. There is, evidently, some great irregularity here, which should 
 perhaps be eliminated if the vapour pressures were grouped. The following table results 
 from doing this, and taking the mean height of the barometer coincident with them. 
 
 Vapour pressure. Barometer pressure. 
 
 .040-. 050 in. 29. 015 in. 
 
 .050 -.060 29.358 
 
 .060 .070 29.282 
 
 .070-. 080 29.186 
 
 .080-. 090 29.266 
 
 .090 -.100 29.123 
 
 .200-. 210 28.934 
 
 .210-. 240 28.938 
 
 But the irregularity is still just as manifest, and further tests are required to make the 
 matter clear. For instance what causes this great difference ? On Jan. 6 at 7 a.m. the 
 vapour pressure was .050 in. ; and the barometer stood at 29.138 in. ; while on the 7th 
 at 9 p.m. the vapour pressure was .051 in., and the barometer indicated 29.454. The 
 difference in the vapour pressure was + .001 in., and the difference in the barometric 
 pressure was +.316. The facts seem to point to the conclusion that the data given are 
 simply local-vapour tension, and that the true vapour pressure is a very different thing 
 as pointed out by Daniell. 
 
 In order to test the statement on p. 26, it would be necessary to ascertain what have 
 been the ranges of the barometer under special circumstances, and what amounts of 
 aqueous vapour in the air have been associated with such ranges. Saul says nothing of 
 temperature nor of wind, which ought to be taken into account. As this has most to do 
 with barometric condition, the point is tested under that heading in various ways, with 
 the result that Boyle's conclusions are not substantiated. 
 
 On p 27 Saul refers to the vapour floating in the air as though he regarded the 
 visible cloud as the sole representative of the vapour in the air, and therefore appears 
 not to take into account the invisible vapour diffused in the air. In the sequel he 
 makes some distinction between vapours and clouds, but seems to think that the less 
 compact vapours are arranged in strata like the clouds. 
 
 On p. 29 he seems to regard the vapour as distinct from the air, and being lighter, it 
 rises like a cork in water, and settles at that height where the air has the same specific 
 gravity as itself. As the weight of the air is ascribed solely to the quantity of air, the 
 heavier the air is the higher such vapour must rise. As the air, varies in weight, the 
 vapour will rise up and sink down. This is a simple view ; but he ignores the property 
 of the diffusion of gases. The exhalation of vapours by subterranean heat probably 
 takes effect only in volcanoes and hot springs ; and is not so general as he would seem 
 to imply. If his ideas were right, the zone of maximum humidity should rise faster 
 during periods of high than of low barometer. At what rate does it rise ? Further, if 
 his view is right, taking heavy to mean dense, then the height of clouds should on the 
 average range with that of the mercury, that is, be higher in cold weather than in hot. 
 This is not the case, as clouds are higher in summer than in winter. Saul gets rid of 
 this difficulty by assuming that the vapours are of different specific gravities. 
 
 303 
 
EXPLANATORY REMARKS. II. 
 
 If we reduce Dr. Halley's estimate on p. 74 to some standard which should be 
 generally adopted, we have the following results. It remains to be decided what 
 standard shall be adopted. For the present one square mile will be tried. The area of 
 the Mediterranean is 734,000 sq. miles, which would give 7193 tons, and 40,871 tons 
 per square mile respectively ; or 11 tons and 63 tons per acre ; or .0043 in. of mercury 
 and .0246 in. of mercury ; or 15.1 grains and 86.5 grains pressure per square inch. The 
 pressure in grains per square inch may be the best standard, more especially if the 
 barometric pressure be expressed by weight, not by inches of mercury. How did Halley 
 form his calculation and where ? and what is the difference between the result indicated 
 by his figures and the conclusion that might be drawn from observations on aqueous- 
 vapour tension? For instance, in the quarter ending Dec. 31, 1881, the elastic force 
 of vapour is given as .234 in. for Bolton and .372 in. for Osborne ; which would give 
 pressures of 853 grains and 1312 grains per square inch. The elastic force is of course a 
 computed thing, and gives no clue to the amount of vapour over any given spot. Books 
 seem to imply that the aqueous-vapour pressure is indicated by this elastic force. It 
 seems rather to indicate the local amount of vapour in the area immediately about the 
 point of observation. The actual pressure is a very much smaller figure as indicated by 
 Halley, as also by Daniell. Much of this really appertains to barometric pressure, but 
 the question requires discussion here in order to ascertain what is the probable amount 
 of vapour in the air per square inch, or per acre, or per square mile. With an elastic 
 force of .234 in. there were 2.7 grains in each cubic foot of air. A cubic inch 
 would contain .0015 grain ; and on the assumption of uniform distribution, this would 
 give an aqueous-vapour column of nearly 9 miles. A cubic inch of rain would 
 weigh about 252 grains, so that it would correspond to an elastic force of .069 in. 
 lleturning to Halley's estimate, it may be observed that the greatest pressure is 86.5 
 grains on the square inch, or .0246 in. of mercury, while the total pressure would be 
 about 30 in. The ratio of the vapour to the air would be as 1 to 1215. Hence it would 
 be inferred that vapour per se has little influence in varying the pressure. The main 
 effect would, then, probably be caused by heat and liberation of latent heat diminishing 
 the specific gravity of the column owing to overflow or passage of the air into neighbour- 
 ing regions as pointed out by Daniell. Hence, then, it will seem probable that the 
 main factor in the variation of the barometric condition is the latent heat liberated by 
 condensing vapour. The barometer may consequently give a rough indication of the 
 amount of heat liberated, and hence indirectly of the quantity of vapour condensed. 
 The difference in the height of the barometer maybe mainly due to the difference in the 
 specific gravity of the air, one important factor in regulating which difference is the 
 unequal diffusion caused by heat and evaporation, and the consequent unequal conden- 
 sation of such vapour giving rise to evolution of heat derived from places of higher 
 temperature. If so, then it will be seen how intimately connected are the climatal 
 elements, aqueous vapour, barometric condition, temperature and wind. 
 
 5J04 
 
SCIENTIFIC UNION. 
 
 Srimfifk 
 
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 The members of the British Association Committee for drawing up suggestions upon 
 
 305 
 
SCIENTIFIC UNION. 
 
 methods of more systematic observation, and plans of operation for local societies, have 
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 National Board of Health with respect to water analysis, and other subjects, and by 
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 ncourage our local societies to combine cordially and unanimously in prosecuting some 
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 subjects which might be taken up in this way, and there are many branches of industry 
 and art which do not receive adequate systematic investigation, because those who practise 
 them for profit will not give the time and care necessary for the purpose. There is no 
 doubt practical men would derive great advantage from well-organized systematic 
 observations, and it is to be regretted that so few have been made. The valuable and 
 long-continued work of Drs. Lawes and Gilbert, of Rothamsted, has induced a spirited 
 American gentleman, Mr. Lawson Valentine, to acquire a farm for the purpose of carry- 
 ing out a system of agricultural experiments. His present plans, he states, are : " First, 
 that the farming operations be carried on in accordance with the best-known methods, 
 and under the best possible organization and management, with a view of educating 
 and enlightening others by furnishing valuable examples and results in practical agri- 
 culture. Second, that there be a scientific department devoted to agricultural investi- 
 gation and experiment, and that such department be of the highest order so as to 
 command the respect, interest and co-operation of the leading scientific minds of this 
 and other countries. Third, that Houghton Farm be a comfortable, healthful and 
 attractive home for the family of its proprietor, and afford large hospitality for friends 
 and guests." If a dozen establishments of this kind were started in various parts 
 of the world, it would not be long before agriculturists reaped benefits which in the 
 ordinary way of farming would not be acquired! for centuries. In the preliminary 
 report which the present director of the experiments, Mr. Penhallow, has kindly sent us, we 
 have an account of the experiments on Indian corn carried on by Mr. Manley Miles 
 during 1880 and 1881. We do not propose to analyze those results, but we would 
 quote a passage indicating the spirit in which enquiries will be made : " Two distinct 
 although closely related and parallel lines of investigation are needed to furnish that 
 accurate knowledge of natural laws that is best adapted to the wants of the practical 
 farmer. In the first place, we must leave the purely scientific work of the laboratory to 
 gain a knowledge of the elements of animal and vegetable nutrition and of their relations 
 tinder known definite conditions ; and investigations in this direction may with advan- 
 tage be very much extended. The most obscure fact in organic chemistry, that has no 
 apparent relation to the practical affairs of life, is of great value ; and when its bearings 
 are fully appreciated it may be found to have an influence on matters of e very-day 
 interest. In this utilitarian age, when the so-called practical side of affairs is kept pro- 
 minently in view and industrial education is so generally demanded, there is danger 
 that the importance of pure science, which furnishes the means of exact investigation in 
 matters pertaining to practical ends, may be overlooked, and opportunities for extending 
 its domain by original research neglected. 
 
 " In the second place, accurate and well-planned experiments in the feeding of animals, 
 iiiicl with crops in the field, are needed to answer the various practical questions that 
 arise in the management of the farm, and to determine the agricultural value of the 
 facts and theories that are presented as the result of purely scientific investigations. 
 Experiments under t'nis second head, without departing too widely from established 
 methods of farm practice, must be conducted in accordance with strictly scientific 
 methods, notice being taken of every condition that may possibly influence results ; 
 and they demand on the part of those who conduct them an extended knowledge of 
 practical farming, and the trained skill and ability for original investigations that are 
 required in researches in pure science." 
 306 
 
THE SCIENTIFIC ENQUIEER. 
 
 In 1882 the present director of experiments commenced a series of methodical inves- 
 tigation into the causes of the disease called " yellows " in peaches. As this investiga- 
 tion is still in progress, and as many horticulturists both in the United States and 
 elsewhere may be willing and able to co-operate, the questions issued by Mr. Penhallow 
 are reprinted here. 
 
 Sciwiifit inquirer. - 
 
 Correspondence is invited on Science matters of all Jdnds. In all cases 
 names and addresses sJiould be given ; but these will not be published without the 
 writer's consent. The Conductor will not be responsible for the opinions expressed 
 by correspondents. All communications should be addressed to the Conductor, 
 7, Red Lion Court, Fleet Street, London, E.G. 
 
 Eeplies to questions should be numbered in accordance with the questions to which 
 they refer. The contractions following the questions and answers, indicate the class of 
 notes to which they will ultimately be assigned, and the place where full reference will 
 be given to the details bearing upon them. The following request and set of questions 
 are reprinted from the circulars sent us by Mr, Penhallow. The numbers in paren- 
 theses are those given in the original, those which precede them are those adopted 
 for the ' Scientific Roll ' for the purpose of reference. 
 
 P=Plantae. 
 
 Experiments and observations are now being made at the Houghton Farm Experiment Station, 
 upon the diseases of fruits, with a view to determining their cause and the remedies which may 
 be applied. To make our work of the greatest practical value, it is earnestly desired that fruit 
 growers and Horticultural Societies will lend us their aid, and those whom these circulars 
 with their accompanying forms may reach, will confer a favour by making careful observations 
 upon their trees according to the following questions ; and at the end of the growing season 
 when the fruit is ripe fill in the answers and return to Houghton Farm. Any information 
 concerning the disease in past years will be of great value. Those who feel an interest in this 
 work and desire to avail themselves of what is already known concerning the treatment of 
 Peach Yellows and Pear Blight, will be furnished with printed directions upon application. 
 Address, 
 
 D. P. PENHALLOW, 
 Botanist to Houghton Farm Experiment Station, 
 
 Mountainville, Orange Co., 
 
 New York, U.S.A. 
 
 QUESTIONS RELATING TO THE PEACH TREE AND THE DISEASE CALLED YELLOWS." 
 
 Please observe carefully, fill in your answers concisely, and return as soon as the fruit ripens. 
 
 Make careful distinction between Slight and Yellows. 
 
 151. (1.) At what time of year does the disease first appear ? (P. 1) 
 
 152. (2.) Does the disease first appear before or after the tree has come into bearing, or is 
 that a matter of indifference ? Which is the more common ? (P. 2) 
 
 153. (3.) Which is the more liable to attack, seedlings or grafted trees ? Is there any 
 difference? (P. 3) 
 
 154. (4.) What is the first indication of disease in an apparently healthy tree ? (P. 4) 
 
 155. (5.) Where does it first appear? (P. 5) 
 
 156. (6.) Is the disease localized, i.e., confined to particular parts of the tree, or is the whole 
 
 tree gradually involved ? (P. 6) 
 157. (7.) Wh 
 
 Then a tree is attacked, how long before it dies ? (P. 7) 
 
 158. (8.) Is there any difference in the health of trees on account of location, as between high 
 land and low, or on account of different exposure ? (P. 8) 
 
 159. (9.) How old are your trees ? (P. 9) 
 
 100. (10.) How long has the disease run ? (P. 10) 
 161. (11.) What manures have been applied ? (P. 11) 
 
 307 
 
ANNOUNCEMENTS. 
 
 162. (12.) Has there been any apparent effect ? (P. 12) 
 
 163. (13.) What has been your method of treating diseased trees ? (P. 13) 
 
 164. (14.) What has been the result ? (P. 14) 
 
 165. (15.) How is the fruit affected when it forms before disease is evident ? (P. 15) 
 
 166. (16.) How is the fruit affected when.it forms on the diseased tree ? (P. 16) 
 167*. (1?!) How long has the disease been known in your locality ? (P. 17) 
 
 168. (18.) What has been the effect upon the annual yield of fruit ? (P. 18) 
 
 169. (19.) How long have you cultivated the peach ? (P. 19) 
 
 170. (20.) Has the disease increased or decreased during that time ? (P. 20) 
 
 171. (21.) How many diseased trees have you ? (P. 21) 
 
 172. (22.) How many healthy trees have you ? (P. 22) 
 
 173. (23.) What is the yield in bushels, for this year, of the healthy trees ? (P. 23) 
 
 ANNOUNCEMENTS. 
 
 Part III. of the ' Scientific Koll ' will be commenced, if life and health and support be 
 granted to the Conductor, in November 1883. In order that the Bibliography may be as 
 full as possible, authors and publishers are respectfully solicited to send copies of, or re- 
 ferences to, all their publications dealing with the barometrical condition of the air. 
 
 As soon as 200 persons have expressed a wish to subscribe for any one of the subjects 
 mentioned below, the publication of that section of the ' Scientific Koll ' will be forthwith 
 commenced. The subscription price will be 7s. 6d. and 10s. for each volume, according as 
 the residence of the subscriber is at home or abroad. Each volume will comprise about 
 400 pages ; and each volume will, in most cases, contain two or more parts, each of which 
 may be subscribed for separately. The extent of these parts will depend upon the 
 amount of matter in hand, so that the subscription price for each cannot be fixed at present, 
 but will be settled when the publication of each part is commenced. The following is a 
 list of the principal subjects : 
 
 Atmosphere, Water, Ocean (5), Eivers, Lakes, Springs, Floods, Glaciers, Land, Elevation 
 and Subsidence of Land and Sea-Bottom, Denudation, Orography, Earthquakes, Volcanoes, 
 Earth Magnetism, Marshes, Minerals, Stratigraphy, Eocks, Plants generally and in classi- 
 fied groups; Animals generally ; Protozoa, Actinozoa, Hydrozoa, Echinodermata, Crustacea, 
 Scolecida, Annelida, Mollusca, Myriapoda, Arachnida, Bhynchota, Orthoptera, Diptera, 
 Coleoptera, Lepidoptera, Neuroptera, Hymenoptera, Pisces, Amphibia, Eeptilia, Aves, 
 Mammalia, and Man. 
 
 Subscribers' names only are asked for now. The sending of these will not involve any 
 pecuniary liability, but will simply be taken as implying that the senders take an interest 
 in the work, and will probably undertake to subscribe when asked to do so. At the moment 
 of going to press the subject for which the largest number of names has been received is 
 Ocean. 
 
 308 
 

 AQUEOUS YAPOUR: NOTES. 
 
 1854. 
 Livingston, Dr. Journ. Boy. Geog. Soc., vol. xxiv. (1854.) (rvp.} 
 
 (Page 291.) When near Kamakama (in S. Africa) he observes, " The greater leafi- 
 ness of the trees showed we were in a moist climate." 
 
 Maclaren, C. (B. 1854, 1.) 
 
 (Page 671.) The winds transport the moisture from the surface of the ocean to the 
 interior of the great continents where it is precipitated. Mountains attract the moisture 
 which floats in the atmosphere ; they also obstruct the aerial current, and, presenting 
 (Page 672) great inequalities of temperature, favour precipitation. He believes that 
 in all countries with a summer heat above 70 the presence or absence of woods, and 
 their greater or less luxuriance, may be taken as a measure of the amount of humidity 
 [or, as the context shows, rainfall, not humidity]. 
 
 1855. 
 
 Journ. Roy. Geog. Soc., vol. xxv. (18o5.) (7T.) 
 [Nothing for notes on aqueous vapour.] 
 
 1856. 
 Austin, Robert. Journ. Roy. Geog. Soc., vol. xxvi. (1856.) (rv.) 
 
 (Page 261.) Mt. Welcome, in West Australia, Oct. 21-25, -1855. Weather very cloudy 
 till towards night, when the wind veered to the westward, and the sky became clear, 
 till about 2 A.M., when a heavy cloud-bank came up from the N.W., and soon spread in 
 dense cumulus above us, but low enough to touch the hills. There was a rise of "03 in. 
 in the barometer every evening, when the cloudy canopy was dissipated. 
 
 Hopkins, Thomas. Journ. Roy. Geog. Soc , vol. xxvi. (1856.) 
 Head April 14, 1856. (rv.) 
 
 (Page 158.) There are certain areas of condensation of aqueous vapour, within and 
 near to mountainous regions of the tropics, towards which general winds blow from parts 
 far distant, constituting what are called the tropical trade-winds of the Atlantic and 
 Pacific Oceans. The N. and N.E. winds that blow over the continents of Europe and 
 Asia are aerial currents flowing towards partial vacua which are produced in areas of 
 condensation, presenting evidence of the nature of the disturbances that produce these 
 great movements of the atmosphere. When winds which are dry pass over the surface 
 of the ocean, they readily take up moisture, which is subsequently condensed, creating a 
 vacuum and producing rain at their termini. But when a partial vacuum in the 
 PART II. No. 11. Y 309 
 
AQUEOUS VAPOUR. 1856. Hopkins, Thomas. NOTES. 
 
 atmosphere is thus produced, heavier air presses in and flows as a wind from distant 
 parts not only over the ocean, but also sometimes over the low lands of continents, such 
 as those of Asia and Europe. There are other winds which blow from dry to moist 
 re-ions In the northern portions of America, particularly during the winter, the air 
 generally flows from the north, from one part that is comparatively dry and heavy to 
 another part which has been rendered light by condensation of vapour brought by the 
 
 tropical wind from the Atlantic Ocean to the Gulf of Mexico. The great mass of air 
 therefore, that passes over this continent in the winter flows southward to the Gulf of 
 Mexico in the neighbourhood of which, and against elevated land, the vapour that is at 
 the same time brought from the tropical Atlantic is largely condensed. A part only of 
 (Page 159) the vapour of the tropical seas passes into the Gulf of Mexico, as large 
 portions of it turn northward over the Atlantic as well as over the Pacific Oceans, which 
 portions are condensed on the western coasts of America and Europe. But the air 
 which contained the vapour does not, after that vapour has been condensed, return to 
 the tropics over the same two oceans, as in neither of them do north winds prevail. 
 The moist south-west winds of the Atlantic, after being deprived of a large part 
 of their vapour by cold, return in a dry state over the low lands of the continent ; 
 while the north-west winds of the northern part of the Pacific, after furnishing the rains 
 of W. America, pass over Russian America and Behring Strait towards the Arctic Ocean, 
 and return over the low lands of the central part of America as dry winds. Both of 
 these land winds are dry, because they have been deprived of much of their vapour 
 among mountains by cold ; and they afterwards pass from colder to warmer latitudes, 
 which renders them more capable of taking up moisture, and they press and flow towards 
 their termini because there vapour has been brought from other parts by other winds 
 to be condensed and to create a comparative vacuum in the atmosphere. Being in the 
 northern hemisphere, these winds, with their peculiarities, are known to European 
 meteorologists, but these meteorologists do not admit that the prime disturbing cause is 
 the condensation of the vapour producing a vacuum in certain localities within the 
 tropics. In the southern hemisphere we have facts of a similar character which are not 
 equally well known. In that part of the world, as in the north, dry. winds blow from 
 cold to warm latitudes ; and they also, as in the north, terminate in localities where 
 a partial vacuum in the atmosphere has been created by condensation of vapour which 
 has been brought from other parts. And thus we find that in both hemispheres cold 
 and dry winds blow not generally towards the equator as N.E. and S.E. winds, as is 
 commonly assumed, but directly towards local areas of condensation of vapour, which 
 are always found to be elevated land, against which, at the same time, warm and moist 
 winds also blow. In the southern hemisphere there are not such broad continents as 
 there are in the northern, yet the same flow of air over land rather than over water, 
 (Page 160) from cool to warm latitudes, is observable in the former as in the latter. But 
 there is ample breadth of ocean in the southern hemisphere, over which a cold aerial 
 current might pass from the Antarctic Ocean to the tropics, and thus restore the equili- 
 brium of pressure in a disturbed atmosphere in the way indicated in the Hadleian theory 
 of winds, if the causes recognised in that theory were those which are really in operation. 
 Over the whole Southern Ocean no palpable polar wind is to be found blowing to the 
 tropics, such winds being confined to the comparatively small portions of land which 
 exist in that hemisphere. Four separate winds in the southern hemisphere may be 
 traced blowing from the south in a way that makes them correspond with the dry 
 northern winds in the northern hemisphere ; namely, two in America, one in Africa, and 
 one in Australia. The first of these that may be noticed is the wind that blows along 
 the low land of the western coast of S. America. It is first found about Valparaiso, say 
 in lat. 33, blowing moderately, but it increases in strength as it proceeds towards the 
 equator, until it reaches the province of Guayaquil, a place which may be described as 
 being in the most southern part of a very rainy district, included between 5 S. and 8 N., 
 310 
 
AQUEOUS VAPOUR. 1850. Hopkins, Thomas. NOTES. 
 
 into which vapour is brought from the heated surface of the Bay of Panama, extending 
 westward into the Pacific Ocean, and the Mexican and California]! Seas. Now, if an 
 atmospheric current is made to flow from the polar to the equatorial regions in 
 the way alleged in the Hadleian theory of winds, why have we not a IS.E. wind 
 "blowing over the whole Southern Ocean between America and New Zealand, instead 
 of the limited Peruvian wind over a narrow strip of land? In this wide range 
 of open sea a west wind of a decided character blows across the part south of lat. 38, 
 and nearer to the equator a broad strip of calm occurs until the eastern trade-winds of 
 the S. Pacific is reached ; but over the whole of this extensive ocean no such S.E. wind is 
 found blowing from the polar towards the equatorial regions as would certainly blow 
 there if the Hadleian theory were true. The second dry American south wind is found 
 (Paye 161) on the east side of the Andes. It commences near the Straits of Magellan, 
 and passes over E. Patagonia and the pampas of Buenos Ayres, approaching the great 
 region of condensation that exists on the east side of the Andes ; a region where the 
 atmosphere must be made light by the large amount of vapour coming from the tropical 
 Atlantic that is known to be there condensed, forming a partial vacuum, into which the 
 cool and dry air passes from the line of country that has been pointed out. The 
 {Page 162) dry air itself does not take sufficient vapour to produce a considerable 
 vacuum at the place of its termination ; nor does much rain fall, excepting among 
 the Andes, to the south of say 25 lat. The vacuum that gives birth to this southern 
 wind is therefore evidently produced by condensation of vapour, which is mostly 
 brought up the broad valley of the Amazon from the tropical Atlantic Ocean, and that 
 condensation, by producing an atmospheric vacuum, must be considered the prime 
 disturber of the aerial equilibrium in this part of the world, which the influx from the 
 south tends to restore. In like manner, Hopkins gives details respecting Africa, from 
 which he infers that in the central part of Africa there exists a region of condensation 
 {Page 165) of aqueous vapour, which vapour is brought principally from the Gulf of 
 Guinea and condensed among mountains, producing a vacuum towards which the air 
 from more southern parts presses and flows as a southern wind ; and being carried 
 into the vacuum, and ascending to a sufficient height, its own portion is cooled and con- 
 densed, increasing the vacuum and augmenting the rainfall in the area. As regards 
 Australia little is known. There are extensive dry regions, but there do not appear to 
 (Page 166) be any great areas of condensation. In the East Indian Archipelago there 
 is an area of condensation of aqueous vapour probably equal in magnitude to any other 
 on the surface of the earth. Currents of air are known to set in towards this area, and 
 probably the dry south wind of Australia is one of those indraughts which only produces 
 rain on the higher lands. It may be observed that some of the most southern lands in 
 the south hemisphere have considerable rainfall where the winds just strike them. This 
 {Page 167) must cause them to be drier in the regions north of them. In July 1853 
 Mr. L. Blodget described a dry wind which terminated in a rainless district. It 
 (Page 168) blows from the Gulf of Mexico inland. But is it exhausted in a rainless 
 district ? Rather, is it not that it blows over the dry region and reaches to the sources 
 of the Red River, Mississippi River, and other large streams. If heavy rain falls in a 
 locality towards which a dry wind blows, we may safely infer that it blows towards a 
 rain-made atmospheric vacuum ? Should the part described by Mr. Blodget prove to 
 bo a district made rainless in summer by condensation in the country to the north of it, 
 it will prove a striking instance of the power of vapour to cause a wind to blow towards 
 the place where its condensation is occurring. The vacuum about the sources of the 
 Missouri would be proved to be sufficient to draw air even from the Mexican Gulf, in 
 opposition to the powerful influences that exist in other parts around that Gulf, and 
 also to make the air pass northward over the rainless district described. For the sake 
 (Page 170) of clearness we have confined our attention to the more general and per- 
 manent winds. The discussion of the smaller and temporary disturbances would have 
 
 Y 2 311 
 
AQUEOUS VAPOUR. 1856. Parish, Alfred. NOTES. 
 
 made the matter obscure. The general laws which govern the changes in the atnio- 
 (Page 171) sphere are usually not complicated. Under the operation of these laws certain 
 localities have great influence in producing motion in the atmosphere, and creating the 
 general currents in it which determine its circulation. Over the ocean evaporation is 
 continually taking up vapour, which by its elastic force expands and diffuses itself 
 through the gases ; and the amount of heat thus taken up to be afterwards used in ex- 
 panding the gases in particular localities is enormous. Through a difference in the laws 
 of cooling by expansion of vapour and gases, this heat would in all parts be given out at 
 certain heights, when the cold of the gases condensed the vapour, and rain would fall 
 with considerable uniformity. But as there are certain elevated lands distributed over 
 the surface of the earth, against these the vapour is largely condensed, and towards those 
 lands atmospheric currents flow, or must flow, producing continuous aerial movements 
 and ascents in the area of condensation. The ascents cause a boiling up and overflowing 
 of large masses of the atmosphere in the higher regions, where they diffuse themselves. 
 These localities of condensation may here be given in their order of importance. The 
 first is found on the east side of the Andes, where the rivers La Plata, Amazon, and 
 Orinoco have their sources. The second is in and about the Himalaya Mountains. The 
 great Asiatic Archipelago is the third. The tropical African mountains may be next, 
 giving rise to the Nile and Congo. Then follow the Eocky Mountains of North 
 America, the mountains of Chili, West Patagonia, and Terra del Fuego, the Alps and 
 {Page 172) mountains of central Europe, the Scandinavian and the British mountains. 
 Over all these mountainous countries aqueous vapour is largely condensed, and the atmo- 
 sphere is made to boil up and overflow each place in proportion to the amount of vapour 
 brought for condensation, and the height to which the vertical current ascends. The 
 air discharged above in due time comes down to the surface, and thus a general circula- 
 tion of the atmosphere is established. There is no evidence that dry air ascends over 
 hot plains to any considerable height. The higher currents in the atmosphere probably 
 flow from the areas of condensation to the regions where the dry winds commence at 
 {Page 173) the surface, deriving their supply from descending currents. 
 
 [The controlling influence of evaporation and of the condensation of aqueous vapour 
 in producing the disturbances in the equilibrium which generate winds was fully and 
 clearly enunciated by Daniell in 1823. The remarks made by Hopkins find a place on 
 account of its giving his conception, or rather what may be inferred to be his concep- 
 tion, of the distribution and circulation of aqueous vapour. As it was difficult to give 
 this without bringing in his more general ideas, no attempt has been made to separate 
 them.] 
 
 Parish, Alfred. Journ. Boy. Geog. Soc., vol. xxvi. (1856.) (??;.) 
 
 (Page 156.) In some parts of the equatorial regions the southern cyclone seems to 
 rise from the surface at that point which represents the S.W. or S.S.W. winds, and the 
 northern one at that representing the N.W. or JST.KW. winds ; while in other parts, 
 especially towards large continents, the due westerly winds appear to extend over many 
 degrees of longitude. May this not be from local influences or differences in the 
 humidity of the atmosphere causing a variation in the angle at which the surface strikes 
 the surface diagonally. 
 
 1857. 
 
 Grant, W. C. Journ. Roy. Geog. Soc., vol. xxvii. (1857.) (rvp.) 
 (Page 275.) In Vancouver Island a parching heat prevails from March to October, 
 which dries up all the small streams. In the commencement of autumn dense fogs 
 prevail, enveloping everything in obscurity. 
 312 
 
AQUEOUS VAPOUR. 1857. 1860. Osborn, S. NOTES. 
 
 Osborn, Sherard. Journ. Roy. Geog. Soc., vol. xxvii. (1857.) (rvp.) 
 
 (Page 144.) In the Gulf of Azov, after the end of August, short fierce squalls set in 
 from the northward, varied with S.E. winds, which are preceded by dense fogs. These 
 true S.E. winds are sometimes turned into easterly winds by the land, but their 
 character, and the fogs which accompany them, distinguish them clearly from the hot 
 summer wind. Great and sudden variations of temperature are now experienced, which 
 fully account for the squalls from the northward and the dense sudden fogs from the 
 south. These squalls give plenty of indication by a dense body of black clouds in the 
 quarter from whence they may be expected. 
 
 1858. 
 Hopkins, J. (B. 1858, 1.) 
 
 [Nothing appertaining to these notes which is not to be found in his earlier paper in 
 
 1856.] 
 
 1859. 
 English Cyclopaedia. (B. 1859, 1.) 
 
 (Col. 973.) In the equatorial zone the air is clear till about two hours before noon, 
 when the clouds begin to appear until rain sets in at noon. Towards evening the 
 clouds disappear, and the sun sets in a clear blue sky. No rain falls in the night. 
 (Col. 974.) During the rainy season the rains frequently flood the low and level 
 country a foot deep with water, so that the atmosphere of such tracts is continually 
 loaded with vapour and exhalations, which render the stars invisible at night, and are 
 doubtless a principal cause of the unhealthiness of these countries. 
 
 English. Cyclopaedia. (B. 1859, 2.) 
 
 (Col. 984.) From what has been observed at Teneriffe, it seems that in all climates, 
 the rainless tracts excepted, a considerable stratum of clouds commonly exists over 
 the land, the inferior surface of which is at a height varying from 2500 to 3000 feet, 
 whatever of cloud there may or may not be above or below that altitude. 
 
 Journ. Roy. Geog. Soc., vol. xxix. (1859.) (rv.) 
 
 [Nothing for these notes.] 
 
 1860. 
 English Cyclopaedia. (B. 1860, 1.) 
 
 (Vol. iii. Col. 498.) The vapour plane where clouds form re presents an area where the 
 dew-point prevails and the cloud corresponds to the dew. A. de Candolle and A. 
 (Vol. iv., Col. 150.) Henfrey infer from the distribution of the species that ligneous 
 plants established themselves in northern and temperate countries when the climate 
 must have been more humid and more cloudy than at present. [The greater dryness at 
 present may be due to the destruction of forests, which* formerly seem to have been 
 (Col. 158) general.] If all the forests on the globe were destroyed the atmosphere 
 (Col. 740) would be exceedingly deficient in moisture. The leaves of plants which 
 thrive in the dry air of the tropics are large and succulent. In the tropics generally 
 the degree of dryness of the air seldom exceeds 10 of Daniell's hygrometer. In 
 tropical countries the air is saturated with vapour during the night, or at least it is 
 
 313 
 
AQUEOUS VAPOUR. I860. 1861. Grey, Earl de. NOTES. 
 
 (Col. 752) seldom otherwise in the open air. As a general law it may be stated that the 
 humidity [=high dew-point] of the atmosphere decreases from the surface of the 
 earth upwards. The great dryness [= low dew-point] of the atmosphere near the 
 summits of mountains has been frequently remarked by travellers. Biot observes that 
 the fall of the mercury is a more certain sign of rain than is its rise of fine weather, 
 since the ascent of the clouds is not necessarily accompanied by their dispersion. From 
 the agitation produced by wind the upper regions of the atmosphere arc often charged 
 (Col. 794) with aqueous vapour. Hygrometry is that part of natural philosophy which 
 (Vol. v., Col. 272) relates to the humidity particularly of the atmosphere. Early in a 
 thunder-storm there is some alteration of temperature as well as considerable barometric 
 (Col. 273) and hygrometric changes. Evaporation increases the electrical condition of the 
 (Col. 708) air. [Since the Bibliography was published the statements in this column 
 (Col. 709) have been entered from earlier publications.] Soon after sunrise in fair weather, 
 the vapour near the earth having been precipitated by the night cold in the form of 
 dew, and the sloping rays of the sun having little power to raise more vapour, the air is 
 almost perfectly transparent, and every object has a clearness and sharpness of outline 
 which it never has at any other time of the day. On our rivers and seas towards the- 
 end of summer, throughout the autumn, and the beginning of spring, the frequency and 
 amount of mists are remarkable. 
 
 Grey, Earl de. (B. 1860, 2.) 
 
 (Paye cxlv.) The prevalence of moist air, much or little cloud, can be predicated 
 approximately of any place, although no observations have been made there. Cold dry 
 (Page cxlvii.) air from a polar direction is heavier than warm moist air blowing from 
 (Page cxlviii.) tropical or equatorial regions. Evaporation, rarefaction, or condensation 
 of vapour in air, reduces its specific gravity, the two former by expanding bulk and 
 rendering it lighter through mechanical diminution of quantity by falling to the earth 
 in rain, &c. 
 
 1861. 
 
 Eaton, H. S. Proc. Brit. Meteorol Soc., No. 1. Nov. 1861. (ru.) 
 (Page 12.) Various theories have been advanced as to the cause of the increase of 
 rain in hilly districts. One (the most commonly received) is, that a current of air 
 saturated with vapour, on coming in contact with the cold hills, has its vapour con- 
 densed, which falls as rain. This cannot, however, be so; if it were, we should 
 invariably have rain when in the winter months a warm and saturated S.W. wind 
 succeeded a frost as long as the ground remained unthawed, instead of a thin surface- 
 fog, as usually obtains. In the autumn, too, after clear nights the dew-point temperature 
 is often higher than that of the ground and pavement, under which circumstances we 
 find the vapour condensed on the surface, which appears wet in consequence. The true 
 explanation is, that whereas the temperature of the air decreases U F. for every 
 100 yards of ascent, the dew-point only decreases i ; if then a stratum of air, in which 
 the comp ement of the dew-point is 5, be raised through a vertical space of 1200 feet, 
 (Page lo) the vapour which it contains will begin to condense into cloud. Now, let us 
 imagme a south-westerly surface wind to be setting in from the Atlantic, at a tempe- 
 e of 02 and a dew-point of 48, as is frequently the case in autumn and early 
 
 ft reaching the land a ripple is produced > and on crossin s th - 
 
 * *?*** ^ UP ab Ut 170 ** In *S through this 
 
 * 
 
 * S rug 
 
 e b Xl f "^ ^ * * ^ f 75 feet the -Id* produced 
 < 
 
 w 1 Vap Ur lnt cloud > a d a11 ^e hills above this 
 
 will be capped with fog, the temperature at this point being 48 ; in a further 
 
AQUEOUS VAPOUR. 1861. 18G2. Bellingham. NOTES. 
 
 ascent the latent heat evolved by the process of condensation will prevent the air 
 cooling as fast as it did, to the extent of nearly three-fourths the amount; so that at 
 1700 feet the temperature will not be lower than 47'3 ; under favourable circumstances, 
 however, rain will ensue. On passing the hills the mist sinks, becomes warmed under 
 greater pressure, and evaporates. 
 
 English Cyclopaedia. (B. 1861, 3.) 
 
 (Col. 928.) In general the lowest stratum of air above the earth contains the greatest 
 quantity of aqueous vapour, and hence it might be expected that more rain should fall 
 on low level plains than in elevated countries. The contrary is the fact, and this may 
 be accounted for by the variety of currents among mountains and by clouds descending 
 frequently on the summits of hills without descending to the plains. 
 
 (B. 1861, 6.) (ra.) 
 
 (Page 573.) During the eclipse of the sun, July 18, 1860, there was a marked 
 increase of humidity at the various places where the eclipse was observed. 
 
 Journ. Boy. Geog. Soc., vol. xxxi. (1861.) (rvp.) 
 
 [Nothing for these notes.] 
 
 1862. 
 Bell, C. N. Journ. Boy. Geog. Soc., vol. xxxii. (1862.) (rvp.) 
 
 (Page 247.) In the Mosquito country, towards the end of May, every day, towards 
 the afternoon, the clouds which are brought over from the sea are piled in a dark bank 
 (Page 248) to the westward. This gathering of clouds is occasioned by the land breeze, 
 which begins to be prevalent now during the night. 
 
 Bellingham, W. (B. 1862, 2.) 
 
 (Page 110.) The recurrence of phenomena indicating the existence of a tide or belt 
 of vapoury clouds, traversing the atmosphere alternately from pole to pole at regular 
 intervals of 40 days, has for some years past attracted the author's attention. This 
 tide, which would pass and repass the latitude of Peru at intervals of 20 days, may 
 be connected with the Peruvian period of 20 days, at intermediate regions between the 
 equator and the poles would return at longer or shorter intervals according to the 
 (Page 111) latitude of the place. For example, from the time it passes northwards over 
 London to its return to the same latitude would be about 10 days, if it moved at an 
 estimated rate of 20 miles in an hour ; its next return after going south would be in about 
 30 days. Owing to many counteracting influences it would be difficult to predict the 
 eifects of the tides. Under certain conditions of the atmosphere, however, it would 
 probably produce storms and rain. Though the belt of vapour is supposed to be 
 continuous, it is probable that some parts of it would be considerably in advance of 
 others in those regions where least resistance is offered to its progress. The supposed 
 periodic tide of 40 days would sometimes combine with the lunar atmospheric tide of 
 about 27 days, and at other times be in opposition to it. The theory is founded upon 
 observations in the latitude of London. 
 
 FitzRoy, R. Journ. Boy. Geog. Soc., vol. xxxii. (1862.) (rvp.) 
 
 (Page cxxxii.) Air currents retain their characteristics for a considerable time. Thus 
 we may have by deflection, for short times only, cold dry winds from the S.W., or warm 
 
 315 
 
AQUEOUS VAPOUR. 1862. Glaisher, J. NOTES. 
 
 (Page cxxxv) moist winds from the north. With polar currents of air, clouds have a 
 hard oily appearance ; with the tropical currents they have a soft watery aspect, with- 
 out hard edges or outlines. 
 
 Glaisher, James. Proc. Brit. Meteor. Soc., vol. i. (No. 5, published Nov. 19, 18G2.) 
 
 [Plate vii. He shows the balloon track rising to 23,500 feet, and cirri above, 
 between five and six miles, the highest at over 31,000 feet. This was during the 
 ascent from Wolverhampton.] The observations made during his balloon ascents 
 (Page 259) [which are detailed in the paper] indicated that the temperature of the dew- 
 point decreases on leaving the earth less rapidly than the temperature of the air, so 
 that the difference becomes less and less till the vapour plane is reached, when they are 
 usually together, and always most nearly approach each other (this elevation was about 
 5000 feet high) ; that immediately after leaving the upper surface of the cloud the dew- 
 point decreased more rapidly than the temperature, and in the extreme high stations 
 the difference between these two temperatures is wonderfully great, indicating an 
 extraordinary degree of dryness and an almost entire absence of aqueous vapour. 
 Under these circumstances the presence of cirrus clouds far above the dry region 
 (Page 260) is very remarkable ; on all occasions when seen they appeared still as far 
 above as when viewed from the earth. Of what can they be composed? 
 
 Gregory, F. T. Journ. Roy. Geog. Soc., vol. xxxii. (1862.) (nip.) 
 
 T (Page 428) N.W. Australia, 1861. Latterly the wind was alternately S.E. in the 
 morning and N.W. or westerly in the afternoon, the sky frequently becoming overcast. 
 [By latterly is meant getting on for October.] The rainy season, from the observations 
 of previous explorers, is from about the beginning of November on to March. 
 
 Herschel, Sir John P. W. Meteorology, 2nd Ed., 1862. 
 
 (Page 2.) Supposing there were no latent communication or transfer between the 
 columns of air incumbent on adjacent parts of the earth's surface, the totality of 
 atmospheric and climatic change in any given locality would be limited to periodical 
 and perfectly regular fluctuations of temperature, and to the alternate generation and 
 condensation of vapour, equally periodic and regular, immediately consequent on such 
 fluctuations, over those parts of the surface occupied by water. No rain would ever 
 fall or cloud form over any part of the land, which would be perfectly arid. Air 
 (Page 17) contains on an average 0' 45 per cent, of aqueous vapour. When aqueous 
 (Page 25) vapour ascends by its levity it drags air up with it not by heating it, but by 
 mechanical impulse ; and thus we see that the mere fact of a circulation of air in the 
 atmosphere, in so far as that circulation is due to the generation and condensation of 
 vapour, or even to the downward mechanical impulse of the fall of rain or snow, 
 must of necessity cause a deficiency of sensible heat in the higher as compared with the 
 (Page 48) lower regions. Mr. Glaisher's observations clearly show that the higher the 
 cloud the greater is the radiation upward. Thus on nights uniformly and totally 
 cloudy, the mean heights of the clouds being respectively 1700, 2800 and 3700 feet 
 (which his peculiar situation enabled him to ascertain), the depressions were found to 
 (Page 49) average 1-6, 2-5, 3*9, clearly indicating the lower temperature of the higher 
 clouds. Water freely exposed to the air evaporates at all temperatures, even when in 
 (Page 50) the state of snow or ice ; cwteris paribus, the amount of water evaporated 
 is proportionate to the surface exposed to air. It is much greater, therefore, from rough 
 and porous solid substances kept wetted (as for instance from moist soil or from 
 vegetation wetted by rain) than from the surface of water itself, and from the latter 
 (Page 51) when agitated by winds or lashed into spray than when tranquil. Vapour, 
 316 
 
AQUEOUS VAPOUR, 1862. Herschel. NOTES. 
 
 introduced into the air, acts as a moving power in two ways first, by a simple addition 
 of volume ; second, by its less specific gravity, in consequence of which as soon as it 
 (Page 52) is generated it tends to rise in the air by its buoyancy, and in so doing carries 
 up much of the air with which it is intermixed, disengaging itself no doubt from it in 
 its upward progress to become entangled with fresh particles, which again it raises 
 upward to abandon them for others. In this way not only is its upward diffusion far 
 more rapid than its horizontal, but in its struggle upwards it tends to produce an 
 ascensional movement in the air itself, and thus to act as a powerful agent in the 
 {Page 53) production of wind. In every case the condensation of vapour is 
 accompanied with a mitigation of cold at the point where it actually takes place. It is 
 clear, moreover, that the generation of vapour under any extensive region more rapidly 
 than it is carried off by diffusion or otherwise, must be attended with an increase of 
 barometric pressure, since the total weight of the atmosphere vertically over any region 
 must be supported by the total area of surface, and equally so that its condensation, 
 provided that the condensed water be abstracted from the 'atmosphere, must lead to a 
 diminution of pressure. The contrary will happen if the vapour generated be carried 
 off as fast as produced by such a general upheaving of the aerial strata over any region 
 AS shall subvert their equilibrium and cause them to overflow upwards and laterally. In 
 such a case, since air also will be carried off bodily from the region and be replaced by 
 vapour, the mean specific gravity of the whole aerial column and its total weight will 
 be diminished and the barometric pressure lowered. This takes place on a most 
 extensive scale over the intertropical seas. The temperature of the surface water in 
 (Page 54) them is habitually very elevated (from 78 at the tropics to 83 at the 
 equator) and varies very little. A steady and copious evaporation is therefore continually 
 going on. Vapour, carrying with it air, is constantly thrown up beyond the levels of 
 equilibrium, where it flows over and spreads itself out over the upper regions of higher 
 latitudes. The immediate consequence is a habitual deficiency of barometric pressure 
 at the sea level on the equatorial as compared with that on the extratropical seas. In a 
 voyage to the Cape of Good Hope in 1833-4 the writer of these papers found the 
 decrease from the tropics to the equator on either side to amount to 0'24 in. Schouw 
 and Humboldt had previously noticed this fact. Air is less dilated by heat than by the 
 (Paye 55) introduction of vapour, but in both cases a local relief of pressure is equally 
 produced. Winds subvert the solar climate and produce its real climate directly by 
 transferring heat and aqueous vapour with its latent heat from one region to another ; 
 (Page 81) and indirectly by means of the oceanic currents they cause. The winds act 
 indirectly as distributors of heat and moisture by producing currents in the ocean. 
 {Apparently he attributes the great ocean currents mainly to wind influence.] The most 
 (Page 84) immediate, though assuredly not the most obvious result of this state of 
 things [that is, of unequal distribution of temperature and system of winds] is the 
 iiabitual hygrometric or relative dryness of the higher regions in clear weather. This 
 is shown by very demonstrative facts. Thus Deluc remarked that the head of his 
 walking-stick always fell off in high mountain ascents from the shrinking of the wood. 
 Every (Essays by Sir J. Herschel, 1835) act of precipitation withdraws from the total 
 mass of air some portion of its entire amount of vapour. As such precipitations are 
 constantly going on in some place or other, the atmosphere as a mass, though incumbent 
 on a wet and evaporating surface, is necessarily always deficient in moisture ; and for 
 the very same reason every superior stratum is relatively deficient in comparison with 
 that immediately beneath it, from which its supply is derived. In point of ultimate 
 causation, then, there is a constant drain on the aqueous contents of the atmosphere 
 arising from changes of temperature. This drain extends to all its strata, but while the 
 (Page 85) lower renew their losses from a surface hygrometrically wet, the upper draw 
 their supply from sources more and more deficient in moisture. What the equatorial 
 depression of the barometer at the sea level, then, is to the system of winds, such is the 
 
 317 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 habitual hygrometric dryness of the air above the clouds to that of rain at once an 
 indication of a process in progress and an efficient agent in continuing it. Wherever 
 such relative dryness exists, vapour, by its own expansive nisus, is in the act of transfer 
 in an invisible state from one atmospheric region to another, and the rapidity of that 
 transfer is proportional, cateris paribus, to the degree of dryness. This by no means 
 supposes a universally prevalent deficiency of vaporous tension. Complete saturation 
 must exist at the points of evaporation and deposition, but at intermediate ones any 
 amount of irregularity may prevail according to local circumstances. The method no\v 
 (Page 86) adopted in preference to all others [for ascertaining the amount of vapour in 
 the air], or the most simple and convenient in practice, and leading to results which a 
 very severe examination has proved to be quite satisfactory, is the simultaneous obser- 
 vation of the Avet and dry thermometers. The formula of reduction, as it results from Dr. 
 Apjohn's investigations, is as follows : Let t, t' be the respective readings of the wet 
 and dry thermometers (in degrees Fahr.), h the barometric pressure in inches, / the 
 elastic force of the saturated vapour at the temperature t t and F its elastic force at the 
 dew-point. Then will 
 
 Or, *.,..,.. . . . . .(*) 
 
 the equation (a) or (6) being used according as t, the reading of the wet thermometer, is 
 above or below 32 ; / is found from a table ; and F being calculated from the above 
 expression, the dew-point may be had from the same table used reversely ; F known, 
 the weight of water per cubic foot is found by multiplying the weight of a cubic foot of 
 dry air at 30 in. (563'214 grains) by the specific gravity of steam for elasticity F; i.e. by 
 F x G'6235. Copious tables for facilitating the whole process have been published by 
 Mr. Glaisher (1847). Although Button's theory of solution is exploded, its language, 
 being convenient, is retained. When the air in contact with a radiating surface has 
 (Page 91) been reduced in temperature to the dew-point, it remains saturated, and at 
 the same time colder than that above it. On level ground, in a calm, little or no- 
 mixture of the upper and lower air will occur ; but on a slope the cold air will run 
 downwards, and mixing with the air below, if sufficiently near to saturation, will 
 depress the mean temperature of the mixture below its resultant dew-point, and produce 
 fog. If the low ground be occupied by water or marsh, as the air in it is sure to be 
 saturated, copious precipitation will necessarily result. If dry, the mist produced will 
 (Page 92) be less copious, and may not even take place at all. In the Weald of Kent, 
 a district abounding in grassy slopes and branching valleys, in the calm clear nights 
 which are there so frequent, beautiful instances of radiation fogs are of perpetual 
 occurrence. Immediately after sunset dew commences ; streams of cold air set down- 
 wards, following the line of shortest descent, their course being marked with mist, thin 
 and filmy at first, but acquiring density in its downward progress, and by degrees filling 
 the valleys with fog, which in the morning before sunrise presents exactly the aspect 
 of a winding lake or river of water, whose surface, perfectly even and horizontal, runs a 
 sharply-defined line round every promontory, and into every retreating nook. A 
 (Page 93) radiating fog, once formed, tends to its own increase by radiating off heat from 
 its own particles. When the warm current in the open ocean encounters a shoal, the 
 lower water (of inferior temperature) is thrown up to the surface. The surface water, 
 therefore, on the shoal is colder than that of the surrounding ocean, and the atmospheres 
 (saturated at the respective temperatures) mingling, produce those fogs which are 
 observed to be prevalent in such localities. The fogs of Newfoundland are a remarkable 
 instance in point, Fogs, too, are produced in the neighbourhood of icebergs on a similar 
 principle. The Arve, in its descent from Chamouni, occasionally presents the appearance 
 318 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 of warm water throwing up steam (though in fact many degrees colder than the air), 
 from the mixture of the cold air above it with the saturated warmer air of the valley 
 through which it flows. (Obs. August, 1821.) 
 
 Barometric Fogs. The temperature of a mass of air may be lowered beneath the 
 dew-point by the simple effect of its own expansion. This may take place in two ways : 
 {Page 94) viz., first, by a rapid and considerable relief of barometric pressure from above ; 
 or secondly, by its own ascent into a higher region of the atmosphere. The first case 
 takes place when the trough of an atmospheric wave passes rapidly over the place of 
 observation. The fog so produced comes on for the most part suddenly and without 
 any obvious cause. It is not rolled in from a distance by wind, nor does a moderate 
 wind dissipate it. It is not confined to the surface of the ground, but extends at onee 
 to great altitudes. It does not resolve itself into rain, but disappears, when the atmospheric 
 equilibrium is restored by the recondensation of the air and the reappearance of its 
 sensible heat. Such fogs are very common, and are precisely analogous to the cloud 
 produced in the receiver of an air-pump by a rapid partial expansion of the air. They 
 want a name, and that of " barometric fogs " seems not inappropriate. There is a fog of 
 not very frequent occurrence in our [= British] climate which comes on gradually in a 
 perfectly calm state of the air, without any sudden or considerable diminution of 
 barometric pressure, and which evidently arises from a gradual increase of humidity in 
 the air, at length attaining the dew-point. Such fogs would seem not unnaturally to- 
 result from the quiet lateral diffusion of vapour as a gas from some neighbouring or 
 slowly approaching mass of vapour-loaded air, in anticipation of its bodily arrival as a 
 moist or rainy S.W. wind. To such a fog the epithet of " diffusional " may not 
 {Page 95) improperly be applied. When a body of vapour is generated from any 
 warm evaporating surface it ascends by its relative levity, losing sensible heat as well 
 by its own expansion as by its bodily transfer into and intermixture with colder 
 air. When clouds form in a calm state of the air, and the evaporating surface is- 
 limited in extent or irregularly distributed in patches (as over marshy ground, rivers, 
 lakes, &c.), or if any other cause dispose the vapour to rise in columnar bodies of 
 greater or less extent, the summits of these clouds are marked by protuberant massc-s 
 or piles of clouds, with generally rounded outlines, which appear to repose on flat bases, 
 indicating the vapour plane. To such clouds Howard gave the name of "cumulus."" 
 They abound in the calm latitudes of the equatorial seas, and form a distinguishing 
 {Page 96) feature in the meteorology of that region. That the self-expansion of the 
 ascending air is sufficient to cause precipitation of some of its vapour when abundant,, 
 is rendered matter of ocular demonstration in that very striking phenomenon so 
 common at the Cape of Good Hope, where the S. or S.E. wind, which sweeps over the 
 Southern Ocean, impinging on the long range of rocks which terminates in the Table 
 Mountain, is thrown up by them, makes a clear sweep over the flat table-land (about 
 3850 feet high), and thence plunges down with the violence of a cataract, clinging close 
 to the mural precipices that form a kind of background to Cape Town, which it fills- 
 with dust and vapour. A perfectly cloudless sky prevails meanwhile over the town,, 
 the sea, and the level country, but the mountain is covered with a dense white cloud,, 
 reaching to no great height above its summit, and quite level, which, though evidently 
 swept along by the wind and hurried furiously over the edge of the precipice, dissolves,, 
 and completely disappears on a definite level, suggesting the idea (whence it derives its 
 name) of a " table-cloth." Occasionally, when the wind is very violent, a ripple is 
 {Page 97) formed in the aerial current, which, by a sort of rebound in the hollow of the- 
 amphitheatre in which Cape Town stands, is again thrown up just over the edge of the- 
 sea, vertically over the jetty, where we have stood for hours watching a small white- 
 patch of cloud in the zenith, a few acres in extent, in violent internal agitation (from 
 the hurricane of wind blowing through it), yet immovable, as if fixed by some spell, the 
 material ever changing, the form and aspect unvarying. [See Notes, 1823, Daniell,, 
 
 319 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 p. 123]. The form and aspects of clouds are very indicative of the circumstances under 
 which they are in the act of forming or dissipating. The form of the cumulus clearly 
 (Page 98) indicates the act of self-dissipation in invisible vapour into the upper rela- 
 tively dry air. Stratus may be considered as intermediate between cloud and fog, 
 being chiefly formed at night, and under the influence of radiation either from the 
 surface of a ground fog or from impurities floating in the air itself. The latter is 
 remarkably the case in great cities in which coal is chiefly consumed as fuel, and gives 
 rise to those dense, yellow, suffocating fogs which infest London in the winter months. 
 It would seem that each particle of soot, acting as an insulated radiant, collects dew on 
 itself, and sinks down rapidly as a heavy body. Stratus is also formed very suddenly 
 on a higher level, when in a clear calm night the general temperature of the air sinks 
 by radiation or by diminution of atmospheric pressure till at some definite altitude 
 above the surface the dew-point is attained. Thus on the night of April 19, 1827, the 
 {Paye 99) sky up to 16 h. 16 m. sid. time being perfectly cloudless, and not a breath of 
 wind stirring, stratus at a high level commenced in the eastern horizon, and in eight 
 minutes had extended to the western, obscuring the whole sky, the calm remaining 
 unbroken. In this case the velocity of propagation of the edge of the cloud from E. to 
 W., or following the sun, could not have been less than 300 miles per hour. The 
 filamentous structure of the cirrus clouds, occupying the highest regions of the atmo- 
 sphere, clearly indicates them as either in the act of originating from the union of 
 aerial currents running parallel to each other, or as the residues of dissolving cloud 
 drawn out into fibres by the wind. The cirrus is said to be often a precursor of windy 
 {Page 100) weather. The cirro-cumulus clouds usually float at great elevations, and 
 often appear as a loftier stratum through the intervals of lower clouds. They are 
 frequent in summer, and attendant on dry and warm weather. The cirro-stratus 
 appears to result from the subsidence of the fibres of cirrus to a horizontal position, at 
 the same time approaching laterally. It often precedes wind and rain. The cumulo- 
 etratus would seem to be the modification of cumulus formed when the columns of rising 
 vapour which go to form it arrive in an upper atmosphere not sufficiently dry to round 
 off its summits by rapid evaporation, thus allowing them to spread horizontally and form 
 flat-topped, mushroom-shaped masses, the upper parts of which are often curled by the 
 wind of an upper current into cirrous wisps, or cleanly cut off by a horizontal plane, 
 forming an " anvil-shaped cloud " with a lateral projection, generally considered as a 
 precursor of wind below. The tendency of cumulo-stratus is to spread, overcast the 
 sky, and settle down into the nimbus, and finally to fall into rain. When two strata 
 ^Paye 101) of clouds on different levels tend to unite, it is evident that the intermediate 
 region must be nearly or quite in a state of hygrometric saturation. The cloud then forms 
 -confusedly and in irregular masses through the whole region, and finally resolves 
 itself into heavy rain. When cloud is present the sun's rays are of course prevented 
 from reaching the earth directly, and their heat is diffused through the general atmo- 
 sphere, thus softening and mitigating their ardour. When the sun shines on a cloud 
 which absorbs its heat, the cloud itself is necessarily partially evaporated, and the 
 vapour by its levity tends to produce an upward current, and thus to counteract the effect 
 of gravity on the globules of which it consists. A globule of water l-4600tbs in. in 
 diameter, in air of five-sixths of the density on the surface, or at the height of about 5000 
 feet, would have its gravity counteracted by resistance with a velocity of descent of one foot 
 per second (supposing no friction and no drag), and even if the terminal velocity were 
 .uced to half that quantity by these causes, would still require some such upward 
 action to enable it to maintain its level, a circumstance which sufficiently accounts for 
 lower level generally observed of cloud during the night. It is more than probable 
 that when it is not actually raining a cloud is always in process of generation from 
 d dissolution from above, and that the moment this process ceases, rain in the 
 1 " C0mmences ' In a >d > a cloud in general would seem to be merely 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 (Page 102) the visible form of an aerial space in which certain processes are at the 
 moment in equilibrio, and all the particles in a state of upward movement. The 
 (Page 104) increased quantity of rain measured by the rain gauges nearest the ground 
 is usually accounted for on the hypothesis that the cold rain-drop condenses moisture in 
 falling through an atmosphere nearly or quite saturated. But this cause is insufficient, 
 as rain falling from 12,000 feet, and bringing a temperature of 40 F. to 213 feet, 
 would have its weight increased by ^ on ty> or TT f tne quantity to be accounted for. 
 (Page 105) Visible cloud rests on the soil at low altitudes above the sea-level but rarely - 7 
 and from such a cloud only would it seem possible that so large an accession of rain could) 
 arise. (Note. These remarks were made in 1857. More recently, March 29, 1860, a paper 
 was read by Mr. Baxendell to the Lit. and Phil. Soc. of Manchester on this subject. 
 He arrives at the same conclusion as to the insufficiency of the mere condensation of 
 vapour on the falling drops to account for the phenomenon in question, and concludes 
 that it is impossible to account for it except by the admission of the existence of water 
 not in the state of true vapour, but already deprived of its latent caloric in the 
 atmosphere though not affecting its transparency, so that a shallow stratum of the 
 lower and comparatively clear atmosphere may supply as much rain as a densely-clouded 
 and much deeper stratum in the higher regions. Mr. Baxendell hesitates to admit that 
 the water can be present in the actual state of water, on account of its invisibility. He 
 adds a very remarkable fact recorded by Mr. Binney, who, in descending the shafts of 
 deep coal mines, has observed that the drops of water which drip from the upper park 
 of the shaft increase to an extraordinary size in their descent to the bottom). The 
 (Page 106) greater part of the enormous evaporation of the equatorial seas is at once 
 condensed, and discharged again in rain from the cumuli which marks its uprush into 
 the higher and colder regions of the air, the rain being most continuous where the sun. 
 is most vertical, or in the region of calms. The trade winds themselves, coming from 
 higher latitudes, are acquiring temperature and taking up moisture from the sea. The 
 returning counter-currents having discharged their first overload of moisture, pursue 
 their course aloft, free from cloud and relatively dry; and in the neutral interval 
 between them and the opposite lower current, cloud is not generated or rain produced 
 by the intermixture of the two, the upper portions of the trades not being saturated. 
 The clouds which do occur in these winds belong not to their higher strata, but to 
 (Page 107) a much inferior level, not exceeding 5000 or 6000 feet in altitude, while 
 the medial line between the winds has nearly double that elevation. Such at least are 
 the phenomena on Teneriffe, as seen by C. P. Smyth in August. Between the tropics 
 the year is divided into a wet and dry season ; the dry, when the sun is in the opposite 
 hemisphere and the trade winds blow strong; the wet, when in.the same, and approach- 
 ing the zenith. In the neighbourhood of the equator, where the sun passes the zenith 
 twice at several months' interval, there are two dry and two wet seasons. Beyond the 
 tropics, where the anti-trade or returning current descends to the level of the earth's 
 surface, and by degrees takes up the temperature of our milder latitudes, its vapour, 
 held so far in abeyance, becomes available for the production of rain, unless inter- 
 Page 108) cepted by some mountain-barrier tossing up the stream, and prematurely 
 precipitating its vapour. Where this obstacle does not exist, however, the rains are 
 distributed in the extra-tropical regions with considerable indifference as to season ; in 
 some, indeed, a certain approach to a wet and dry season of the year prevails. Since, 
 however, the deposit of water from the air must of necessity bear some rude proportion 
 to the actual quantity in transitu, the amount of rain or snow which falls on any 
 country must, on a general average, diminish as the latitude increases. The origin of 
 (Page 126) aerial electricity has been traced with every appearance of probability to 
 (Page 127) evaporation. Pouillet showed that electricity was developed only when 
 chemical change attended the evaporation. The processes of vegetation in which water 
 is abundantly separated from the other constituents of plants, and perhaps also other 
 
 321 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 vegetable processes, are also sources of electricity. Thus we are led to look to the 
 immense evaporation both from sea and land, and to the vital processes going on in 
 the latter, as furnishing at least .the chief supply of electricity in the air. Volcanic 
 eruptions and conflagrations contribute their quota. The periodic fluctuations of the 
 (Pat/e 156) barometer are annual and diurnal. The consideration of the former will 
 enable us to form a neater conception of the mode in which the latter arise. When it is 
 summer in one hemisphere, it is winter in the other. Hence the air generally in- 
 cumbent on the heated hemisphere is dilated, and expands both upwards and laterally, 
 not only by its increased elasticity, but also by the increased production of vapour. It 
 therefore not only encroaches on the other hemisphere by lateral extension, but, what 
 is far more influential, flows over upon it. In order to perceive clearly the nature of 
 the process, we must separate in idea the aqueous and aerial constituents of the portion 
 of the air so transferred. The generation of the former goes on in the heated atmo- 
 sphere, and replaces, in part at least, the loss in pressure arising from the transfer of 
 air, while in the other the excess of vapour so introduced is constantly undergoing pre- 
 cipitation, and is thus constantly being withdrawn from the total mass, leaving behind 
 it, however, to accumulate, the dry air which accompanied it. Thus, if we regard the 
 total barometric pressure as subdivided into that of the dry air and of the aqueous 
 vapour, and denote the former by P, the latter by Y, we see that the dry pressure is 
 diminished in the hot and increased in the cold hemisphere without any countervailing 
 action, while P is in process of increase from below by evaporation and of diminution 
 from above by overflow in the former, and vice versa in the latter. If, then, the 
 observed barometric pressure at every point in either hemisphere be analysed by calcu- 
 (Paye 157) lation into its two constituents, by taking account of the hygrometric state 
 of the atmosphere, and subtracting from the total pressure, P x Y, the portion due to 
 the amount of vapour present, the remainder ought to exhibit, as a general result, an 
 excess of dry pressure, P, in the winter hemisphere over that in the summer. So far as 
 observation has hitherto gone, this result is perfectly corroborated, though, unfortu- 
 nately, there are not yet accumulated sufficiently numerous and extensive series of obser- 
 vations in which the effects of the aqueous pressure can be duly separated from the dry. 
 As examples, we shall select the series from the Indian stations, Calcutta, Benares, 
 Seringapatam, and Poonah, calculated by Dove from the observations of Prinsep, Spar- 
 tnann, and Col. Sykes, as compared with that at Apenrade from those of Neuber, and with 
 the results obtained at the meteorological observatories of Prague, Toronto, and Hobart 
 Town : 
 
 P, pressure of dry air. V, pressure of vapour. 
 
 Stations. Max. JVlin. DifF. Max. Min. Piff. 
 
 in in in. in in in. 
 
 Calcutta Jan. July 1-019 Aug. Jan. -551 
 
 Benares Dec. July 1-244 July Dec. -645 
 
 Seringapatam Jan. June -455 May Jan. -217 
 
 Poonah Dec. July -760 July Dec. '435 
 
 Apenrade Feb. July -450 July Jan. -346 
 
 Prague Dec. July -383 July Jan. -285 
 
 Toronto Dec. July -271 Aug. Feb. -380 
 
 Hobart Town July Dec. -21S Feb. July '125 
 
 (Page 158.) These differences are large quantities ; but we see that as the maxima 
 
 P correspond in point of time with the maximum of Y, it is only their differences 
 
 which constitute the total or observed annual fluctuation of barometric pressure. Since, 
 
 is observed, the annual fluctuation of Y is the result of an excess of supply over 
 
 expense in one hemisphere, and of expense over supply in the other, it may very well 
 
 happen that the annual fluctuation of Y in certain localities may exceed that of P and 
 
 eing m a contrary direction, may either neutralise the fluctuations of the gross pressure 
 
 - V, or convert it into one of an opposite character. This, however, is rarely the case, 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 and where instances of it do occur, as at the Sta. Fe de Bogota and Bangalore, they are 
 for the most part readily enough accounted for by the influence of local peculiarities. If 
 we consider that, in general, the values of P and V, regarded independently, fluctuate 
 in opposite directions, and hence the maximum of the one corresponds, or nearly so, in 
 epoch with the minimum of the other, we shall easily see that, representing P by 
 
 P = A + B sin. (0 + C) + B' sin. (20 + C') + &c. 
 we shall have at least approximately for V an expression such as 
 
 V = a + sin. (0 + C + 180) + ' sin. (20+ /) &c. 
 
 the value of C in the term differing by 180, while those in other terms (C'y', G"y", 
 &c.) may or may not stand to each other in a similar relation the only condition being 
 that they shall be such as to render the co-efficients BB', /3/3', &c., all positive. The 
 gross pressure P + V then will come to be expressed by the form 
 
 P + V = (A + a) + (B - 0) sin. (0 + C) + M sin. (20 + N) + M" sin. (30 + N'), &c. 
 Since B' sin. (2 + C') + /3' sin. (2 + /) may always be reduced to the form 
 
 M sin. (20+ N), &c. 
 
 Thus we see that the tendency of the cotemporary action of the two elements com- 
 posing the gross pressure is 1st, to produce a mean annual pressure (A + a) equal to 
 the sum of the separate pressures ; 2ndly, to subdue the influence of the term depending 
 on by reason of the opposition of signs affecting B and ft in the joint co-efficient 
 B and ft ; and thus, Srdly, to give a greater comparative influence to the terms depend- 
 ing on 2 0, 3 0. Now it will be observed that a series thus constituted of series of 
 0, 2 0, &c., when made to run through its whole period by varying from to 360, will 
 have only a single maximum and minimum when the co-efficient of sin. (0 + C) is large 
 in comparison with those of the other sines ; but when the contrary is the case, a 
 double, or even triple or multiple maximum and minimum may result from such 
 (Page 160) mutual relations among the co-efficients as may very easily occur. The 
 principal terms nearly neutralising each other by their mutual opposition, leave the, 
 general character of the law of periodicity of the compound effect to be decided by the 
 relations inter se of the subordinate ones, and thus is explained, without prejudice to 
 the general reasoning in arts. 77, 78 [pp. 71-73] (which remain true as regards the form 
 of the atmosphere as disturbed by the sun's action), the fact, which appears on first sight 
 in opposition to that conclusion, that the annual oscillation of the gross barometric pressure 
 presents in a great many localities the phenomenon of a double maximum or even a still 
 more complex character. Thus, in Paris, to take a single instance, from a mean of eleven 
 years' observations (1816-1826) the total pressure exhibits two maxima, in January and 
 in July, the former being highest ; and two minima, in April and October, the latter being 
 (Page 161) the lowest. In the same way the diurnal oscillations may be accounted for. 
 To simplify our conception of the diurnal oscillation we will suppose the sun to have 
 no declination, but to remain constantly vertical over the equator. The surface of the 
 globe will then be divided into a day and a night hemisphere, separated by a great circle 
 passing through the poles coincident with the momentary horizon, and revolving with 
 the sun from east to west in twenty-four hours. The contrast of the two hemispheres, 
 both in respect of heat and evaporation, in this case will evidently be much greater than 
 in that of art. 165 (p. 156), and therefore the dynamical cau?e, the motive force trans- 
 ferring both air and vapour from the one to the other, will l.e much greater. But, on 
 the other hand, much less time is afforded for this power to work out its full effect ; and 
 long before this can be accomplished for any locality the circumstances are reversed 
 and a contrary action commences. The causes, then, and the mode of their agency, are 
 perfectly analogous in the production whether of the annual or diurnal oscillation ; but 
 
 323 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 in the former the feeble acting cause is aided by the very much greater length of the 
 period; in the latter, its superior intensity is in great measure neutralised by the 
 (Page 162) frequency of its reversal. There is another consideration, moreover, which 
 cannot be without a great effect in establishing a distinction between the two cases. By 
 far the larger portion of the land is distributed over the northern hemisphere, and of the 
 water over 3 the southern. The former is more uniformly terrene, the latter is more uni- 
 formly aquatic; and as, under the circumstances now considered, the transfer of air 
 does not take place in the direction of meridians, but at right angles mainly to their 
 direction, we should be led to expect that the amount -of counteraction in the diurnal 
 fluctuations of the dry pressure p by those of the wet v would be, generally speaking, 
 very different in the two hemispheres, and that therefore the extent of fluctuation m 
 the gross pressure p + v would, generally speaking, present a corresponding difference. 
 A sufficient amount of observations has not yet been accumulated to bring this 
 conclusion to the test of experience ; but we cannot help remarking that the very same 
 cause (the excess of water on the southern hemisphere), acting according to the difference 
 of conditions, ought in the case of the annual oscillation to result in an average uncom- 
 pensated action on the dry air, urging it towards the northern hemisphere, and to its 
 replacement, bulk for bulk, by vapour, which being lighter than air, [is assuredly one, 
 and it may be the most efficient] of the causes of the generally lower atmospheric 
 pressure over the Southern Ocean a certain percentage of the due proportion of dry air 
 (Page 163) being permanently driven out and prevented from returning by the constant 
 outflow of vapour. That the double maximum and minimum of the barometric march 
 really originates by the approximate destruction of the second term in the series 
 
 (A + o) + (B - j8) . sin. (0 + C) + ft . sin. (20 + 7), &c. 
 
 owing to the opposite march of the dry and wet elements of the total pressure, has been 
 put out of doubt by the calculations of Dove. Yet there are localities where there is an 
 apparent double maximum in the dry-pressure itself. "We have seen that moisture in 
 (Page 169) the form of clouds, or even in that excessively divided yet unevaporated 
 state which is sufficient to injure the transparency of the atmosphere, and which must 
 be confessed to belong to the yet unresolved problems of meteorology, produces absorp- 
 tion of the sun's rays and the conversion of sensible into latent heat. The diurnal 
 march of temperature, then, in the general atmosphere, is intimately connected with its 
 hygrometric state, and especially with its degree of relative dryhess. And for the same 
 reason that the heat of the day is mitigated by the evaporation of the diffused moisture, 
 so is also the cold of night by its deposition, and hence arises a phenomenon of very 
 general prevalence, viz., that the difference between the daily and nightly extremes of 
 temperature or the extent of its diurnal fluctuations is greater in summer than in 
 winter ; or rather, to speak more generally and in language applicable alike to inter- and 
 (Page 170) extra- tropical localities, in those seasons when the air is relatively drier or 
 moister. In fact, it is evident that when the air is relatively dry, evaporation during the 
 day is more active, and a larger portion of the incident heat becomes latent. On the 
 other hand, as it is necessarily the dew-point which limits (at least approximately) 
 the temperature of the lowest stratum at night, since in the act of condensation the 
 vapour gives out its latent heat, and therefore so long as the supply is continued pre- 
 vents its further depression the further removed from saturation the air is, the greater 
 depression can be effected by radiation before that limit is reached. The near coinci- 
 dence of the dew-point with the lowest nightly temperature, at every season of the year, 
 has been shown by Anderson from observations made at Kinfauns Castle during the 
 year 1815 ; and the calculations of Kamtz show that the difference between the daily 
 extremes of temperature is universally greatest in those months of the year when the 
 (Page 171) relative dryness of the air is greatest. The greater uniformity of an insular 
 as contrasted with a continental climate is at least partly referable to the same cause, 
 324 
 
AQUEOUS VAPOUR. 1862. Hersehel. NOTES. 
 
 viz., the alternate conversion of sensible into latent heat, and vice versa, by the evapora- 
 tion and condensation of moisture disseminated through the atmosphere during day and 
 {Page 191) night. With the exception of a few very limited regions in which fogs are 
 {Page 192) habitually prevalent, and certain points here and there occurring in which 
 rain is almost constantly falling, the general state of the atmosphere is one of more or 
 less hygrometric dryness ; so that, as a rule, evaporation may be considered as going on 
 continually over the whole surface of the globe, being only interrupted where that 
 surface is, during certain hours of the night, cooled by radiation below the dew-point. 
 During these the earth is actually abstracting moisture from the air at all other times 
 supplying it ; but far more copiously during the day than during the night. Meanwhile, 
 the very highest regions of the atmosphere being from time to time drained of their 
 moisture by precipitation, there is always a demand for vapour upwards, which is no 
 way intercepted in its ascent by the existence of a region where it assumes for awhile 
 a visible form, and which can only be looked upon as a temporary halting-place, the upper 
 surface of the cloud evaporating while the cloud itself is renewed by condensation of 
 ascending vapour at the lower ; unless, indeed, the radiation from the cloud itself should 
 for a time so far lower its temperature as to suspend for awhile, or even reverse, the. 
 process. At the epoch of maximum cold, when the surface of the earth is at or near 
 the dew-point, the hygrometric state of the air to a considerable altitude is near satura- 
 tion, and frequently either a stratus cloud rests on the ground or exists at a much lower 
 (Page 193) altitude than in the day ; and when this is not the case, still the whole 
 column of air, by reason of the general depression of temperature, is much nearer to its 
 point of saturation than in the daytime. It is the practice of meteorologists to designate 
 by the expression " humidity of the air " the degree of its approach to complete satura- 
 tion with vapour, and to give precision to this language by attributing to that degree a 
 numerical value, viz., the ratio of the quantity of vapour actually present per cubic 
 foot to that which would exist per cubic foot were the air saturated, or were the dew-, 
 point identical with the actual temperature. Thus a scale of degrees of humidity is 
 formed, 1*00 being that of complete saturation, and that of absolute dryness. In this 
 sense of the word it will of course be readily understood that a low degree of humidity 
 is compatible with the presence of a large quantity of aqueous vapour. It is not the 
 vapour as such, but its readiness to be deposited in a wet state on a surface but little 
 lower in temperature, that is intended to be expressed. To obviate the discordance 
 between this language and that of common parlance, the terms relative humidity and 
 relative dryness are sometimes used. As a general meteorological fact, however, there 
 is not merely a want of accordance, but an actual opposition between both the diurnal 
 and annual progress of the " degree of humidity " or " relative humidity " of the air and 
 (Page 194) the tension of vapour as indicated by hygrometric observation. To take the 
 case in hand the diurnal variation we have seen that at those epochs of the night 
 when the temperature has reached its lowest point, and dew is either actually deposited 
 or nearly so, the humidity is at its maximum. But it is precisely at that moment that 
 the supply of vapour from the earth having been for several hours cut off, or even a 
 reverse process in progress, while yet vapour has been diffusing itself into the non- 
 saturated regions aloft, and is still continuing to do so the actual amount of moisture 
 per cubic foot is small, and is still in process of diminution. This epoch is usually 
 a little before sunrise. As the day advances the temperature increases, and becomes 
 more and more in excess of the dew-point. The air therefore becomes relatively drier, 
 evaporation goes on more rapidly, the lower strata become fuller of vapour, as measured 
 by its tension, which at length becomes such as to keep pace with the upward diffusion, 
 which now in its turn is stimulated. The cloud level, or vapour plane, rises, and if the 
 night has been clear, the air calm, the sun powerful, and the soil wet, the appearance of 
 cumuli soon begins to render visible testimony to the nature of the process in progress. 
 When the heat of the day has reached its minimum, the process is in its greatest 
 
 z 325 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 activity The humidity has now reached its maximum, and the evaporation, which is 
 in the direct ratio of the temperature and dryness, its minimum. From this epoch, 
 (Page 195) however, the supply of vapour from below being most copious, while the 
 temperature no longer increases, it is evident that the humidity must begin to increase, 
 while the tension also, for a longer or shorter time, will do the same, until by the decline 
 of the sun the increase of humidity so far puts a stop to the evaporating process as to 
 render it barely competent to supply the expense of upward diffusion, at which moment 
 the tension becomes a maximum, and from which it also decreases, and continues to do 
 so the humidity increasing during the remainder of the twenty-four hours until next 
 sunrise, when the same cycle of causes and effects will recur. Such at least will be 
 their succession in calm and clear weather and in a normal state of circumstances ; and 
 as regards the generally contrary march of the relative humidity as compared with that 
 of the temperature and the vapour tension, such is really the course of the phenomena. 
 The epochs, however, and the order of priority, are obviously very liable to be disturbed 
 by a variety of circumstances, among which the most influential are rain, winds 
 (especially such as recur in daily periodicity, as sea and land breezes), and cloud, which 
 cuts off the sunbeams from the soil and puts a stop to the increase of evaporation before 
 the temperature has attained its maximum, thereby tending to bring the epoch of 
 maximum tension towards coincidence with that of maximum heat. We find, for 
 example, on comparison of the three elements in question, as derived from six years' 
 {Page 196) two-hourly observations at the Royal Observatory at Greenwich (1842-1847), 
 the following results : 
 
 Maximum. Minimum. 
 
 Temperature . 55'22F. 1 h. 20 m. p.m. 44'85F. 4 h. 10 m. a.m. 
 
 Vapour tension . '345 in. 1 h. 20 m. p.m. '303 in. 3 h. 40 m. a.m. 
 
 Humidity . . '938 4 h. 30 m. a.m. '753 1 h. 20 m. p.m. 
 
 where it should be observed that the amount of cloud at Greenwich is a maximum at 
 h. 20 m. p.m., at which hour 73 per cent, of the sky, on a general average, is covered ; 
 and a minimum at 9 h. 44 m. p.m., when 60 per cent, of cloud prevail ; the general 
 average of the year being two-thirds cloudy. The annual march of humidity and 
 vapour tension, as compared with that of temperature, depends on the same principles, 
 and is governed by the same laws ; the humidity, however (as is also the case with the 
 diurnal cycle), being much more regular in its progress than the vapour tension, and 
 the limits between which the latter element oscillates being much wider, as might be 
 expected from the greater duration of the cycle, and the consequently longer time given 
 for the causes in action to work out their full effect before removal. Thus at Greenwich 
 the annual maxima and minima and their approximate epochs, as appears from the 
 series of observations already referred to, are for the 
 
 Annual Maximum. Annual Minimum. 
 
 Temperatui'e . 63 '37 F. in July 34-20 F. in Jan. Feb. 
 
 Vapour tension . *466 in. in July *195 in. in Jan. 
 
 Humidity . . 930 in Jan. ' '783 in June 
 
 {Page 197) Locally and temporarily nothing can be more capricious than either the 
 humidity or vapour tension as we ascend into the higher regions. Meteorologists, from 
 Saussure and De Luc downwards, have sought in vain for anything like a regular law 
 of decrement like that which, at least approximately, prevails respecting temperature. 
 Mr. Rush relates that in his sixteenth ascent to the height of 19,400 feet in the Nassau 
 balloon, June 29, 1850, with Mr. Green, they traversed a stratum of air 8600 feet in 
 thickness, in which absolute hygrometric dryness, the zero of vapour tension, existed. 
 This must of course be received with some reserve ; but it suffices at least to show that 
 in regions of the globe where cloud is the rule and pure sky the exception, masses of air 
 are occasionally intermingled with the generally moist atmosphere, which would seem 
 326 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 to have been all but absolutely drained of their moisture, either by long sojourn in the 
 polar regions or in the highest and coldest strata of the atmosphere. Meanwhile, at the 
 ordinary levels we know little at present of the average or climatic distribution of 
 aqueous vapour. Of some things, however, we may be certain, viz. : 1st, That on 
 the open ocean, far from land, the dew-point in the daytime can never be many degrees 
 below the actual temperature of the air, and at night must always be very nearly 
 identical with it. 2ndly, That the mean vapour tension in hot climates must neces- 
 (Page 198) sarily be greater than in cold. 3rdly, That, cceteris paribus, the relative 
 humidity of the air must be a maximum over the sea and a minimum in the interior of 
 continents, especially where there is much sand, which allows the rain-water to sink, 
 and which speedily dries at the surface ; or much bare rock, which, never being more 
 than superficially moistened, affords no supply of vapour to the air. For it is obvious 
 that in such regions there must be less evaporation for an equal incidence of 
 sunbeams ; that, therefore, less of the heat will become latent, and their efficacy in 
 heating the air will be in consequence greater, so that the temperature will rise in the 
 daytime faster than the dew-point, and that in an increasing ratio ; and, moreover, 
 that from the very combination of these causes there will be less tendency to the forma- 
 tion of clouds over such regions, and therefore a greater amount of direct sunshine 
 thrown on the soil. Thus we have a system of mutually reacting causes and con- 
 sequences, all tending to exaggerate both the heat of the climate and its relative dryness ; 
 the only counteracting power being that of radiation, both diurnal and nocturnal, but 
 especially the latter. Where, in addition to all these causes, those winds which blow 
 from warmer regions or from tropical seas, before arriving at the place in question, have 
 to pass over lofty mountain ranges, and have been chilled in so doing, and drained 
 of their moisture by the precipitation of snow or rain, it may well be imagined that a 
 (Page 199) state of extreme aridity will prevail. 4thly, and lastly, we may perceive 
 that the upper regions of the atmosphere not only as being colder, and therefore 
 incapable of retaining without deposition a quantity of vapour equal to that of the lower 
 must be habitually and on a general average drier than the lower ; though the 
 existence of cirrus clouds at very high levels (certainly sometimes exceeding 30,000 feet) 
 sufficiently proves that even at such altitudes saturation with moisture occasionally 
 takes place. During the sojourn of Mr. P. Smyth on the Peak of Teneriffe the aridity 
 of the air was found to be always excessive. On one occasion at Guajara (alt. 8843 feet) 
 the depression of the, dew-point below the temperature of the air was observed to be no 
 less than 54 F. In actual cloud (although in the earlier history of hygrometry the fact 
 was questioned owing to the imperfection of hygrometers usec^ both common sense and 
 observation go to prove that the extreme point of humidity is attained, since where 
 water is bodily present in every cubic inch of air, and refuses to disappear by evapora- 
 tion, a state of absolute saturation must exist. Hence we are led to some singular 
 enough conclusions with respect to the law of decrement of humidity as distinct from 
 (Page 200) vapour tension. In the daytime, so long as the sky is cloudless over any 
 spot, it is evident that there is no point in the aerial column above it at which the dew- 
 point is surpassed so that the supply of moisture from below is carried off by diffusion 
 upwards, and it will depend entirely on the copiousness of this supply, and the rapidity 
 with which it ascends into the higher regions, whether, as the day advances, the vapour 
 tension and humidity shall follow a contrary or similar progression. If the supply be 
 abundant and borne up rapidly to a colder level, a cloud will be formed, and it is 
 obvious that for some time before its actual visible appearance the air in that region 
 where it is about to be formed must be gradually approaching saturation, and attain it 
 at the moment of deposition of the first molecule of water in a liquid state. From the 
 ground, then, up to the vapour plane, wherever such plane exists, whatever be the law 
 of vapour tension, the humidity (with, perhaps, some interruptions in respect of 
 regularity) continually increases up to TOO, its natural limit, which it maintains 
 
 z 2 327 
 
NOTES. 
 
 AQUEOUS VAPOUR. 1862. Herschel. 
 
 through the whole thickness of the cloud stratum. This surface passed, the upper 
 surface of the cloud performs, to all intents and purposes as regards the higher 
 atmosphere, the office of a lake, being a thoroughly wet surface on which that atmo- 
 sphere reposes. Henceforward the law of decrement of moisture will be the same as 
 (Page 201) it would be over the sea itself under the same circumstances of tempera- 
 ture and pressure. Nor does anything prevent (the sun striking on and evaporating 
 it) why a second layer of cloud should not be formed again at a higher level, and 
 
 go on a phenomenon, in fact, of no rare occurrence. In such a case, if we take the 
 
 height for an abscissa, as AB, the curve of humidity 
 will be an undulating one, such as EFGHI, attain- 
 ing its maximum TOO (= BF or CH) at F or H, 
 and having a minimum between them as at G, 
 while the curve of tension PQRST follows a pro- 
 gression totally different, the relation between 
 any pair of their respective ordinates CH, CS 
 being that which subsists between the tempera- 
 ture, tension, and humidity generally, a relation 
 expressible by the equation 
 
 V = H . 4, (0, 
 
 where Y is the vapour tension, H the humidity, 
 and (f> (2) the function of the temperature t, which 
 
 A E P expresses the force of saturated vapour at that 
 
 (Page 203) temperature. The winds are originally caused by the equatorial heat and 
 generation of aqueous vapour, or by extensive local agencies of the same kind elsewhere. 
 (Page 204) Dove, in his Meteorologische Untersuchungen ' (1832), has succeeded in 
 exhibiting in a very distinct manner, by an extensive induction from observations in 
 almost every region of the globe, the close and immediate dependence of all the three 
 great meteorological elements, temperature, moisture, and atmospheric pressure, on the 
 direction of the wind. In other words, assuming to represent the angle which that 
 direction makes with the meridian of the place, any one of these elements is found to be 
 expressible on an average or mean value during a whole year or series of years by the 
 equation of the form 
 
 E = A + B! . sin. (0 + C,) + B 2 . sin. (2 -f C 2 ) + &c. . . (a) 
 
 The mode in which a law of this kind may originate is not difficult to understand. 
 Suppose, first, the earth without diurnal rotation and the sun to move round it from 
 east to west, and at any given spot (suppose in the north hemisphere) let a wind blow 
 direct from the south with a certain force and during a certain time, this will bring over 
 the place of observation the warmth and moisture of a latitude more southerly (suppose) 
 by 10. But from the eastward or westward of south, at an angle with the meridian, 
 the atmosphere of a place 10 remote, measured in a great circle, will be still transferred 
 to the place, but owing to the inclination of the path only 10 x cos. more south. If, 
 therefore, the former wind brought with it an accession of temperature or moisture, 
 represented by e, this will bring the accession e . cos. proportional to the difference of 
 latitude travelled over. It may happen, however, from the circumstances of the locality 
 that the warmest or moistest region in the neighbourhood may be not due south of the 
 place, but in a direction making an angle 90 - C with the meridian. In this case, then, 
 the extraneous temperature or moisture so induced will obviously be represented, not 
 simply by e . cos. 0, but by e . cos. (0 + C - 90), or e . sin. (0 + C). As the effect of the 
 earth's diurnal rotation is to cause the wind to veer, the wind from the southern region 
 will have more or less westing in it at the place according to circumstances. The effect 
 of a wind will depend upon its degree of frequency and duration. Dove and others find 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 {Page 207) that in the wind rose there are two points not far from diametrically opposed 
 to each other ; the one in the neighbourhood of the N.E. point, the other in that of tho 
 S.W., from which, when the wind blows, on the long average, both the temperature and 
 the vapour tension have their maxima and minima, the former at the N.E. and the 
 latter at the S.W. The same, or nearly the same, points indicate reversely the maximum 
 and minimum of barometric pressure. There are deviations according to localities. On 
 {Page 208) the whole, however, for each locality and for each of the three elements 
 in question it is found practicable to represent its variation in terms of the azimuths 
 of the direction of the wind by the expression 
 
 E = A + B 1 . sin. (0 + CJ + B 2 . sin. (20 + C 2 ). 
 
 in which C is very nearly the same angle for all of them, and in which B 2 , the 
 co-efficient of the term of the second order, is found to be smaller in comparison of B lf 
 that of the first. And it is evident that the total barometric pressure P + V and the 
 vapour pressure V, having both this form of expression, their, difference P, or the pressure 
 of dry air, will admit of a similar one by a proper determination of its co-efficients, which 
 are easily deduced from those of its component elements by putting 
 
 P + P! . sin. (0 + CO + P 2 . sin. (20 + C 2 )+ V + V l . sin. (0 + C,) + V 2 . sin. (20 + C 2 ) 
 = P' + P\ . sin. (0 + C',) + P' 2 . sin. (20 + C' 2 ), 
 
 where P' represents the mixed pressure and the several numbered and accented 
 letters the respective co-efficients of the general formula, and which, reduced by the 
 usual trigonometrical transformations, afford equations by which any one set of these 
 {Page 209) values may be easily derived from the other two. It is evident, moreover, 
 without any calculation of this kind, that since the elastic power of the vapour has its 
 maximum at the S.W. point, where the total barometric pressure has its minimum, the 
 dry pressure P must have its minimum there also ; in other words, that C lf being 
 approximately = C x + 180, C' will be nearly identical with C. Dove further finds that 
 these co-efficients are severally and separately, like all meteorological local elements, 
 periodical functions of the season of the year or of the sun's mean longitude. A similar 
 set of relations ought to subsist in the south hemisphere, mutatis mutandis ; that is 
 to say, with the maxima and minima at south-east and north-west. As an example 
 of the results obtained in this branch of meteorological inquiry we shall here set down 
 the values of the co-efficients in the expression E =A + Bj sin. (0 + Cj), &c., as calcu- 
 lated by Prof. Johnson from the series of meteorological observations made under his 
 superintendence at the Radcliffe Observatory at Oxford. These are (Radcliffe Obs. 
 
 1854, p. xxvi) for the > 
 
 A. BL d. Bf 2 . 
 
 Temperature, T. 48 60 F. 2-34 254-35 
 
 Dry pressure, P. 29 -404 in. -108 in. 75-33 
 
 Vapour pressure, V. -307 in. '026 in. 259-39 
 
 where it will be noticed that 180 + 75 33' =255 33', and therefore, comformably to 
 the theoretical views above delivered, the dry pressure has its minimum very nearly 
 corresponding to the maximum of temperature and of vapour pressure. Whenever, as 
 in this case which is the most common the terms of the second and higher orders 
 are inseparable, or nearly so, the coefficient B determines the maxima and minima, 
 so that the respective values of 2 B x will express the total amount of fluctuation in 
 temperature, pressure, &c., at the stations which have their origin in changes of wind. 
 It is very easy to perceive that, with this dependence of the great elements of the 
 weather upon the direction of the wind, the other features which stand to them in the 
 relation either of immediate consequences or proximate causes must go hand in hand, 
 such as cloud, rain, &c. For instance, at Karlsbad, from the calculations of Eisenlohr 
 it appears that during the prevalence of south wind, one day out of 17'29, on an average, 
 
 329 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 (Page 211) only is free from cloud, and during that of north-east one out of 3'04; 
 the intermediate winds being accompanied by intermediate degrees of frequency. 
 So also for the other elements. The tables at the end of this work afford numerous 
 (Page 212) and striking exemplifications of these laws, especially as regards the contrary 
 march, both annual and diurnal, of the humidity and vapour tension, the greater range 
 of the annual as compared with the diurnal fluctuations, and the dependence of the 
 average amount of the vapour present in the air, and the extent of both kinds of 
 fluctuation in the latitude. 
 
 (Page 230.) In describing the cause of polarisation of skylight, he decides it cannot 
 be due to the refractive action of ice, nor of water, nor of reflection of air upon air. 
 Newton's explanation is the least unsatisfactory ; he assigns it to the reflection of light 
 on their transparent particles. [H. does not say more, but seems to hint that these 
 particles are vapour, as he states that its explanation will probably be found to carry 
 with it that of the blue colour of the sky itself. If so, then it may be that facts con- 
 nected with this subject which are given under " Climate : Luminous Hays " may afford 
 clues as to the distribution of vapour. At present the connection is not sufficiently 
 clear to warrant notes being entered here ; but when the phenomena of polarisation 
 afford data of this kind such notes may be given here.] 
 
 (Page 236.) In certain phases of an auroral display indications of a very unequivocal 
 character are afforded of a distribution of a material substance in forms which, could 
 they be seen under ordinary circumstances, would be called clouds. We allude to 
 those luminous bands extending across the sky, and patches of auroral light which are 
 either stationary or nearly so in the sky, but which, when attentively watched, are 
 usually perceived to be slowly drifting southwards. These, perhaps, belong to com- 
 (Page 237) paratively less elevated regions, and are, perhaps, in some cases identifiable 
 with the very highest perceptible cirrus cloud. 
 
 Proc. Brit. Meteor. Soc., vol. i. 1863. (No. 2, for Jan. 1862.) (rv.) 
 
 (Page 116.) Notice of " Meteorological Tables," by G. H. Simmonds. 1861. 
 
 (Page 117.) Table XVII. shows the weight in grains of a cubic foot of vapour, 
 assuming that at 212 it weighs 257'13 grains. Table XVIII. shows the weight of 
 a cubic foot of air saturated with moisture under a pressure of 30 in. from 20 to + 120. 
 (Page 129.) Fisher, in 1845, says that the principal displays of the aurora occur in the 
 vicinity of the edge or margin of the Frozen Sea, and that it is an electrical phenomenon, 
 and arises from the positive electricity developed by the congelation of these [humid (by 
 Editor of Proc.)] vapours, and the consequent induced negative electricity of the upper 
 and surrounding portions of dry atmosphere. It is the accompanying indication of the 
 restoration of the electrical equilibrium, which equilibrium is restored by the interven- 
 tion and conducting power of minute frozen particles, which particles are rendered 
 luminous by the transmission of electricity. In early winter, before the sea was frozen 
 over, the aurora had a diffused character. As the winter advanced and the edge of the ice 
 became more remote, so the aurora diminished in splendour, assumed a low arched appear- 
 ance, and was seen only in the direction of open waters. Its height above the surface of 
 the earth is very inconsiderable in high latitudes. The sudden deposition of extremely 
 minute frozen particles when auroral displays took place near to the zenith was several 
 times observed by the author. Joslyn, in 1838, states among other conditions that it [the 
 aurora] requires for its development a cold adequate to the crystallisation of aqueous 
 vapours ; that crystals of snow more minute and simple than those which produce halos, 
 are always present in the atmosphere, above the region of ordinary clouds, during the 
 appearance of this meteor. Fisher considers that perhaps the strongest proof of the 
 important agency of these particles in an auroral display is to be derived from the fact 
 that the auroral light can be distinctly traced to those localities where humid vapours 
 330 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 are known to be undergoing rapid congelation, and where such particles must in con- 
 sequence abound, and that in the usual arch formation, whatever may be the nature of 
 the night, yet the auroral fringe clearly arises from the illumination of the frozen 
 particles which are formed from the extreme portion of the vapours being under the 
 influence of the cold atmosphere immediately above them. Fisher obtained sufficient 
 evidence of the direction of the situation of the open water from the dark masses of 
 vapour known as sea-blink. The upper limit of the auroral arch was generally dark 
 and dense, as if charged with humidity ; the lower, being nearer the water surface, was 
 warmer and more transparent. When ice breaks up by the action of spring tides, and 
 water is suddenly exposed, a difference of more than 70 F. is often found between the 
 water surface and the atmosphere immediately over it; so that the latter becomes 
 immediately impregnated with the extremely minute frozen particles known as frost- 
 (Page 130) smoke ; and he conceives that the alternate opening and closing of the ice, 
 by which means different portions of vapours are detached from the surface of the sea con- 
 secutively, give rise to the appearance of different concentric arches of aurora. Vertical 
 streamers are columns of icy particles in the act of restoring equilibrium between 
 higher and lower strata. Low temperature and humidity are, in his opinion, the 
 conditions required for the production of aurora, and hence the water limits of the 
 Frozen Sea will be most favourable to the production of the aurora, from the circum- 
 stance of there being there the greatest supply of humidity. He infers that the auroral 
 zones will not approach nearer the poles than the margin of fixed ice, for lack of humidity. 
 (Page 135.) De la Rive considers he was the first to notice the close connection 
 between auroras and the small icy particles suspended in the elevated regions of the 
 air. Secchi concludes that the character of winter clouds in the polar regions is different 
 from that of the ordinary clouds, and that the appearance of these latter clouds at the 
 poles is a signal, the harbinger of the fine season and of humidity, whilst the auroras 
 then disappear ; that the aurora does not appear unless when the weather is humid ; 
 that even when the sky in the polar regions appears limpid it is nevertheless filled 
 with small icy particles. The fact that the aurora is contemporary with a very dry 
 atmosphere, the temperature of which is below 0, containing small icy particles, may 
 be considered beyond all doubt. 
 
 Proc. Brit. Meteor. Soc., vol. i. 1863. (No. 2, for Jan. 1862.) (TV.) 
 
 (Page 167.) Espy (1834) believes that all the phenomena connected with storms 
 are explained by the following theory. When the air in any locality acquires a higher 
 temperature or a higher dew-point than that of surrounding regions, it is specifically 
 lighter, and will ascend ; in ascending it comes under less pressure and expands ; in 
 expanding from diminished pressure it grows colder about a degree and a quarter for 
 every 100 yards of ascent ; in cooling as low as the dew-point (which it will do 
 when it rises as many hundred yards as the dew-point at the time is below the tempera- 
 ture of the air in degrees of Fahrenheit) it will begin to condense into cloud ; in con- 
 densing its vapour into water or gloud it will evolve its latent caloric ; this evolution of 
 latent caloric will prevent the air from cooling so fast in its further ascent as it did in 
 ascending below the base of the cloud now forming ; the current of air, however, will 
 continue to ascend and grow colder about half as much as it would do if it had no 
 vapour in it to condense ; and when it has risen high enough to have condensed, by the 
 cold and expansion from diminished pressure, one-hundredth of its weight of vapour, it 
 will be about 48 less cold than it would have been if it had had no vapour to condense 
 nor latent caloric to give out that is, it would be about 48 warmer than the surrounding 
 air at the same height ; being lighter it will ascend and spread out gradually, overlapping 
 (Page 168) the air all round and causing the barometer to rise around the storm and 
 to fall in the centre, and, being under less pressure, will ascend, carrying the vapour it 
 
 331 
 
AQUEOUS VAPOUR. 1862. Herschel. NOTES. 
 
 contains with it, and so continue the process of cloud-forming. The phenomena of 
 tornadoes, hailstorms, and whirlwinds may all be explained by the theory, and whatever 
 cause induces an up-moving current of air in a calm saturated condition of the atmo- 
 sphere produces rain. Mackay in a letter describes how, in 1845, during a survey, he 
 set fire to a patch of grass, and confined the flames to it. Soon a refreshing breeze 
 sprang up, and a refreshing shower occurred. Capt. A. Mackay afterwards observed 
 that he noticed the formation of a cloud at the apex of the smoke, and said it suggested 
 Espy's theory to him. Accordingly it was determined to put the idea to the test. During 
 a period of unusual heat and dryness, and on a cloudless day, we (states Mackay) told the 
 (Page 170) negroes we could bring rain. We set fire to the grass. As the smoky 
 column broke the cloud began to form. Then it thundered, and the cloud spread, and 
 the rain descended in torrents, though the clear sky could be seen in all directions 
 tinder the cloud. We often fired the sawgrass marshes, and whenever there was no 
 wind stirring we were sure to get a shower; if there was wind there would be the 
 appearance of rain on the horizon. Mr. A. H. Jones says he has performed similar 
 experiments with success, and farmers in the dry season frequently fire the grass in 
 order to get rain. By means of a nepheloscope Espy made experiments on the degree 
 of cold produced, both in dry air and in moist, by sudden expansion from diminished 
 pressure. He found that air in contact with water in a closed vessel will not saturate 
 itself with water, or if saturated will cease to be so after a few days ; that vapour 
 permeates air from a high to a low dew-point with extreme slowness, if indeed it 
 (Page 171) permeates at all ; and that vapour rises into the regions where clouds are 
 formed only by being raised up by ascending currents of air containing it. The 
 manner in which up-moving currents of air carry vapour with them may be seen in the 
 formation of cumuli during a hot summer's day, when the summits increase by the 
 addition of thin films of cloud, produced by the air immediately above, the cloud being 
 pushed up, and the cold of expansion from diminished pressure causing its temperature 
 to sink below its own dew-point. Dissolving clouds frequently occasion strong winds at 
 the surface of the earth ; they are termed wind-clouds by the farmers in America. The 
 air on the outer body of the trade winds is remarkably dry, and thus to some extent 
 contribute to the greater height of the barometer there. The upper trade at the 
 equator carries very little vapour in it, as, before it rises over the equatorial regions to 
 one-third of the height of the atmosphere, nearly all its vapour is condensed into clouds, 
 and therefore, when it rises above the clouds and rolls off to higher latitudes, it carries 
 with it but little vapour. In short, the air does not carry so much vapour to high 
 latitudes as the air below to the low latitudes, and when it descends to the surface it 
 (Page 172) appears very dry, as its capacity for vapour is greatly increased by the heat 
 of compression. Cloud is never formed except in an up-moving current, for air coming 
 downwards always becomes drier; and if it be supposed that cold air in the same 
 horizontal level should mingle with warm so as to produce condensation of vapour, the 
 evolution of caloric in this air would immediately diminish its specific gravity, and it 
 would begin to ascend. Wherever there is an up-moving column of air sufficient to 
 form a large cloud, there is of necessity a down-moving current of air all round it ; and 
 where this current reaches, it is clear, if any clouds existed at first, they are soon dissolved 
 by the heat of compression. Were it not for this cause there are large regions of the 
 torrid zone which would be covered with eternal cloud. 
 
 Proc. Brit. Meteor. Soc., vol. i. 1863. (No. 3, for March 1862.) (r.) 
 
 (Page 182.) The object of Glaisher's balloon ascent from Wolverhampton on March 
 22, 1862, was to determine the distribution of moisture throughout the atmosphere, but 
 the balloon failed. 
 
 332 
 
AQUEOUS VAPOUR. 1863. Airy, J. B. NOTES. 
 
 1863. 
 
 Airy, J. B. Proc. Brit. Meteor. Soc., vol. i. 1863. (No. 8, for June 17.) (rv.) 
 (Page 365.) Bloxara does not seem to have fixed his attention on the supposed 
 -error Lament endeavoured to correct. I apprehend Dalton's experiments amount to 
 this : " In a limited space, of such a form as is very favourable to the motion of masses 
 or particles of gas, the dry air and the aqueous vapour exist through the whole space, 
 each exerting the same elastic pressure as if the other was not there." In ordinary 
 (Page 366) quotation this law has been cited to some such effect as the following : 
 " In any spaces we may consider separately the law of distribution of vapour as that of 
 an elastic gas, supposing no air present ; and the law of distribution of air as that of an 
 elastic gas, supposing no vapour present ; and we may represent the actual state by com- 
 bining these two gases in the densities thus indicated." For instance, the hygrometer 
 shows a great density of vapour near the ground. It has been supposed that the density of 
 vapour in every stratum above it can be computed from that lower density by the same 
 laws as if vapour were the only gas above the ground, disseminating itself by the 
 ordinary laws of gaseous dissemination. I do not know that any one has stated the 
 principle so broadly ; some have come near it, and I have no doubt it is the latent idea 
 which guides many meteorologists. It is against this idea of dissemination that Lament's 
 experiments are directed. He does not dispute that where air and vapour are mixed 
 Dalton's law holds truly, but he shows that the dissemination does not at all take place 
 according to the law of simple elastic gases. A gas, if no other gas were present, would 
 with great rapidity disseminate itself into every chamber connected with the place 
 where it is set free. Aqueous vapour, there is no doubt, would do so if it were alone ; 
 but aqueous vapour combined with air will long remain in one place, as if the mixture 
 of vapour and air produced viscosity. This is what Dr. Lament shows. 
 
 Blake, H. W. Proc. Brit. Meteor. Soc., vol. i. 1863. (No. 7, for March 18.) (rv.) 
 
 (Page 331.) Describes cirri seen near Welwyn, Herefordshire, on Dec. 14, 1862, 
 which presented auroral appearances after dark. Coupling this with Glaisher's observa- 
 (Page 332) tions on the great height of cirri, he suggests that we must look for some 
 other cause for their formation than that of aqueous vapour, especially when the dryness 
 and the extremely low dew-point of those regions are likewise considered. [He implies 
 that cirri may be simply auroras as seen by daylight] 
 
 Bloxam, J. C. Proc. Brit. Meteor. Soc., vol. i. 1863. (No. 7, March 18, 1863.) (rt>.) 
 
 (Page 324.) In discussing the occurrence of the black-thorn winter in spring, he con- 
 cludes that it is not due to any retrogression in the temperature. We must then seek for 
 some other peculiarity that will serve to account for the sensible character of the season. 
 [He does not say to what place his observations refer, but I presume it is Newport 
 or some place in England. The general principle underlying the figures and discussion 
 is of wide application.] What is the hygrometric state of the air? The mean 
 temperature of the dew-point for the year, which is 43, occurs on May 12 ; the mean 
 value for April is 38'6, that for May 44, and the value for April 21 is 38'9. The 
 daily rate of increase for April is 0'09, and that for May 0> 23 the mean rate from 
 lowest to highest being 0'12. On April 21 the dew-point temperature has risen 25 per 
 cent, of its total annual rise, but the atmospheric temperature has risen at the same 
 date 39 per cent. On April 21 the humidity is at its minimum value for the year, viz., 
 71*1. This is the essential fact which solves the problem ; the 21st of April differs from 
 every other day in the year in this respect, and the black-thorn winter reaches its 
 
 333 
 
AQUEOUS VAPOUR* 1863. Bloxam, J. C. NOTES. 
 
 culminating point on this date ; the evaporation produced by this low degree of humidity 
 crives rise to that peculiar feeling of cold which characterises the season. But this 
 excessive evaporation depends as much upon the high temperature of the atmosphere as 
 upon the low temperature of the dew-point. The sky is far more clear of cloud than on 
 the average, but it is not at its minimum ; the lowest value for this particular is 6-0 on 
 (Page 325) Sept. 4. The heat from the sun's rays at this period of the year is great, 
 owing to the transparency of the atmosphere and the clearness of the sky; this 
 perhapfl renders the sense of coldness the more conspicuous and distressing. The low 
 value for humidity is thus shown to be the dominating characteristic of the equi- 
 noctial winter. At this season of the year a great advance is observable in temperature, 
 and the peculiarity of the season is explained by the fact that it is the period of the 
 year in which the temperature rises to its highest point with an arctic atmosphere ; the 
 temperature continues to rise subsequently as the north declination of the sun increases, 
 but this progress in the sun's position brings to our latitude in the temperate zone a 
 moist as well as warm tropical atmosphere. The tendency in the atmosphere to flow 
 from the north-east quarter is at its maximum intensity on April 19. At the period of 
 the year which is under review the source from which our atmosphere proceeds is a 
 region of ice, in which the temperature had been much below the freezing-point for 
 months, and the vapour of its atmosphere is reduced to its lowest amount prior to its 
 (Page 326) flowing to the lower latitudes. Similarly, as regards the St. Martin's 
 summer the peculiarity of the season is evidently due to some other element than 
 temperature. Dec. 3 is marked as having the maximum humidity for the year. On 
 Nov. 9 the value is 82'6, and this may be regarded as the day on which the equinoctial 
 or St. Martin's summer culminates, because the humidity attains a high and a maximum 
 value on that day. Excessive humidity and consequent defective evaporation are the 
 cause of the sensible warmth which attracts attention. The south-west wind has the 
 ascendant during the season. The amount of cloud is great during the season, though 
 not at the maximum. The high value for humidity is assuredly the essential meteoro- 
 logical characteristic of the equinoctial summer, and this high value seems to be brought 
 about in a great measure by the rapid decline of temperature. May the low temperature 
 of the atmosphere and the comparatively high temperature of the dew-point be 
 explained by the fact that the atmosphere proceeds from higher latitudes than it does 
 during our summer, and from cold land districts ; but whilst crossing the Atlantic it takes 
 (Page 362) up a large quantity of vapour ? (No. 8, for June 17.) Lament's article does 
 not afford a definite decision as to the relation of the atmospheric aqueous vapour to the 
 air. The aqueous vapour probably does not form an atmosphere totally independent of, 
 nor absolutely dependent upon, the -air ; the vapour is probably not merely mechanically 
 mixed with the air ; it is probably not chemically combined with the air ; the connection 
 subsisting between vapour and air, as the two exist together in the atmosphere, may be 
 dependent upon electric conditions. Neither Dalton's theory nor Lament's theory asserts 
 either the positive or the negative view of either of the propositions absolutely. It is 
 to be remembered that Dalton's theory is not merely a theory ; the laws he announced 
 are laws deduced from and clearly indicated by experiment carefully conducted ; and 
 he deals with the physical results of the combination rather than the law by which the 
 combination is effected. No one perhaps will at present venture to pronounce on the 
 essential nature of the combination. Professor Lament's experiments rather confirm the 
 three principal results deduced from Dalton's experiments. " As to the mutual relations 
 subsisting between vapour and air, when they are simultaneously present, the experi- 
 ments (of Dal ton) afford no information." This is, perhaps, not quite a correct state- 
 ment ; but what are the mutual relations indicated by the professor's experiments ? They 
 seem to be nothing more than this : ^If the portion A of the space AB is occupied with 
 air, and the portion B with vapour, whatever the elastic force of the air may be under 
 this arrangement, the amount of that force will be diminished by withdrawing the 
 334 
 
AQUEOUS VAPOUR. 1863. Bloxam, J v %f slT?; NOTES. 
 
 ff ^ ^ *_, 
 
 (Page 363) vapour from B, and allowing the same Air to occupy the whole of the 
 space AB. The interpretation that Dalton gives to the 'second of the, three propositions 
 is that when air and vapour are mixed together in the manner (though 
 perhaps not in the same degree) that obtains in the atmosphere, neither of 
 the two influences the elastic force of the other, or, more correctly, this is 
 the result obtained by experiment. He gives no such interpretation as that 
 *' no mutual relation whatever existed between vapour and air ; " he would 
 doubtless have acknowledged such mutual relation as the diagram above refers 
 Dalton's theory does not imply that the atmospheric vapour is sustained in equili- 
 brium by itself alone, but that it can attain to a state of equilibrium by virtue of 
 its gravity only; and its tendency to acquire equilibrium as an independent agent 
 helps to determine its movements and to regulate its quantity in any particular 
 locality. The third proposition properly declares that there is indeed always a tendency 
 to a normal relation " in so far as that each of the constituents has always a normal 
 (though constantly varying) condition belonging to it ; but this does not ignore the fact 
 that neither the normal condition nor the normal relation can ever be reached, owing to 
 the law that one of the two bodies is being perpetually exhausted at one point and re- 
 produced at another, which necessarily leads to this one being always in motion and 
 never in equilibrium. It may be strictly true, or it may be true in a limited sense, that 
 " a mass of vapour and a mass of air placed in communication with each other 
 mutually preserve a state of equilibrium without the vapour penetrating into the air or 
 the air into the vapour " ; but this is not contradictory to Dalton's theory. Dalton 
 states that the two constituents do not readily mix spontaneously ; the professor con- 
 trives artificial means to counteract the natural tendency to mixing; but Dalton's 
 theory does not gainsay the possibility of doing this. Dalton's theory is not adverse to* 
 the proposition that if air be preserved unmixed in the space A, and vapour be preserved 
 in the space B, the elastic forces of these two bodies will press one upon the other. It 
 is quite clear that whilst each maintains its own separate position, each must press- 
 (Page 364) against the other where they come in contact. According to Dalton, if as- 
 much vapour be forced into a limited space as can exist in that space in the form of 
 vapour, the quantity that can so exist will not be diminished by forcing air into the 
 same space with the vapour, provided the two be intermixed in the manner they admit 
 of. Lament's experiments or reasoning are not opposed to this. .If vapour is slow in 
 diffusing itself through the air, and a portion consequently remains unmixed, this- 
 portion will then be subjected to the pressure of the air, and it may then be condensed,, 
 although it could not have been so condensed by its own pressure. A mass or layer of 
 vapour may be imagined as held in the grasp, as it were, of the atmosphere, and it 
 would then comport itself the same as if it were enclosed in an elastic bag ; it would be- 
 subjected to the pressure of the atmosphere. It is probable that masses of vapour 
 (Page 365) often exist in the midst of the atmosphere mixed with a comparatively 
 small proportion of air ; it would then not press upon the atmospheric vapour beneath 
 in the same manner that it would do if diffused equally through the atmosphere ; it 
 would press against the surrounding atmosphere, and the atmosphere would not press- 
 upon it. The vapour pressure thus transmitted through the atmosphere would not be 
 distinguishable at the surface of the earth from the air pressure ; we should not be able 
 to detect the vapour existing in this state by any of our instrumental aids at the 
 surface of the earth. The Dalton law is correct, but a false interpretation has been, 
 given to it by the invention of hygrometers. The hygrometer detects that portion of 
 the vapour pressure only which arises from the vapour diffused through the air ; and 
 the quantity of vapour in the air is probably always greater than the vapour pressure- 
 indicates; the air pressure must be to the same extent at least less than the estimate. 
 This may lead to the conclusion that the atmospheric vapour is a more powerful agent 
 i n giving motion to the atmosphere than it has hitherto been supposed to be. Pure 
 
 335 
 
SCIENTIFIC UNION. 
 
 vapour in the midst of air is subjected to foreign pressure, and it is not governed by its 
 own laws ; if it be mixed with a comparatively small proportion of air it will be placed 
 more or less in the same predicament. If it has expanded itself fully through the 
 texture of the air it will then be subject to its own laws ; the pressure it then exercises 
 is the pressure of itself, and of the whole of itself. 
 
 Scientific Simon* 
 
 The rapid progress of science now going on is, in part, the result of the 
 great increase in the number of workers. This is accompanied by a larger 
 and larger host of scientific serials. The consequence is that the student 
 finds an increasing difficulty in ascertaining what has been done, or is in 
 process of being accomplished, not only in his own special line of study, but 
 also, and more particularly, in such as do not immediately interest him. 
 Every student finds, from time to time, that he has a desire for full informa- 
 tion on subjects in these outlying sciences, for the purpose of throwing light 
 upon his special studies. The state of literature is such that he is frequently- 
 daunted by the difficulties attending his research, or, if he perseveres, he finds 
 a great deal of time unnecessarily wasted. The remedy for this is the focali- 
 sation of knowledge round a series of centres. The two main steps in the 
 process are, first, collection, and, next, classification. It is with this ulterior 
 object in view, that all persons interested in meteorology are earnestly asked 
 to forward their names and addresses, particulars as to the work they have 
 done in meteorological and other sciences, their present lines of study, ways 
 in which help is desired, and any other items that may occur to them. These 
 details will be classified, and, when the opportunity offers, selections from 
 them will be published. The Conductor will exercise careful discretion in 
 the selection, as also in the use he may make of the more private details. 
 The first list will be published, if circumstances permit, in November, 1883 ; 
 hut correspondents are requested to send in answers soon, in order to allow 
 of ample time for their classification, and for their utilisation in private 
 correspondence in the interests of correspondents. 
 
 In order to prevent any misconception, it may be stated that the Con- 
 ductor's object is solely to promote scientific union, and is no way intended 
 to be of a charitable nature in any pecuniary sense. If there is a sufficient 
 response to these requests, the same line of proceeding will hereafter be 
 suggested, from time to time, for the students in other branches of science. 
 
 Newspapers and scientific journals of all countries, willing to help in 
 this matter, are asked to make the above requests known to their readers. 
 
 Address, Conductor, 'Scientific Eoll' office, 7 Red Lion Court, Fleet 
 Street, London, E.G. 
 
 The above notice first appeared in August, 1882, and has been repeated in the subsequent 
 ffwrnbers. As yet only a few individuals have complied with the request made. It is 
 336 
 
SCIENTIFIC UNION. 
 
 only from individuals that reliable materials can be obtained ; consequently, if nr> 
 adequate response is made, no list of the kind proposed will be attempted. 
 
 Communications have been received from Prof. Robert B. Warder intimating that he 
 is compiling a list of papers relating to the speed of chemical action, and the intensity 
 of chemical affinities. There are many papers dealing with these subjects which are 
 liable to be overlooked owing to the titles being of no assistance. All individuals who. 
 have made observations on the subjects mentioned would help Prof. Warder by com- 
 municating with him. He has two papers on the subject in No. 4 of the ' Scientific 
 Proceedings of the Ohio Mechanics' Institute.' One is on * A Criterion for Measure- 
 ments of the Speed of Chemical Action' ; and the' second is a summary of * Urech's- 
 Investigation of the Speed of Inversion of Cane Sugar.' Any chemist or physicist 
 interested in this subject can have a copy of this number supplied to him gratis on, 
 applying to the " Publishing Committee, Ohio Mechanics' Institute, Cincinnati, Ohio,. 
 U.S.A." There is another reason why such persons should put themselves in communi- 
 cation with Prof. Warder through this committee, which is, that it will strengthen his 
 hands to carry out an organised enquiry into the subject, should such an enquiry seem 
 as practicable as it is desirable. 
 
 We have also recently received the earlier numbers of * Science,' and take this 
 opportunity of drawing attention to it, because it is, we believe, the first weekly periodical 
 which has adopted the methodical arrangement which is advocated by the * Scientific 
 Roll.' As stated in the prospectus issued in No. 5, " this prominent feature will be 
 particularly attractive to the specialist in whatever branch, as he will at once know 
 where to look for the latest information about all the more important work in his own 
 field of investigation." The reviews are severely critical, yet judicious and fair, being as 
 unsparing in blame as in praise, when each seems deserved; the articles are of the 
 highest quality ; and the abstracts are compact and pointed, and are drawn up by 
 specialists of high repute. We are glad to see that due prominence is given to the work 
 performed by Government and other organisations, and would refer to the following 
 paragraph as an example, which we hope will be followed in other countries and in 
 other subjects. The paragraph is from No. 10, published on April 13, 1883, p. 291 : 
 
 Contagious Diseases of Animals The subject of the prevention and cure of con- 
 tagious diseases of animals has for many years been considered in this country. For a 
 long time extirpation was resorted to, and with good results, notably in the work of the 
 Commission appointed by the State of Massachusetts in 1860, which entirely succeeded 
 in freeing that State of pleuro-pneumonia. Of late years inoculation or vaccination 
 has been employed with such success abroad by Pasteur, that we are justified in antici- 
 pating most beneficial results from the prosecution of his methods in this country. 
 Pasteur has been engaged in efforts to establish some law through the agency of which 
 such diseases as pleuro-pneumonia, charbon, foot-and-mouth disease, and other diseases- 
 of domestic animals, could be controlled and cured. Dr. D. E. Salmon has been 
 pursuing similar experiments under the direction of the U.S. Department of Agriculture, 
 though necessarily in a more limited way, and has met with such success, that he has 
 great faith in the result of the more elaborate and extensive experiments which he is- 
 about to undertake in the district of Columbia. Commissioner Loring has determined 
 to place at the disposal of Dr. Salmon the necessary land, buildings, animals and 
 apparatus to enable him to make the proper microscopical observations, and to carry on 
 any experiments that will tend to establish some economical method by which our 
 farmers or breeders may control the diseases of their animals. Dr. Salmon is of 
 opinion that such diseases as Texas fever, charbon, and pleuro-pneumonia are the 
 results of germs which he has found in his post-mortem examinations, and that it is- 
 possible to protect unaffected animals from these diseases by dilute inoculation. 
 
 The election of a recorder of economic entomology is another example which we trust 
 will be soon followed in other counties. Mr. S. L. Mosley, Beaumont Park, Hudders- 
 
 337 
 
THE SCIENTIFIC ENQUIRER. 
 
 field is the recorder, and in the Naturalist ' for May 1883, he appeals to all Yorkshire 
 naturalists to help forward this desirable work by sending him notes or specimens, or 
 both, of any kind of insect ravages which may come under their notice. He observes 
 that he can do little without such help, and particularly solicits communications on all 
 insects found to be injurious to field or garden crops, such as daddy-long-legs, turnip- 
 flea, beetles, aphides, wireworms, larva? of various kinds, &c. ; also notes of any remedies 
 which have been found serviceable, either artificial, as chemical dressings, or natural, as 
 the counteraction of other insects, insectivorous birds, &c. Anyone so assisting will 
 probably have any report that may be issued sent to him free. Part of the recorder's duty 
 is to give advice upon the best known and most simple remedies to all applicants, who are 
 requested to accompany their communications with specimens of the insects, as also with 
 illustrations of the injury done by them. 
 
 Skmtiifit (Snqttrrer. 
 
 Correspondence is invited on Science matters of all lands. In all cases 
 names and addresses should be given ; but these will not be published without the 
 writer's consent. Tlie Conductor will not be responsible for the opinions expressed 
 by correspondents. All communications should be addressed to the Conductor, 
 7, Eed Lion Court, Fleet Street, London, E.G. 
 
 Eeplies to questions should be numbered in accordance with the questions to which 
 they refer. The contractions following the questions and answers, indicate the class of 
 notes to which they will ultimately be assigned, and the place where full reference will 
 be given to the details bearing upon them. The following request and set of questions 
 are reprinted from the circular sent us by Dr. Kellogg. The numbers in paren- 
 theses are those given in the original^ those which precede them are those adopted 
 for the * Scientific Roll ' for the purpose of reference. 
 
 H=Homo > or Man. 
 
 CIRCULAR OF INQUIRY BY A COMMITTEE CONCERNING DIPHTHERIA. 
 
 Office of the Michigan State Board of Health, 
 Lansing, Michigan, October, i882. 
 
 DEAR SIR, The undersigned, having been appointed a committee 'of the Michigan State 
 Board of Health to prepare a paper setting forth what is known concerning Diphtheria, and 
 wishing to make their data as complete as possible, respectfully invite your attention to the 
 following questions, and ask that if you have made observations on any of the several points to 
 which attention is directed, you will have the kindness to put the committee in possession of the 
 facts observed, by answering, at your earliest convenience, such of the following questions as you 
 may be able to answer. Facts, and so far as possible personal observations, constitute the kind of 
 information which is considered the most desirable and useful. Those who have made observa- 
 tions which are not covered by the questions asked below, are also invited to communicate the 
 same to the committee. Please address replies to this circular to John H. Kellogg, M.D., Battle 
 Creek, Michigan; or to Conductor, 'Scientific Roll' Office, 7, Red Lion Court, Fleet Street, 
 London, E.C. 
 
 174. (1.) Please state facts concerning instances of marked communication of Diphtheria by 
 contagion. (H. 1) 
 
 175. (2.) Have you observed sporadic cases of Diphtheria which could not fairly be traced to 
 any source of contagion ? If so, please give full details concerning such case, stating also what 
 efforts were made to discover a possible origin by contagion ; what about visitors from or to 
 other places ; trunks, clothing, or other packages or articles received, &c. ? (H. 2) 
 
 176. (3.) Please state in full the sanitary condition of the premises where each such sporadic 
 case occurred. (H. 3) 
 
 338 
 
THE SCIENTIFIC ENQUIEEE. 
 
 177. (4.) At or shortly before the time you observed the sporadic cases, if you have observed 
 any such, was Diphtheria present in the vicinity or in neighbouring districts ? (H. 4) 
 
 178. (5.) If so, how were the "sporadic cases " situated with reference to the other cases, as 
 regards direction of prevailing winds, lines of travel, &c. ? (H. 5) 
 
 179. (6.) Have you observed severe and unmistakable cases of Diphtheria which were 
 apparently contracted from cases so mild that they were not distinguished from ordinary sore 
 throat or acute follicular pharyngitis ? If so, please state in full the facts respecting each 
 case. (H. 6) 
 
 180. (7.) Have you observed mild cases of Diphtheria to give rise to the disease in a severe 
 or malignant form ? (H. 7) 
 
 181. (8.) What were the sanitary conditions (such as water-supply, milk-supply, exposure to 
 foul air, &c.) where, under your observation, mild cases of Diphtheria have given rise to severe 
 cases of the disease ? (H. 8) 
 
 182. (9.) Have you observed any cases of the disease in domestic or other animals ? (H. 9) 
 
 183. (10.) If you have observed the disease in animals, please state how it was communicated 
 to them, whether from human beings or from other animals. (H. 10) 
 
 184. (11.) Have you observed cases in which the disease was communicated to human beings 
 by domestic or other animals. (H. 11) 
 
 185. (12.) Please state results of any observations as to the communication of Diphtheria by 
 other discharges than the sputum, as the fecal or vesical discharges, or by the breath, or other 
 emanations from the body. (H. 12) 
 
 186. (13.) Please state all facts within your observation which point to the contamination of 
 the water-supply as a probable means of communicating Diphtheria. (H. 13) 
 
 187. (14.) Please state facts within your observation which point to contaminated water- 
 supply as a probable origin of Diphtheria. (H. 14) 
 
 188. (15.) If you have observed any such facts, please state what was the probable source of 
 contamination of the water. (H. 1 5) 
 
 189. (16.) Please state the facts concerning each case observed by you in which Diphtheria 
 was communicated by means of milk. (H. 16) 
 
 190. (17.) What other sources of contagion have you observed, if any ? Please state facts 
 concerning each case. (H. 17) 
 
 191. (18.) How long have you known the contagium of Diphtheria to retain its power of 
 infection when confined, as in clothing or bedding, &c., hung in a closet or packed away in a 
 trunk ? (H. 18) 
 
 192. (19.) How long have you known the contagium of Diphtheria to retain its power of 
 infection when exposed freely to the action of the air, as in the walls of a house? (H. 19) 
 
 193. (20.) Have you known Diphtheria to reappear, without anew importation of contagious 
 matter, in a house which was suppossd to be thoroughly disinfected? If so, state what disin- 
 fectants were used aud describe carefully the mode of application. (H. 20) 
 
 194. (21.) Please describe methods of disinfection employed in undoubted cases where the 
 disease did not reappear. (H. 21) 
 
 195. (22.) Have you observed cases in which the local symptoms of Diphtheria were so slight 
 that it could scarcely be distinguished from a common sore throat ? (H. 22) 
 
 196. (23.) What symptoms or physical signs do you regard as characteristic of Diphtheria ? 
 (H. 23) 
 
 197. (24.) Have you observed cases in which there was no local expression of the disease in 
 the throat ? (H. 24) 
 
 198. (25.) Have you observed cases in which the nervous symptoms alone were present ? 
 (H. 25) 
 
 199. (26.) What course do you advise in the interests of public safety respecting the manage- 
 ment of a case of suspected Diphtheria, when you are in doubt whether it be a genuine case of 
 Diphtheria ? (H. 26) 
 
 200. (27.) Please give facts as to relapses, particularly relating to cases in which the relapse 
 was a considerable time after apparent convalescence or recovery. (H. 27) 
 
 201. (28.) Have you ever observed the occurrence of undoubted Diphtheria a second time in 
 the same person ? (H. 28) 
 
 202. (29.) If so, please state the length of time which elapsed between the attacks. (H. 29) 
 
 203. (30.) Please state all facts under your observation relative to the occurrence of Diphtheria 
 a second time in the same person. (H. 30.) 
 
 204. (31.) Under your observation, what proportion of persons who escape on full exposure 
 to Diphtheria have previously had the disease ? (H. 31) 
 
 205. (32.) Please state all the facts (relative to age, intervals between attacks, severity of 
 previous attack, other exposures, &c.) as to previous attacks of Diphtheria, concerning persons 
 whom you have observed to escape the disease when fully exposed. (H. 32) 
 
 206. (33.) Please state all other facts, under your observation, relative to immunity from 
 Diphtheria among persons apparently exposed to the disease. (H. 33) 
 
 207. (34.) What proportion of the mild cases o Diphtheria observed by you have been of 
 persons under ten years of age ? (H. 34) 
 
 339 
 
ANNOUNCEMENTS. 
 
 208. (35.) What proportion of the severe cases of Diphtheria observed by you have been of 
 persons under ten years of age ? (H. 35) 
 
 209. (36.) What proportion of the cases of Diphtheria observed by you in persons aged unler 
 ten years have proved fatal ? (H. 36) 
 
 210. (37.) What proportion of the cases of Diphtheria observed by you in persons aged over 
 ten years have proved fatal ? (H. 37) 
 
 : JOHN H. KELLOGG, M.D. \ 
 
 JOHN AVERY, M.D. $ 
 
 ANNOUNCEMENTS. 
 
 Part III. of the ' Scientific Eoll ' will be commenced, if life and health be granted to- 
 the Conductor, as soon as a sufficient number of subscribers' names have been received. It 
 will comprise the whole of Vol. II. of the * Scientific Boll,' and will be issued to subscribers 
 at home for Is. 6d., and to those abroad for 10s. In order that the Bibliography may be as 
 full as possible, authors and publishers are respectfully solicited to send copies of, or re- 
 ferences to, all their publications dealing with the barometrical condition of the air. 
 
 As soon as 200 persons have expressed a wish to subscribe for any one of the subjects 
 mentioned below, the publication of that section of the ' Scientific Eoll ' will be forthwith 
 commenced. The subscription price will be la. 6d. and 10s. for each volume, according as- 
 the residence of the subscriber is at home or abroad. Each volume will contain about 
 400 pages ; and each volume will, in most cases, contain two or more parts, each of whicb, 
 may be subscribed for separately. The extent of these parts will depend upon the- 
 amount of matter in hand, so that the subscription price cannot be fixed at present, but will 
 be decided upon when the publication of each part is commenced. The following is a list 
 of the principal subjects : 
 
 Atmosphere, Water, Ocean (5), Rivers, Lakes, Springs, Floods, Glaciers, Land, Elevation 
 and Subsidence of Land and Sea-Bottom, Denudation, Orography, Earthquakes, Volcanoes,. 
 Earth Magnetism, Terrestrial Heat, Marshes, Minerals, Stratigraphy, Eocks, Plants gene- 
 rally and in classified groups ; Animals generally ; Protozoa, Actiuozoa, Hydrozoa, Echino- 
 dermata, Crustacea, Seoleeida, Annelida, Mollusca, Myriapoda, Arachnida, Ehynchota, 
 Orthoptera, Diptera, Coleoptera, Lepidoptera, Neuroptera, Hymenoptera, Pisces, Amphibia, 
 Eeptilia, Aves, Mammalia, and Man. 
 
 Subscribers' names only are asked for now. The sending of these will not involve any 
 pecuniary liability, but will simply be taken as implying that the senders take an interest 
 in the work, and will probably undertake to subscribe when asked to do so. At the moment 
 of going to press the subject for which the largest number of names has been received is 
 Ocean. 
 
 The Conductor is very desirous of continuing the publication of his work, but he is both 
 unwilling and unable to do so if such continuance involves a pecuniary loss. He has no- 
 desire to claim any merit for what he has done beyond what he may deserve, and as some 
 guarantee that he is able to perform what he undertakes to do, he would refer to the eleven 
 numbers of the ' Scientific Eoll' now published. If it is considered that such a work will 
 be of any advantage to scientific research, it is to be hoped the requisite support will not be 
 withheld until it is too late; if the work is useless or radically defective, then the sooner 
 it is terminated the better. It seems certain, however, that if not called for now, a work 
 conducted upon a similar plan will be called for before many years have passed. In all 
 probability the prosecution of the task will then be more difficult and more expensive. 
 In the present state of the case a few hundred subscribers only will suffice to establish the 
 work on a safe basis, and allow of a quicker publication. 
 
 340 
 
AQUEOUS VAPOUR 1863. Lament. NOTES. 
 
 Lament, Prof. Proc. Brit. Meteor. Soc., vol. i. (No. 6, published Jan. 21, 1863.) 
 Translated by W. T. Lynn. From Phil. Mag., Nov. 1862 (rv). 
 
 (Page 311.) We are now arrived at a point in meteorology where it is absolutely 
 necessary to come to a definite decision as to what is the relation in which the 
 aqueous vapour existing in the atmosphere stands to the atmosphere itself. Does 
 the aqueous vapour form an atmosphere itself, independent of the air ; or is it 
 merely mechanically mixed with the air,, so as only, as a gas standing in mechanical 
 relation to the air, to increase the volume and the weight of the atmosphere 1 I 
 think I have arrived at a decisive result one which is opposed to the generally 
 prevailing views of physical geographers and meteorologists. Nothing of import- 
 ance has been added to Dalton's theory of the action of aqueous vapour by later 
 investigators. Dalton's experiments tend to the following results : 1. In space 
 destitute of air the evaporation of water goes on only until the vapour has attained 
 a determinate expansive force, dependent on the temperature ; so that in every 
 space void of air which is saturated with vapour a determinate vapour pressure 
 corresponds to a determinate temperature. 2. In space filled with air the same 
 (Page 312) amount of water evaporates as in space destitute of air ; and precisely 
 the same relation subsists between the temperature and the expansive force, 
 whether the space contains air or not. 3. The evaporation of water goes on rapidly 
 in space devoid of air, but very slowly in space filled with air in a state of quies- 
 cence ; and even when it is assisted by a tolerably brisk motion of the air a con- 
 siderable time is notwithstanding always required. In this way are the development 
 and extent of aqueous vapour, in space void of air and space filled with air, deter- 
 mined by means of Dalton's experiments ; as to the mutual relations subsisting 
 between vapour and air, when they are simultaneously present in the same space f 
 the experiments afford no information ; and this deficiency Dalton supplied by 
 giving to the second of the above-quoted propositions such an interpretation as if 
 no mutual relations existed between vapour and air, and as if they remained near 
 each other without producing the slightest mechanical effect upon one another. 
 It is strange that philosophers have accepted this theory without remarking that it 
 constitutes only a possible result of the experiments ; and that meteorologists have 
 treated it as available for application to the aqueous vapour of the atmosphere, and 
 have supposed an atmosphere of vapour to exist independent of the air, notwith- 
 standing that the third of the above propositions properly declares that there is 
 indeed always a tendency to a normal relation, which is conceived to be in a state 
 of restoration, but which is never reached, because, in consequence of the changes 
 constantly taking place, the requisite time to produce an equalisation is never 
 afforded. Objections have from time to time been brought forward to the existence 
 of an atmosphere of vapour independently subsisting. Bessel has (' Astr. Nachr.,' 
 No. 236) adduced the consideration that in such a vapour atmosphere the expansive 
 force of the strata incumbent upon one another must diminish according to a certain 
 proportion, but that from different observations it may be concluded that this pro- 
 portion does not really exist. The experiments of Broun in Makerstoun (Report 
 to Sir T. Brisbane) and Jelinek in Prague (' Denk. Wien. Akad.,' vol. ii.) proved 
 that in different localities situated very near together, where the same reading of 
 the barometer is observed, a very different vapour-pressure may be indicated. Espy 
 opposed the theory, and exposed its defects, without furnishing a precise refutation. 
 I believe I first brought forward a proof of its incorrectness in 1857, when I showed 
 (Page 313) by means of observations extending through many years, that in a small 
 vapour-pressure the mean reading of the barometer stands quite as high as in a 
 great vapour-pressure ; at the same time I contrived an easily-performed experiment 
 in which, contrary to Dalton's theory, a mass of vapour and a mass of air placed in 
 communication with each other mutually preserve a state of equilibrium without 
 
 A A 341 
 
AQUEOUS VAPOUR 1863. Lament. NOTES. 
 
 the vapour penetrating into the air or the air into the vapour. As the result of this 
 I laid down the proposition that the vapour exerts a pressure upon the air and the air 
 upon the vapour ; and that the atmosphere is to be regarded as a mixture of masses 
 of air, some more and some less humid. Strachey furnished a second very strong 
 proof of the inadmissibility of Dalton's theory in a paper read to the Royal Society 
 in 1861. Proceeding upon considerations which are fundamentally identical with 
 those developed by Bessel, he gave a collection of the results of observations which 
 had been obtained upon high mountains and in air balloon expeditions, and showed 
 that they were incompatible with the supposition of an independently subsisting 
 atmosphere of vapour. To instance one point only, it may be here mentioned that 
 the observations of Walsh, who ascended in a balloon to the height of 23,000 feet, 
 place us in a position to calculate the pressure which the vapour contained in the 
 atmosphere would exert upon the earth's surface ; but the value determined in this 
 manner amounts only to the fourth part of the pressure actually assigned by the 
 psychrometer. Nevertheless we find in the most recent times that the pressure of 
 the dry air and the pressure of the vapour atmosphere are kept distinct. The only 
 way of removing the rooted ideas based on Dalton's laws is to prove that these laws 
 themselves contain an essential error. Air and vapour spread into each other with 
 extreme slowness ; it is mainly the circulation of air that carries off the vapour 
 from the evaporating surface ; one would almost believe that the individual mole- 
 cule of air must come to the surface of the water to take thence the moisture, and 
 to the chloride of calcium to give up to it the moisture ; the expansive force of the 
 vapour itself is in every case a matter of small influence on its diffusion in the air. 
 Now, if we take a closed tube ABCD, fig. 1, filled with air, and introduce a small 
 C| _ |D quantity of water through an aperture near A, which is immediately 
 afterwards closed, into the bottom AB of the tube, the water begins 
 gradually to evaporate, and the vapour ascends after the expiration of a 
 certain time up to ab. How then will the pressure be distributed upon 
 the interior sides of the tubes ? If the vapour and air exert a mutual 
 pressure upon one another, the expansive -forces of the air and of the 
 vapour will act together in such a manner that an amount equal to their 
 Fig. 1. sum w ^* P res s upon all points of the interior wall ; and if we take sepa- 
 rately the pressure peculiar to the vapour alone, it is precisely as great as 
 if the mass of vapour was uniformly distributed in the whole space ABCD. A totally 
 different state of things will result if the view set up by Dalton is well founded ; for 
 as, according to this view, the vapour diffuses itself in the interstices of the molecules 
 of air without producing any mechanical effect upon the molecules themselves, no 
 pressure at all can be produced upon the interior side of the tube by the expan- 
 sive force of the vapour under the circumstances indicated above, and no pressure 
 takes place until the vapour reaches the upper surface CD. The state of things 
 here indicated is only a transitory one ; a similar state may, however, be made 
 permanent by maintaining in the lower space ABa6 a higher and in the upper space 
 a&CD a lower temperature. If we denote the lower space by V, the upper by V, 
 the lower temperature by t, the higher by t' t and the corresponding expansive forces 
 of the vapour by/ (t) and / (tf) ; also the expansive forces of the enclosed masses 
 of airbyfc (1 + at) and fc (1+af), we have, according to the hypothesis advocated 
 by me, the expansive force of the mixture 
 
 = * + 
 
 whereas, according to Dalton's theory the expansive force will only amount to 
 
 342 
 
AQUEOUS VAPOUR 1863. Lament. 
 
 NOTES. 
 
 while the vapour passing into the space a&CD with the force (t) + / (0 must be 
 immediately condensed. Thence it immediately follows that if the temperature 
 t' of the upper space remains constant, while the temperature of the lower space 
 gradually increases, the pressure upon the upper surface CD is increased, according 
 to Dalton's theory, only by the expansion of the air, but not by the newly 
 forming vapour itself ; whereas, according to my hypothesis, besides the effect 
 which is produced by the expansion of the air, a very considerable augmen- 
 (Page 315) tation of the pressure arises from the newly-formed vapour. As we 
 can imitate these conditions, we have a simple means of deciding as to the 
 correctness of Dalton's theory. I selected the following experiment : A glass 
 tube, bent in the form represented in Fig. 2, was provided at one end with 
 a globe K, whilst the other end e was left open ; in the straight part de it 
 was made to contain a drop of quicksilver q. The curved part ckd of the tube 
 was plunged into a vessel BB filled with clear water ; into the vessel AA, where 
 the globe K was placed, cold and warm water could be poured. The globe K was 
 first filled with dry air, and the experiment showed that if the temperature was 
 increased from 67'3 to 126 the drop of quicksilver moved forwards by 12 - 224 in. 
 During this experiment a thermometer placed in the vessel BB stood at 59. 
 Afterwards the globe was opened by breaking off the fine point a, some water 
 introduced, and the point again joined on by melting. Again cold and warm water 
 
 
 
 
 c- 
 
 & f i & 
 
 
 r 
 
 
 tl 
 
 
 ,*" 
 
 ^ 
 
 ,- 
 
 
 n 
 
 ^ 
 
 *"' : 1 ... 
 
 
 
 "* __ 
 
 
 A (^ 
 
 1 A 
 
 
 
 
 B 
 
 s 
 
 f K 
 
 
 v. 
 J 
 
 J J 
 
 t 
 
 1 
 
 [ 
 
 
 
 \ 
 
 - 
 
 
 
 _ . 
 
 
 (* 
 
 " v 
 
 
 Y" 
 
 *N 
 
 Fig. 2. 
 
 were poured into the vessel AA, while the temperature of' the tube remained 
 unaltered, by which means, according to the theory of Dalton, a rise of temperature 
 from 67 "3 to 126 would, if the vapour had not penetrated in the tube up to the 
 drop of quicksilver, move the latter, as before, 12 '224 in., and if the vapour had 
 so penetrated, at the most T \th further ; instead of which the motion actually 
 produced amounted to nearly the double of this. It resulted from accurate 
 measurement that the 12*224 in. were passed over as soon as the temperature had 
 been raised from 67'3 to 101 0> 5. A second glass tube was employed of a similar 
 form, but with a smaller globe, and with this, as long as there was only dry 
 air in the globe, an increase of temperature from 64 '4 to 131 '5 occasioned 
 in the drop of quicksilver a motion of 13 '706 in. ; but after a small quantity 
 of water had been introduced into the globe, the quicksilver moved the same 
 distance when the temperature was raised only from 64 '4 to 102. As it 
 might be imagined that it was possible that after a longer interval of time 
 the vapour would extend up to the drop of quicksilver and then produce 
 (Page 316) a different result, the globe was left for a whole hour in warm water, 
 but the position of the water remained unchanged. Also, after the termination of 
 the experiment, neither in the first nor in the second tube could a trace be per- 
 ceived of the vapour having passed down into the bent part between c and d y so 
 that it probably penetrated into the tubes not at all, or only to a small extent. 
 
 343 
 
AQUEOUS VAPOUR 1864. Buchan. NOTES. 
 
 On this supposition the observed effect would require the conclusion that the 
 increase in the expansive force of the dry air in a change of temperature from 67 '3 
 to 126 is precisely as great as the increase in the expansive force of the air and 
 the aqueous vapour in a change of temperature from 67 '3 to 101 '5 ; and this 
 also agrees exactly, for the former increase is calculated to be '119, and the latter 
 amounts to 
 
 For the air O'OTO 
 
 For the vapour 0'048 
 
 Therefore, together O'llS 
 
 In the second experiment we have the increase of the expansive force 
 For dry air from 64-4 to 131 "5 O076 
 For vapour 0'052 
 
 Therefore, together 0-128 
 
 little differing from the preceding number. I repeated the experiment in a modified 
 (Page 317) form, calculated to give more accuracy. The result was substantially 
 the same. The conclusion is, that the air exerts a pressure upon the vapour, and 
 the vapour upon the air. I hope at a future opportunity to show that the humidity 
 must be regarded as adhering to the molecules of air, and that the phenomena 
 admit of a simple explanation by means of a natural hypothesis concerning the 
 expansion of dry and wet molecules of air. If it be desired to apply the above to 
 the circumstances of the aqueous vapour in the atmosphere, it is in the first place 
 to be inferred from that (since the diffusion of the vapour in the air takes place 
 (Page 318) but very slowly, and since in different places, according to the tem- 
 perature and the magnitude of the surface of water exposed to the air, very 
 different quantities of vapour pass into it), in regard to the humidity of the air, 
 strictly speaking, no relations subsist conformable to any law. Of course the 
 continually listing currents of air occasion a complete mingling of the more or 
 less dry masses of air ; but this takes place in no uniform manner, and therefore 
 no exact relation of dependence exists between the degrees of humidity in different 
 points of any space. But particularly the idea of an atmosphere of vapour sub- 
 sisting independently by itself appears to be inadmissible, and the data furnished 
 by the psychrometer can no longer be regarded in any other light than as the 
 expression of local humidity. 
 
 Speke, J. H. Journ. Roy. Geog. Soc., vol. xxxiii. (1863) (rs). 
 
 (Page 333.) In Africa, beyond 3 lat. both north and south, the land is subject to 
 continual droughts for five, six, or more months in the year, which last systemati- 
 cally longer as the distance increases from the equatorial zone. The rain follows the 
 sun, and the opposite region is dry. 
 
 1864. 
 Buchan, A. (B. 1864, 1.) 
 
 Monthly means will not serve for ascertaining when are the periods^the clouds 
 begin to disperse and when brighter skies take their place. In Scotland [and no 
 (Page 9) doubt in other places under like conditions] the highest temperature occurs 
 in the broad plains, particularly those which are bounded on the south-west by high 
 and extensive ranges of hills, which by more effectually^draining the south-west 
 winds of their moisture, clear the skies of clouds, and thus allow freer passage to 
 (Page 137) the sun's rays. When the air is clear and transparent, but loaded with 
 muck moisture in an invisible state in other words, when the dew-point is high 
 the invisible particles of water offer a powerful obstruction to the free passage of the 
 caloric of radiation, in much the same way as stones in the channel of a river oppose 
 
 34* 
 
AQUEOUS VAPOUR 1865. Buchan. NOTES. 
 
 its course ; so that in a moist though perfectly clear atmosphere the process of 
 radiation proceeds at a very slow rate. Let, on the contrary, all or nearly all the 
 vapour be drained out of the air, the escape of heat from the earth's surface by 
 radiation would then be so swift and great that the temperature would fall low 
 (Page 149) enough to destroy life. For turnips the weather should be mild and 
 dry, during the middle of May [Scotland being the country specially alluded to] to 
 the middle of June, when they are sown ; moisture and warmth are required in 
 their brairding, and their growth towards the time for singling. At singling and 
 after-growth the weather should be dry and warm. These include the second half 
 of June and most of July. From July to October the weather should be showery 
 at intervals. For cereals, the sowing month of March for oats, and April and half 
 of May for barley, should be cool and dry. In the after-growth of wheat, barley, 
 and oats, till the blooming season in July, the weather should be dropping and 
 warm. The blooming season in July should be dry, warm, and calm. After that, 
 till within a month of harvest, at the end of August or beginning of September, there 
 should be showers and warmth. During the period from that to and after harvest 
 it should be dry and hot. 
 
 1865. 
 Becquerel, A. C. (B. 1865, 1.) 
 
 [The name is misprinted Becqueral in the place cited. The paper is translated 
 from ' Comptes Rendus,' Ix. p. 136.] The influence of forests on climate depends 
 (Page 235) in part on the process of evaporation possessed by the leaves. Evapora- 
 tion from the leaves is a constant and active cause of humidity, which a little 
 lowering of the temperature condenses into vapour [as the translation has it] ; and 
 the water which is thus produced tends to keep the soil moist. The effect which the 
 (Page 236) cutting down of forests has on the sources and volumes of the rivers 
 which water a country is too important an element to be lost sight of. The difficulty 
 of discovering the causes of these effects is sometimes so great that we could not 
 predict whether a particular spring or river would be increased by cutting down a 
 forest and bringing the soil under cultivation. Forests contribute to the sources, 
 not only by the humidity they cause and the condensation of vapour which accom- 
 panies it, but also by the obstruction they offer to evaporation from the soil ; and it 
 may be remarked that the roots of the trees, by breaking up the soil, render it more 
 (Page 237) porous, and thus facilitate the process of infiltration. In considering the 
 important question of the influence which the cutting down of woods has on springs 
 and rivers we arrive at the following conclusions : 1. Extensive clearings of wood 
 lessen the volume of the rivers which water a country. We are not yet able to 
 decide if this diminution is to be attributed to a less quantity of rain falling annually 
 or to a more active evaporation, to both causes combined, or to a different distribu- 
 tion of the rainfall. 2. Cultivation carried on in a dry and rainless region lessens 
 the amount of spring- water. 3. In countries which have not undergone any change 
 in the amount of land under cultivation the quantity of spring- water appears to be 
 always the same. 4. Forests, in the better protection they afford to springs, 
 husband the water and regulate its flow. 5. The humidity is increased by forests, 
 and the roots of trees render the soil more pervious to the rain-water. 6. Clearings 
 in mountainous countries exercise an influence on the sources of the water supply 
 and on the rivers. 
 
 Buchan, A. (B. 1865, 4.) 
 
 (Page 200. ) From the observations collected [on the storms of Europe towards 
 the end of 1863] we learn that as long as the barometer did not fall below the 
 mean there was no continuous rain anywhere ; but blue sky, varied with sky 
 partially clouded or with fog, prevailed. When, however, the barometer fell in the 
 
 345 
 
AQUEOUS VAPOUR 1866. Mitchell. NOTES. 
 
 west, the sky began to be obscured and showers to fall at intervals. When the 
 centre of the storm had passed, or the barometer had begun to rise, the rain 
 became less heavy, the clouds began to break up, and fine weather, ushered in with 
 (Page 228) cold breezes, ultimately prevailed. Oats require a lower temperature 
 (Page 229) and more moisture to bring them to perfection than wheat or barley. 
 (Page 230) The greatest number of victims to consumption [in Scotland in 1864], 
 and perhaps also brain diseases, occur in spring, when the air is driest ; and the 
 least number in October and November, when the humidity of the air is greatest. 
 
 Forbes, C. Journ. Roy. Geog. Soc., vol. xxxiv. (1865) (rsp). 
 
 (Page 157.) In Vancouver Island the ordinary course of the seasons is as 
 follows. After the gales with rain, which generally mark the period of the equinox, 
 fine clear weather sets in, and continues till about the middle of November. Then 
 the rains set in. 
 
 Palgrave, W. G. Journ. Roy. Geog. Soc., vol. xxxiv. (1865) (rsj}). 
 
 (Page 136.) In the Nejed between March and November the fine weather is 
 uniformly clear and dry. 
 
 Watts, H. (B. 1865, 14.) 
 
 (Page 100.) The action of the sun upon the water at the surface of the earth 
 causes a natural process of distillation upon an enormous scale to be always going 
 on. The water evaporated from the earth's surface rises in the air as vapour, and 
 being afterwards deprived of its heat of vaporization, partly by radiation into space, 
 and partly by contact with mountain-summits or with the cold air existing at high 
 elevations, returns to the earth in the various forms of dew, mist, rain, snow, hail, etc. 
 In this way an immense quantity of water is being continually lifted from the sea- 
 level, a large portion of which does not fall again directly into the sea, but being 
 deposited on elevated portions of the land, becomes the mechanical source whence 
 rivers and streams are supplied. The watery vapour which reaches the higher and 
 colder regions of the atmosphere is there condensed into snow. This, as it falls again 
 towards the earth, returns to the condition of water, if the air is sufficiently warm 
 to liquefy it ; but part of it reaches the earth unmelted, and that which falls upon 
 regions whose temperature is below C. accumulates to form the masses of ice 
 known as glaciers. 
 
 1866. 
 
 Buchan, A. (B. 1866, 2.) 
 
 (Page 352.) [Since the bibliography was published the facts have been entered 
 from an earlier source, so that this bibliographical reference should be cancelled.] 
 
 Home, D. Milne. (B. 1866, 5.) 
 
 (Page 330.) Evaporation will take place much more rapidly from a soil that is 
 bare, or partially so, than from a soil that is well clothed with grass. I filled two 
 zinc boxes with sandy loam and with strong clay, and adjusted them on a balance. 
 Into each the same quantity of water was put. The thermometer in the sandy 
 loam was lowest, and in less than a week this box rose above the other with clay, 
 in consequence, I suppose, of more water having been evaporated from it. 
 
 Mitchell, A. (B. 1866, 10.) 
 
 (P^e303.) Little ragged clouds, something resembling uncut horsetails, are 
 filhe-tails, 5 and forebode windy weather when they seem to come from the 
 south- 
 When frae the south whusk fillie-tails, ^ 
 Then high ships wear low sails. 
 
 (Galloway.) 
 
AQUEOUS VAPOUR 1867. Brumham. NOTES. 
 
 Noah's Ark. In the winter season for the ark is not common in any other 
 when the sky is clear and the weather frosty, curious light grey clouds, in the shape 
 of ribs, will oft arise from a point in the horizon, and stretch over the sky to its 
 opposite point on the other side. These cloudy ribs narrow in bulk towards the 
 horizon, and are at the widest right over our heads, or in the zenith. In this form 
 (Page 304) it will appear for a day together or even longer. What is singular, too, 
 is we have no half-arks ; the one half never sinks below the horizon, and leaves the 
 other half alone. We have it as if it were calculated to appear in our latitude and 
 longitude ; for it begins to form, comes to perfection, and vanishes away all in our 
 canopy. When seen in frosty weather and it generally is weather-wise folk 
 prognosticate a thaw, instantly attended ' wi' an awful spate.' The ark is a great 
 thaw sign. The ark is not always regarded as a forerunner of bad weather. When 
 it runs north and south, the aftercome is not so much dreaded as when it is stretched 
 between any of the other points. (Galloway.) 
 
 (Page 305.) Clear to the south will drown a ploughman. (Berwickshire.) 
 
 G-rumphie smells the weather, 
 And grumphie sees the wun', 
 He kens when cluds will gather 
 And smoors the blinking sun. 
 
 (Galloway.) 
 [? Should it not be smoor,] 
 
 Semenof. Journ. Roy. Geog. Soc., vol. xxxv. (1866) (rsp). 
 
 (Page 226.) Dry atmosphere has the effect of raising the snow-line. Hence the 
 elevation of this line above the normal altitude for the latitude indicates a dry air. 
 (Page 227) Rhododendrons mark a moist atmosphere. 
 
 Temple, R. Journ. Roy. Geog. Soc., vol. xxxv. (1866) (rsp). 
 
 (Page 71.) On the plateau of Chutteesgurh the soil is so moist that the sugar 
 cane can be grown without irrigation. It is itself destitute of wood, but is 
 surrounded by forests. 
 
 "Wilson, J. Fox. Journ. Roy. Geog. Soc., vol. xxxv. (1866) (rsp). 
 
 (Page 113.) During the year 1862 a severe drought prevailed throughout Cape 
 (Page 114) Colony and South Africa. Livingstone refers to the dry season in the 
 Bakwain country, and mentions, as indicative of the dryness of the air, that needles 
 lying out of doors for months did not rust ; that a mixture of sulphuric acid 
 and water parted with its water to the air ; that the leaves of indigenous plants 
 were drooping, soft and shrivelled ; and that the leaves of mimosse were closed by 
 day as well as by night. 
 
 1867. 
 Blackmore, R. D. Symons's Meteorol. Mag., vol. ii. (1867) (rsp). 
 
 (Page 81.) Teddington. On the evening of July 24th there was noticed a very 
 peculiar appearance in the south-east after sunset. The sky was chiefly overcast with 
 a free display of red streamers all over the east and south ; but in the south-east 
 was a beautiful fan of blue divergent radii, rising 30 above the horizon, and 
 breaking across the redness like a windmill with blue sails. On the night of the 
 25th there was a tremendous downpour of rain. 
 
 Brumham, G-. D. Symons's Meteorol. Mag., vol. ii. (1867) (rsp). 
 
 (Page 40.) [He conjectures that there may be a 29-year period in meteorology, 
 
 347 
 
AQUEOUS VAPOUR 1867. Buchan. 
 
 NOTES. 
 
 and he extracts from Whistlecraft's works all the cases that appear to indicate this. 
 Those only are given here which refer to dry weather.] 
 
 1746 An exceedingly hot and dry summer. 1775. Summer dry and hot. 
 
 1747* Dry season 1776. Chiefly dry and fine from June. 
 
 1759* A hot summer and dry. 1788. A hot summer and dry year. 
 
 1760 Very hot and dry summer. 1789. Bather wet summer. 
 
 17C2] A very hot and dry summer, and a 1791. A very hot and dry summer, and a 
 
 very dry year. very dry year. 
 
 17<r> A verv drv summer, and often very 1794. Bather a dry summer and very hot 
 
 hot. from June 12th to July 18th. 
 
 1771 'A very dry summer and year. 1800. Excessive drought from June 22nd to 
 
 August 19th. 
 
 1775. A hot and dry summer. 1804. Extremely hot and dry in September. 
 
 1776. Chiefly dry and fine from May. 1805. Very hot. 
 . (Page 41.) 
 
 1781. A hot, dry summer. 1810. A dry year to October. 
 
 1793. Intensely hot and dry part of sum- 1822. Great heat and drought part of sum- 
 mer. mer - 
 
 1802. Hot and dry two months of the 1831. Hot and dry two months of the sum- 
 summer (August and September). mer (July and August). 
 
 1818. A remarkably dry and hot summer. 1847. A remarkably dry and hot summer. 
 
 1819. A hot and dry summer. 1848. A wet summer. 
 
 1822. Great heat and drought part of sum- 1851. Great heat and drought part of sum- 
 mer. Very fine till October. mer. Very fine till end of October. 
 
 1834. Sharp drought in spring and greater 1863. Sharp drought in spring and summer, 
 part of summer, and generally very hot. and generally very hot. 
 
 1835. A very hot and dry summer, and very 1864. A very hot and dry summer, and 
 great drought in July and August. very great in July and August. 
 
 1867. 
 Buchan, A. (B. 1867, 3.) 
 
 (Page 3.) The hygrometer is an instrument of great value in meteorology, 
 (Page 4) as indicating the quantity of vapour in the air, and inferentially the 
 changes of weather depending thereon. De Saussure may be considered the founder 
 of this department of meteorology by his researches. Pictet made valuable obser- 
 vations on dew. Patrick Wilson missed the point of the argument in continuing 
 (Page 5) to entertain the notion that the cold accompanying dew was after, instead 
 of before, its deposition. Dr. Wells collected the observations into a coherent 
 whole, and accounted for them by his theory of dew, which all succeeding inquiry 
 has confirmed. His ' Theory of Dew,' published in 1814, must always be regarded 
 as one of the greatest contributions made to meteorology. Dr. Wells made the 
 discovery that during those nights when dew is deposited, the temperature of bodies 
 on the earth's surface is colder than that of the surrounding air. In 1823, Daniell 
 discussed in his ' Meteorological Essays ' the hygrometry of the atmosphere and 
 evaporation. Hygrometry is indebted to him more than to any other philosopher. 
 The law of the diffusion of vapour through the air, its influence on the barometric 
 pressure, and its relation to the other constituents of the atmosphere, are among the 
 least satisfactorily determined questions in meteorology. Since this element is so 
 important as an indicator of storm and other changes of the weather, it is to be 
 hoped it will soon be more thoroughly investigated. A most important addition 
 to our knowledge of the atmosphere was made in 1862 by Prof. Tyndall, in his 
 (Page 6) experiments on radiant heat, especially as regards the gases, by which it 
 is shown that the vapour of water exerts extraordinary energy as a radiant and 
 absorbent of heat. It is to be expected that the relations of atmospheric vapour 
 will soon be turned to account in explaining many questions of meteorological 
 (Page 24) inquiry. The barometer is influenced to a large extent by the elastic 
 force of the vapour of water, invisibly suspended in the atmosphere, in the same 
 way as it is influenced by the dry air. But the vapour of water also exerts a 
 
 348 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 pressure on the barometer in another way. Vapour tends to diffuse itself equally 
 through the air ; but as the particles of air offer an obstruction to the watery 
 particles, about 9 or 10 a.m., when evaporation is most rapid, the vapour is 
 accumulated or pent up in the lowest stratum of the atmosphere, and being 
 impeded in its ascent, its elastic force is increased by the reaction, and the baro- 
 meter consequently rises. When the air falls below the temperature of the dew 
 point, part of the vapour is deposited in dew, and since some time must elapse 
 before the vapour of the upper strata can diffuse itself downwards to supply the 
 deficiency, the barometer falls most rapidly at 10 p.m., when the deposition of dew 
 is greatest. As regards vapour in the atmosphere, the barometer is subject to two 
 maxima and minima of pressure the maxima occurring at 10 a.m., when, owing 
 to rapid evaporation, the accumulation of vapour near the surface is greatest, and 
 about sunset, or just before dew begins to be deposited, when the relative amount 
 of vapour is greatest ; and the minima in the evening, when the deposition of dew 
 is greatest, and before sunrise, when evaporation and the. quantity of vapour in 
 the air is least. Thus the maximum in the forenoon is brought about by the rapid 
 evaporation arising from the dry ness of the air, and the increasing temperature. 
 But as the vapour becomes more equally diffused, and the air more saturated, 
 evaporation proceeds more languidly ; the air becomes more expanded by the heat, 
 and flows away to meet the diurnal wave of cold advancing from the eastward. 
 Thus the pressure falls to the afternoon minimum about 4 p.m. From this time 
 the temperature declines, the air approaches more nearly the point of saturation, 
 and the pressure being further increased by accession of air from the warm wave 
 now considerably to the westward, the evening maximum is attained. As the 
 deposition of dew proceeds, the air becomes drier, tjie elastic pressure of the 
 vapour is greatly diminished, and the pressure falls to a second minimum about 
 (Page 25) 4 a.m. The amount of these daily variations diminishes from the 
 equator towards either pole, for the obvious reason that they depend, directly or 
 indirectly, on the heating power of the sun's rays. Thus, while at the equator the 
 daily fluctuation is 0'125in., in Great Britain it is only a sixth part of that amount. 
 It is very small in the high latitudes of St. Petersburg and Bossekop ; and in still 
 higher latitudes at that period of the year when there is no alternation of day and 
 night, the diurnal variation probably does not occur. In the dry climate of 
 Barnaul, in Siberia, there is no evening maximum ; the lowest minimum occurs 
 as early as midnight, and the only maximum at 9 a.m. So far as the dry air of the 
 atmosphere is concerned, the atmospheric pressure will be least in the summer and 
 greatest in the winter of each hemisphere [warm and cold hemispheres north and 
 south]. But the production of aqueous vapour by evaporation being most active 
 in summer, the barometer will be much increased from this cause. As the aqueous 
 vapour is transferred to the colder hemisphere it will be there condensed into rain, 
 and being thereby withdrawn from the atmosphere, the barometer pressure will 
 be diminished, but the dry air which the vapour brought with it from the warm 
 (Page 26) hemisphere will remain, thus tending to increase the pressure. The 
 barometer is high at Calcutta in January, owing to the dry, cold, dense air of 
 Central Asia being conveyed southward over India. At places where the amount 
 of vapour in the air varies little from month to month, but the variations of 
 temperature are great, the differences between the summer and winter pressures are 
 very striking. Thus, at Barnaul and Irkutsk, both in Siberia, the pressures in 
 July are respectively 29 '243 and 28'267, and in January 29'897 and 28 '865, the 
 differences being upwards of six-tenths of an inch. The great heat of summer in 
 Siberia causes the air to expand and flow away in all directions, and the diminished 
 pressure is not compensated for by any material accession being made to the 
 aqueous vapour of the atmosphere ; and, on the other hand, the great cold and 
 
 349 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 little rain in that region during winter causes high pressures to prevail during that 
 season. The same peculiarity is seen, though in a modified degree, at St. Petersburg. 
 Moscow, and Vienna. At Reykjavik, in Iceland, the pressure in June is 29717. 
 and in December 29 '273 ; at Sandwich [ = Sand wick], Orkney, 29775 and 29'586 : 
 and at Sitcha [ = Sitka], in Russian America, 29 '975 and 29'664. In all these places 
 the distribution is just the reverse of what obtains in Siberia, being least in winter 
 and greatest in summer. The high summer pressures are due to the cool summer 
 temperature as compared with surrounding countries ; thus causing an inflow from 
 these regions ; and to the large amount of vapour in the atmosphere, thus still 
 further raising the barometric column. On the other hand, the low winter 
 pressures are due to the high winter temperatures, causing an outflow toward 
 adjoining countries, and the large winter rainfall, which sets free great quantities 
 of latent heat. The variations in mean pressure are very slight, and not marked 
 by any decided regularity in their march through the seasons, at Dublin, Glasgow, 
 London, Paris, and Rome. As compared with Barnaul and Reykjavik, their 
 temperature is at no season very different from that of surrounding countries, and 
 the rainfall and vapour are at no time much in excess or defect, but are more equally 
 {Page 48) distributed over the different months of the year. The temperature of 
 plants exposed to the sun's rays is not so high as that of the soil under the same circum- 
 stances, partly because a portion of the solar heat is lost in the process of evapora- 
 tion from the pores of the plants. Evaporation goes on slowly from damp ground 
 under the trees, being screened by them from the sun's heat. But since the air 
 among the trees is little agitated or put into circulation by the wind, the vapour 
 which arises from the soil is mostly left to accumulate above it. Hence, though 
 exact observations are wanting to settle the question, it is probable that forests 
 diminish the evaporation and increase the humidity. It is not deposited in cloudy 
 weather because the clouds obstruct the escape of heat by radiation into space ; nor 
 in windy weather, because wind constantly renews the air in contact with the ground, 
 and thus prevents the temperature from falling sufficiently low. No dew is de- 
 posited on the surface of deep water, because its temperature scarcely ever falls 
 below the dew point. When the temperature is below the freezing point the dew 
 (Page 68) freezes as it is deposited, and hoar frost is produced. The specific gravity 
 of the ocean is high where the evaporation is great, as in the region of the trade 
 (Page 74) winds. The equatorial current [wind] losing heat as it proceeds on its 
 (Page 75) course is thereby brought nearer the point of saturation, and consequently 
 becomes a moister wind ; while the polar current, gaming heat in its progress 
 towards the equator, becomes a drier wind. The chief effect mountain ranges have 
 on temperature is to drain the winds which cross them of their moisture, and thus 
 to cause colder winters and hotter summers in places to the leeward, as compared 
 with places to the windward, by more fully exposing them to both solar and terres- 
 trial radiations. The western parts of the continents in the north temperate zone 
 are protected from extreme cold by their moist atmosphere and clouded skies. But 
 in the interior of continents it is otherwise ; for the winds getting colder and drier 
 as they advance the soil is exposed to the full effects of radiation during the long 
 (Page 76) winter nights. Since the air over continents is drier than on sea shores, 
 (Page 80) the heating power of the sun's rays is very great during the long days of 
 summer. The quantity of aqueous vapour in the atmosphere is by the processes of 
 evaporation and condensation varying every instant. Vapour diffuses itself through 
 dry air, the presence of dry air having only the effect of retarding the rate of its 
 diffusion. If the vapour of water remained permanently in the atmosphere that 
 is, was not liable to be withdrawn from it by being condensed into rain the 
 mixture would be as complete and uniform as that of the oxygen with nitrogen. 
 But the equilibrium of the vapour atmosphere is being constantly disturbed by 
 350 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES- 
 
 every instance of condensation, by the ceaseless process of evaporation, and by 
 every change of temperature. From these condensations and from the circum- 
 stance that the dry air greatly obstructs the free diffusion of the vapour, it follows 
 that the law of the independent pressure of the vapour and of the dry air of the 
 atmosphere does not absolutely hold good, but that from the constant effort of the 
 vapour to attain to a state of equilibrium there is a continual tendency to approach 
 to it. And since the independent and equal diffusion of the dry air and the vapour 
 is owing to disturbing causes never reached, it follows that the observations of the 
 hygrometer only indicate local humidity, and should only be regarded as approxi- 
 mations to a correct indication of the quantity of vapour in the atmosphere over 
 the place of observation. It should, however, be added that, though in exceptional 
 cases the amount of vapour indicated may be wide from the mark, yet in long 
 averages a very close approximation will be obtained. When water evaporates into 
 air the maximum density of the vapour is not acquired till some time has elapsed. 
 (Page 83) And since every addition to the vapour increases the pressure, the rate of 
 evaporation is continually diminishing. The amount of evaporation is measured 
 by an evaporimeter, which is usually an evaporating dish about 5 in. in diameter, 
 with an overflow pipe and wirework cover. The best is Mitchell's, which is made 
 on the principle of the fountain inkstand. The advantages are that dew and rain 
 are at once carried away, and that minute quantities can be read off. James 
 Procter Barry's is a modification. The surface is 10 in. square. The small quantity 
 evaporated daily is measured by a scale of brass divided into 10 equal parts placed 
 diagonally in the evaporimeter, so that during the evaporation of one inch of water 
 the line of contact of the surface of the water with the diagonal scale will traverse 
 the whole length of the scale. The T fg- of an inch can be easily read. The atmo- 
 (Page 84) meter is of some practical use. It is a long glass tube attached to a 
 hollow ball of porous earthenware. The tube is filled previous to observing. There 
 is no class of observations which show such diversity of results as those made by 
 observers of evaporation owing to different methods being employed. The object 
 sought to be obtained is the drying power of the atmosphere. The ocean loses 
 more heat from evaporation than land, because the quantity evaporated from its 
 surface is much greater. Theory should lead us to suppose that the temperature of 
 drained land would be higher than that of undrained, because being drier less heat 
 (Page 85) is lost by evaporation. In 1862 the Marquess of Tweeddale offered 
 prizes for sets of observations on this point. Two sets of observations for a year 
 were made, one at Otter House, in Argyle, on arable land, under a rye-grass 
 crop, the soil being light and sandy, and the slope being 1 in 40 ; the other set 
 at North Esk reservoir, Pentland Hills, on hill pasture, the soil being clay 
 mixed with decayed moss. The following results were drawn. 1. The mean 
 annual temperature of the arable land was raised 8 by drainage, and (2) 
 that of the pasture land, 4. 3. During sudden falls of temperature and during 
 protracted cold weather, the cold passed more quickly and completely through 
 undrained land than through drained land. 4. When the temperature of the air was 
 higher than that of the soil, drained land received more benefit from the higher tem- 
 perature than the undrained land, less of its heat being lost by evaporation. 5. 
 Since when rain or sleet fell the superfluous moisture soon flowed away from the 
 drained land, drainage tended to maintain in the soil a comparatively equable 
 temperature ; whereas the undrained land was liable to considerable fluctuation, 
 for when soaked with warm rain water its temperature was temporarily raised, and 
 when soaked with melted snow it was temporarily lowered. On one occasion sleet 
 lowered the drained land 2 and the undrained land 4. 6. The temperature of 
 drained land was in summer occasionally raised above undrained land 3, and often 
 2, and still more frequently T5. Since these different temperatures are chiefly 
 
 351 
 
AQUEOUS VAPO UR 1867. Buchan. NOTES. 
 
 caused by the different amounts of water evaporated from the land, it is evident 
 that different results will be obtained from different soils with different crops and 
 with different slopes and exposures. In 1847 Prof. James Elliott made a number of 
 experiments which shed some light on this extensive subject. He found that peat 
 moss can absorb more than twice its own weight of water, dry clay nearly its own 
 weight, dry earth or garden mould more than half its own weight, and dry sand 
 little more than a third of its own weight. With equal times of drying under the 
 same circumstances peat moss lost two-thirds of all the water it contained ; clay 
 and earth each more than three-quarters, and sand more than nine-tenths. Evapo- 
 (Page 86) ration was greater from the surface of loose earth than from the surface 
 of water^ till the earth became so far dry as to be of a light colour. Evaporation 
 from saturated moss was excessive during the first day, being far more than from 
 the surface of water, but on the second day the water began to evaporate most, 
 and on the third day very much more than the moss, although the moss was still 
 wet 10 in. below the surface. From these experiments [those by Dr. Milne Home 
 under 1866 being included] a few practical conclusions may be drawn. In all cases 
 the amount evaporated from wet substances and the consequent decrease of tem- 
 perature is proportional to the number of evaporating points, or to the whole 
 extent of the evaporating surface in contact with the air. This explains why 
 evaporation is greater from wet moss and grass than from wet soils, and greater 
 from wet soils than from a surface of water. But as evaporation proceeds and the 
 substances begin to dry, the rate of evaporation is modified by the facility with 
 which the water is drawn by capillary attraction from the interior of the substances 
 to their evaporating surfaces. Thus dry sand parts with its moisture sooner than 
 clay, and clay sooner than peat moss. At all temperatures, even the lowest, 
 moisture exists in the atmosphere in an invisible state, so that the air is never 
 (Page 87) absolutely dry. Prof. J. D. Everett found that the exact correspond- 
 ence of the dry and wet bulb thermometers which happens when the air is quite 
 saturated was as rare as eclipses of the sun or moon. The air a few feet above 
 the ground is seldom perfectly saturated. The capacity of the air for moisture 
 increases at a more rapid rate than the temperature. Thus air can contain at 32 
 the T ^ part of its own weight ; at 59 the -$ ; and at 86 the ^ ; the law being that 
 for every increase of 27 the capacity is doubled. Some hygrometers are formed of 
 substances which readily take up and part with moisture, as Saussure's hair hygro- 
 meter. Adie's is made with two pieces of wood glued together. It is of little 
 (Page 88) or no scientific value. It is this property of substances to be changed 
 in bulk in attracting moisture or in parting with it, which explains a large number 
 of popular prognostics of the weather, especially such as refer to the feelings and 
 conduct of animals, the opening and closing of flowers, and the lengthening and 
 shortening of strings, cordage, and other materials. Hygrometers constructed on 
 the principle of absorption are faulty, not only because they are irregular in their 
 action, but also because, in the course of time, they are subject to great change. 
 The most accurate hygrometers are those constructed on the principle of condensa- 
 tion or of evaporation. Daniell's and Regnault's are constructed on the principle 
 (Page 89) of ascertaining the dew-point temperature. Daniell's is the simplest, 
 but Regnault's requires less time in making the observations. The dry and wet 
 bulb thermometer is the most convenient. Some precaution is required in taking 
 the observations when the temperature of the air is below 32. If the wet bulb 
 reads higher than the dry the observation should not be recorded. If the muslin is 
 (Page 90) dry it should be wetted, and time allowed for the water to freeze before 
 reading the temperature. When the temperature rises above 32 the ice 
 should be removed. Both the thermometers should be exactly the same. All 
 foreign matter should be washed out of the cotton or muslin. The water 
 352 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 used should be pure, either rain or distilled. The muslin should not be touched 
 with the fingers, which cause it to become slightly greasy. The glass vessel should 
 be as far as possible from the dry bulb. The best hours for observation are 9 A.M. 
 and 9 P.M. An additional observation is recommended at 3 P.M. By means of 
 observations of the dry and wet bulb thermometers we may determine or approxi- 
 mate to by means of tables : (1) The dew-point ; (2) the elastic force of vapour ; 
 (3) the quantity of vapour in a cubic foot of air ; (4) the additional vapour required 
 to saturate a cubic foot of air ; (5) the relative humidity ; and (6) the weight of 
 a cubic foot of air at the pressure prevailing when the observation is made. 
 {Page 92). The elastic force of vapour may be regarded as representing the absolute 
 quantity of vapour suspended in the atmosphere. It may also be termed the 
 absolute humidity. It is greatest within the tropics. It is greater at midday than 
 in the morning. It also diminishes with height, but the average rate at which it 
 diminishes is not known. The balloon ascents of Mr. Glaisher and some other 
 aeronauts have thrown some light on the question. But the number of ascents 
 are by far too few to warrant the drawing of general conclusions as to the mean 
 rate of the decrease. The chief point established is that in particular instances the 
 decrease is generally far from uniform, as different strata are super-imposed on each 
 other, differing widely as regards dryness and dampness. Relative humidity is 
 distinct from this, and by humidity of air meteorologists mean the degree of its 
 approach to saturation. Air of a humidity of 73 would feel very dry to an inhabit- 
 ant of Great Britain, 73 being about the lowest mean humidity that occurs in 
 Scotland during May, the driest month. This low humidity is, however, greatly 
 exceeded when the east winds of spring happen to acquire their greatest virulence 
 and dryness. Thus during May 1866, at Corrimony in Inverness-shire, the dry bulb 
 at 9 A.M. of the 21st was 65, and the wet 47, thus giving a humidity of 29, perhaps 
 as low a humidity as has hitherto been observed in the British Isles ; and of course 
 later in the day this extraordinary dryness must have been still further increased. 
 In the ocean at a distance from land the humidity is always great, and during the 
 {Page 94) night generally approaches 100. In the interior of continents it is less,, 
 especially in sandy deserts, which allow the rain water speedily to sink, thus drying 
 the surface ; and in rocky countries which are never wetted more than on the 
 surface. Thus at Djeddah, in Arabia, on 12th March, 1864, the humidity was as 
 low as 11. The humidity is greatest during the night, when the temperature is at 
 its minimum ; it is also great in the morning, when the sun's rays have evaporated 
 the dew and the vapour has not yet had time to find its way into the air. And it is 
 least during the greatest heat of the day, and for some time thereafter or before the 
 temperature has yet begun perceptibly to fall. Now between the vapour present 
 in the air and the temperature of the air there is a vital and all-important connection 
 (Page 99) which recent experiments and researches have done much to elucidate. 
 When rivers are considerably warmer than the air they give rise to fogs, because the 
 more rapid evaporation from the warm water pours more vapour into the atmo- 
 sphere than it can hold suspended in an invisible state, and the surplus vapour is 
 condensed into mist by the colder air through which it rises. Thus deep lakes and 
 rivers flowing out of them are in winter generally much warmer than the air, and 
 hence, when the air is cold and its humidity great, they are covered with fogs. 
 When Sir Humphry Davy descended the Danube in 1818, he observed that mist 
 was always formed during the night, when the temperature of the air on shore was 
 from 3 to 6 lower than that of the stream ; but when the sun rose, and the tem- 
 perature was brought to an equality, the mist rapidly disappeared. The densest 
 fogs occur during the cold months in large towns built on rivers, the causes which 
 produce fogs being then at the maximum. The denseness of the London fogs is 
 notorious. This peculiar denseness is caused by the warmth of the river bed, and 
 
 353 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 it is increased by the sources of artificial heat which London affords ; and from the 
 circumstance that the temperature is falling everywhere, and the humidity being 
 then great, the vapour of the atmosphere is qiuckly and copiously condensed by the 
 gently flowing cold easterly winds which generally prevail in November. In all 
 these cases fogs 'are very locally distributed, being confined to the basin of the 
 river or lake where they are formed, and do not extend far up into the atmosphere. 
 There are, however, other fogs that spread over large districts which are originated 
 under different meteorological conditions. Fogs often accompany the breaking of 
 frosts in winter. For when the humid south-west wind has gained the ascendency, 
 and is now advancing over the earth's surface as a light air, it is chilled by contact 
 with the cold ground, and its abundant vapour thereby condensed into a wide- 
 spread mist. Hills and mountains are frequently covered with mists. Since the 
 temperature of the air falls with the height, it follows that as the warm air is driven 
 up the slopes of the mountains by the wind, it becomes gradually colder, and its 
 capacity for moisture is thereby diminished until condensation takes place, and the 
 (Page 100) mountain is swathed with mist. Owing to the peculiarity of their 
 temperature, forests have a marked effect on the mists of mountainous regions 
 Mists often appear sooner on the parts of hills covered with trees than elsewhere. 
 This happens especially when the mist begins to form after midday, because then 
 the temperature of the trees is lower than that of grassy slopes. Mists also linger 
 longer over forests, probably on account of their increased cold arising from the 
 large extent of evaporating surface presented by their leaves when drenched with 
 mists. During his residence at the Cape of Good Hope, Sir John Herschel observed 
 a remarkable instance of the influence of trees in condensing the vapour of 
 the atmosphere. On the side of Table Mountain from which the wind blew, 
 the clouds descended very low, frequently without any rain falling, while on 
 the opposite side they covered the mountain in dense masses of vapour. When 
 walking beneath tall fir-trees, at the time these clouds were closely overhead, he 
 was subjected to a heavy shower of rain ; but on going out from beneath the trees 
 the rain ceased. The explanation he gave of the phenomenon was that the clouds 
 were condensed into rain on the cool tops of the trees. And doubtless the innu- 
 merable fine leaves of the fir-trees adding largely to the surface of evaporation, 
 increased the cold, which condensed the vapour into a more copious shower. I am 
 informed by the Rev. J. Farquharson, Selkirk, that when the atmosphere is very 
 moist, and the S.W. wind is blowing strongly, a mist or cloud is sometimes seen to 
 settle over Bowhill, which is situated at the junction of the Yarrow and Ettrick ; and 
 that the cloud thus formed is subject to great and rapid changes, both as regards its 
 outline and its size. This is a highly instructive observation considered with reference 
 to the causes which produce the phenomenon. Both valleys lie nearly in the direction 
 of the S.W. wind, but the vale of Ettrick is the more highly wooded of the two ; hence 
 the temperature of the two valleys will, from what has been stated above, be 
 generally different the one from the other. Now when a steady humid S.W. wind 
 is blowing, each will acquire the temperature of the valley down which it has flowed, 
 and be at the same time near the point of saturation ; and at Bowhill, where the 
 two aerial currents meet and mix together, cloud will be formed, in accordance with 
 the well-known law by which two volumes of air, each saturated but of different 
 temperatures, can, when mixed, no longer hold all the vapour in suspension, so that 
 consequently part is condensed into cloud or vapour. Extensive fogs also prevail 
 (Page 101) where great differences occur in the temperature of contiguous regions. 
 Thus promontories running out into the sea are frequently enveloped in mist ; for 
 since land is generally warmer than the sea in summer and colder in winter, the 
 difference of temperature is generally sufficient to cause mists with the veerings of 
 the wind landward or seaward. The same cause explains the mists and fogs which 
 354 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 frequently prevail on the coast. These mists generally occur in the morning and 
 evening, seldom advance far inland, and usually accompany fine weather. The 
 British Isles being bounded by the warm waters of the Atlantic on the one side, 
 and separated from the Continent on the other only by narrow belts of sea, are 
 subject to fogs during winter. For the same reason dense thick fogs are prevalent 
 in Norway, Newfoundland, along the coast of Peru and South Africa, and in the 
 Polar regions. The Gulf Stream is notorious for dense and long-continued fogs, 
 particularly at its northern limit, where it meets the Polar current. The high 
 temperature of the stream, which is often from 16 to 18 and sometimes 30 higher 
 than that part of the sea past which it flows, fully explains the denseness and per- 
 sistency of these fogs. Occasionally the summit of a hill or isolated peak is wrapped 
 in mist or cloud, while elsewhere the atmosphere is clear, and though a breeze be 
 blowing over the hill, still 
 
 Overhead 
 The light cloud smoulders on the summer crag,' , 
 
 apparently motionless and unchanged. This phenomenon is instructive and easily 
 explained. The temperature at the top is below the dew-point of the atmospheric 
 (Page 102) current. Hence when the air rises to this region its moisture is condensed 
 into cloud, which is borne forward over the top of the hill and down the other side, 
 acquiring heat as it descends till it is again dissolved and disappears. Meanwhile 
 its place is constantly supplied by fresh condensations which take place as the 
 current, rising to the height of the cloud, falls below the temperature of saturation. 
 Thus, though the cloud on the top of the hill appears to remain motionless and 
 unchanged, the watery particles of which it is composed are continually undergoing 
 renewal. There is another sort of fog of occasional occurrence differing from any 
 of the foregoing, which, from its relation to storms, is of considerable importance in 
 meteorology. It would appear to arise from the juxtaposition of the Polar and 
 equatorial currents. When these currents flow side by side, fog frequently fills up 
 the comparatively calm space intervening between them. It results from the 
 mixing together of the two currents, the cold of the Polar current condensing the 
 vapour of the S.W. wind. It sometimes stretches several hundred miles in th 
 form of a long narrow strip. At other times, and more usually, it is a precursor of 
 storms, which succeed fine dry weather, during which the wind has been chiefly 
 from the N.E. The S.W. wind is seen to prevail in the upper regions of the 
 atmosphere, by the direction in which the thin cirrus cloud is blown, some time 
 before it is felt on the surface of the earth. During this interval the humid 
 equatorial current overlaps the Polar current, and the fog which prevails is due to 
 the mixing of the two currents. Hence in discussing storms, fogs constitute one of 
 the most important elements which require consideration, and they supply valuable 
 help towards the foretelling of storms. Clouds, mists, and fogs arise from the same 
 causes. During the warmest part of the day, when evaporation is greatest, moist 
 air currents are constantly ascending from the earth. As they rise in succession, 
 the moist air is pushed high up into the atmosphere, and losing heat by expansion, 
 a point is at length reached when it can no longer retain in solution the moisture 
 with which it is charged ; hence condensation takes place, and a cloud is formed, 
 which increases in bulk as long as the air continues to ascend. But as the day 
 (Page 103) declines, and evaporation is checked, the ascending current ceases, and 
 the temperature falling from the earth's surface upwards, the lower stratum of the 
 air contracts, and consequently the whole mass of air begins to descend, and the 
 clouds are then dissolved by the warmth they acquire in falling to lower levels. 
 The whole of the process is frequently seen on a warm summer's day. In the 
 morning the sky is cloudless, or nearly so ; as the heat becomes reater, clouds 
 
 355 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 begin to form, and increase in number and size, often presenting scenes of un- 
 paralleled beauty, as lighted up by the sun into dazzling brilliance, they sail slowly 
 and smoothly across the blue sky ; but as the heat diminishes, they contract their 
 dimensions and gather round the setting sun, lit up with the fiery splendours of his 
 beams. In a short time they disappear, and the stars come out, shining in a 
 cloudless sky. When a dry and heavy wind begins to set in, or takes the place of 
 a moist and light wind, it generally does so by edging itself below the moist wind, 
 and forcing it wedgeways into the upper regions of the atmosphere, where con- 
 densation rapidly follows, and dense black clouds, often heavily charged with rain, 
 are formed. This is a frequent cause of cloud and rain in Great Britain, when the 
 cold heavy east wind or Polar current thrusts high up into the air the rain-bringing 
 S.W. wind, thus causing it to darken the sky and bring down its surplus moisture 
 (Page 104) in torrents of rain. Espy has reasoned that every cloud is either a 
 forming cloud or a dissolving cloud. While it is connected with air-ascending 
 currents it increases in size, is dense at the top, and well defined in its outlines ; 
 but when the ascending current ceases, the cloud diminishes in size and density. 
 When a cloud overspreads the sky its lower surface is, for the most part, horizontal, 
 or more generally, it seems as if it was an impression taken from the contour of the 
 earth's surface beneath it. This arises from the high temperature of the air below 
 the cloud, which is sufficient to dissolve the particles as they descend below its level. 
 On ascending through this lower stratum of cloud the temperature is found fre- 
 quently to rise, and the air to be quite clear of clouds for a considerable thickness. 
 Higher up a second stratum of cloud succeeds, and again another clear space, and 
 so on, cloud and clear sky following each other several times in succession. These 
 phenomena arise from the different currents which are encountered superimposed 
 over each other, and differing in temperature and humidity. Kaemtz has deduced 
 (Page 105) the heights between which clouds range as from 1,300 to 21,320 feet. 
 The extreme height is, however, much too small, as has been proved by balloon 
 ascents. Thus Gay Lussac in September 1804, when at the height of 23,000 feet, saw 
 clouds floating apparently at a great height above him. It is probable that the 
 cirrus cloud is often ten miles above the earth. Since clouds are subject to certain 
 distinct modifications from the same causes which produce the other atmospheric 
 phenomena, the face of the sky may be regarded as indicating the operation of these 
 causes. The ancient meteorologist was content with discerning the face of the sky, 
 in order to predict the coming weather. It is to this that the weather-wise sailor 
 and the farmer still look in foretelling the weather. The classification of clouds 
 universally adopted is that proposed by Luke Howard in 1803. The cirrus is the 
 cloud first seen after serene weather. The duration of the cirrus varies from a few 
 (Page 106) minutes to many hours. It remains for a short time when formed in the 
 lower parts of the atmosphere, and longest when it appears alone in the sky, and at 
 a great height. The cirrus, though apparently motionless, is closely connected with 
 the movements of great atmospheric currents. It is this intimate connection which 
 has long caused it to be considered as a most valuable prognostic of stormy weather, 
 and as such it deserves more attention than has hitherto been given to it. Small 
 groups of regularly-formed and arranged cirrus scattered over the sky often 
 accompany fair weather and light breezes ; these do not indicate the approach of a 
 storm for some time at least. Horizontal sheets of this cloud, which fall quickly, 
 and pass into the cirro-stratus cloud, indicate in an unmistakable manner con- 
 tinued wet weather, when streaks of cirrus run quite across the sky in the 
 direction in which a light wind happen* to blow, the wind will probably soon blow 
 hard, but it will continue in the same direction ; in other words, the variable winds 
 and fitful gusts which accompany storms are not likely to be experienced when the 
 fine threads of the cirrus appear blown, or brushed backwards at one end, as if by a 
 356 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 wind prevailing in those upper regions, the wind on the surface will ultimately veer 
 round to that point. If the direction indicated be from south-west, whence the 
 storms of Europe come, wind and rain may be expected ; and it matters not how 
 fair and settled like the weather appear at the time, a storm more or less severe is 
 advancing, and may be looked for within thirty or forty-eight hours. When the storm 
 seems past, and the sky has cleared, should a few fine cirrus clouds be seen slightly 
 blown back at their eastern extremities, the storm has in all likelihood really passed, 
 and fair weather may be expected with some confidence, since the dry Polar current 
 has already begun to prevail overhead. But if, instead of this, innumerable groups and 
 streaks of cirrus cover the sky, crossing each other in all directions, and presenting 
 the appearance of a skein of yarn inextricably tangled together, we may be sure a 
 second storm will shortly follow the one already past. The cumulus clouds are formed 
 in the lower regions of the atmosphere, and are carried along in the current next 
 the earth. The cumulus has been well called the cloud of day, being caused by 
 (Page 107) the ascending currents of warm air which rise .from the heated ground. 
 When the cumulus clouds are of moderate height and size, of a well-defined curved 
 outline, and appear only during the heat of the day, they indicate a continuance of 
 fair weather. But when they increase with great rapidity, sink down into the lower 
 parts of the atmosphere, and do not disappear towards evening, rain may be 
 expected. If loose, fleecy patches of cloud begin to appear, thrown out from their 
 surfaces, the rain is near at hand. The stratus is the lowest sort of cloud, its lower 
 surface commonly resting on the earth. The stratus may be called the cloud of 
 night, since it generally forms about sunset, grows denser during the night, and 
 disappears about sunrise. It is caused by the vapours which rise during the day, 
 but towards evening fall to the earth with the falling temperature ; and since 
 during night the cooling of the air begins on the ground, and thence proceeds 
 upwards, the stratus first appears like a thin mist floating near the surface of the 
 earth ; it thence increases from below upwards as successive layers of the air are 
 reduced below the point of saturation. It includes all those mists which in the 
 calm evening of a warm summer day form in the bottom of valleys and over 
 low-lying grounds, and then spread upwards over the surrounding country like an 
 inundation. When the sun has risen, and begun to shine on the upper surface of 
 the stratus cloud, it begins to be agitated, and heaved up in different places into the 
 rounded forms of the cumulus, while at the same time the whole of" the lower 
 surface begins to rise from the ground. As the heat increases, it continues to 
 ascend, and becomes broken up into detached masses, and soon disappears alto- 
 gether. These appearances indicate a continuance of the finest and serenest 
 (Page 108) weather. While the cirrus changes into the cirro-cumulus, it generally 
 descends to a lower position in the atmosphere. This beautiful cloud, commonly 
 known as a ' mackerel ' sky, occurs frequently in summer, and is attendant on dry 
 and warm weather. It is also sometimes seen between showers. But in this case 
 the cirro-cumulus will be found wanting in the settled order which it wears in fine 
 weather. The cirro-stratus is markedly a precursor of storms ; and from its greater 
 or less abundance and permanence, it gives some indication of the time when the 
 storm may be expected. It may generally be seen between storms, occasionally 
 with the cirro-cumulus, and from what then takes place, important information 
 may be learned regarding the continuance or non-continuance of the stormy weather 
 then prevailing. For if the cirro-cumulus give way, or pass into the cirro-stratus, 
 more wind and rain may be confidently expected ; but if the cirro-cumulus prevail, 
 (Page 109) the storm is past, and fair weather may be looked for. The cumulo- 
 stratus appears indistinctly in the intervals of showers. The distinct cumulo- 
 stratus is formed when the cumulus becomes surrounded with small fleecy clouds 
 just before rain begins to fall, and also on the approach of thunderstorms. The 
 
 B B 357 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 rain-cloud often has its origin in the cumulo-stratus, which increases till it over- 
 spreads the sky and becomes black, or bluish-black, in colour ; but this colour soon 
 changing to grey, the nimbus is formed, and rain soon begins to fall. At a con- 
 siderable height a sheet of cirro-stratus cloud is spread out, under which cumulus 
 clouds drift from the windward ; these rapidly increasing, unite at all points, 
 forming one continuous grey mass, from which the rain falls. It is evident from 
 this that the whole mass of air under the upper sheet of cloud into which the 
 clouds drift must be completely saturated. The breaking up of the loose grey mass 
 indicates that the rain will soon cease. When a rain-cloud is seen approaching at a 
 distance, cirri appear to shoot out from its top in all directions, and it has been 
 observed that the more copious the rainfall, the greater is the number of the cirri 
 thrown out from the top cloud. In observing clouds, the kind, the direction in 
 which they are carried, and the proportion of the sky covered with them, should be 
 noted. In estimating the amount, that portion of the sky from the horizon half-way 
 to the zenith should not be taken into account, because the clouds being there fore- 
 shortened, the estimate would be too great. The scale generally adopted in this 
 country is to 10 ; indicating a clear sky, 5 that it is half covered, and 10, 
 (Page 111) that it is totally obscured. The rainfall is diminished, if the winds have 
 passed over large tracts of land, particularly mountain ranges, and are, therefore, 
 (Page 112) dry. The more specilic conditions under which rain is precipitated, 
 as stated by E. Renou, include : 1. Two layers of clouds at least an upper layer, 
 the cirrus, and a lower layer, the cumulus, or cumulo-stratus, which has its density 
 increased, and its temperature lowered by the descent of the ice crystals of the 
 cirrus. The geographical distribution of rain is proportioned to the humidity, etc. 
 (Page 114) Rain rarely or never falls on the coast of Peru, in the great valley of 
 the rivers Columbia and Colorado, the Sahara, and the desert of Gobi. The 
 (Page 115) trade winds are in the condition of taking up moisture rather than 
 parting with it ; and the return trades which blow above them, having discharged 
 the greater part of their moisture in the region of calms, are also dry and cloudless. 
 In the region of calms the sun almost invariably rises in a clear sky ; but about 
 midday clouds gather, and in a short time the whole face of the sky is densely 
 (Page 116) covered with black clouds, which pour down prodigious quantities of rain. 
 Towards evening the clouds disappear, the sun sets in a clear sky, and the nights are 
 serene and fine. The reason of this daily succession of phenomena in the belt, of 
 calms is that the air, being greatly heated by the vertical rays of the sun, ascends, 
 drawing with it the whole mass of vapour the trade winds have brought with them, 
 and which has been largely added to by the rapid evaporation from the belt of 
 calms ; this vapour is condensed as soon as it rises to the line of junction of the 
 lower and upper trades. As evening sets in, the surface of the earth and the 
 superincumbent air being cooled, the ascending currents cease, and the cooled air 
 descends ; the clouds are thus dissolved, and the sky continues clear till the 
 returning heat of the following day brings round a recurrence of the same pheno- 
 mena. The daily rains of the belt of calms are to some extent analogous in their 
 origin and causes to the formation of the cumulus cloud of temperate climates. 
 (Page 135) An important characteristic of winds is their quality, being dry or 
 humid, etc., according to their direction and the nature of the earth's surface over 
 which they have passed: Thus in the north hemisphere southerly winds are warm 
 and moist, while northerly winds are cold and dry ; and in the south hemisphere 
 (Page 136) vice versa. In certain parts of the earth circumstances occur intensifying 
 (Page 146) these effects, and causing excessive drought, etc. In front of a storm 
 the dew-point is high ; in the rear, low ; the high dew-point is accompanied by 
 great humidity, and the low dew-point by a small one. When the barometer has 
 been falling for some time, clouds begin to overspread the sky, and rain to fall at 
 358 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 (Page 147) intervals ; after the centre of the storm has passed, the rain becomes less 
 heavy ; the clouds break up, and fine weather ultimately prevails. The physical 
 (Page 158) cause of the ascending currents in the centre of storms is to be found 
 in the moist and warm, and therefore light, air which all observation shows to 
 prevail in the front and in the central part of storms. And since most of the rain 
 which accompanies storms falls in those parts of the storm, the barometer will be 
 still further reduced by the removal of the elastic aqueous vapour which is con- 
 densed into raindrops, and by the latent heat set free in the condensation of the 
 vapour. Storms generally contract in area as they traverse a dry climate, and die 
 out when they come to a dry polar current, as less vapour is condensed there. 
 The usual place where the vapour brought by the trade winds is condensed is the 
 region of calms, where heavy rains and thunderstorms occur. But since the con- 
 densation takes place simultaneously over a somewhat broad belt of the earth's 
 surface, which for the time is stationary, it follows that the storm is neither rotatory 
 nor progressive, the only effect of the condensation being the flow of the regular 
 trade winds towards the belt where it takes place. When the condensation is more 
 copious than usual, the effect will be the acceleration of the speed of the trade 
 winds. Suppose that the atmosphere of the West Indian islands has from some 
 cause become exceptionally warm and moist, and that at the same time a high 
 barometer is interposed between that region and the belt of calms. In such cir- 
 cumstances, as the trade winds cannot flow towards the belt of calms, the usual 
 provision for draining them of their moisture is taken away, and a rapid accu- 
 mulation of aqueous vapour takes place to the north of the high barometer, ready 
 (Page 167) to burst into rain and tempest. This would appear to have been the 
 (Page 180) case before and after the Bahama hurricane of October 1866. The cirrus 
 cloud sometimes appears of a texture so delicate as to elude the eyes of all but the 
 (Page 181) most practised observers, and no doubt it is sometimes so thin, that the 
 eye cannot detect it till it is revealed by electric discharges passing through it. 
 This cloud probably originates in. the equatorial current beginning to prevail in the 
 higher regions of the atmosphere, and depositing the watery vapour necessary for 
 the electric discharges, the faint light of which reflected by the minute crystals of 
 the cirrus clouds forms the aurora. A large quantity of ozone in the air is 
 associated with increasing humidity, and a small quantity with decreasing humidity. 
 (Page 182) Since rainbows in the morning are always seen in the west, they indicate 
 the advance of the raincloud from the west at the time when it is clear and bright 
 in the east ; and since the fall of rain at this time of the day, when the temperature 
 should be rising, is an additional evidence of increasing moisture, a morning 
 rainbow is regarded as a prognostic of a change to wet, stormy weather. On the 
 (Page 183) contrary, the conditions under which a rainbow can appear in the 
 evening are the passing of the raincloud to the east, and a clearing up in the west 
 at the time of day when the temperature has begun to fall, thus further indicating 
 a change from wet to dry weather. Coronas can only be seen when the globules 
 composing the cloud are all, or nearly all, of equal size, and the smaller the size of 
 the globules the greater is the diameter of the corona. , Hence the corona is a 
 valuable prognostic ; for when its diameter contracts round the moon, we know 
 that the watery particles composing it are uniting into larger ones, which by-and-by 
 will fall in rain ; whereas, if the corona be extending, the particles are growing 
 less, thus indicating increasing dryness, and consequently fair weather. Scoresby 
 observed that Anthelia or glories are always seen in the Polar regions whenever 
 (Page 185) sunshine and fog occur at the same time. The red and golden- 
 coloured clouds are observed to be the accompaniment of cumulus clouds while in 
 the act of dissolving, as they sink slowly down into the lower and warmer parts of 
 the atmosphere ; consequently they disappear from the sky soon after sunset. Such 
 
 359 
 
AQUEOUS VAPOUR 1867. Buchan. NOTES. 
 
 aunsets are universally regarded as prognostics of fine weather. Frequently small 
 thin clouds appear high up in the eastern sky some time before sunrise, or when 
 
 ' The dappled dawn doth rise,' 
 
 and when the sun has risen they disappear. They are probably caused by the sun 
 shining on and warming the upper layers of the atmosphere before it appears above 
 the horizon; thus small ascending currents are formed, the vapour of which as 
 they ascend is condensed into small clouds, as the cirro-cumulus. Their rounded 
 definite forms show them to be produced in the same way as the cumulus viz. , by 
 ascending currents forcing their way through colder strata. They may thus be 
 regarded as heralding the cumulus, and as sure prognostics of fine weather. If in 
 (Page 186) the evening sky after stormy weather the yellow tint deepens into orange 
 and red, the atmosphere is getting drier, and fine weather may be looked for. In 
 the morning a red and lowering sky is a prognostic of unsettled weather. 
 
 (Page 196.) Table V. showing elastic force of aqueous vapour. 
 
 (Page 197.) Table VI. Factors for multiplying the excess of the dry bulb 
 thermometer over that of the wet bulb to find the excess of the temperature of the 
 air above that of the dew-point. 
 
 Buchan, A. Journ. Scot. Meteorol. Soc., vol. ii. (1869), No. xiv., April 1867 (rvp). 
 
 (Page 41.) The irregular periods of temperature observable in Scotland are 
 intimately connected with the direction of wind, and with the absolute and relative 
 quantity of the vapour in the air. The effect of a diminished quantity of vapour in 
 raising or depressing the mean temperature depends on the season of the year. If 
 it occurs in summer, the mean temperature will be raised ; but if in winter, it will 
 fall. As concerns evaporation, great humidity adds to the mean temperature, and 
 a small humidity lowers it. But as compared with solar or terrestrial radiation the 
 effects of evaporation on the temperature are very slight. The following examples 
 illustrate the dependence of the changes of temperature on the amount of vapour in 
 the atmosphere. Lieut.-Col. Strachey (Phil. Mag., 1866) has examined the Madras 
 meteorological observations of several years, and compared the elastic force of the 
 vapour with the number of degrees the temperature was reduced by terrestrial 
 radiation from 6.40 P.M. to 5.40A.M., and the number of degrees the solar radiation 
 was raised from 5.40 A.M. to 1.40 P.M. In all cases examined, the sky was either 
 quite, or all but quite, free from clouds ; the only difference being in the amount of 
 vapour. The following are selected from the results arrived at : 
 
 TERRESTRIAL KADIATION. 
 
 Tension of vapour . . . . - . -888 in. -605 in. -455 in. 
 Fall of temperature from 6'40 P.M. to 5.40 A.M. 6 12-1 16-5 
 
 SOLAR RADIATION. 
 
 Tension of vapour , . . y ' . '824 in. -670 in. '394 in. 
 Rise of temperature from 5.40 A.M. to 1.40 P.M. 12'4 19 -3 27'0 
 
 Thus when the quantity of vapour in the air was very large (tension '888 in.), 
 the temperature only fell on an average 6 during the night ; but when the quantity 
 of vapour was small (-455) the temperature fell 16'5. And when the quantity of 
 vapour was large ('824) the temperature during the day rose only 12'4 ; but when 
 the amount of vapour was small, the temperature rose in the same space of time 
 27. These remarks wiU be applied to the August cold and warm periods. The 
 mean tension of vapour at Sandwick for August is '360 in. For the four cold days 
 it is only "353 in., and on the 9fch as low as '343 in. ; but for the four warm days 
 immediately following it is "396 in., or '043 in. greater. The mean humidity of the 
 360 
 
AQUEOUS VAPOUR 1867. Lyell. NOTES. 
 
 month is 85 ; of the four cold days 84 ; of the four warm days 89. Thus then, from 
 the 8th to the llth of August, characterised by a depression in the temperature, 
 there was a diminished amount of vapour and less humidity. But from the 12th to 
 (Page 43) the 15th, when the temperature rose, the tension increased about *05 in. and 
 the humidity increased from say 84 to 87. These two periods present a very striking 
 character as regards the moisture of the air, the warm period from the 12th to the 
 16th showing an amount of vapour in the atmosphere such as occurs at no other 
 time of the year, and the cold weather of the four days preceding a deficiency of 
 vapour greater than occurs during August until the close of the month, when, owing 
 to the falling of temperature, the quantity of vapour is diminished. If the cold 
 period of August was caused by the interception of heat by meteors, we should 
 then expect with the fall of temperature an increase in the rainfall, and as the tem- 
 perature would thus be brought nearer the dew-point, an increase in the humidity ; 
 and after the earth has emerged from the shadow of the meteors along with the rise 
 of temperature, we should have a diminished rainfall and less humidity. Since 
 the reverse of this happens, the cold of August must be explained by other causes. 
 For this no combination of circumstances can be considered adequate which does 
 not account for the dry, cold air prevailing during the cold period, and the warm, 
 moist air during the warm period. 
 
 [He then investigates the condition of Western Europe as regards wind, atmosphere, 
 pressure, and temperature relatively to Scotland, and arrives at the conclusion that 
 the cold and warm periods of August are determined by the wind, and that the ob- 
 served relations of moisture depend on the wind. The whole inquiry has a local 
 bearing, and therefore the details are omitted here.] 
 
 Calvert, H. H. Journ. Scot. Meteorol. Soc., vol. ii. (1869), No. xvi., October 1867 (rvp). 
 
 (Page 115.) At Erzeroom, June is remarkable for the regularity of the daily 
 atmospherical change. At sunrise the sky is perfectly bright ; towards 10 A.M. 
 clouds begin to appear, which gather rapidly ; and at noon, or 1 P.M., the heavens 
 are quite overcast with heavy thunder clouds. At about 2 P.M. thunder is heard. 
 Towards sunset the clouds are gradually dispelled, and by 9 or 10 A.M. the sky 
 reassumes its clearness. 
 
 Laughton, J. K. (B. 1867, 12.) 
 
 (Page 445.) The dew-point in the equatorial oceanic district is perhaps seldom 
 so much as 5 below the air temperature. Daniell has estimated the difference as 
 generally 2 or 3. 
 
 Lyell, Sir Charles. (B. 1807, 13.) 
 
 (Page 271.) Croll observes that when the winter occurs in aphelion during a 
 high eccentricity of the earth's orbit the aqueous vapour would fall as snow in high 
 latitudes, and during the summer, when the heat would be one-fifth more intense 
 than at present, the melting of the accumulated ice and snow would give rise to 
 (Page 286) constant fogs and overcast skies. When certain dry winds blow the 
 snow wastes away like camphor by evaporation ; and as it is observed that the rain- 
 fall diminishes towards the poles, it is probable that the snowfall also diminishes in 
 that direction, so that there may be a dry air at the poles, especially if warm air from 
 (Page 430) the south parts with its moisture in passing over snow-clad areas. The 
 evaporation from some lakes is nearty equal to the quantity flowing in ; and in the 
 (Page 497) Caspian quite. [He says solar evaporation is a cause of oceanic cur- 
 rents. If so, then such currents may in some cases afford valuable evidence as to 
 the distribution of aqueous vapour.] 
 
 361 
 
AQUEOUS VAPOUR 1867. Russell. NOTES. 
 
 Markham, C. E. Journ. Soy. Geog. Soc., vol. xxxvi. (1867) (rs}. 
 
 (Page 89.) The effect of vegetation is undoubtedly to retard evaporation and to 
 check the rapidity of drainage ; and the removal of forests of course has an opposite 
 effect. The hill districts of India afford proofs of this. The floods caused by the 
 monsoon rains are yearly increasing in size and violence. 
 
 Mitchell, A. Journ. Scot. Meteorol. Soc., vol. ii. (1869), No. xv., July 1867 (rvp). 
 
 (Page 80.) The injurious effects of the March winds of Scotland are due to their 
 coldness and dryness. Such winds blowing over a moist surface tend to reduce 
 the temperature of that surface to the temperature of evaporation, and thus ab- 
 (Page 81) stract a large quantity of heat. Places protected from the wind will 
 have less evaporation. The proverb says : ' Better be bitten by a snake than 
 (Page 82) warmed by a March sun.' The risk may be owing to the diathermancy 
 of the air, which is due to its dryness. It may be said that the moisture of the air 
 is the preserver of life ; for without it every living thing would be burnt to death 
 after sunrise or frozen to death after sunset. 
 
 Moore, J. W. Symons's Meteorol. May., vol. ii. (1867) (rsp). 
 
 (Page 118.) The explanation of the peculiar haze which accompanies an easterly 
 wind lies in its dryness, coldness, and consequent density with but a small capacity 
 for vapour. The effect of its dryness the result of its passage across land and of 
 its coming from intensely cold regions is excessive evaporation. But the vapour 
 drawn up in this way is immediately condensed before it can reach to any height by 
 the extreme coldness of the air, not in the form of a cloud, but as a haze of a most 
 peculiar bronze hue. And this is more marked in spring, because at that season 
 (Page 119) the coldness of the N.E. current is greatest and the amount of vapour 
 carried up by evaporation reaches a maximum, from the sun, with increasing 
 power, acting on the land drenched by the winter's snow and rain. With respect 
 to the S.E. wind ; in the first place we must carefully distinguish two distinct forms 
 of the same. The one is nothing more than a bent polar or N.E. current, and is 
 accompanied by all its characteristics viz., a high barometer, great cold, the 
 usual bronze hue, dry weather, etc. The other is a deflected S.W. or equatorial 
 current, and is attended with a low barometer, warmth, moisture, and often heavy 
 rain. The latter occurs in two aspects ; first, as forming one side of a cyclone, which 
 is the most usual ; and secondly, as a comparatively steady wind, the result of an 
 equilibrium established by opposite currents from N.E. and S.W. holding each 
 other in check. If in the second case there is no intermingling of currents, we have 
 towards the S.W. border of the S.E. wind a singularly transparent air and 
 large quantities of cirrus, and towards the N.E. edge of the same the haze and 
 high barometer characteristic of N.E. wind. The colour of the E. wind haze is 
 the same as that of the inner edge of a solar halo, and is no doubt due to a peculiar 
 arrangement of the vapour particles. 
 
 Russell, R, Symons's Meteorol. Mag., vol. ii. (rsp.) 
 
 (Page 117.) Tyndall has exaggerated the influence which the vapour of water 
 
 xerts in modifying the intensity of solar and terrestrial radiation. The radiant 
 
 power of the atmospheric vapour would not form clouds, though it might form mists. 
 
 our atmosphere [English] the vapour of water had little power of transmitting 
 
 s heat into space when it approaches or reaches the dew-point. If any cloud had 
 
 ^een caused by the radiation of heat into space its upper surface would be flat, like 
 
 the mists in the meadows before sunrise. These and other reasons led him to the 
 
 o62 
 
AQUEOUS VAPOUR 1867. Thomson. NOTES. 
 
 conclusion that the radiation of heat into space has directly a very slight influence 
 on the production of rain. 
 
 [Sir W. Thomson's remarks on this paper will be found under his name at the 
 bottom of this page.] 
 
 Sorby, H. C. (B. 1867, 16.) 
 
 (Page 357.) The blue colour of the sky is due to the absorption of a considerable 
 amount of the red light by the vapour of water present as a transparent gas in a 
 clear pure atmosphere. If, however, minute particles of water are present in the 
 form of thin mist, the depth of the blue colour will be diminished, and hence in 
 winter and in cold countries we have not the clear, deep blue sky of summer or of 
 subtropical districts. The blue colour of mountains may also be explained in the 
 same way, being due partly to the influence of the aqueous vapour, and partly to the 
 shaded parts being illuminated by the blue sky. If the air be much charged with 
 dry transparent vapour, the blue colour will be deeper, whereas if there be any fog 
 or mist it will be obscured, and hence the blue colour is a sign of the air being 
 loaded with vapour. 
 
 Stow, F. W. Si/mom's Meteorol. Mag., vol. ii. (rsp.) 
 
 (Page 82.) At Tunbridge Wells on 27th June, four feet above ground, the humidity 
 sank to 29 '6 at 2.30P.M. The least vapour occurred at noon; dew-point 41 '1. 
 The temperature of the dew-point was so uniform throughout the day, that from 
 the temperature of the air the reading of the wet bulb, almost at any time, might 
 have been predicted when the dew-point had once been ascertained. This seems 
 to be generally the case, at least in dry weather. 
 
 Symons, Gr. J. Symons's Meteorol. Mag., vol. ii. (rsp.) 
 
 (Page 68. ) The driest day I have hitherto recorded at Camden Town was on 
 June 28th, 1857, when the humidity was as low as 33. On June 27th, 1867, it reached 
 29 at 3 P.M. four feet above the ground, the wet bulb being 581 and the dry 78 '5. 
 At twenty feet above ground the lowest was at 2 P.M., being 36 ; dry bulb 77*1, wet 
 (Page 69) 59 -9. The dryness was much greater near the earth than at twenty feet 
 above it. In both years the greatest drought was preceded by a period of easterly 
 winds and high barometer. The range of temperature was also greatest in 1867. 
 It was 35*1 in 1867; 31 '3 in 1857. At Aldersliot Mr. Arnold registered a 
 humidity of 22 at 3 P.M. ; dry bulb being 82, wet 57. 
 
 Thomson, Sir "W. Symons's Meteorol. Mag., vol. ii. (rsp.) 
 
 [Remarks made in a discussion on Russell's paper referred to under his name.] 
 (Page 117.) He thought Russell was right that the cold of expansion had a very 
 small effect in causing torrents of rain ; but that he had undervalued very consider- 
 ably the influence of radiation in producing that minor condensation by which 
 mists and clouds were constituted. He said minor condensation, meaning conden- 
 sation from a gaseous condition into small spherical globules, was so small that the 
 resistance they met with kept them suspended. The reason why a cloud did not fall 
 down as rain was that every part of the cloud was composed of very minute drops 
 of water. The larger the drops were that constituted a cloud the more rapidly 
 would they fall ; but when very small they fell insensibly, as Professor Stokes has 
 shown, only perhaps a few inches in an hour. When somewhat larger, they fprmed 
 what we called a Scotch mist, which was something between a shower of globules 
 coming down appreciably, and a shower of globules in which the descent was insen- 
 sible. As to the influence of radiation and the influence of minor condensation as 
 
 363 
 
AQUEOUS VAPOUR 1867. Georg Ludwig von . NOTES. 
 
 soon as a cloud exists, whether high or low, each particle becomes a radiator. 
 It radiates heat and becomes itself a little cooler than the surrounding air, and so 
 becomes a reservoir of condensation. That takes place at the top of the cloud if 
 there is clear air above it, and so with the mists of the valleys. A blade of grass 
 (Page 118) could not go to a temperature lower than the dew-point of the air touch- 
 ing it, and so was it with particles of mist. By an arrangement which they 
 could not but regard as an admirable and wonderful exemplification of design, 
 there was nothing destitute of protection. The protection was sometimes in- 
 sufficient, and plants were killed by frost : but some degree of protection was never 
 wanting, and there was enough of that protection always to allow plants to live, 
 as we saw them doing, and to survive during weather when, were it not for one 
 of these causes, the cold would be so great as to destroy them altogether. Phy- 
 sically it was interesting to remark how it was that in each instance the protection 
 was obtained. There was first the protection afforded by clouds. These prevented 
 the surface of the earth from radiating and reaching a lower temperature than that 
 of the clouds. The temperature of a blade of grass on a cloudy evening would 
 therefore be very nearly the temperature of the lower surface of the clouds over- 
 head. When there were no clouds and no wind the office of each blade of grass 
 was to collect the air touching it, condense vapour from that air, and to take heat 
 from part of the air around it. Thus we had a source of heat taken from the air 
 several feet above the surface. The protection was more complete, however, when 
 dew did not fall, for when there was no dew, the wind made up so large a portion 
 of heat from the air that the leaves of plants were never allowed to go down even 
 to the dew-point. Thus wind was a more complete protection than dew, and it 
 would have been observed that plants were never injured by frosts on windy nights, 
 and that in the morning the grass was found dry. It was sometimes remarked that 
 flowers were frosted in hollows, but that close at hand and on hillocks they escaped 
 damage. The air in the hollows remained unchanged, and unless there was moisture 
 enough in the air to provide dew as long as the severe conditions of weather lasted, 
 and to keep the dew point from going down too low, inj urious effects would follow. 
 The plants, in short got dry, drying the air around them, and if that air was not 
 changed very much for the better then they were destroyed by frost. This, however 
 rarely happened. 
 
 Georg Ludwig von . Journ. Roy. Geog. Soc., vol. xxxvi. (1867) (r). 
 
 (Page 273.) Akhtulimba (in the Belor country). Fog is of frequent occurrence 
 in spring, and is called omimir. The mist lasts till two o'clock in the afternoon, 
 when it suddenly disappears. 
 
 Journ. Scot. Meteor ol. Soc., vol. ii. (1869), No. xvi., October 1867 (rvp). 
 (Page 122.) The observer at Glencairn remarks that according to the old saw 
 the leafing of the oak before the ash indicates a dry summer. [The observer is 
 Rev. Robert Home.] 
 
 Symons's Meteorol Man., vol. ii. (rsn.) 
 [No. for April 1867.] 
 
 (Page 35.) Steinmetz in his Sunshine and Showers ' says : ' Much wet in May 
 is worse than excessive drought ' ; hence the proverb 
 
 ' A May flood 
 
 Never did good.' 
 
 It is said that a great drought always enters during the period comprising the last 
 eight days of February and the first twenty days of March. He also states that 
 ram-clouds are attracted to certain localities more than others. 
 
AQUEOUS VAPOUR 1867. Georg Ludwig von . NOTES. 
 
 Symons's MeteoroL Mag., vol. ii. (rsp.} 
 
 [No. for July.] 
 
 (Page 67.) Saussure notices that before his time the hygrometers in use were 
 formed of strings, animal fibres, and other substances which elongate or contract 
 with damp. He points out that no one had examined the effect on any of them 
 of variation in the pressure, density, movement, etc., of the air, nor had they 
 examined if the varying indications of the instrument were proportional to 
 (Page 68) the amount of vapour in the air. The 1'Abbe Fontana rendered the 
 method of indicating the humidity adopted by the Academicians of Cimento 
 more portable by weighing a clean, well-polished plate of glass, reducing it to a 
 certain temperature, and then reweighing ; the difference representing the moisture 
 condensed on it. Le Roi stood a glass in water, cooled the water till dew stood 
 upon the glass, and then registered the temperature. Saussure rejects all these on 
 account of inconveniences attending their use, and the liability to disturbances 
 in the indications from the presence of grease and from .other causes. Saussure 
 tried sal-ammoniac in Le Roi's process, but states that he found that the 
 dew did not appear at the same temperature under apparently the same cir- 
 cumstances. Saussure often suspended his hygrometer four feet above the 
 (Page 88) ground in the middle of a large plain, waited until it took exactly 
 the humidity of the air, and observed afterwards its momentary variations. 
 We know that there are days when the air is calm, or no violent or decided wind 
 agitates it ; but, nevertheless, in a place perfectly open there arise from time to 
 time slight breezes which give a momentary agitation. He invariably remarked that 
 (Page 89) these slight breezes, from whatever quarter they came, caused the hygro- 
 meter to go towards dry, sometimes 1, sometimes 2 ; after which, when the air 
 became dry, it retreated little by little to the point at which it was previously. 
 Reflecting that these puffs arising all at once in the middle of a calm cannot surely 
 come from far, that they are, in fact, but portions of the surface air of the same 
 plain, compelled by a momentary rupture of equilibrium to change places ; in such 
 a plain, when the air is calm, it may be assumed that the whole was nearly of the 
 same humidity. Why, then, should these breezes always give drier indications ? 
 Returning home he suspended the same hygrometer in the middle of a room, closed 
 the doors and windows, sat down six feet from the hygrometer, over which he had 
 suspended a large screen, waited quietly until he was certain that the screen and 
 hygrometer were in the same state as the air of the room, and had taken up all 
 possible effect from the presence of his body ; then, without changing his position, 
 he agitated the screen rapidly (like a fan) ; at the end of eight or ten minutes he 
 found the hygrometer indicated | drier. From subsequent rough experiments 
 Saussure decided that these effects were due to the mingling of air from a higher 
 level, which he assumed to be always drier. We think the point open to further 
 investigation, the relation of aspirated and ordinary dry and wet thermometers 
 being, we believe, only a partially investigated question. Saussure's third essay is 
 an excellent resume on evaporation. When speaking of evaporation he ridicules the 
 idea of evaporation from a small vessel of water in a garden representing that of a 
 large water surface like a lake or sea, and says that in order to do this fairly we 
 should have the vessel floating even on the surface of the sea, and with the water as 
 near as may be at the same level. The evaporator should be of such size that the 
 water is at the same temperatures. He adopts Richmann's suggestion that the 
 water surface should be nearly at a constant level. He notices that ice is subject to 
 evaporation, and proves that the rate of evaporation from it is proportional to the 
 humidity of the air. In his fourth essay he says it is the coldness of the upper 
 regions of the air which retains and imprisons the water which nourishes the surface 
 of the earth. Dew, which we may regard as a species of rain without clouds is 
 
 365 
 
AQUEOUS VAPOUR 
 
 1868. Buchan. NOTES. 
 
 (Page 90) explained in the same manner ; nevertheless it is sometimes accompanied 
 by fog, and even this vapour which renders the air slightly thick when the dew falls 
 is produced probably by some of the vesicles which are formed when cooled air is 
 depositing its superfluous humidity. He criticizes Bouguer for limiting the altitude 
 of the clouds to 8,000 feet, and says they may exist at 168 miles. 
 
 Notice of Clouston's Explanations of Weather Prognostics (same vol.). 
 
 (Page 93.) Easterly gales without rain during the spring equinox foretell a dry 
 summer. Dr. Kirwan's rules, verified by Howard in 1808, are (1) when there has 
 been no storm before or after the vernal equinox the ensuing summer is generally 
 dry, at least four times in six ; (2) when a storm happens from an easterly point on 
 the 19th, 20th, or 21st of March, the succeeding summer is dry four times in five ; 
 (3) when a storm rises on the 25th, 26th, or 27th of March, and not before, in any 
 point, the succeeding summer is generally dry four times in five. Dry summers, 
 Dr. Kirwan says, are a consequence of uniform winds, from whatever quarter they 
 may blow ; as wet summers are of variable winds, particularly in opposite directions. 
 
 1868. 
 Buchan, A. A Handy Book of Meteorology. 2nd Ed. (n;.) 
 
 (Page 35.) It is probable that the vapour of water exerts a pressure on the 
 barometer in another way than by its elastic force. The maximum barometric 
 (Page 36) pressure in the forenoon is brought about by the rapid evaporation 
 arising from the dryness of the air and the increasing temperature, together with the 
 overflow of air in the upper regions of the atmosphere from the wave of heat which 
 (Page 39) has been going on for some hours. In the neighbourhood of the equator, 
 where the temperature and moisture differ little in the course of the year, there is 
 little variation in the mean pressure from month to month. Thus at Cayenne the 
 (Page 40) pressure in January is 29 '903 in., and in July 29 '957 in. The low 
 winter pressure at Reykjavik, Sand wick, and Sitka is due to the comparatively 
 high winter temperature, the large amount of moisture in the air, and the heavy 
 (Page 47) rainfall, The July distribution of atmospheric pressure is due primarily 
 to temperature, and secondarily to the moisture of the atmosphere. The effect of 
 the Mediterranean, Black Sea, Caspian Sea, North Sea, and Baltic Sea, in deflecting 
 and otherwise determining the position of the curves of pressure is very interesting. 
 Air charged with vapour of water is considerably lighter than dry air ; consequently 
 when moist air accumulates over any region an ascending current takes place. But 
 as moist air ascends into the upper regions of the atmosphere, it is cooled below the 
 point of saturation, condensation follows, and rain is precipitated. In the act of con- 
 densation heat is liberated which, by heating the air in the higher parts of the atmo- 
 sphere, tends still further to diminish the pressure, and so accelerates the ascent of 
 the current. This influence of the vapour on the isobarometric curves is illustrated 
 in Plate I. [not given here]. In the North Pacific, where at this season the two trade 
 (Page 50) winds meet and mingle, there occurs a belt of low pressure caused by the 
 vapour accumulated by these constant winds. In the Atlantic at 15 N. lat. there is 
 a similar belt of low pressure, at least lower than what prevails to the north and 
 south of it. The crowding together of the isobarometric lines in the south and 
 east of Asia is caused by the vapour which the summer monsoon brings to these 
 regions, and which is there precipitated in a copious rainfall. The low pressures 
 which prevail during all seasons in the Antarctic Ocean are no doubt due to the 
 saturated state of the atmosphere resulting from the KW. winds, which blow 
 thither from an almost unbroken sheet of waters which embraces the S. Pacific, the 
 S. Atlantic, and the Indian Ocean, and which meet with little land to condense the 
 (Page 52) vapour till they flow within the Antarctic Circle. Two of the January 
 areas of diminished pressures are caused by there being vast reservoirs of moist air 
 
 366 
 
AQUEOUS VAPOUR 1868. Buchan. 
 
 ff ttNlxT r " f "^^ 
 
 viz., the north part of the Atlantic and the north parxkof the FaeAic^' aijd.the parts 
 (Page 55) of the continents adjoining. The influence or-J^i^W^m^ejnature in lower- 
 ing the mean annual pressure over any portion of the earftr^surface is slight, as 
 compared with the depressing influence of the vapour of the atmosphere. It may 
 therefore be concluded that the chief disturbing influences at work in the atmo- 
 sphere are the forces called into play by its aqueous vapour thus giving to this 
 element a paramount claim on our regard in studying winds, storms, and other 
 (Page 95) atmospheric changes. The quantity of dew deposited is in proportion to 
 (Page 124) the degree of cold produced and the quantity of vapour in the air. 
 Illustrations of this [that is the effect of mountain ranges in drying winds and thereby 
 increasing radiation to the leeward, so as to make the temperature range greater] 
 (Page 129) are afforded by Norway and Sweden and the British Isles. In summer 
 (Page 131) the interiors of continents are hotter and drier. When an area of low 
 pressure is bordered on either side by an area of high pressure, long-continued rains 
 occur in the area of low pressure, while on the southern side the weather is close 
 (Page 148) and warm. Though in exceptional cases the amount of vapour indi- 
 cated by hygrometers may be wide of the mark, yet, in long averages, a very close 
 approximation will be obtained, except in confined localities, which are exception- 
 (Page 153) ally damp or exceptionally dry. Professor Elliott remarks that 
 (Page 154) moss can retain five times its weight of water on the surface of the 
 soil always prepared for evaporation, and prepared in the manner that it can most 
 readily evaporate. JSTo one need be astonished at the coldness of our hills and the 
 dampness of our mountain climate when they consider that the surface of the soil 
 is either moss or grassy turf. This moss or turf retains most of the water that falls 
 from the clouds, permitting little, except in very wet weather, to enter the soil; this 
 water is almost immediately evaporated, and the turf prepared to receive other 
 supplies. The coldness caused by evaporation must therefore be very great. It 
 follows from this that the conversion of a swamp or a low-lying damp piece of 
 ground into a lake will add materially to the dryness and amenity of the climate of 
 the surrounding district, and the rainier the locality the greater will be the advan- 
 (Page 171)tage gained. Dr. James Bryce notices that occasionally a cloud is formed 
 at Brodrick at the point where Glens Rosa and Shiraig meet. The explanation is the 
 (Page 186) same as that of the cloud formed at Bowhill. Rain sometimes falls 
 from a cloudless sky. Sir C. Ross describes a case which occurred near Trinidad, 
 December 25th, 1839. It was a beautiful clear night, not a cloud to be seen, yet 
 there was a light shower of more than an hour's continuance. The temperature of 
 (Page 212) the dew-point was 72, of the air 74. Differences of atmospheric pres- 
 sure, and consequently all winds, arise from changes occurring either in the tempera- 
 (Page 213) ture or in the humidity of the air. If the atmosphere of one region 
 become more highly charged with aqueous vapour than the atmosphere of sur- 
 rounding regions, the air of the more humid atmosphere being on that account 
 lighter will ascend, while the heavier air of the drier regions will flow in below and 
 take its place. And since part of the vapour will condense as it descends and heat 
 be thereby disengaged, the equilibrium will be still further disturbed. It is in this 
 way that all the more violent commotions of the atmosphere, gales, storms, hurri- 
 (Page 225) canes, and tempests originate. J. K. Laughton lays too much stress 
 (Phil. Mag., 1867) on the condensation of vapour as the cause of wind. Winds 
 are the simple result of differences of pressure, whether such differences be caused 
 by temperature, or from the presence of aqueous vapour or from its condensation. 
 (Page 232) An inquiry into the disturbing influences caused by evaporation and 
 unequal temperature as compared with the surrounding land would be a valuable 
 contribution to meteorology such, for exam pie, as a statement of the local and other 
 causes by which the direction of the winds in January is N.E. at Christiania 
 
 367 
 
AQUEOUS VAPOUR 18,68. Buchan. NOTES. 
 
 (Page 282), whilst at Skudesnes, Christiansund, and Hammerfest, the mean direction 
 is S.S.E. For a theory of storms to be satisfactory, it must account for the satu- 
 ration of the atmosphere with vapour, often over a most extensive region which 
 must be considered as the necessary precursor of storms. How can we account 
 (Page 283) for the first part of the course of the West Indian hurricanes, which is at 
 right angles to the prevailing trade winds of that region ? Dr. E. Lommel has shown 
 { Page 321) that in passing through different thicknesses of vapour, the blue rays 
 of light are first absorbed, then the yellow, and finally the red. When the sun is high 
 in the heavens the thickness of the vapour screen between the sun and the eye is 
 (Page 322) not sufficient to produce any perceptible action on the rays of light, 
 which consequently appear white ; but as the sun descends to the horizon, the 
 thickness of the vapour is greatly increased, and at sunset it is calculated that the 
 light of the sun has to pass through two hundred miles of air in illuminating a 
 cloud a mile above the earth. Hence, as the rays fall more and more obliquely on 
 the clouds, they appear successively yellow, orange, and finally red. The varied 
 colours of the sun at sunset are caused by the clouds appearing at different heights 
 and in different parts of the sky, so that various thicknesses are interposed between 
 them and the sun. At dawn the clouds first appear red, but as the sun rises higher 
 the yellow light ceases to be absorbed, and the clouds appear orange, yellow, and 
 finally white. It is evident that a high red dawn may be regarded as prognostic of 
 settled weather, because the redness seen in clouds at a great height, while the sun 
 is yet below the horizon, may be occasioned by the great thickness of the vapour 
 screen through which the illuminating rays must pass before reaching the clouds, 
 and not to any excess of vapour in the air itself. But if the clouds be red and 
 lowering in the morning, it may be accepted as a sign of rain, since the thickness 
 (Page 323) traversed by the illuminating rays being now much less the colour must 
 arise from an unusual amount of vapour in the vesicular sta.te and in the state in- 
 termediate between the vesicular and the gaseous, when the yellow and red rays 
 (Page 325) pass. The time of diminution of atmospheric polarisation occurs in the 
 earlier part of the day, when vapour is carried by the ascending currents into the 
 higher regions of the atmosphere by which the cumulus cloud is formed, and no 
 doubt higher up invisible crystals are deposited similar to those of the cirrus ; and 
 the period of increase occurs towards evening when the temperature of the lower 
 (Page 326) stratum of air is falling, and the ascending currents having ceased, the 
 cumulus clouds are dissolving and the quantity of invisible crystals likewise di- 
 minishing. Thus the maximum of polarisation occurs at that time of the day when 
 the air is least encumbered with the invisible crystals of ice and the minimum when 
 the crystals are in greatest abundance. From the above results, especially those 
 showing the influence of the different state of the aqueous vapour of the air on its 
 polarisation, we see the importance of this property of the atmosphere as a branch 
 of meteorology ; when the subject has been more widely observed and the law of 
 its modification by the presence of aqueous vapour is more accurately known, it is 
 probable that the knowledge may be turned to excellent practical account, in giving 
 the earliest indication of the commencement of the saturation of the air in the 
 upper regions, and inferentially of the approach of storm and of the rainy season 
 (Page 331) within the tropics. If, after an unusual prevalence of S.W. wind, the 
 N.E. wind should set in, it is probable that easterly winds will prevail. If the season 
 be summer, the weather will become dry, warm, and bracing, particularly if the 
 (Page 332) wind be E. or S.S.E. If easterly winds preponderate largely above 
 the average in spring, the summer is likely to be characterized by S. W. winds 
 with much rain and moisture ; but if easterly winds nearly fail in spring they are 
 likely to prevail in summer, bringing in their train dry, warm, bracing weather, 
 clear skies, and brilliant sunshine. Sir John Herschel, in his ' Familiar Letters,' 
 368 
 
AQUEOUS VAPOUR 1868. Buchan. NOTES. 
 
 states that the moon has a tendency to clear the sky of cloud and to produce not 
 only a serene but a calm night when so near the full, as to appear round to the eye, 
 William Ellis examined the records at Greenwich from 1841 to 1847, and shows, 
 that such a striking effect does not exist. The popular opinion probably arises 
 (Page 333) from the circumstance that the clearing of the sky near the time of full 
 moon arrests the attention, whereas the clearing of the sky when the moon is not 
 present is less likely to be noticed. Park Harrison has shown that shortly after 
 full moon there is a tendency to dispersion of cloud, which though not very marked 
 is yet very appreciable. Dr. Arthur! Mitchell, in his ' Prognostics,' states that the 
 farmers of Berwickshire say that when a long strip of cloud they call a salmon or 
 Noah's Ark stretches in an E. and W. direction it is a sign of stormy weather, 
 when in a N. and S . direction it is a sign of dry weather, or, as a weather saw 
 has it 
 
 ' North and south the sign o' drought, 
 East and west the sign o' blast.' 
 
 When the cirrus cloud stretches from north to south, or more correctly from 
 N.W. to S.E., atmospheric pressure is at the time, at least, in regions immedi- 
 ately surrounding Great Britain at the normal height, and there being thus 
 no disturbance indicated, drought or settled weather may be looked for as the 
 barometric pressure in Europe is about the average. But when the cirrus stretches 
 in bands lying E. or W., or from S.W. to N.W., there is great atmospheric; 
 disturbance indicated pointing to a system of low pressure somewhere to the 
 W. or S.W., from which a column of moist air is ascending and flowing as an 
 upper current over Great Britain, and from experience we know that this current 
 will ultimately prevail lower down, saturating the air as it descends in preparation 
 for the storm which is advancing. The pocky cloud described by Dr. Clouston is 
 stated to be followed invariably by a storm in about twenty-four hours. Its lower 
 edge must be well denned, for a similar cloud with the lower edge of the festoons 
 shaded away is followed by rain only. This cloud is probably caused by large- 
 volumes of saturated air forcing their way through drier and colder air, the form of 
 this cloud suggesting moist air diffusing itself horizontally or from above, just as the 
 formation of the cumulus indicates diffusion upwards. If this supposition be correct 
 it shows the moist warm current to be of greater strength than usual, and a sudden 
 commingling of air currents, differing widely in temperature and degree of satu- 
 ration. 
 
 Buchan, A. Jovrn. Scot. Meteorol. Soc., vol. ii. (1869), No. for October 1868 (rvp). 
 (Page 208. ) Of the causes which render the atmosphere specifically lighter, and 
 therefore lower the readings of the barometer, may be stated an excess of vapour 
 over a restricted region, or the withdrawal of vapour from the atmosphere where it 
 is condensed into rain or snow. Observation indicates that the greatest quantity of 
 vapour at any place occurs immediately in front of a storm, the amount increasing 
 as the barometer falls ; and that immediately after the storm has passed, or as soon 
 as the rear of the storm begins to advance over a place, the quantity of vapour 
 rapidly, and in some cases suddenly, diminishes. Now since air when it contains a 
 (Page 209) considerable amount of vapour is specifically lighter than air which 
 contains less, there is presented in the front part of storms, as compared with 
 what prevails in contiguous regions, a disturbing cause, which, by making the whole 
 mass of air lighter, necessitates an ascending current. Charts show that in storms the 
 centre of the clouded and rainy region approximately corresponds with the space 
 of least pressure, or to state it more accurately, it lies a little to the east of the place 
 where barometers are lowest. When vapour is condensed into drops which fall as 
 rain or snow, its pressure is withdrawn from the air ; and, for a time, a diminution^ 
 
 369 
 
AQUEOUS VAPOUR 1868. Mann. NOTES- 
 
 of pressure proportional to the amount of vapour abstracted is the consequence. 
 But in the act of condensation latent heat is given out, which, by passing into the 
 surrounding air, maintains a higher temperature in the ascending currents than 
 could otherwise hold good. Thus the tendency of cloud and rain is to lower the 
 (Page 200) barometer, and so bring about the disturbance of the atmosphere which 
 we see prevailing everywhere in storms. 
 
 F. R. H. Symom's Meteor ol. Mag., vol. iii. (?vp.) 
 
 (Page 102.) While we were in Abyssinia February, March, April, and May 
 the sky was invariably clear from dawn to noon ; but at some time during the after- 
 noon, in the later part of the season, clouds appeared in the sky, and this occurred 
 with a most remarkable punctuality. It was evident to us that at the same place 
 the phenomenon would occur day after day at the same time within an hour or so. 
 There was often mist at dawn, but this mist was soon dispelled by the sun, and only 
 precipitated at all on three occasions. This would be merely a local accident, and 
 may be neglected. But the daily punctuality of the gathering clouds from which 
 we often got a hail or rain shower could not pass unnoticed. This was no peculiarity 
 of the year we were there, for mention of rain frequently occurs in the statements of 
 travellers over the same ground at the same time of the year, and almost invariably 
 towards the end of the day's march, which would naturally be between 3 and 6 P-M. 
 While we were along the Eastern Highland I believe the wind was constant from 
 E.N.E., or N.W., although it was often deflected by the hills and valleys. 
 This being the case, of course it brought with it from the lowlands, or perhaps 
 even from the sea, vapour, which would be precipitated on striking against the lofty 
 mountains. Hence the punctuality and also the reason of rain not falling in the 
 morning. For during the night the evaporation would not take place in any con- 
 siderable quantity. Perhaps it would be possible to calculate from whence the 
 major part of the vapour came by noting the speed of the wind and the time of the 
 arrival of the vapour which formed cloud on striking the mountain tops. 
 
 Gritton, F. B. Symons's Meteorol. Mag., vol. iii. (rsp.) 
 
 (Page 106.) Sir J. Herschel, in Good Words for 1864, says that a clear sky and 
 a serenity of weather at night are the usual accompaniments of the period of full 
 moon, a tendency of which we have assured ourselves by long-continued and 
 registered observations. (Editorial. Ellis finds from observations made every two 
 hours day and night at Greenwich during seven years, 1841-47, that Herschel's 
 theory is unsupported. Arago says, ' La lune mange les miages,' and our sailors 
 say, ' The full moon eats up the clouds." 
 
 Luck, Richard. Symons's Meteorol. Mag., vol. iii. (rsp.) 
 
 (Page 106.) I have noticed in North Wales that before a coming gale of wind the 
 light clouds are, especially soon after sunrise, brilliantly illuminated with gorgeous 
 orange colour. What is the connection between them '? 
 Lyell, Sir C. (B. 1868, 5.) 
 
 (Page 496.) Peat only grows in moist places having a sufficiently low temperature. 
 Mann, R. J. Journ. Roy. Geog. Soc., vol. xxxvii. (1868) (rs). 
 
 (Page 57.) The summer in Natal is a season of very frequent cloud. The sum- 
 mer heat is tempered by cloud screens and constant evaporation. The winter is a 
 season of almost constant sunshine. At the Cape of Good Hope the summer is dry 
 (Page 58) and the winter wet. Almost every day in summer gets cloudy soon after noon, 
 and the clouds continue to shroud the sky and screen the ground until far into the 
 
 370 
 
AQUEOUS VAPOUR 1868. Strachan. NOTES. 
 
 night, when the sky clears. The mean humidity at Maritzburg at 9 A.M., based on 
 (Page 63) eight years' observations, was 71'2 ; at 3 P.M., 60'1 ; and at 9 P.M., 8'34 ; 
 mean for the year 70'8. 
 
 Raimondi, Ant. Journ, Roy. Geog. Soc., vol. xxxvii. (1868) (rs). 
 
 (Page 121.) The town of Ayapata in Peru is subject to neblina, or mist, generally 
 towards the evening. It is so dense that objects are not to be distinguished a few 
 paces off. Nearly all the towns situated on the eastern slope of the great chain, and 
 "between 8,000 and 12,000 feet above the sea, have this visitation of the neblinas. 
 The phenomenon is owing to the currents of air being in one direction during the 
 day and in another during the night. In the morning the elevated portions are free 
 from mist, but the lower and hot parts are then filled with a dense stratum o 
 vapours. The elevated portions of land being at these hours first exposed to the 
 sun are heated, and a current of air from the lower and hot parts is thereby caused, 
 and the vapours are carried from below upwards, and are dissolved in the higher 
 regions owing to the sun having heated them. In the evening the atmosphere 
 (Page 122) becomes cold, and the vapours are condensed to form the neblinas. At 
 night a down current is set up by the cooling of the lower regions, the mists fall as 
 water, leaving the air clear. 
 
 Strachan, R. (B. 1868, 11.) 
 
 (Page 18.) The forecasting of cloudy, overcast, or clear sky must be rather a 
 matter of shrewd guessing than an application of any definite rules. 
 
 Symons's MeteoroL Mag., vol. iii. (rsp.) 
 
 (Page 111.) The observer at Derby remarks on the absence of dew at that place 
 during July arising from the dryness of the air, hot nights, and bleached condition 
 of the grass (colour being an element in its formation). 
 
 (Page 118.) Fournet, in ' Commission Hydrometrique et des Orages,' 1866, notices 
 that during stormy weather the S.W. winds arrive in the Rhone department 
 almost saturated with vapour, which at times produce detached clouds around the 
 mountain tops ; at others banks of clouds, whose thickness varies, according to the 
 intensity of the operating causes. In either case, owing to the currents of air, these 
 clouds are so elongated that they may for distinction be called ' storm columns,' 
 from their resemblance to columns of troops. Sometimes it happens that these 
 bands are dissolved in passing from the mountains above the plains, while if the 
 atmosphere is nearly saturated the elongation becomes considerable, and as our 
 (Page 119) mountain tops are close together the celestial vault is carpeted 
 with these columns, which remain parallel among themselves in a S.W. N.E. 
 direction ; lastly, if they are in a state of saturation, the vapour is condensed all 
 along the bands ; then also a very large dense and low stratus is formed, rain falls 
 throughout, but traces of the column arrangement remain. Occasionally bands 
 are formed from N. to S., when prolonged thunderstorms reign amid the peaks 
 of our western mountains. Sometimes the phenomenon is confined to the S., 
 sometimes to the N., and sometimes one or two bands alone are formed. Among 
 the many interesting phenomena connected with these columns motion is but one ; 
 the unequal distribution of wind force, of lightning, and of vapour often appearing 
 at intervals like waves, fully merit the notice of meteorologists. 
 
 (Page 194.) C. Meldrum, in his ' Meteorology of Port Louis,' in the Mauritius, 
 notices that the curve of elastic force of vapour harmonizes exactly with that of 
 temperature. The air is driest (63 '6) at 1 A.M., and most humid about 3 P.M. (69'9). 
 During seven years the air was never saturated, the nearest approach being 967 on 
 August 21st, 1860. He refers to A the double maximum and minimum of atmo- 
 spheric pressure and to Dove's explanation. But he finds that at Mauritius the 
 
 371 
 
AQUEOUS VAPOUR 1869. Bnimham. NOTES. 
 
 pressure (exclusive of the assumed vapour pressure) has a progression similar in all 
 respects to that of the total pressure. Therefore, the phenomenon in question 
 cannot be accounted for by the direct action of the vapour pressure . The nights 
 (Page 195) and mornings are comparatively cloudless ; towards 10 A.M. the clouds 
 gather ; by 2 P.M. it is often wholly overcast, and in the. evening clear again. The 
 mean amount of cloud is 4 "7. 
 
 1869. 
 Brumham, G. D. Symons's Meteorol. Mag., vol. iv. (rsp.) 
 
 (Page 56.) The position of the moon in the equator with regard to our [British] 
 meridian has an important influence on drought. The rules are : 1. When on any 
 day between the middle of March and the middle of September the moon reaches 
 perigee or apogee in the afternoon within about an hour (say seventy minutes) of 
 the time she comes to our meridian (and here I may say that the southing must 
 occur in the afternoon, or at any rate at not more than twenty minutes after mid- 
 night) a long period of deficient rainfall will occur about that time or set in a few 
 days afterwards. 2. In any year when lunar perigee occurs entirely or very frequently 
 (Page 59) in south declination, if the moon crosses the equator on some day between 
 March and October, within fifteen minutes of her southing, a long period of drought 
 will set in (if it has not already commenced) shortly after the day when these latter 
 phenomena occur. [A table is given of all the instances which have occurred of 
 these two laws since 1833, with descriptions of the weather which was associated 
 with them in South-east England.] When the sun reaches perigee within forty 
 minutes of noon or midnight, the succeeding summer has always several months of 
 very dry weather, and the rainfall of the period from March to September inclusive 
 is always below the average. [All the instances which have occurred since 1833 are 
 given.] The foregoing rules appear to be very infallible. 
 
 (Page 59.) According to the law, fine weather for harvest should set in soon 
 after August 9th, and be dry for a long period. There should also be a month of 
 deficient rainfall in the latter part of May. 
 
 [These notes, of course, refer to rainfall, but as they indirectly indicate dryness 
 of the air they are entered here.] 
 
 (Page 88.) I did not regard the slight deficiency of rainfall noticed by Mr. Ryves 
 as evidence of drought. There may be drought with an average rainfall, as by 
 drought is meant a number of days in succession without rain. My rules refer to 
 (Page 89) my district, and are correct for it. I do not know how other districts 
 may be affected by them. 
 
 (Page 107.) I should have mentioned that in 1868 lunar perigee occurred in our 
 meridian on March 5th. This may have inclined the weather to drought. 
 
 (Page 108.) There are other causes of great drought, such as great heat. The 
 principle of uniformity with regard to the moon's positions near the equator (in 
 December, January, April, or May) appears to cause a high summer temperature, 
 and in that way to influence the rainfall. For instance, on April 20th, 1868, the 
 mocn at midnight was 045' north of the equator, and on May 3rd she was 46' south 
 of the equator at the same time. The period of great heat and drought which set 
 in about the end of April appears to have been caused by this uniformity. The 
 instances that have occurred since 1766 are rare, but in every case great heat and 
 drought accompanied the lunar phenomena. 1788, 1800, 1807-8, 1818, 1826, 1842, 
 1859, and 1868 were the only years in which this particular lunar uniformity 
 occurred, and each year gave us a summer of. great heat and drought. In 1846, 
 1857, 1859, and 1868 another kind of lunar uniformity occurred, and these years also 
 gave us intense heat and much dry weather. 
 
 372 
 
AQUEOUS VAPOUR 1869. Stewart. NOTES. 
 
 Buchan, A. Journ. Scot. MeteoroL Soc., vol. ii. (1869), No. xxiv., October 1869 (rvp). 
 (Page 342. ) In Scotland the monthly curve of lightning without thunder roughly 
 (Page 343) follows the curve of relative humidity. 
 
 Griffith, C. H. Symons's MeteoroL Mag., vol. iv. (rsp.) 
 
 (Page 40.) Which is the correct way of computing mean daily humidity? By 
 using Glaisher's tables at low temperatures I sometimes get a much greater mean 
 temperature of the wet bulb than of the dry. Thus on October 24th I had 
 
 9 A.M. 3 P.M. 
 
 Dry Bulb. Wet Bulb. Dry Bulb. Wet Bulb. Max. Min. 
 
 45 -<; 45 55-4 55-3 60'2 38'4 
 
 Sum. 2)98-6 
 
 Mean 41F3 
 
 Corr". from Table 0-9 
 
 48'4 mean from max. and min. 
 Dry Bulb. Wet Bulb. 
 
 9 A.M. 3 P.M. 9 A.M. 3 P.M. 
 
 45-6 55-4 45-0 55'3 
 
 Corr n .fromTableIII.JV2 7-4 0-8 3-9 
 
 45-4 48-0 44^2 51'4 
 
 2)93-4 2)95^ 
 
 4(>-7 mean from dry bulb. 47'8 mean from wet bulb. 
 
 Home, D. Milne. Journ. Scot. MeteoroL Soc., vol. ii. (1869), No. xxiii., July 1869 (rvp). 
 
 (Page 313.) Baddeley says when whirlwinds are running about white patches of 
 cirro-cumulus are frequently seen in the clear blue sky exactly resembling flakes of 
 teasled cotton, having rotatory motions throughout, forming and then rapidly dis- 
 solving, or ascending with whirling motions in the upper regions. 
 
 Kesteven, W. B. Symons's MeteoroL Mag., vol. iv. (rsp.) 
 
 (Page 179.) The dry bulb is generally from '5 to 1'5 too low, owing to evapora- 
 tion of moisture condensed on it from a very moist air. 
 
 Ryves, Gr. T. Symons's MeteoroL Mag., vol. iv. (rsp.) 
 
 (Page 67.) Mr. Brumham's rules do not seem to be infallible. He regards '03 
 in. ['3 in. Ed.] deficiency of rain as evidence of drought ; and this rule should, but 
 does not, apply to all places in the same meridian. In the summer of 1868 it was 
 dry here, but in South Europe it was exceptionally wet and cold. At Rome we find 
 June and July were wet and cold ; August and September scarcely warm ; Novem- 
 ber and December wet, cold, and foggy. The difference of meridian from Greenwich 
 is not more than fifty minutes. Hence the moon was within fifty-five minutes of its 
 southing at Rome, and the case was fairly within Mr. Brumham's rule. Scotland 
 has the same meridian as England, yet we sometimes have extreme wet there, while 
 South England is exceptionally dry. 
 
 Stewart, Balfour. Symons's MeteoroL Mag., vol. iv. (rsp.) 
 
 (Page 153.) The amount of vapour present in the air affects the skin of the 
 human body and the leaves of plants ; but I am not aware that it has yet been 
 determined by the joint action of naturalists and meteorologists what is the precise 
 physical function which expresses proportionately the effect of moisture upon animal 
 and vegetable life. Is it simply relative humidity ? or does not a given relative 
 humidity at a high temperature have a different effect from that which it has when 
 the temperature is low ? I will, however, here consider the matter from the physical 
 science point of view. As such it is one of our objects to ascertain the distribution 
 
 c c 373 
 
AQUEOUS VAPOUR 1869. Symons. NOTES. 
 
 and laws of motion of the dry and wet components of our atmosphere ; and it can- 
 not be denied that at the present moment we are in very great ignorance of these 
 laws. As we cannot trace the motions of individual particles of air, or vapour, we 
 must arrive at it indirectly, by frequently ascertaining the amount present at any 
 one station at any moment. The best way of measuring the amount is the mass of 
 vapour present in a cubic foot of air. With regard to the motion of the atmosphere, 
 and of the -vapour, we can gauge the mass of air and the mass of vapour passing a 
 station horizontally. We have no means of getting at the vertical motion, and we 
 (Page 154) must detect this indirectly. We ought also to determine the production 
 or consumption of the vaporous element of our atmosphere as it passes from place 
 to place. This might be done could we keep an accurate account of the evaporation 
 and the precipitation ; but this would be a very difficult operation. To recapitulate 
 we can now determine 1. The mass of vapour actually present at a station from 
 hour to hour. 2. The mass that passes a station in one hour going east and west. 
 3. The same going south and north. There are wanting 4. The vertical compo- 
 nent of the motion of vapour. 5. Its production or consumption as it passes from 
 place to place. These deficiencies maybe, to some extent, overcome by the following 
 considerations. First, the atmosphere moves as a whole when it moves, the dry and 
 moist air moving together ; secondly, dry air is neither capable of production nor of 
 consumption, but always remains constant in amount. To illustrate this part of 
 the subject, let it be supposed we wish to investigate the vertical motion of the 
 atmosphere at a certain station. Make this station the imaginary centre of a circle, 
 the circumference of which may be supposed to be studded with other stations at 
 sufficiently frequent intervals so that we can tell hour by hour how much dry air passes 
 in towards the centre, and how much passes out away from it. Suppose more air 
 passes in than passes out. But if we find a diminution in the stock of air at the 
 centre, some must pass upwards and carry the vapour with it. Now as to the 
 vapour. The hygrometric quality oj: the air may be represented by 
 
 Mass of vapour in a cubic foot. 
 Mass of dry air in a cubic foot. 
 
 This quotient can only alter by evaporation, or by precipitation, or by mixture. 
 The hygrometric quality of the air may perhaps be considered as a quality suffi- 
 ciently constant to aid us in tracing the actual motion of the air. But besides 
 this aid we may make use of it to enable us to tell the precipitation or evaporation. 
 For instance, a very damp air in passing over a very dry country may be supposed 
 to emerge less damp, having its hygrometric quality changed, and so with regard 
 to dry air traversing a damp country, the change being in the opposite direction. 
 Thus by actual observation of the quality of the air at the time of its reaching some 
 particular tract of land or ocean, and at the time of its leaving it, we may possibly 
 get much better observations of what goes on in the country, as far as this particular 
 (Page 155) research is concerned, than if it were studded with gauges. Meldrum 
 suggests that summaries should be given of the aggregate wind in definite directions, 
 and Airy suggested that the phenomena could be best studied when the wind was 
 constant in the same direction for a long period. 
 
 Stow, F. W. Symons's Meteorol. Mag., vol. iv. (rsp.) 
 
 (Page 85.) The drought in 1868 began in April, and wet weather set in on 
 August 6th. But Mr. Brumham claims it was dependent on the position of the moon 
 on July 20th. This is like putting the cart before the horse. 
 
 Symons, G. J., and R. Field. Symons's Meteorol. Mag., vol. iv. (rap.) 
 (Page 132.) They notice the variable results given by the observers of evapora- 
 tion, 11 in. in one case, and 48 in. in another, for the same year ; and they 
 374 
 
AQUEOUS VAPOUR 1870. Ansted. NOTES. 
 
 condemn the method proposed by Daniell. The chief source of error is the ab- 
 normal heating of the water in the evaporators. They made a series of experiments 
 on the canal of Burgundy in large tanks, and found the amount to be half that 
 generally assumed. More reliable instruments are necessary. 
 
 Symons's Meteorol. May., vol. iv. (rsp.) 
 
 (Page 65.) Would it not be an advantage if a few observers would concentrate 
 their attention on the character of the sky as indicative of weather ? Clouds should 
 (Page 66) be methodically observed and the observations reduced to a tabular form, 
 as for instance, thus : On left-hand page of a foolscap-sized book rule 16 columns 
 for 1, date ; 2, hour ; 3, temperature ; 4, barometer ; 5, wind direction ; 6, wind 
 force ; 7, rain ; 8, amount of cloud ; 9, forms of cloud ; a, cirrus ; 6, cirro-cumulus ; 
 c, cirro-stratus ; d, cumulus ; e, cumulo-stratus ;/, stratus ; g, nimbus ; h, scud. The 
 (Page 84) proportion of sky occupied might be given as nearly as can be estimated. 
 The colour of the sky is modified by the combination of three tints viz., the blue, 
 which is reflected by the particles of air ; the black of space ; and the white of the 
 vesicles of fog and flakes of snow. The blue rays are darkened by the one, and 
 lightened by the white of the vesicles of fog. When we ascend in the atmosphere 
 we leave a great portion of the vesicles of vapour beneath us, so that while the 
 rays reach the eye in less proportion, and the sky being covered with a lesser number 
 of particles reflecting its light, the colour becomes of a deeper blue. For the same 
 reason the blueness of the horizon is less intense than at the zenith. If the sky is 
 paler in the open sea and in high latitudes than in the interior of the continents 
 and in the neighbourhood of the equator, it must be attributed to the vesicles 
 of fog. 
 
 Wild, H. (B. 1869, 12.) 
 
 (Page 294.) When objects in the distance are obscure and hazy, it is regarded as 
 a sign of fine weather, but when they come out unusually distinct it is considered to 
 be a sign of approaching rain. De la Rive's explanation is that the air is rendered 
 opaque by the presence of dust and vegetable germs. When the S.W. winds blow 
 the air becomes moist, the corpuscles absorb moisture, and being rendered heavier, 
 fall to the ground, leaving the air more than usually transparent. Marshal Yaillant 
 explains the difference by the greater or less prevalence of vertical air currents. 
 
 1870. 
 Ansted, D. T. Physical Geography, 4th Ed., 1870. 
 
 (Page 59.) Area of water is 145 million of square miles. Water area north of 
 (Page 61) the equator equals 59 millions of square miles ; south of the equator, 
 (Page 150) 86 millions of square miles. The excess of evaporation above rainfall is 
 (Page 238) directly or indirectly one of the most important causes of oceanic cur- 
 rents. The sun's heat reflected from the shining moon is absorbed by our atmo- 
 sphere before it reaches the earth, and thus tends to disperse cloud, and produce 
 (Page 271) coolness on the earth by allowing of increased radiation. When rain 
 has recently fallen, it is often curious in mountain countries to watch the incessant 
 and rapid formation of cloud over some small wooded patch of land, the moisture 
 from the warm earth steaming into the chilled air, and being immediately con- 
 verted into mist, which gradually accumulates until it breaks away and drifts to a 
 distance, assuming a distinct cloud nature. It is equally curious to observe a nar- 
 row side valley in a mountain district, covered for hours together with mist and 
 rolling cloud, while the larger and more open valley into which it opens has a per- 
 fectly clear sky. The cause of this is obvious. The lateral valley, enjoying less of 
 the sun's rays, is colder than the more open valley adjacent ; the air as it passes la 
 
 375 
 
AQUEOUS VAPOUR 1870. Ansted. NOTES. 
 
 therefore sucked up the side valley, and coming into the cooler temperature of its 
 sides is at once condensed into mist. Such mist may often turn, into cloud. The 
 clouds below 10,000 feet are more massive than those above, and are more influenced 
 (Page 272) by local causes. The quantity of' vapour existing in the air in an in- 
 visible form depends on local temperature, and is probably at no time uniform 
 over any considerable area, and certainly never the same for twelve hours together 
 in the same place. It is found that when the temperature is 50 F. each cubic yard 
 of dry air (about 168 gallons) can hold nearly 150 grains of water ; at 32 F. 
 (Page 273) only half this ; and at 70 F. nearly double. Condensed vapour has a 
 tendency to assume the form of the object by which it is caused. Thus, when 
 mountains are present, a cloud seems to fix itself at the summit or on the sides of 
 the mountain at a certain level, and there obstinately remain, as on Table Mountain 
 and Mount Pilate. The warm wind loaded with moisture is chilled. The chill 
 commences a short distance to windward of the object, and continues at a distance 
 to the leeward of it, until the air is no longer affected by the cool surface it has 
 (Page 274) been in contact with for a time. The cloud is a driving mist. At the 
 equator Humboldt observed the general direction of cirrus clouds to be N. and S. 
 (Page 279), but with us they seem more frequently N.W. and S.E. Clouds neither 
 float in the air like boats, nor are they retained only for a short time, like feathers, 
 by friction and resistance ; nor do the particles of water in a cloud consist of hollow 
 spheres with void cavities or with their interior filled with light gas. Neither is 
 the water cloud like the cloud of incense that rises and for a time floats in air while 
 disseminating its fragrance. The permanence of clouds is due to the vapour at- 
 mosphere being independent, and to the gases diffusing into each other, so that the 
 (Page 280) heavier gases are held up by the lighter. The vapour may be set free 
 without assuming a fluid form. It is possible that clouds are limited to air in 
 motion, for it is quite certain that a cloud may appear in repose, even when violent 
 and shifting winds are all around. The conversion of what may be called a dry 
 cloud into a mist seems to be accompanied in all cases with electrical action. Owing 
 (Page 285) to the unequal distribution of land in the two hemispheres, the aqueous 
 vapour, which from the autumnal to the vernal equinox is developed to an im- 
 mense extent in the southern hemisphere, returns to the earth in the other half of the 
 year in the form of rain and snow. Immense physical force is exerted in the evapo- 
 ration of water from the ocean. The total estimated rainfall is not much less than 
 200 millions of millions of tons. Hence about 7000 Ib. weight of water are 
 (Page 286) evaporated every minute, on an average, throughout the air from each 
 square mile of ocean. The conversion of this into vapour, its conveyance through 
 the air, and its recondensation involves an expenditure of force equivalent to the 
 lifting of very much more than 1,500,000 millions of millions of pounds of water, 
 one foot high per minute of time during the whole period. Besides evaporation 
 from the sea, there is also a very large evaporation from the surface of the land. 
 This is a fraction of the real amount of force exerted, for much of the water raised 
 by eTaporation falls back as rain directly into the ocean. It is a work going on in- 
 cessantly, and one that has probably been going on at nearly the same rate during 
 (Page 302) all time. By the drainage of land and the removal of forests, the 
 conditions of a country are so far altered with respect to its rainfall and the moisture 
 (Page 306) of the air, that the temperature becomes permanently affected. Cirrus 
 clouds are often the first signs of coming wind and change of weather. In summer 
 (Page 307) they announce rain, in winter thaw. When the round heaped clouds 
 appear early in the morning they often gradually disappear as the day advances, 
 and after noon the sky is clear ; but when they come on after noon and increase 
 towards evening, they generally terminate in rain. Among signs of fine weather, 
 an early and heavy dew has often been noticed. 
 376 
 
AQUEOUS VAPOUR 1870. Bidie. NOTES. 
 
 Bidie, George. Journ. Roy. Geoff. Soc., vol. xxxix. (1870). Paper read January 25th, 
 
 1869 (rsp). 
 
 (Page 78.) In the shade of the dense jungle forest of Coorg there is a 
 dense undergrowth of moisture-loving plants, such as cardamom, canes, areca, 
 plantain, tree and other ferns, wild pepper, arums, and orchids. The rain in 
 (Page 79) Coorg mainly comes from the S.W. monsoon, which is the S.E. trade wind 
 deflected westerly by the diurnal rotation of the earth, and as this passes over 
 an immense expanse of ocean ere it reaches the land, it becomes heavily charged 
 with moisture in its course. The presence or absence of forests can have no appre- 
 ciable influence on the amount of rainfall. At the same time, it must be stated that 
 the natives of Coorg complain that of late years their country has become hotter 
 and drier from want of rain, and that rice crops have been diminished or lost 
 from a failure of water in streams that used to run throughout the year. These 
 changes they attribute to the cutting down of forests on coffee estates. It is 
 (Page 80) only since the advent of the European planters, or during the last twelve 
 years, that felling of forests to any considerable extent has taken place in 
 Coorg, and as the clearing has progressed in annual instalments of comparatively 
 small extent, the results have crept on gradually. There can be no doubt, too, that 
 the evil influences called forth by forest destruction do not attain their full 
 force immediately, but go on increasing from year to year until they acquire a most 
 disastrous power. The spots that have been selected as sites for estates are chiefly 
 situated on the flanks and crests of low hills, the sides and bottoms of ravines, and 
 the slopes and passes running down on the west side of the Ghats to the low country. 
 Such localities are, as a rule, densely wooded, and being well supplied with springs, 
 give rise to numerous small streams. In fact, they may be looked upon as the 
 fountains of the river system of the country. The question then arises, To what 
 extent are springs and streams in such situations dependent on the forests for their 
 supply of water, and what will be the effect on them of its removal ? Springs and 
 small streams are fed by the water stored up in the earth during the rainy season. 
 As the rain descends on natural forests, it is conveyed in various directions by the 
 leaves towards the ground, and on reaching this is prevented from running rapidly 
 off by the dense undergrowth of shrubs and herbaceous plants, and a carpet of dead 
 leaves. Below this it encounters a layer of vegetable mould, which, having a great 
 affinity for moisture, absorbs it like a sponge. As soon as the humus is fully 
 saturated, it passes on what water may subsequently fall to the subjacent earth, and 
 this process of percolation is in various ways aided by roots, which descend to great 
 depths, perforating the densest subsoil, and even forming passages in rock. The 
 quantity of water thus transferred to the depths of the earth and the reservoirs of 
 springs is enormous, and when the dry season arrives the forest again plays an 
 (Page 81) important part by husbanding and giving off gradually the subterranean 
 supplies. As the water rises, it meets with many obstacles, preventing its collecting 
 into streams and passing rapidly away. Although the quantity of water taken 
 up and exhaled by trees is very great, a proportion of it is returned as dew or fog, 
 and what is wafted away is fully compensated for by other advantages resulting from 
 the presence of forest. The influence of shade in modifying evaporation is well 
 illustrated by what happens in the coffee districts after the April showers, which 
 herald the advent of the S.W. monsoon. On an estate freely exposed, a day or two 
 of sunshine after a. heavy fall will have rendered the soil quite dry and hard 
 again, whereas on an estate under forest shade the ground will continue damp for a 
 week or more. Although their insignificance might lead to their being overlooked, 
 there can be no doubt that the mosses, lichens, and succulent herbaceous plants 
 which abound in tropical forests are also of considerable benefit in retaining 
 
 377 
 
AQUEOUS VAPOUR 1870. Bidie. NOTES. 
 
 moisture, as during rain they absorb water like a sponge, and part with it again very 
 slowly. It would, therefore, appear that there are numerous agents and conditions 
 in natural forests favourable to the production and permanence of springs and streams 
 which are not to be found in open ground, originally so or denuded of its trees by 
 man. The facts thus elicited go far to prove that tropical forest is the alma 
 mater of springs and streams. Various instances have been brought to my notice 
 of springs and small streams having become quite dry since the forest was cleared 
 away in their neighbourhood ; while in numerous cases, those that used to be 
 perennial only contain water now during, and for a short period after, the monsoon. 
 Similar results have been found to follow the destruction of forests growing near 
 the sources of streams in all parts of the world. Thus Palestine and other Eastern 
 countries have been rendered desolate by the destruction of the forests that existed 
 in them when they were so famous for their beauty and fertility, and in modern 
 (Page 82) times many districts in France and America have had their water supply 
 diminished, and fertile land converted into arid wastes, by the clearing away 
 of woods around the head waters of streams. In a recent Mauritius paper it 
 was stated that the culture of the sugar-cane had of late become precarious in 
 the island, owing to the excessive dryness of the air and soil consequent on 
 the cutting down of forests. For several years, too, the nutmeg trees of 
 Singapore have been dying. A most graphic account of the disaster will be found 
 in Cameron's ' Malayan India,' and judging from the information there given as to 
 the cutting down of forests to make way for the nutmeg, and the manner in which 
 the trees died, there seems every reason to believe that their death was accelerated, 
 if not entirely induced, by the reduction of humidity resulting from extensive 
 clearing. The effect of forest-clearing and burning of the undergrowth is to make 
 the soil friable and easily removed, so as to leave the barren stony subsoil 
 (Page, 85) exposed. The rainfall drains away rapidly. The plants which 
 spring up in neglected clearings are such as grow in hot, dry situations. 
 Forests reduce the temperature of the air chiefly by transpiration. The 
 amount of water exhaled in this way is enormous, a sunflower having been 
 found to give off from 20 to 30 ozs. daily. Although a tree under certain 
 (Page 86) conditions will absorb moisture from the air, still the amount thus 
 withdrawn is as nothing compared with what it gives off by transpiration. By 
 a beneficent arrangement, too, the amount of exhalation increases within certain 
 limits in exact ratio with the heat and dryness of the air, and thus the severity of 
 the hot season is partially mitigated. Plants in the immediate neighbourhood 
 of forest, even although enjoying no shade, show by the colour and luxuriance 
 of their leaves that they are living in moister earth and air than those 
 at a distance. As regards the soil, it is always very much damper in forests 
 than in open ground. Forests are of "great benefit to cultivated plants in their 
 neighbourhood by promoting the deposition of dew, and causing fog. They also 
 obstruct the passage of drifting fogs, and so make them part with some of 
 their moisture ; and when a dry, scorching wind sweeps over a damp wood it is 
 moistened, and rendered much less hurtful to vegetation. Again, when a 
 cultivated valley lies at the base of a forest-clad hill, the moist stratum of air above 
 the trees rolls down the slope to it in calm nights, covering each leaf and blossom 
 with copious dew. That the cutting down of forests in Coorg has rendered both the 
 earth and air there drier is clearly shown by many plants perishing that used 
 to flourish during the dry season, and by other remarkable changes. The most 
 (Page 87) remarkable change produced by forest obstruction on vegetation has been 
 the increase in species that formerly grew in hot and barren situations in the 
 province. Thus we have in clearings several kinds of ficus, two macarangas, 
 Sponia Wightii (charcoal tree), two solanums, Clerodendron infwtunatiim, Calli- 
 
 OY o 
 
AQUEOUS VAPOUR 1870. Dines. NOTES. 
 
 88) carpa curia, several grasses, etc., all naturally inhabitants of pasture land. 
 At the same time, several moisture-loving plants, such as ferns, aroideae, canes, 
 wild plantain, cardamom, etc. . have become much less common, or have disappeared 
 in various tracts. The Solanum rubrum has become common in some places. 
 Physalis Peruviana, an exotic, has also increased in a wonderful manner, growing 
 spontaneously in clearings all over the country. The plant that has been most 
 influenced by forest destruction is the White Weed, or Ageratum Cordifolium, 
 which pursues the footsteps of the planter wherever he goes, springing up all over 
 {Page 89) his clearings. Forests on the crests or slopes of hills on which important 
 streams arise should always be carefully preserved, and the banks of streams should 
 always, to the distance of twenty or thirty yards on each side, be left under wood, as 
 its presence serves to keep up the water supply in the dry season. The rice lands 
 in Coorg are very peculiar, being long, narrow, winding patches, surrounded by 
 low forest-clad hills, from which they derive their water supply. Forest in the 
 upper end of ravines should also be preserved, as it invariably gives birth to springs 
 and streams. 
 
 Chambers, C. Symons's Meteorol. May., vol. v., November. Paper read to tho British 
 
 Association (rs). 
 
 (Page 168.) Two distinct causes are assigned for the larger quantity of rain in 
 the lower gauges : first, that damp air transferred by the agency of winds from a 
 warm to a cold district, finds the latter region colder, not in the upper strata only, 
 but also in the lower, and in cooling, has its vapours condensed as well in the lower 
 strata as in the higher. Consequently a rain-gauge placed at any given elevation 
 will catch rain, amounting to the sums of the condensations above it, and, there- 
 fore, the lower a gauge is placed the greater will be the quantity of rain it receives. 
 The second cause suggested supposes the particles in the air to be susceptible of 
 electrical induction, and consequently, to be electrically polarized by induction 
 from the ground, which is known to differ in electrical tension at all times from the 
 atmosphere above it. This polarization of the particles of vapour gives rise to 
 mutual attractions between them, and to their successive coalescence forming rain- 
 drops, and the attractions being strongest near the ground the coalescence will 
 there be most rapid. Consequently, not only should more rain be caught by a 
 gauge at a lower elevation than by one at a higher, but the rate of variation with 
 heights of the quantities received should be more rapid near the ground ; and this 
 is in accordance with observation. The second cause also seems to explain the 
 greater fall of rain over forest land ; and also, in part, the greater fall in moun- 
 tainous districts, over land without trees, and over plains. 
 
 Compton, T. A. Symons's Meteorol. Mag., vol. v. (rs.) 
 
 (Page 22.) At Bournemouth, on February 12th, at 2 P.M., the dry bulb stood at 
 27'5 Fah. , and the wet at 23, indicating a humidity percentage of 28. 
 Dines, Gr. Evaporation. Symons's Meteorol. Mag., vol. v. (rs.) 
 
 (Page -70.) As April has been very favourable for evaporation experiments 
 (with a total rainfall of 4 in. on five rainy days), I send you a description of my 
 gauges, with the amount of evaporation from each. No. 1 is 18 in. in diameter, 
 and can be measured to ^ in. It was observed daily every morning. The results 
 
 were as follows : 
 
 No INCHES. No INCHES. No. INCHES. No. INCHES. No. INCHES. 
 
 1 -012 7 -120 13 '140 19 '146 25 '149 
 
 2 -078 8 -117 14 -148 20 '173 26 '168 
 
 3 -042 9 -153 15 "093 21 "211 27 '213 
 
 4 -091 10 -132 16 109 22 '205 28 "120 
 
 5 -090 11 -041 17 '128 23 '251 29 '064 
 
 6 -094 12 -087 18 '165 24 '208 30 '068 
 
 379 
 
AQUEOUS VAPOUR 1870. Poey. NOTES. 
 
 The temperature of the water varied from 32 to 77 Fahr., that of the water in 
 the river Mole from 39 to GO'S . No. 2 is 8 in. in diameter, 6 in. deep, and exposed 
 to the air. The measurements are taken with a vertical float and an attached 
 vernier. No. 3 is 5 in. in diameter, 2 in. deep, and exposed to air. No. 4 is 4 in. 
 in diameter, 2 in. deep, and fixed at the top of the thermometer-stand. The 
 (Page 71) outside is covered with felt to keep the temperature more even. 
 No. 5 is a 5-in. Casella rain-gauge. The total evaporation during the month was 
 respectively 
 
 No INCHES. No. INCHES. No. INCHES. No. INCHES. No. INCHES. 
 
 1 3-816. 2 5-660. 3 6710. 4 6 -370. 5 4'650. 
 
 Nos. 2 and 3 were placed by the side of the 18-in. gauge, about 4 ft. from the 
 ground. No. 5 stands by the side of the other rain-gauges, one foot above ground. 
 In Nos. 1, 2, 3, and 4 the water was generally kept ^-in. below the edge of the 
 vessels. No. 5 was rather lower, or about 1 in. The evaporation from No. 3 was 
 76 per cent, greater than that from No. 1. Had the evaporation during the day 
 only been given, the difference would have been far greater, as whenever the 
 opportunity of observing the gauges twice during the twenty-four hours has 
 occurred, the evaporation from the smaller gauges during the night has been much 
 less than from the larger ones. In 'British Rainfall' 1869, p. 156, it is said 
 that the accuracy of an evaporation is largely dependent on its capabilities of 
 retaining the temperature of the contained water at, as nearly as possible, that of 
 large volumes of water, such as reservoirs, rivers, and ponds, which statement I 
 endorse. One experiment showed this. From water at a temperature of from 90 '7 
 to 85 the evaporation was at the rate of '015 in. per hour ; from water at 62, the 
 temperature of the room, it was '0031 in. per hour. During May the evaporation 
 from my gauges was : 
 
 No. INCHES. No. INCHES. No. INCHES. No. INCHES. No. INCHES. 
 
 1 4-927. 2 5-621. 3 6'542. 4 S'lll. 5 5'340. 
 
 The positions of Nos. 2 and 3 were varied, being sometimes in the earth, and 
 sometimes in water, nearly to the level of the upper rim. The temperature of 
 the water in gauge No. 1 varied from 33 to 84 ; that of the water in the river 
 Mole 46 to 66-8. (See Notes, 1786, Williams, Exp. 2.*) 
 
 Dines, G. (B. 1870, 3.) 
 
 (Page 79.) Paper on evaporation and evaporation-gauges, read before the 
 Meteorological Society of London. His conclusions are : 1. The greatest cause of 
 evaporation is the movement of the air. 2. Whatever tends to increase the 
 temperature of the air increases evaporation, and vice versa. 3. That which tends 
 to lessen the temperature of the dew-point increases evaporation, and vice versa. 
 
 Erskine, St. Vincent W. Journ. Roy. Geog. Soc., vol. xxxix. (1870). Eead June 14th, 
 
 1869 (rs}. 
 
 (Page 245.) On the Bembe the sky was generally clear towards early morning, 
 and until 10 or 11 o'clock ; but after that, bank after bank of clouds would blow 
 up from seaward and completely obscure the sun. 
 
 Fuller, F. Symons's JfcteoroL Mag., vol. v. (rs.) 
 
 (Page 59.) A self -constituted instrument similar to Snell's aneroid hygrometer 
 may be seen at the Charing Cross lift, which is regulated by a thick rope passing 
 along its whole length. The porter in charge will tell you any day what the 
 weather is going to be by the slackness or tightness of the rope. 
 
 Poey, A. (B. 1870, 14.) 
 
 (Page 382.) He says, each country, according to its geographical position, has its 
 380 
 
AQUEOUS VAPOUR 1870. Somerville. NOTES. 
 
 own type of clouds. Here the cirrus predominates, there the cumulus, elsewhere 
 such and such forms, which do not exist in other places. 
 
 Somerville, M. (B. 1870, 17.) 
 
 (Page 218.) The ocean covers three-fourths of the earth's surface. There is 
 three times more land in the north than in the south hemisphere. The superficial 
 extent of the ocean is probably unaltered. The difference in the composition of 
 (Page 223) sea water depends upon local circumstances. Thus the. ocean contains 
 more salt in the south than in the north hemisphere, which is supposed to arise 
 from the S.E. trade-winds blowing over a greater expanse of water than the N.E., 
 and causing a greater evaporation. The sea is heated at its surface by the 
 (Page 229) direct rays of the sun, which produce a strong and rapid evaporation y 
 especially in the tropical seas of the ocean. It is computed that 186,240 cubic 
 miles of water are annually raised from the surface of the globe in the form of 
 vapour, chiefly from the inter-tropical seas. The enormous. quantity of water thus 
 carried off by evaporation in the warm seas disturbs their equilibrium, which is 
 (Page 252) restored by means of the currents. There is probably not a drop of 
 water on the earth's surface that has not been borne on the wings of the wind. 
 (Page 254) Jets of steam of high tension are frequent in volcanic countries. 
 (Page 296) Many salt lakes may be remnants of the ancient ocean left in the 
 depressions of its bed as the waters retired when the continents were raised above 
 its surface. There are more lakes in high than in low latitudes, because evaporation 
 is much greater in low than in high latitudes, and in this respect there is much 
 analogy between the northern plains of the two principal continents. By the 
 (Page 306) constant evaporation of their surface lakes maintain the supply of 
 humidity in the atmosphere so essential to vegetation. The evaporation over the 
 (Page 314) surface of the ocean is so great, that were it not restored, it would 
 (Page 316) depress its level about five feet annually. In consequence of the unbounded 
 extent of the ocean in the south, the air is so mild and moist that a rich vegetation 
 covers the ground, while in the corresponding latitudes in the north the country is 
 barren from the excess of land towards the Polar Ocean, which renders the air dry 
 (Page 319) and cold. [See statement at p. 421.] The aqueous vapour is most 
 abundant in the torrid zone, and, like the heat on which it depends, varies with the 
 latitude, the season of the year, the time of the day, the elevation above the sea, 
 and also with the nature of the soil, the land, and the water. The N.E. trade-wind 
 (Page 323) arises from the south side of the calm belt of Cancer, and a S.W. wind from 
 its north side. They leave the calm belt loaded with vapour, which is precipitated 
 as they pass into a colder zone. These S.W. winds do not obtain that enormous 
 quantity of vapour while crossing the Atlantic, for they probably give by rain as 
 much as they receive by evaporation ; therefore it can only come from the south 
 hemisphere. The S.E. trade -winds carry the moisture evaporated from the great 
 southern ocean to the equator ; there they rise into the higher regions of the 
 atmosphere, and blow as an upper current in the calm belt of Cancer ; and now, 
 being chilled, they sink down and come out from the north side of the calm belt as 
 the rainy S.W. winds of the extra-tropical north hemisphere. The same reasoning 
 (Page 326) applies to the calm belt of Capricorn. The influence of the heated great 
 plains is felt 1,000 miles or more at sea. Thus, though the desert of Gobi and the 
 sun-burned plains of Asia are for the most part north of the latitude of 30, their 
 influence in producing monsoons is felt south of the equator. In like manner the 
 Central American monsoons of the Pacific are caused by the heated plains of Texas 
 and Utah ; those of the Mexican Gulf by the dry lands of New Mexico ; and the 
 monsoons of the Gulf of Guinea by the sandy deserts of Africa. Similarly, also, the 
 heated interior of Australia causes an indraught of air during the time the sun is 
 
 381 
 
AQUEOUS VAPOUR 1870. Somerville. NOTES 
 
 south of the equator, and a N.W. monsoon, caused by the reversal of the S.E. trades 
 (Page 334), brings rain to all the north coast. A thick lurid appearance, with dense 
 (Page 338) masses of cloud on the horizon, is a harbinger of typhoon. There are 
 about twenty-five millions of square miles of sea in the north hemisphere, and nearly 
 seventy-five in the southern ; besides, the zone of the S.E. trade-wind is much 
 greater than the northern, and covers three times as much water, yet the mean 
 annual amount of rain in the northern hemisphere is probably about 37 in., 
 and 26 in. in the southern ; for the vapour from the great reservoirs at 
 the equator and the southern hemisphere is wafted by the S.E. trade-wind 
 in the upper regions of the atmosphere till it comes to the calms of Cancer, 
 where it sinks down and becomes a S. and S.W. surface-wind, and then the 
 condensation begins that feeds all the great rivers of the world. Rains, fogs, etc., 
 are much more frequent and irregular on this side of the equator than on the other. 
 Throughout all the countries in the north hemisphere, where observations have 
 been made on the variations of atmospheric moisture, it appears that the air contains 
 absolutely less vapour in January than in any other month of the year, yet at that 
 (Page 339) time there is the greatest dampness to our sensations ; while in July the 
 air feels driest, although, on account of the heat, evaporation is the greatest. In 
 summer the dew-point is much further below the temperature of the air than in 
 winter, hence the air is drier. When the moisture is abundant and the tension 
 great, which is often the case before rain, the air is very transparent, and distant 
 objects appear nearer, and all their details are more distinctly seen ; from this 
 circumstance, the clearer view of distant mountains and headlands indicates wet 
 (Page 340) weather. Dew is very abundant on the shores of continents, but it is not 
 deposited on small islands in the midst of large seas, because on them the difference 
 between the temperature of the day and night is not sufficiently great. There is 
 (Page 341) very little dew in the interior of continents, except near lakes and rivers. 
 Pogs rarely occur at sea between the parallels of 30 N. and S., that is, over half 
 the globe. The cloud region of the trade winds is from 3,000 to 5,000 feet high, 
 and it is generally higher over the sea than over the land for the same amount of 
 vapour in the wind. In the north temperate zone the cloud region is high over the 
 land and low over the water ; and, as a rule, the further inland, the drier the air 
 (Page 344) and the higher the cloud region. The equatorial belt of calms lies mostly 
 north of the equator in the Atlantic ; in it the winds meet, and, being highly 
 -elastic, they ascend, till, by the cold of the atmosphere, they are condensed into the 
 cloud ring which surrounds the earth and overhangs the belt of calms, but leave 
 the sky clear on both sides. New vapour is continually rising to the under-surface 
 of this cloud ring, is condensed, and falls in constant rains. These rains fall during 
 the day, and morning and evening are free from storms. In the belt of calms, the 
 air, being greatly heated by the vertical rays of the sun, ascends, drawing with it 
 the whole mass of vapour the trade winds have brought with them, and which has 
 been greatly added to by the rapid evaporation from the belt of calms. This 
 vapour is condensed as it rises to the line of junction of the lower and upper trades. 
 In countries between 5 and 10 S. and N. there are two rainy arid two dry seasons ; 
 one which lasts four months, and another which lasts two. Within the tropical belt 
 of calms and rains one period of the year is extremely wet and the other extremely 
 dry, the change occurring at the equinoxes. The monsoon region furnishes another 
 instance of the effect of mountain chains upon the fall of rain. Throughout the 
 whole of that region it is not the sun directly, but the winds, -that regulate the 
 periodical rains. That region extends from the east coast of Africa and Madagascar 
 across the Indian Ocean to the north districts of Australia, and from the tropic of 
 (Page 346) Capricorn to the face of the Himalaya, the interior of China to 
 Corea, and even round the north of Siberia. In the south hemisphere the rainy 
 382 
 
AQUEOUS VAPOUR 1870. Somerville. NOTES. 
 
 season corresponds with the N.W. monsoon, and the dry with the S.E. The 
 extent of country on which rain seldom or never falls is five-and-a-half million of 
 (Page 347) square miles. The prevailing winds are deprived of their vapour by 
 condensation before arriving at the rainless deserts. Between the tropics it rains 
 rarely during the night, and for months together not a drop falls ; while 
 in the temperate regions it often rains in the night, and rain falls at all 
 (Page 352) seasons. The atmosphere, where rarefied, absorbs all the colours of the 
 sun's light, except the blue, which is its true colour. In countries where the 
 air is pure the azure of the sky is deep ; it is still more so at greater elevations, 
 where the density of the air is less, and its colour is most beautiful as it gradually 
 softens the outlines of the mountains into extreme distance, or blends the earth 
 with the sky. When the sun is near the horizon, the atmosphere, on account of its 
 superior density, absorbs the violet and blue, and leaves the yellow and red rays in 
 (Page 353) excess ; that property, together with the refractive power of the aqueous 
 vapour, which is most abundant near the earth's surface, gives the roseate hue to 
 the early morning, and the gold and scarlet tints to the closing day. The blending 
 of these colours with the blue above produces the beautiful vivid green so frequently 
 seen in warm countries. The last reflected rays of the setting sun are red. The 
 (Page 357) electrical state of the air arises from evaporation, condensation, and 
 chemical changes, but the water evaporated must contain matter susceptible of 
 (Page 376) chemical action during evaporation. The greater part of the land is 
 (Page 381) clothed with vegetation. The periodical phenomena of the appearance 
 of the first leaves, the flowering, the ripening of the fruit, and the fall of the leaf, 
 depend upon the annual and diurnal changes of temperature and moisture, 
 and succeed each other with so much harmony and regularity that, were 
 there a sufficient number of observations, lines might be drawn on a globe 
 approximately indicating lines where the leaves of certain plants appear 
 simultaneously, and illustrating the other phase of vegetation. The gentianella, 
 veronica, and other plants close their blossoms on the approach of rain. Since 
 (Page 383) the constitution of the atmosphere is very much the same everywhere, 
 vegetation depends principally on the sun's light, moisture, and the mean annual 
 temperature or heat of summer. Where rain does not fall the soil is unfruitful, 
 but where moisture is combined with heat and light, the luxuriance of the vegetation 
 (Page 389) is beyond description. Mosses are found everywhere in damp situations. 
 (Page 393) The labiates are remarkable for their aromatic qualities and love of dry 
 (Page 421) situations. Beyond Kerguelen Land and Terra del Fuego not a lichen 
 covers the rocks. In the Arctic regions no land has been discovered destitute of 
 (Page 426) vegetable life. Rice requires excessive moisture, and a temperature of 
 (Page 436) 73'4. Each soil has its own kind of insects, whether dry or moist, etc. 
 As the rainy and dry seasons within the tropics correspond to our summers and 
 winters, insects appear there after the rains, and vanish during the hot months ; the 
 rain, if too violent, destroys them ; and in countries where that occurs there are 
 two periods in the year in which they are most abundant, one before and one after 
 the rains. Culex pipiens passes two-thirds of its existence in water. They swarm 
 (Page 460) in the Arctic regions. In hot countries reptiles fall into a state of torpor 
 (Page 461) during the dry season. Batrachians are aquatic in their early stage. 
 (Page 462) Frogs are amphibious. Toads frequent marshy, damp places. Newts 
 (Page 463) are aquatic. In sterile, open countries the proportion of venomous 
 snakes is greater than in those that are covered with vegetation. All the crocodiles 
 (Page 466) are amphibious, living in rivers or in their estuaries. Alligators are 
 (Page 489) most numerous in the estuaries of great rivers. Monkeys chiefly occur 
 (Page 494) in tropical forests. . The jerboa burrows in sandy deserts. By converting 
 (Page 526) the desert into a garden, draining marshes, cutting canals, turning the 
 
 383 
 
AQUEOUS VAPOUR 1870. Strachan. NOTES. 
 
 courses of rivers, clearing away forests in one place and planting them in others, 
 man has altered the climate, and increased or diminished the quantity of rain. 
 Man's influence on vegetation has been immense, and it is chiefly through his 
 tendency to cut down forest trees that he has produced the greatest amount of 
 change on the surface of the earth. In warm countries, districts which have no 
 clothing of trees, the rainfall descends in sudden deluges, and the dry seasons are 
 excessively prolonged. Thus the violent rain-wash prevents the accumulation of 
 humus, and the surface of the earth is scorched to sterility by months of fierce sun. 
 Stow, Eev. F. W. Symons's Meteorol. May., vol. v. (rs.) 
 
 (Page 180.) The air is generally saturated most of the day during a sea fog here, 
 whatever Dr. Allnatt may say to the contrary. [No place is mentioned, but it is 
 probably near Whitby.] 
 
 Strachan, R. Symons's Meteorol. Mag., vol. v. (rs.) 
 
 (Page 73.) Lament's evaporimeter consists of two bowls connected by a glass tube ; 
 one is covered, the other exposed to the air. The tube rests on a scale of 25 in. ; 
 it contains an air bubble, which moves along the scale as the water is evaporated 
 from the open vessel. 
 
 Symons's Meteorol. Mag., vol. v. (i~s. ) 
 
 (Page 2.) Snell's aneroid hygrometer is made by a private gentleman at Saltash. 
 It is made of a piece of whipcord, dipped in some solution (salt and water), fastened 
 so as to act on an axle, and kept stretched by a lead weight. W. B. Kesteven 
 tested it. He reports that it is extremely sensitive to the slightest change of 
 atmospheric dryness or moisture, its rise or fall often anticipating change of the 
 barometer and of the wet and dry bulb hygrometer. It is so far uniform in its 
 (Page 3) susceptibility that an accurate scale would give indications of humidity in 
 the same way as the dry and wet bulb thermometer. It might be rendered more 
 (Page 74) exact than it is. H. C. Russell's table gives the humidity by simple 
 inspection by means of curves. His values agree closely with Glaisher's hygro- 
 (Page 75) metrical tables, 4th ed. ; but not with the first edition nor with Guyot. 
 It does not give a lower humidity than 40. 
 
 (Page 93.) The country [England] is suffering from lack of rain for months, yet 
 the moisture has always been close at hand. The upper regions of the air have been 
 abundantly supplied with water. The moist south-westers have blown over the land. 
 The skies have even been for the most part cloud-laden, yet the winds have drifted 
 onward those vehicles of the precious moisture. The moisture-laden air current 
 which comes from over the Atlantic may flow so low that the western hills rob it of 
 its wealth of water, and suffer dry air alone to pass over the rest of the country ; 
 or, on the other hand, the south-westers may range so high as to carry the moisture- 
 laden clouds past our isles ; or the south-westers may be beaten back through all 
 the summer months by the dry winds from the east, and so a real dryness of the air 
 prevail, as during the exceptional weather of May 1866. Yet it is comparatively 
 seldom that we owe our droughts to such a real dryness of the upper regions 6f the 
 atmosphere. This is proved by the fact that our summer nights are seldom cold. 
 Tyndall notices, that a day's steady rainfall in a region no larger than Middlesex 
 corresponds to the action of a force capable of raising more than 30,000 million of 
 tons to the height of a mile. All the coal which men could dig from the earth in 
 many centuries would not give out enough heat to produce, by the evaporation of 
 (Page 94) water, the earth's rain supply for a single year. But there are few 
 subjects on which meteorology throws less light than on the causes which influence 
 the dryness or wetness of our summers. At times it would almost seem as though 
 the weather of tropical or sub-tropical regions were brought to us with the northing 
 of the sun. But during other summers an irregular variation prevails. The 
 
 384 
 
AQUEOUS VAPOUR 1871. Dines. NOTES. 
 
 attempts to discover any traces of periodicity in the recurrence of dry and moist 
 summers have not hitherto been rewarded with success. Nor does there seem to be 
 any evidence that our climate is gradually changing as regards humidity. 
 [No. for September.] 
 
 (Page 130.) The observer at Cirencester says the extreme dryness of -the weather 
 from January to May has been due to the tendency of the wind to cling to the 
 north. 
 
 [No. for October.] 
 
 (Page 135. ) The Report of the Kew Committee states that the staff" at Kew 
 continue to make occasional absolute hygrometrical observations, by means of 
 Regnault's instrument, with the view of testing the accuracy of the method of 
 deducing the dew-point from the observations with the dry and wet bulb 
 thermometer. 
 
 [No. for November.] 
 
 (Page 169.) The Rev. R. B. Belcher, in a paper read to the British Association, 
 stated that the explosion on the Mersey of the Lotty Sleigh was heard where he 
 lived, a hundred miles off. It was followed by an immense black cloud and heavy 
 rain. 
 
 1871. 
 
 Chandless, Wm. Journ. Roy. Geoy. Soc., vol. xl. (1871) (rs). 
 
 (Page 432.) The following were the results of ten months' observations at 
 Manaos, scattered over several years. The maximum and minimum were those 
 obtained at the regular hours of observation. 
 
 VAPOUR TENSION. HUMIDITY. 
 
 3 A.M. '796 inches. 92 
 
 9A.M. -830 81 
 
 3p.M. -811 70 
 
 9p.M. -833 ,, 88 
 
 Mean -818 83 
 
 Max. -980 98 
 
 Min. -602 42 
 
 Dines, George. Evaporation. Symons's Meteor ol. Mag., vol. vi., pp. 190 192 (rsp). 
 (Page 191.) 1 should prefer Dr. Hudson's Proposition I. to be expressed thus : 
 When air is saturated with moisture, and the water is of the same temperature as 
 the air, neither evaporation nor condensation can take place. I do not like the 
 words " when air is saturated," as they tend to convey a false impression ; except as 
 it regards the dew-point, it is a matter of little consequence whether the air is 
 saturated or not. Other circumstances being the same, it is the difference between 
 the temperature of the water and that of the dew-point which determines the 
 amount both of evaporation and of condensation. In paragraph 5, p. 167 (see Notes, 
 1871, Hudson), a case is supposed, which, in my opinion, cannot exist ; air, under 
 the circumstances named, is not capable of abstracting vapour, and, therefore, 
 cannot surrender its previous spoils again ; on the contrary, water of a lower 
 temperature than the dew-point will rob the driest air of a part of the small quantity 
 of moisture which it contains ; this I have found to be the case by placing water of 
 a lower temperature than the dew-point in the heated air of a drying-room, when I 
 have invariably found it to increase in weight. It is true that in Table 2 of my 
 paper evaporation appears to take place from water when at a lower temperature 
 than the dew-point, but it will be observed that the words " calculated dew-point " 
 are generally used, and the tendency of my experiments was to throw a doubt upon 
 the correctness of the tables used for the determination of the dew-point ; further 
 
 385 
 
AQUEOUS VAPOUR 1871. Frere. NOTES. 
 
 experiments have convinced me that they generally, but not always, give the dew- 
 point too high, but some anomalies which I have noticed lead me, at times, to doubt 
 if the wet and dry bulbs can ever give more than an approximation to the moisture 
 in the atmosphere. The time at which evaporation commences from water or from 
 any other substance covered with moisture in its relation to the dew-point, can only 
 be determined by the most delicate experiments. To me it has sometim.es appeared 
 to differ in different currents of air, but the whole question is beset with difficulties, 
 of no ordinary kind, one of which would be to determine the temperature, not of 
 the water, but of its surface, and, at the same time, to get the correct dew-point ; the 
 latter at times appears very changeable. It seems that masses of air, very differently 
 charged with moisture, are rolling over the surface of the earth in the same manner 
 as the clouds above, the difference being that they are invisible. Nothing yet said 
 (Page 192) shakes my conviction that condensation occurs if the surface tempera- 
 ture of water is below the dew-point, evaporation if it is above. 
 
 Everett, J. D. (.1871,6.) 
 
 (Page 353. ) The formulae used for calculating the dew-point have been based on the 
 specific gravity of air, as determined by Delaroche and Berard, or '267 ; the correct 
 value is that obtained by Regnault, or "237. With this correction, the discrepancies, 
 found to exist between calculation and observation are increased, and amount, on 
 an average, to about 25 per cent, of the difference between wet bulb temperature 
 and the dew-point. August and Apjohn erred in assuming that the air round the 
 wet bulb falls to the temperature of the bulb, and becomes saturated. These two 
 assumptions would jointly produce no error in the result if the depression of 
 temperature in the different portions of air were exactly proportional to their 
 increments of vapour tension, and if some of the air were saturated at the tempera- 
 ture of the wet bulb. But it is probable that when there is little or no wind, the 
 mass of air which falls sensibly in temperature is larger than that which receives a 
 sensible accession of vapour, and that in high wind the supposition that some of the 
 air has fallen to the temperature of the wet bulb is more nearly fulfilled than the 
 supposition that it has taken up enough vapour to saturate it. The effect of 
 radiation, which is ignored in the formulae, leads in the same direction as these 
 two inequalities, and all three are roughly compensated for by attributing to air a 
 greater specific heat than it actually has. 
 
 Ferrell, William, (B. 3871, 8.) 
 
 (Page 226.) Buchan attributes the low barometer in the Polar regions to the effect 
 of vapour in the atmosphere ; but the amount of vapour in the equatorial regions 
 is far greater than in the cold Polar regions. 
 
 Prere, Sir Bartle. Journ. Roy. Georj. Soc., vol. xl. (1871) (rs). 
 
 (Page 203.) In the Thurr droughts occur for months, and sometimes for years. 
 Still, grasses thrive and spring up with amazing rapidity after the fall of a few 
 inches of rain. The soil is loose, and the roots of the plants are of prodigious 
 (Page 204) lengths. No animal requiring much water can stand its protracted 
 droughts. Thus tigers are never seen in the desert, although they abound wher- 
 ever jungle is to be found in these regions ; leopards and lions are rare. Three 
 (Page 205) foxes and a jackal are known. Wolves are numerous. The wild hog is 
 absent. Of deer and antelopes, the only one is the gazelle, which is said to subsist 
 without any moisture except that afforded by dew and herbage. Jerboas are the 
 most characteristic animals. Snakes are numerous. There are horned cattle, 
 sheep, and camels. 
 
AQUEOUS VAPOUR 3871. Hudson. NOTES, 
 
 Hudson, Henry, On Evaporation of Water. Symons's Mtteorol . May., vol. vi., 
 
 pp. 1M-16* (rap). 
 
 (Page 166.) The following propositions appear to embrace and explain the 
 phenomena of evaporation observed by Mr. Dines : 
 
 1. When air is saturated with moisture at temperature of atmosphere, neither 
 evaporation nor condensation can take place. 2. When air is saturated, but the 
 water of a higher temperature, evaporation must take place, for the air, which is- 
 warmed by contact with the water, being no longer saturated, is capable of 
 receiving and carrying away additional moisture ; hence the water must lose 
 weight, and also be cooled by the abstraction of the latent heat of the vapour thus 
 eliminated. 3. When air is saturated, but the water of a lower temperature, 
 condensation must take place on the surface of the water, for the air, chilled by 
 contact, can no longer retain the same amount of vapour, consequently the weight 
 of the water will be increased, and its temperature also must rise from the influence 
 (Page 167) of the warmer air. 4. Let us suppose both the air and water to be 
 several degrees above the temperature of the wet bulb, the air in contact with the 
 water will obviously carry off vapour from it. Hence the weight of the water will 
 diminish, and its temperature must fall, as in the case of the wet bulb, until the 
 latent heat of the vapour so abstracted is exactly compensated for by the heat, from 
 all sources, which the water- vessel receives. After this occurs, evaporation will 
 still go on, and consequently the water will lose weight, although the temperature 
 of the water may remain stationary. 5. Let us suppose the water to be several 
 degrees below the dew-point temperature, while the air is several degrees above it - T 
 the air now in contact with the water is capable of abstracting vapour until it 
 reaches its temperature of saturation. But, being chilled further by the contact 
 with the water, it is compelled, as 1 may say, to surrender its previous spoils again,, 
 so that when the water is a certain number of degrees below the dew-point, the 
 weight of moisture which the air could vaporize, in falling to the temperature of 
 the wet bulb, will be exactly balanced by the quantity of vapour which the colder 
 water would abstract from the air after it had attained the condition of saturation * 
 so soon, however, as the temperature of the water rises above this point, although 
 still, perhaps, some degrees below the dew-point, the evaporative influence will 
 prevail, contrary to the first proposition laid down by Mr. Dines, that no evaporation 
 takes place from water unless the temperature of the water is greater than that of, 
 the dew-point. At the close of the second table (p. 201) he gives an experiment 
 totally opposed to such a conclusion. In the last line of his table, his dry bulb is. 
 at 59 and the wet bulb at 53 '8; his calculated dew-point being 49*2, and 
 temperature of water 38'6. After about a quarter of an hour, condensation 
 ceased, temperature of water being 44, and two minutes afterwards evaporation 
 commenced, with water at 45. He has not stated the temperatures of the wet and 
 dry thermometers at these precise points, but I cannot believe that the dew-point 
 had fallen, in the time specified, below 45 ; in fact, in the previous quarter of an 
 hour the temperature of the dry bulb had risen from 58 '1 to 59, and of the wet 
 bulb from 531 to 53'8 (his calculated dew-point having also risen). Now, 
 assuming the temperatures of dry and wet bulb to remain at 59 and 53*8 
 respectively, my views lead to the following results : I find the weight of water 
 which 1000 cubic inches of dry air could vaporize in falling from 59 to 53 '8 to be 
 0'35836 grains, and the maximum weight of 1000 cubic inches of vapour at 53'8 is 
 270631 grains. Hence, deducting the former from the latter, we have 2 '347 95 
 grains, which is the maximum weight of 1000 cubic inches of vapour at 49 '69, and 
 this, by my calculation, is the dew-point, instead of 49 '2. Now, if we again deduct 
 (Page 368)0'35836 from 2'34795 grains (in order to find out at what temperature 
 
 387 
 
AQUEOUS VAPOUR 1871. Stewart. NOTES. 
 
 below the dew-point the condensation of vapour is equal to the previous evaporation 
 during the fall from 59 to 53*8) we get 1*9859 grains, which is the maximum 
 weight of vapour in 1000 cubic inches at 45. Hence, according to my views, 
 this is the temperature at which evaporation ought to begin to preponderate 
 over the tendency to evaporation, and it is evident this agrees perfectly 
 with what Mr. Dines has recorded as the result of his experiment. After this, 
 in about eleven minutes, he states the temperature of the water to have risen 
 to 49'8 and that 0'4 grains of water had been vaporized in the interval, so that 
 after this amount of evaporation the water was probably very little, if at all, 
 above the dew-point temperature. 
 
 Malet, H P. Symons's Meteorol. Mag., vol. vi. (rsp.) 
 
 (Page 204.) In West India, at an elevation of 4,000 ft., I have frequently seen 
 showers falling below me. I have walked into the clouds, and met first mist 
 {Page 206), then drizzle, then rain. From numerous facts observed by me, I gathered 
 that rain clouds vary in thickness from about a hundred yards to more than a mile, 
 that the weight or size of the raindrops increases as they reach the point of attraction. 
 This point is the earth, and may be a mountain top or a level plain ; as the latter 
 does not fall in with so much moisture as the hills, it gets less rain. Some seem to 
 think that a cloud discharges its contents in actual raindrops ; if it did, there would 
 be no moisture to go on with. But it is" otherwise, and while some of the vapour 
 is accumulating into raindrops, the rest is passing on. In India there are seldom 
 two layers or more of clouds ; in England, as far as I have been able to ascertain, 
 it never rains without two layers. 
 
 Monck, W H. S. (B 1871,17.) 
 
 (Page 495.) Aqueous vapour is not so important an agent as is usually supposed. The 
 .specific heat of aqueous vapour at constant volume is '313, and that at constant 
 pressure is '475, showing a ratio between the heat units expended on internal and 
 external work of 1 to 0*517. In dry air the proportion is 1 to 0*421. In the one 
 case, in round numbers, 30 per cent, is employed in producing expansion ; and in 
 the other 35 per cent. For equal quantities, the heat absorbed by vapour has 
 little, if any, greater effect in producing air currents or barometric depressions 
 than that absorbed by air. 
 
 Poey, A. (B. 1871, 18.) 
 
 [The new cloud is Dr. Clouston's pocky cloud. He noticed it in connection with 
 the same meteorological conditions as are described by A. JBuchan in 1808.] 
 
 Stewart, Balfour. (B. 1871, 20.) 
 
 (Page 63.) Charts of relative humidity are without value, and do not present the 
 continuity shown in charts of vapour tension. Watery vapour is one of the most 
 important elements in studying the movement of air. Charts representing the 
 distribution of vapour of water would be of the greatest utility. The element of 
 relative humidity is of little use in meteorological researches. Besides these two 
 (Page 64) elements, there is what may be called the hygrometric quality, which is 
 important. It means the weight of aqueous vapour per hundred parts by weight 
 of air. As long as the pressure remains the same it will be represented by the 
 vapour tension, and since the variations of pressure at the surface of the earth 
 differ little, the hygrometric quality will be there approximately represented by the 
 vapour tension. But under small pressure the vapour tension will not represent 
 the hygrometric quality, which will then be indicated by the ratio between the 
 pressure of aqueous vapour and that of air. 
 
 388 
 
AQUEOUS VAPOUR 1871. Stow. NOTES. 
 
 Stow, Rev. F. W. Symons's Meteor ol. May. , vol. vi. (rsp.) (No. for June.) 
 
 (Page 70.) Does the old-fashioned hypothesis suggested for the decrease of 
 rainfall with height account for the facts, especially the greater decrease in winter 
 than in summer ? Does it not assume what can be disproved viz., that the 
 temperature of falling rain is almost always below the dew-point of the air near the 
 ground ? Arid if it were true that the raindrops gain more than they lose till they reach 
 the ground, would not the beginning of rain dry the air near the ground by depriving it 
 of moisture, and even warm it by the latent heat given out in condensation ? I am 
 much more disposed to believe that, on the contrary, the drops lose volume by 
 imparting moisture to the air, for it is a matter of common observation that when 
 it begins to rain the air becomes damp and generally cold. 
 
 Symons's Jfeteorol. Jfag., vol. vi. (rsp.) 
 
 (Page 144.) We give a resume of Mr. Dines' s observations on evaporation. A 
 delicate balance was arranged with a vessel of water in one pan and weights in the 
 other. It was found that evaporation from the hot water continued until its 
 temperature fell below the dew-point temperature, as computed by Mr. Glaisher's 
 tables, and that in cold water condensation ceased some 3 or 4 below the computed 
 dew-point temperature. These results indicate one of three things : 1. That there 
 is some error in the experiments. 2. That there is some error in the hygrometrical 
 tables. 3. That the dry and wet bulb thermometers do not enable us to ascertain 
 the dew-point correctly. The second phase of the investigation is given in the 
 Proc. Meteorol. Soc. for March, 1871. Thus during some experiments it was 
 found that when the difference of the dry and wet bulb thermometers amounted to 
 8 or 9 evaporation commenced from a surface of water at a time when the 
 thermometer immersed in the water showed a temperature of from 3 to 4 below 
 (Page 146) the temperature of the dew-point as obtained by calculation, but on 
 repeating the experiment in air saturated with moisture, when the dew-point 
 temperature could be obtained direct from the thermometer, the dew-point 
 temperature and that of the water, when evaporation commenced, agreed with each 
 other. As no satisfactory reasons have been assigned for this discrepancy, I made other 
 experiments, as follows ; small globes and cylinders, both of glass and metal, were 
 used, the substance of which was made as thin as possible ; these were filled with 
 iced water ; a thermometer, with a bulb 1% inches in length, was inserted in the 
 water, the stem of the thermometer passing through the centre of the stopper ; 
 the whole was then suspended from the beam of a delicate balance. The outsides 
 of the vessels were, of course, immediately covered with condensation, the amount 
 of which was only occasionally noted, the one object of the experiments being to 
 determine the exact temperatures of the water at the time when condensation 
 ceased upon the surface of the vessels, and the moisture deposited upon them 
 commenced to evaporate ; that time was clearly shown by the stationary position of 
 the index rod attached to the balance, just previously to its commencing a retro- 
 grade movement. If the thermometer immersed in the water at the time this 
 change took place fairly represented the temperature of the outside of the vessel, 
 it would, without doubt, give also at the same time the true dew-point temperature. 
 Every care was taken with the covering and supply of moisture to the wet bulb 
 thermometers, and, as an additional precaution, two sets of dry and wet bulbs were 
 used, the difference (8 to 9) of which did not vary much from each other ; but 
 those which gave the widest readings, and, consequently, the lowest dew-points, were 
 taken. Whether the vessels used were larger or smaller, of glass or of metal, or 
 whether the moisture upon the outside was allowed to accumulate almost in drops, 
 or the film of moisture so thin as to be scarcely weighable, the results were nearly 
 
 D D 389 
 
AQUEOUS VAPOUR 1872. Davis. NOTES. 
 
 the same ; condensation ceased, and evaporation commenced from the surface of the 
 vessels at a time when the water inside the vessels was from 3 to 4 below the dew- 
 point temperature, as obtained by calculation. It may be said the thermometer in 
 the water does not give the temperature of the surface from which evaporation takes 
 place ; the objection has force ; but it also applies to both Daniell's and Regnault's 
 hygrometers as at present used. True, there are other differences in the mode of 
 operation ; in them it is a sinking temperature ; in mine a rising one. In them the 
 point of condensation is determined by the eye ; in my experiments by a balance ; 
 but these differences do not seem to account for -the different results. As the 
 indications of the wet and dry bulb hygrometer had been found to accord with 
 those given by Daniell's and Regnault's, I conclude that the factors given in 
 Table I. of Glaisher's hygrometrical tables are incorrect. Now we come to the third 
 phase of the inquiry viz., a consideration of Dines's sensitive hygrometer, made by 
 (Page 147) Casella. In it a stream of cold water passes through the vessel ; at one 
 end is a very thin black glass plate, beneath which is the bulb of a thermometer. 
 The temperature of the upper and lower surfaces of the glass is nearly the same ; 
 and the slab does not differ from the thermometer bulb more than 2 or 3. The 
 glass is cooled by the water ; as soon as dew appears on it the water flow is stopped, 
 and the temperature is taken from the thermometers. This is the dew-point. By 
 using a piece of wash leather to dry the glass successive deposits of dew may be 
 rapidly obtained, when the dew-point will be found sometimes to vary considerably 
 in a short time, the dew upon the glass appearing and disappearing several times in 
 a minute. The instrument has extreme sensibility, and is perfectly under the 
 control of the observer, and its price is very moderate. 
 
 1872. 
 Anderson, J. F. (B. 1872, 1.) 
 
 (Page 221.) He was able (at Pau) to see the small bodies alluded to by Waldner 
 with the naked eye, or with a small telescope, by looking at the sky close to the 
 sun's disc just within a shadow. On June 9th and 10th the haziness round the 
 sun was produced by the reflection of the sunbeams from innumerable little 
 particles. What were these particles ? They certainly look like miniature snow 
 storms. 
 
 Brumham, G. D. Sy mom's Meteor ol. Mag., vol. vii. 
 
 [No. for November.] 
 
 (Pagel72.) Excessive moisture retards wheat. Hence the ripening of wheat depends 
 (Page 173) on dryness of air as weU as temperature. The early maturing of wheat 
 indicates the previous prevalence of dry weather as much as, or more, than it does 
 that of shade heat. 
 
 C., W. H. H. Chemical Hygrometer. Symons's MeteoroL Mag., vol. vii. '(rsp.) 
 (Page 155.) Air is drawn through U-shaped tubes containing chloride of calcium or 
 strong sulphuric acid, by means of two turnover aspirators, each containing a gallon 
 of air. The increase of weight in the chloride of calcium tube indicates the amount 
 of moisture in so many gallons of air. 
 
 Davis, Henry. PresteVs Hygrometer. Symons's MeteoroL Mag., vol. vii., p. 204 (rsp). 
 
 (Page 204.) There are objections to Prestel's hygrometer. Birds can drink from 
 the open vessel ; the wind would blow the water over the side in gales ; and the 
 atmospheric pressure would keep the water permanently in the gauge. 
 
 390 
 
AQUEOUS VAPOUR 1872. Waldner. NOTES. 
 
 Haviland, Alfred. Symons's Meteorol. Mag., vol. vii. (rsp.) 
 
 [No. for July.] 
 
 (Page 116.) In the western sky at Hampstead, on June 23rd, 1872, there were 
 some persistent cirri, forming strange groups, which lasted for more than an hour. 
 The cirri bristled (electrically ?). 
 
 Hudson, Henry. Dew-point and other Hygrometers. Symons's Meteorol. Mag., vol. vii.,, 
 
 pp. 19-20 (rsp). 
 
 (Page 19.) A limit to evaporation does not exist when the temperature of the air is 
 higher than that of the liquid. I consider the dew-point in the case mentioned to 
 be 49'69, and that the air will take up vapour several degrees below, owing to 
 (Page 20) its surplus heat. The amount of evaporation depends on so many 
 circumstances, that in order to discover laws it will be necessary to separately 
 investigate each circumstance. 
 
 Ingram, Hugh. Symons's Meteorol. Mag., vol. vii. (rsp. ) 
 
 (Page 229.) He calls mists vesicles of aqueous vapour (cloud proper). A raindrop, 
 in displacing air as it falls, creates a vortex immediately behind it so as to suck in 
 and attach to itself the particles of vapour nearest its path. Hence its increased size. 
 
 L.,J.K. (B. 1872,10.) 
 
 (Page 442.) Commander Maclear has noticed differences in the spectrum of different 
 areas, and believes the changes in the atmospheric humidity distinctly correspond 
 to the changes in the solar spectrum ; an increasing humidity manifests itself by a 
 shortening of the blue, and by a well-marked development of aqueous bands in the 
 red and yellow. 
 
 Miller, S. H. Evaporation. Symons's Meteorol. Mag., vol. vii., pp. Ill, 129 (rsp). 
 (Page 129.) What methods for measuring evaporation did Vivian, Lament, and 
 Prestel suggest ? 
 
 Rieder. (B. 1872, 17.) 
 
 (Page 39.) At Engelberg, November 14th, 1868, 5 to 6 A.M., repeated flashes of 
 lightning. Shortly before five a swiftly passing flash was observed, while the sky 
 was completely overcast. 
 
 Spottiswoode, William. (B. 1872, 23.) 
 
 (Page 334.) The diffusion of light in the air depends upon the presence of aqueous 
 particles. That scattered by coarse particles is white, that by fine blue. 
 
 Stow, Rev. F. W. Symons's Meteorol. Mag., vol. vii. (rsp.) 
 
 [No. for December.] 
 
 (Page 197.) In moist weather there is little sun, in dry there is much. Perhaps the 
 influence of such weather on wheat is due to variation of sunshine, not of moisture. 
 In the inland districts of Yorkshire the temperature rises faster in the morning 
 than on the coast, owing to the comparative absence of mists, etc. 
 
 Waldner, H. (B. 1872,25.) 
 
 (Page 304.) On looking through his large telescope at Weinheim, he caught sight of 
 a number of luminous little bodies passing rapidly towards the east, which the focal 
 distance of his lens showed were at from 200 to 4,000 metres only from the earth ; the 
 most numerous swarm occurred at about 500 metres. Their diameter varied from 10 
 to 52 mm., the average being 32 mm. The shape varied ; the greater number were 
 oblong, angular, resembling flakes; some few were orbicular, while some were 
 
 391 
 
AQUEOUS VAPOUR 1872. Nature. NOTES. 
 
 stellate. On certain days, especially in April and May, they passed by without 
 interruption for hours. Their number was connected with the purity of the sky. 
 The daily minimum occurred in the morning and evening, and the maximum at 
 noon. The annual minima were in summer and winter, and the maxima chiefly 
 from April 20th to May 15th, and a lower one in August and September. Their number 
 often increased after clouds had passed. Their velocity was irregular in the lower 
 strata, being about two metres in a second, but became more regular in the higher 
 strata, where, at 3,000 metres, I found them to pass eight metres during the same 
 period, a rapidity agreeing closely with the cirri, which often passed at or above 
 (Page 305) this distance. They all glittered in sunlight. In the lower strata they 
 changed their direction every moment, or fell, but slower than gravitation requires. 
 Their direction of movement corresponded nearly always with the wind and cloud 
 movements. These bodies are evidently snowflakes and ice crystals. The minimum 
 during winter may be owing in part to the deficiency of light. 
 
 Whipple, J. M. Chemical Hygrometer. Symons's Meteorol. May., vol. vii., pp. 199-200 (rsp). 
 
 (Page 199.) The chemical hygrometer, described by W. H. H. C. is not of much 
 use to the meteorologist, as it requires much patience and manipulative skill. It 
 is a very laborious method of observing, and, after all, it only gives a mean 
 (Page 200) for the time during which the observation is made. I think eventually 
 we shall have to resort to some such form as Whitehouse's. 
 
 Nature. (B. 1872, 28.) 
 
 (Page 118.) There is much misconception as to the mode in which forests increase 
 the amount of moisture in the air. They do so chiefly by pumping up the super- 
 fluous moisture from the soil and exhaling it from the leaves. Pettenkofer (Sitz. 
 Akad. Mtinchen, 1870. Bd. I., Heft 1) found that in an oak tree evaporation 
 increased from May to July and then decreased till October. The total amount of 
 its evaporation in the air was 539'1 6 centimetres of water. The average rainfall of 
 the same area would be 65 centimetres, so that this evaporation is 8^ times more 
 than that of its rainfall. This excess is drawn up from a great depth, so that the 
 trees restore to the air what would otherwise go to the sea. 
 
 Symons's Meteorol, Mag., vol. vi. (rsp.) 
 
 (Page 213.) Describes Daniell's hygrometer. It was described by Daniell in 1820 
 (Page 214), and at the time was by far the best measurer of atmospheric moisture. 
 Its accuracy has subsequently been overrated. Owing to the necessarily small size 
 of the enclosed thermometer it is impossible to read accurately small fractions of a 
 degree ; and it is open to question if the thermometer indicates the actual tempera- 
 ture of the outer glass surface. 
 
 Vol. vii. (rsp.) 
 [No. for May.] 
 
 (Page 63.) Sawyer, in his < Climate of Brighton,' has some weather proverbs, 
 such as 
 
 4 When Wolsonbury has a cap 
 Hurstpierpoint will have a drap.' 
 
 This is a south country modification of a common prognostic, such as the following, 
 some of which are taken from Inwards' ' Weather Lore.' 
 
 ' If Riving Pike do wear a hood, 
 Be sure the day will ne'er be good.' 
 
 ' When Cheviot ye see put on his cap, 
 
 Of rain ye'll have a wee bit drap ' 
 392 
 
AQUEOUS VAPOUR 1872. Nature. NOTES. 
 
 ' If Roesberry Topping wear a cap, 
 Let Cleveland then beware a clap.' 
 
 ' When Breddon Hill puts on his hat, 
 Ye men of the vale beware of that.' 
 
 ' When Largo Law puts on his hat, 
 Let Kellie Law beware of that ; 
 When Kellie Law gets on his cap, 
 Largo Law may laugh at that.' 
 
 Largo Law is to the S.W. of Kellie. Law. 
 
 [No. for June.] 
 
 (Page 73.) Dr. Ballot enforces the desirability of more frequent observations of 
 the height of clouds. 
 
 [No. for August.] 
 
 (Page 129.) The following description of Prestel's apparatus is from Procs. 
 Meteor ol. Sac., vol. iii., pp. 338-339. It comprises an open vessel of water. 
 (Page 130) Connected with it is a measuring tube with a scale. The tube is filled 
 with water and placed inverted in the vessel. As the water from the large vessel 
 evaporates it is supplied from the tube. The open end of the tube has a brass ring 
 mounting with a semicircular hole in the side through which the tube communicates 
 with the vessel. 
 
 [No. for October.] 
 
 (Page 161.) M. Lemoine, in a paper read to the British Association, refers to 
 Mr . Chapman's observations in South Africa . The desiccation of the country has been 
 going on since the draining off of the waters owing to evaporation. The destruction 
 of herbage and grass by fire, the use of the axe by native and colonist, and the for- 
 mation of sheep walks, had facilitated the process of evaporation. As an illustration 
 of the effects of evaporation producing desiccation, he quoted an experiment made 
 by William Blore, at Wynberg Hill, about eight miles from Cape Town. He sank 
 two cylindrical jars of the same size to the depth of 4 in., leaving them projecting 
 an inch above the surface, and covering each with gauze to prevent ingress of sand, 
 etc., and flies. The one was sunk where it was partially protected, but not covered 
 by bush ; the other was sunk in a newly-cleared plot of ground measuring about 
 60 ft. in diameter, surrounded by sugar bushes (Protea mellifera, Thnnb.), of a 
 considerable height, and otherwise protected from the prevailing wind by a belt of 
 pine trees, about 120 ft. distant. Into each of these jars was put 20 ozs. of water on 
 January 31st, at 10 A.M. On February 5th, at 5 P.M., the water remaining in each was 
 carefully measured. The evaporation from the jar sunk in the cleared ground 
 had been more than double the evaporation from that which was partially protected, 
 though not covered, by the bush ; the former being T854 in. ; the latter '863 in. 
 The same results were obtained on repeating the experiment. Mr. Blore remarked 
 that had the experiment been made in a more arid district the evaporation would 
 have been greater ; and that had it been made in the open country the difference 
 would have been more marked. But taking the results obtained, the conclusions 
 he arrived at were as follows : The excess of evaporation from the more exposed 
 above that from the more shaded jar was 1 in., or more accurately, "991. An 
 inch in six days will give for 102 days (the ordinary duration of the hot windy and 
 dry season in the district) 17 in. This is equal to about 384,000 gallons per acre, 
 and supposing 1,000 acres to be burned, blackened, and dried, what with sunlight, 
 fire, heat, and wind, the evaporation would be an excess of 384,000 gallons of water 
 above what would have been evaporated if the bush or grass had been unburned. 
 Mr. Blore ascertained by experiment that on Wynberg Hill, while the deposit of 
 dew upon a green surface amounted to 4*75, that on a white surface amounted only 
 
 393 
 
AQUEOUS VAPOUR 1873. Maury. NOTES. 
 
 to 2, showing that the deposit of dew upon a green surface is more than double 
 that 'upon a white ; and he further ascertained that while the difference of tempera- 
 ture in the water in the two jars employed in the former experiment was only a 
 few degrees the difference of temperature between black ground and ground shaded 
 by bush was 25, which would occasion a vastly greater difference in the amount of 
 evaporation than that which occurred in his experiment. Humidity of air is of 
 more importance than rainfall, and it is not necessary, in order to account for the 
 phenomena observed, to suppose that forests attract clouds, neither is it necessary to 
 suppose that they increase the rainfall otherwise than they clo by the precipitation 
 of the same moisture in the form of rain. The moisture of the humid atmo- 
 sphere charged with carbonic acid and ammonia, attracted by the soil, does more to 
 promote vegetation than would the same quantity of moisture falling in rain or 
 applied by irrigation. 
 
 [No. for November.] 
 
 (Page 180.) George Dines described a new hygrometer. Objections had been 
 made to the use of glass, owing to its non-conducting qualities, and in this form he 
 used both glass and highly polished gilt metal. The metal was found to have no 
 advantage over glass. [See Notes, 1823, Daniell, p. 142.] 
 
 1873. 
 
 Barns, J. W. Journ. Roy. Geoff. Soc., vol. xlii. (1873) (rs). 
 
 (Page 405.) The date palm characterizes arid climates with extreme summer heat 
 and a low winter temperature. 
 
 Blakiston, T. Journ. Roy. Geog. Soc., vol. xlii. (1873) (r). 
 
 (Page 140.) At Hakodadi, fog is confined to the spring and summer months, but 
 principally June. 
 
 Brine, Lindesay. Journ. Roy. Geog. Soc., vol. xlii. (1873) (r). 
 
 (Page 361.) In crossing the high lands of Guatemala, it is observable that the 
 Indians dwelling among the mountains are much darker than those in the plains, 
 and indeed it may be laid down as a general law that throughout Central America 
 the colour of the native varies according to the height above the sea, and in a 
 manner entirely opposed to what would naturally be expected. The skin of those 
 who dwell in the highest and coldest regions is almost black, while below in the 
 warm valleys and near the coast it is of a pale copper colour. 
 
 Grant, J. A. Journ. Roy. Geog. Soc., vol. xlii. (1873) (rs). 
 
 (Page 259.) While delayed at Karagweh, I was much struck by the extreme black- 
 ness of skin in a race who came there from the Lake Victoria direction to sell coffee. 
 The blackness of their skins reminded me forcibly of the races dwelling in the 
 swampy regions of the Terais of India, and this to me at once marked their origin 
 as a race living among swamps or lakes. They were Wahia, who live on the shore 
 of Victoria L#ke. Their spear is made of a white knotty wood, not of bamboo, for 
 bamboo is not indigenous to swampy countries ; it chooses rather to grow away 
 from water. 
 
 Maury, T. B. (B. 1873, 7.) 
 
 (Page 125.) When once an area of low barometer is formed, it is the nucleus for a 
 vast aggregation of meteoric forces. No matter how small at first, under favourable 
 atmospheric conditions, the courant ascendant is formed, condensation aloft sets in, 
 and the precipitation only seems to add fuel to the flame of the cyclonic engine. 
 This process widens in geographical area, and after a few hours have elapsed, the 
 storm may so develop as to cover a continent with its portentous canopy of cloud, 
 
 394 
 
AQUEOUS VAPOUR 1873. Nature. . NOTES. 
 
 while simultaneously strewing an ocean with wrecks, and throwing out in the open 
 sky, more than a thousand miles in front, the fine filaments of the premonitory 
 cirrus and cirronus. The depression in a cyclone is maintained so long only as the 
 centre moves in a region sufficiently supplied with aqueous vapour to feed it. It is 
 physically impossible for a storm to maintain its course or force over a dry and 
 (Page 147) desiccated surface. The southerly winds of the north hemisphere come 
 from the equatorial regions, and are highly charged with aqueous vapour. This 
 vapour is absolutely essential to the sustenance of storms. The storm vortex is on 
 the side where the greatest quantity of vapour is found. While yet in the band of 
 easterly trade winds, the storm will invariably work its way to the most humid 
 regions unless mechanically borne away by the great aerial current in which it is 
 embedded. The cyclone tracks over all the oceans lie in the central bands of the 
 great ocean currents of high temperature and great evaporation. 
 
 Mott, A. J. (B. 1873, 8.) 
 
 (Page 161.) The amount of evaporation must be the chief element in the question 
 of rainfall ; and the total evaporation must depend on the amount of wind ; and 
 thus be increased in proportion to the speed of the wind and by the increased sur- 
 face caused in storms when waves and foam are created. The evaporation during a 
 cyclone must be enormous. Wind is almost always drying even when rain is falling. 
 The solar spots probably cause inequalities of temperature, which by the formation 
 of barometric differences will give rise to special areas of evaporation. 
 
 Stevenson, T. (B. 1873, 15.) 
 
 (Page 153.) Hygrometric gradients should be used, and there should be horizontal 
 and vertical hygrometric sections of the air made by a series of instruments near 
 together. 
 
 Nature. (B. 1873, 17.) 
 
 (Page 342.) The dry and wet bulb is not trustworthy at low temperatures, and in 
 cases of extreme dryness. No hygrometer yet devised gives approximately exact 
 results in all cases. The instruments for measuring the rate of evaporation are the 
 least satisfactory of those used in meteorology. The data are important elements. 
 
 Symons's Meteor -ol. Mag., vol. viii., p. 36 (***?) 
 
 [No. for April.] 
 
 (Page 36.) At the Leipzig Conference Question 7 was : What apparatus should 
 be employed for determining the hygrometric condition of the air ? Are the wet 
 and dry bulb thermometers sufficient ? Can the hair hygrometer be employed, and 
 under what restrictions I 
 
 The answers were as follows : Sr. F. da Silveira : Psychrometer for continuous 
 observations. The hair hygrometer can never be accurate when exposed to the atmo- 
 sphere. Carl Fritsch : Psychrometer sufficient and preferable to hair hygrometer. 
 Thinks observers are not sufficiently careful to see that the wet bulb is really wet. 
 Carl HofFmeyer : Knows of nothing better than dry and wet bulb. Dr. Mohn : 
 Psychrometer is most convenient, but for low temperatures hair hygrometer must 
 be used with it. Professor Ragona : Strongly recommends a psychrometer by 
 Tecnomasio Italiano in Milan. Calls attention to observations by Belli and Can- 
 toni, showing that the results of thermometers with spherical bulb, covered with 
 linen and moistened by a wetted wick, are unreliable. Believes hair hygrometer to 
 be trustworthy if originally set by a psychrometer ; recommends it to be enclosed 
 in wire gauze. Symons : Dry and wet bulb not perfect, but preferable to Saus- 
 sure's hair hygrometer. Dr. Wolf : Psychrometers always wrong when frost and 
 
 395 
 
AQUEOUS VAPOUR 1874. Markham. NOTES, 
 
 thaw alternate rapidly ; hair hygrometer should, therefore, be used as a check. The 
 Committee : Psychrometers faulty in cases of extreme dryness ; the hair hygrometer 
 is erroneous at the dew-point. Neumayer : Regnault's hygrometer with an aspirator 
 should be used. Von Oettingen : Regnault's hygrometer sometimes fails at very 
 low temperatures. 
 
 [No. for May.] 
 
 (Page 53. ) Question 15 was : What apparatus is to be recommended for the 
 measurement of evaporation ? What is the most suitable exposure for the evapo- 
 rimeter ? 
 
 Answers : 
 
 (Page 54.) Sr. F. da Silveira : Should be exposed to rain, sun, etc. Carl Fritsch : 
 A vessel similar to a rain gauge, but shallower, exposed to sun and rain, but guarded 
 against undue heating. Capt. Hoffmeyer : Attention must be paid to the tempera- 
 ture of the vaporimeter. Professor Ragona : Recommends Tecnomasio Italiano's 
 vaporimeter or his own self-recording one. Bordeaux Meeting : Piche's hygrometer 
 gives the most favourable results. Prestel : Recommends his own vaporimeter. 
 Ebermayer : Recommends Lament's vaporimeter. 
 
 Question 16 : In what way should the proportion of cloud in the sky be esti- 
 mated and indicated ? Is it desirable to introduce a special and universal language 
 for clouds ? 
 
 Answers : 
 
 Sr. F. la Silveira : Clear sky = 10; overcast = 0. The introduction of universal 
 symbols very desirable. Carl Fritsch : During the prevalence of thin cirrus and 
 the breaking up of ground fog, there is difficulty in determining the true amount of 
 cloud. The introduction of general symbols desirable. Dr. Mohn : Blue sky = 0; 
 overcast = 10. Symbols very convenient. Symons : Have symbols if possible. The 
 Bordeaux Meeting : The adoption of tenths of clear or cloudy sky will involve the 
 disadvantages of two figures for telegraphy, instead of one. Approve use of 
 symbols. The Committee recommend = clear sky ; 10 = overcast ; that symbols be 
 used; and that a selection be made from those submitted to next Congress. 
 
 (Page 95. ) Ragona notices that at Modena the minimum is below 20 nine 
 months out of the twelve. The lowest observed was 7 on April 9th, 1867. 
 
 1874. 
 
 Burder, G. F. Symons's MeteoroL Mag., vol. ix. (rsp.) 
 [No. for September.] 
 
 (Page 123.) According to my own observations the inverted cumulus or pocky 
 cloud never occurs in a marked degree except in the neighbourhood of a thunder- 
 storm. 
 
 Elias, K"ey. Jown. Roy. Geog. Soc., vol. xliii. (1874) (rs). 
 
 (Page 143.) From September 24th to November 2nd, on which last date he was 
 near Uliassutai in Mongolia, the day almost invariably broke clear and still, and 
 remained so until nearly noon, when a strong north-wester would spring up, and 
 with a more or less clouded sky, continue to blow until about an hour after sunset 
 when it would die out, and the clouds would roll away. 
 
 Kirkwood, J. P. Symons 's Meteor ol Mag., vol. viii. (rsp.) 
 (Page 196.) Give me titles of books relating to evaporation. 
 
 Markham, C. R. Journ. Roy. Geog. Soc., vol. xliii. (1874) (rs). 
 
 (Page 95.) The great heat of the Polar regions and the excessive cold are due to 
 the dryness of the air allowing of radiation from the sun and from the earth 
 396 
 
AQUEOUS VAPOUR 1874. Wilson. NOTES. 
 
 Ryves, Rev. J. T. Symons's Meteor -oL Mag., vol. ix. (rsp.) 
 
 [No. for August.] 
 
 (Page 103.) At Buildwas, on July 19th, the dry bulb read, between 3 and 4 P.M., 
 87, the wet bulb 26, which indicates a relative humidity of about 24. 
 Stow, Rev. F. W. Symons's Meteorol. Mag., vol. ix. (rsp.~) 
 
 [No. for September.] 
 
 (Page 115.) The absorption of the direct solar rays by the vapour of the atmo- 
 sphere is proved in several distinct ways. 1. It is found that the elastic force of 
 vapour is less on the ten days in each month in which radiation is most powerful, 
 than on an average of the whole month. This is proved by five years' daily observa- 
 tion at Strathfield Turgiss, 186974 ; two years at Hawsker, near Whitby (1869 
 71) ; and one year's observation in 1872 at Harpenden. 2. It was also found by the 
 above observations that N. and N.W. winds, which contain little moisture, are very 
 favourable to solar radiation ; whereas S. and S.E. winds are usually accompanied 
 by much less powerful sunshine. The N.E. winds of spring, which are exces- 
 sively dry, are also accompanied by intensely powerful solar radiation. 3. By 
 frequent observations during cloudless weather, with nearly constant vapour tension, 
 curves are obtained, representing the daily variations in solar radiation, produced 
 by the changes in the sun's altitude, and consequent alteration of the length of the 
 path which the beams pursue through the atmosphere. From these the percentage 
 of the heat rays, which would be absorbed by the atmosphere if the sun was vertical? 
 can be approximately determined, assuming that the tension of vapour remained as 
 it was on the day or days of observation. It is then possible to calculate the amount 
 of radiation due to the altitude of the sun at noon in the middle of each month for 
 a constant vapour tension, and to compare this with the amount actually observed 
 in each month on cloudless days. In this way it is found, that when the tension of 
 vapour falls below the amount on the day which furnishes the data for calculation, 
 the radiation rises above the calculated amount, and vice versa. In fact, the sun's 
 rays are more intense in winter than in summer, when the difference of altitude at 
 noon is allowed for, because the absolute amount of vapour in winter is so much 
 less. About 10 or 12 per cent, is the minimum of absorption of the sun's heat rays, 
 while the maximum equals or even exceeds 20 per cent. Solar radiation increases 
 with elevation above sea-level. Between 470 and 1,800 feet the difference is 5 per 
 cent, of the amount observed at the lower station when the sun's altitude was 
 20, and above 3 per cent, when it was 26. 
 
 Strahan, W. Symons's Meteorol. Mag., vol. ix. (rsp.) 
 [No. for August.] 
 (Page 112.) The following are cases of extreme dryness observed in India : 
 
 DKY. WET. DIFFERENCE. 
 
 June 4th, 1869. Gwalior . . . 110'3 697 46'6 
 
 ,, 19th, 1873. Meean Meer . . 112 '2 70'2 42'0 
 
 Thomson, J. Journ. Hoy. Geog. Soc., vol. xliii. (1874) (rs). 
 
 (Page 104.) In South Formosa the wet season begins in May and ends about 
 September [and hence the dry season would be from September to May. The 
 lat. is about 23 N.]. 
 
 "Wilson, W. Journ. Roy. Geog. Soc., vol. xliii. (1874) (rs). 
 
 (Page 211.) In Palestine the dews are so heavy that they penetrate the tent and 
 wet everything in it. The rainy season commences at the end of October or 
 beginning of November, and lasts till March [so that the dry season would be 
 between March and October], 
 
 397 
 
AQUEOUS VAPOUR 1875. Nature. NOTES. 
 
 k 
 
 ' Symons's Meteorol. Mag., vol. via. (rsp.) 
 
 (Page I960 Many titles of books on evaporation are given in ' British Rainfall,' 
 1867 to 1872. [He gives nine others, which are entered in ' Bibliography.'] 
 
 Symons's Meteorol. Mag., vol. ix. (rsp.) 
 
 [No. for December.] 
 
 (Page 171.) Professor Ragona, in his ' Lettere Meteorologiche,' treats of the 
 increase of humidity and the decrease of temperature which produce rain. He finds 
 that when it rains at Modena the average humidity is 87*8. In England the mean 
 value would be nearer 97*8. 
 
 1875.* 
 Abercromby, Hon. R. 
 
 (Page 274.) The heat and damp which accompany cyclones are phenomena which 
 {Page 275) are never absent in any part of the world. The character and quality 
 of this heat differ greatly from that due to radiation. Extreme damp, mugginess, 
 and a peculiar feeling of oppression are the leading features. As to the source of this 
 heat and damp, it is evident that since their position relatively to the cyclone centre 
 is always the same, they must be due to some phenomenon of cyclonic motion, and 
 their isolated position shows that they are not merely due to the setting in of a 
 (Page 276) southerly wind. There is strong presumptive evidence that the heat and 
 damp which accompany one portion of a cyclone are due to a compression of that 
 portion. Behind the centre of a cyclone is an area, less denned than the heat area, 
 but possessed of opposite qualities, viz., cold, dryness, and an exhilarating influence 
 on man and animals. This is probably due to rarefaction. 
 
 Blanford, H. F. 
 
 (Page 189. ) The effect of increased radiation [solar] must be to increase evapora- 
 tion, and, therefore, the clouds. 
 
 Smyth, P. 
 
 (Page 232. ) He refers to the very heavy rains of July 1875 in France and England 
 notwithstanding the barometer was high and steady. When in London on July 14th 
 to 16th, he saw the line D with the spectroscope dark and broad. When he left the 
 weather cleared up, and at York, where it was fine, the line was sharp, but narrow. 
 In Edinburgh, on July 17th, the line was again seen very broad during bright 
 (Page 253) sunshine, and was followed a few hours after by a steady rain. On 
 July 20th there was a sensible alteration of the abnormal spectrum band. On July 
 23rd it rained with a normal sky spectrum, but then the barometer was low, wind W., 
 and the temperature had fallen. 
 
 Nature. 
 
 (Page 100.) Hon. R. Abercromby (Meteorol. Soc., June 19th, 1875) remarked 
 that a light ascensional column would give rise simply to an overcast sky, and a 
 {Page 244) stronger one to rain. Scott described Lowe's graphic hygrometer. On the 
 relation of temperature and moisture in the lower strata of the atmosphere at 
 daybreak, R. Rubenson, in Kong. Vetensk. Akad. ForhandL, Stockholm, January 
 13th, 1875. 
 
 Nature, 
 
 (Page 79.) Meteorol. Soc., November 17th. On a self- regulating atmometer. 
 H. Miller. 
 
 * For fuller references, titles, and bibliographical details, referring to 1875 and subsequent 
 years, see the Bibliography near the end of this volume. 
 
AQUEOUS VAPOUR 1876. Nature. //^EEsfT^^,. NOTES. 
 
 (Page 399.) Inst. Civil Engineers, February 29t\ ^p eva l p$Fa t tJQn / ari$l percola- 
 tion. C. Greaves. 
 
 1876. 
 Murphy, J. J. 
 
 (Page 6.) If we are drying up, it must arise either from diminished ocean 
 surface, or less heat, both of which would decrease evaporation. There seems to be 
 no evidence in support of either, so that the diminution of rainfall must be a local 
 phenomenon. 
 
 Murray, D. 
 
 (Page 76.) Sir C. W. Thomson, at the British Association, states that the 
 reason why the water is moving in a body from the South Sea is that there is 
 a greater amount of evaporation in the North Atlantic and over the north hemi- 
 sphere generally, than there is of precipitation ; whereas it seems almost obvious 
 that in the south hemisphere, in the huge band of low barometric pressure 
 round the south pole the precipitation is in excess of evaporation. He suggests 
 that certain points should be cleared up before this is admitted. Is there no 
 compensating current from the north ? Is it likely that the evaporation in the 
 north hemisphere is greater than that in the south? Even supposing this is 
 so, is it known that this vapour is carried into the Antarctic regions for pre- 
 (Page 77) cipitation? The wind phenomena militate against the view that a 
 large body of vapour is carried from the north to the south hemisphere. 
 
 Nature. 
 
 (Page 520.) Moisture is, next to temperature, the most important climatic 
 characteristic of wind. The humidity of winds having the same direction varies 
 according as it belongs to a cyclonic or anticyclonic area. 
 
 Nature. 
 
 (Page 161.) Zeits. f. MeteoroL, March 1st. On the relations of temperature 
 and moisture in the lowest atmospheric strata during the formation of dew, by 
 R. Rubenson, Dr. Hamberg concluded that in the lower strata temperature 
 (Page 162) increases with height on frosty nights, and that the absolute 
 moisture is less on the ground than a few feet above it. Dr. Rubenson obtained 
 some results in the summer of 1871. Before the fall of dew the absolute moisture 
 continues to increase, and is greatest on the ground, diminishing with the 
 height. As soon as . dew begins to fall, moisture decreases on the surface of 
 the ground, and the decrease keeps pace with the decrease of temperature. 
 The decrease of moisture extends upwards rather rapidly, and can be detected 
 at 4 feet just after the first deposition of dew. On the ground, the decrease 
 per hour amounts to a maximum of about '73 mm. ; while half a foot above it 
 the decrease only reaches '65 mm., which is less than what corresponds to the 
 lowering of temperature. The higher the instrument the later does the decrease 
 of moisture show itself, and the less the change per hour. It appears that owing 
 to a fall of temperature on the ground the air immediately above it becomes 
 saturated, dew falls, and temperature and moisture diminish. At a certain 
 point, owing either to diffusion or a descending current, fresh vapour supplies 
 the place of that condensed as dew, and part of the loss of each stratum is 
 made up by the moister strata above ; but not the whole, for the diminution 
 continues in all the strata. Time being required for the propagation of the 
 
 399 
 
AQUEOUS VAPOUR. 1876. Nature. NOTES. 
 
 decrease upward, the lowest stratum loses more of its moisture than any of the 
 strata above it. 
 
 Nature. 
 
 (Page 444.) (Acad. Sci., Paris, August 28th.) Fautrat, in testing the influence of 
 pine forests on the humidity of the air, found that the annual difference in 
 saturation was in favour of the air above the pines ten hundredths. 
 
 (Page 562.) (Bull, Acad. Roy., Belgique). Montigny says scintillation increases 
 with increase of vapour tension. It increases with the arrival of moist weather 
 at all seasons. 
 
 Nature. 
 
 (Page 527.) D. Whitney has an article entitled ' Are we drying up ? ' in the 
 American Naturalist for September 1876. It refers to the evidence of the former 
 existence of larger and more extensive lakes in areas which are now without 
 them, and also of diminished lakes and rivers. The drying up may possibly 
 be owing to changes in the obliquity of the ecliptic, or in the perihelion distance 
 of the earth. 
 
 Symons's Meteor ol. Mag., vol. xi. (rsp.) 
 
 [No. for December.] 
 
 (Page 154.) [A description is given of the hygrometers and evaporimeters 
 exhibited at the Loan Collection at the South Kensington Museum. Only those 
 details are given here which bear upon aqueous vapour as an element of climate, or 
 which may elucidate the history of investigation.] An old hygrometer was 
 shown, designed by John Coventry. It consists of a number of discs of paper 
 strung on a wire, and attached to the short arm of a lever ; the long arm 
 travels over a scale. The paper was probably saturated with salt, and its 
 weight varied with the humidity of the air. Klinkerfues's bifilar hygrometer 
 shows the humidity and the dew-point by inspection. The reduction is effected 
 by means of two discs, one outer and one inner. There is an old dew-point 
 instrument which we believe belongs to the Royal Society. It is an ordinary 
 thermometer with a black bulb. The bulb is surrounded by muslin, and cooled 
 by means of ether. The dew-point temperature is read off when dew appears 
 on the black glass. It is the oldest of its class, but has no name attached to 
 (Page 156) it, and no record of its history is given. Dr. Geisler's form seems 
 to have great merits. A large bulb terminating the thermometer has muslin over 
 it, and is cooled by ether. This bulb is connected by a tube with the large 
 bulb of the thermometer. In this latter bulb is a hermetically-closed vessel 
 containing ether. The cooling of the terminal bulb causes the ether of the interior 
 of the thermometer to evaporate. And the thermometer bulb is cooled until 
 dew appears, when the temperature gives the dew-point temperature. The 
 evaporation measurers are not reliable. Lament's atmometer has the defect that 
 the small quantity of water is liable to be unduly heated. Professor Osnaghi shows 
 the steel-yard evaporimeter. A vessel is at one end 5 in. in diameter ; it contains 
 water. As evaporation proceeds an index traverses a scale. The water is liable 
 to undue heating, owing to its small bulk. In Ebermayer's evaporation apparatus 
 (Page 158) is a box filled with soil, kept constantly moist by means of a reservoir. 
 The objections to it are that 5 inches of soil is not the same as so much soil 
 in situ, as the latter can draw upon the soil beneath ; and the whole apparatus 
 is apt to become abnormally hot. Morgenstein's atmometer is based upon the 
 principles of capillarity and of Mariotte's bottle. Sand is saturated with water 
 by capillarity supplied from a burette closed from the air on its upper end. A 
 
AQUEOUS VAPOUR 1877. Ley. NOTES. 
 
 tube runs from the sand into the burette, and supplies air to the latter as the 
 water evaporates from the sand. When the burette is nearly filled with air it 
 is apt to be affected by temperature. This defect is remedied by means of a 
 globular vessel, which receives any water that may be forced out in this way. 
 The evaporating vessel is embedded in some badly conducting material. Its 
 area is one square decimetre (4 in.). The instrument is sensitive to the fraction 
 of a drop of water. It may give accurately the loss from a surface of saturated 
 sand, but it is quite unsuited for exposure to sun and rain. Prestel's atmometer 
 (Page 159) was the earliest in which the bird fountain principle in Mariotte's 
 bottle was applied ; Morgenstein's is a refined edition of it. 
 
 1877. 
 
 Bonavia, E. 
 
 (Page 101.) He refers to the collection and increase of clouds early in October 
 1877, at Lucknow, before 3 P.M., and their gradual complete dissolution by 
 two hours after sunset, as an indication that the cloud region became decidedly 
 warmer after sunset than it had been during the day. 
 
 Broun, J. A. 
 
 (Page 333.) It appears that the monsoons on the west coast of India have a 
 central current of maximum vapour depth or of velocity, which he suggests 
 may be shifted north from year to year, according to some law like that of sun spots. 
 
 [The principle is of general application to other areas.] 
 
 C.,H. 
 
 (Page 43.) For years we [in Newfoundland] have marked an intimate connection 
 between the colours of clouds and the weather. Thus we have the cold dark blue 
 and grey and the reddish-yellow masses of clouds as indicative of cold and snow 
 and we have the light bright grey with bright edges as indicating or accompanying 
 a hard frost ; the inky cloud flying in shreds, as indicative of wind and rain ; the 
 mottled cloud of the same colour or thereabouts is the sure indication of rain ; the 
 sickly-looking green, the deep blue gloom, the muddy, angry-looking red, and other 
 such tints, as forecasts of storm, snow, rain, etc. ; and frequently before a north- 
 easter we have the grey-bluish and whitish clouds setting from N.E. 
 
 Czerny, F. 
 
 (Page 239.) It is purely the winds which determine the condition of moisture of the 
 (Page 240) atmosphere. If an equatorial current was to rise over a high mountain 
 range, it may appear on the other side as a hot, withering wind, the fohn of 
 Continental writers, in the thirsty regions. [See Notes, 1861, Eaton, p. 13.] 
 
 Hill, S. A. 
 
 (Page 506.) It may be said that the fact tha.t the rainfall is greatest in maximum 
 sun-spot years, argues increased evaporation during these years. The great majority 
 of the rainfall stations examined are within or near the tropics, or in the maritime 
 districts of temperate regions, and their more abundant rainfall in years of maximum 
 sun-spots might be explained by the diminished carrying power of the winds at 
 that epoch of the Solar cycle. 
 
 Ley, Rev. W. C. 
 
 Page 254.) Local depressions starting from the edges of the great areas of 
 excessive evaporation seem to be governed in their course by the distribution of 
 
 401 
 
AQUEOUS VAPOUR. 1877. Nature. NOTES. 
 
 relative humidity, and to be determined towards those districts in which precipita- 
 tion is most in excess of evaporation. Consequently their forward development is 
 generally somewhat towards the poles. In the south hemisphere the middle 
 latitudes are almost entirely occupied by surfaces in which evaporation is excessive. 
 In the northern they are represented, to a large extent, by areas of relatively slight 
 (Page 334) evaporation. The easterly winds felt on the south border of a small 
 cyclone, if pursued for a very limited distance, are often found to have undergone 
 a complete change in the aspect of the clouds which they carry and in their 
 humidity. 
 
 Ley, Rev. W. C. Symons's Meteorol. Mag., vol. xii. (rsp.} 
 
 [No. for February.] 
 
 (Page 9.) Picus viridis. Its laughing cry is seldom heard during humid weather, 
 or when the sky is much overcast. The greenfinch is especially noisy in sultry, 
 overcast weather. 
 
 Nature. 
 
 (Page 210.) Contributions to hygrometry. The wet bulb thermometer. By 
 W. Marriott, read to the Meteorol. Soc., December 20th, 1876. The observations 
 were made to determine what a wet bulb should be. Ten thermometers were used 
 as wet bulbs. With three bulbs the water receptacles were placed at different 
 angles, but it was found that the readings were not affected by the position of the 
 water receptacle. Others were used with different thicknesses of muslin and 
 conducting threads ; the thermometers with the thinnest muslins always gave the 
 lowest readings. Three pairs of dry and wet bulbs were used, one with a closed 
 water reservoir, 6 in. from the dry bulb ; the other two having open reservoirs 
 which were respectively 3 in. and 1 in. from the dry bulb. It was found that the 
 dry bulbs of the two latter read lower than the former in fine, dry weather, but when 
 the air was damp, and during rain, they generally read higher. The wet bulbs of the 
 latter read a little higher than the former ; this was mostly the case in damp weather. 
 
 Hon. R. Abercromby, Visibility, read to Meteorol. Soc., December 20th, 1876. 
 Visibility is a very trustworthy prognostic of rain. The usual explanation that 
 much moisture increases the transparency of the atmosphere is not borne out by 
 (Page 541) observation. A correspondent in Journ. Soc. Arts, notices that in 
 Ceylon, where the air is damp, the fruit of the coffee-plant has to be picked at 
 maturity, else it would mould on the tree ; whereas in Arabia, where the climate is dry 
 the fruit is allowed to ripen and drop off. 
 
 Nature. 
 
 (Page 197. ) Steppes are characterized by absence of wood, the sandy surface is 
 covered with grasses, dwarf herbs, and stunted bushes, which increase rapidly after 
 the rainy season, but fade away altogether in the dry season. The steppe is 
 defective in having no regular supply of water, being only here and there covered 
 by streams, marshes, and lakes. The fauna of the steppe is characteristic, and is 
 never met with in woody or marshy places. The most remarkable are the steppe 
 rodents, such as jerboas, sousliks, and voles. 
 
 (Page 295.) (Hoffmeyer, in Naturen, June 1877.) Dr. Hann several years 
 since explained the physical properties of thefohn wind. The air is forced over 
 the mountains; in ascending it expands, and becomes cooled. On descending 
 again it is compressed and heated. Its temperature rises more and more above 
 the dew-point, and moisture will, with continually increasing ease, be held dis. 
 solved in the state of vapour. [See Notes, 1877, Czerny p. 240.] 
 
AQUEOUS VAPOUR 1878. Abercromby. NOTES. 
 
 (Page 336.) (Acad. .Sci., Paris, August 6th.) Comparative influence of leafy 
 woods and resinous woods on rain and the hygrometric state, of the air, by 
 M. Fautrat. If vapours dissolved in the air were apparent like fogs we should 
 find forests enveloped by a large moist screen, and for pine forests the envelope 
 would be greater than for others. Pines retain in their branches more than half of 
 the water poured on them, while leafy trees let 58 per cent, go to the ground. 
 
 (Page 369.) (Dr. Hamberg.) The absolute humidity of the air on clear nights 
 in which no dew is deposited decreases from the ground upwards, just as happens- 
 during the day ; but, on the other hand, with dew the humidity is least nearest the 
 ground and increases with the height, and this influence of dew in diminishing the 
 humidity extends upwards to at least 22 feet. Since his observations clearly show 
 that the absolute humidity begins in the evening to diminish near the ground before 
 any dew is observed to be deposited, and also diminishes at all heights on those 
 nights during which no dew whatever is formed, Dr. Hamberg is of opinion that the 
 diminution of the humidity is to be sought for in other physical causes than the 
 deposition of dew. 
 
 (Page 392.) (Acad. Sci., Paris, August 20th.) Faye : The phenomena relative 
 to the exceptional winter of 1876 7 are attributed by Hebert to a succession 
 of strokes of sirocco which have communicated the heat and drought characteristic 
 of them. The sirocco stroke, which caused the very mild dry weather in the 
 beginning of the year, belonged to three great cyclones, which came, like all the 
 others, from the Atlantic. [Perhaps this refers to Paris.] 
 
 
 Nature. 
 
 (Page 134.) (Hon. R. Abercromby. Meteorol. Soc., November 21st.) In a 
 cyclone the broadest feature of the weather is an area of rain about the centre 
 surrounded by a ring of cloud, beyond which the sky is clear. The position 
 and precise forms of these areas vary with the type of pressure distribution, 
 with the intensity of the cyclone, and with the rate of its progress ; they are also 
 influenced by local, diurnal, and seasonal variations. By recording the appearance 
 (Page 135) to a single observer of any part of a cyclone as it passes over him, it is. 
 discovered that the area of rain and cloud ring may be divided into two portions, 
 the front and the rear, differing in physical appearance and general character of the 
 weather by a line drawn through the centre, in front of which the barometer is 
 falling and in rear of which it is rising. In anti-cyclones synoptic charts show great 
 irregularity in the positions of clouds, etc. 
 
 (Page 156.) (Fautrat. Acad. Sci. Paris, December 10th.) Above pines in the 
 daytime there is always a rise of temperature from the solar heat being retained by 
 the vapour enveloping the tree tops. 
 
 1878. 
 Abercromby, Hon. E. 
 
 (Page 143.) The process of averaging has resulted in the discovery of diurnal 
 (Page 145) and annual variations of vapour and humidity. A watery sky is a 
 sign of rain, because it is characteristic of the front or east part of a cyclone, 
 and as a cyclone usually travels eastwards, an observer will successively be 
 subjected to the influence of the cloudy and rainy parts of a cyclone before an 
 area of fine weather again reaches him. Again, visibility with an overcast sky 
 is a sign of rain, because the general condition of circulation in the atmosphere 
 shown by straight isobars, during which it is observed, is never persistent for 
 long, bu works up to a cyclone and rain. Visibility with a cloudless sky is a 
 
 403 
 
AQUEOUS VAPOUR 1878. Brown. 
 
 NOTES. 
 
 sign of rain when the cyclone is quickly followed by another. When that is 
 not the case visibility is sometimes the precursor of persistent dry JN.W. 
 (Paqe 149) or N.E. winds. As to the 10 A.M. maKimum of the barometer if 
 we look at the barographic trace for May 27th, 1877 [for London], we see that 
 superimposed on the general rise of the barometer between 4 A.M. and 1 1 A.M. 
 there is a very slight depression. The author's observations for the day are 
 not very complete, but a similar depression is very common, and in many 
 -cases he has observed it to be associated with the temporary formation of heavy 
 olouds about that time of day. If this is confirmed by future observation it 
 would point to the conclusion that either overcasting of the sky or the forma- 
 tion of cloud interfere with those statical or dynamical changes which produce the 
 10 A.M. maximum. The author has pointed out in a former paper that there 
 are critical periods of the formation or disappearance of cloud or fog superimposed 
 on the general cyclone or anti-cyclone character of weather corresponding with the 
 {Page 150) hours of diurnal barometer maxima and minima. Cloud produces a small 
 diurnal range of temperature ; at night it reduces the cold, and by day k 
 reduces the sun's rays, so that a temporary clearing up of the sky might make 
 the minimum temperature at almost any hour of the night, and the maximum 
 (Page 151) at almost any hour of the day. If ever meteorology is to be a 
 science, it is of the utmost importance to discriminate between the different 
 kinds of clouds, and to determine their position in synoptic maps relative to 
 cyclones and anti-cyclones. 
 
 Archibald, E. D. 
 
 (Page 505.) The hypothesis started by Hill and myself, that the solar radiation 
 varies inversely with the sun spot frequency takes account of the probable 
 effects of such a variation upon the vapour currents throughout the globe with 
 respect to velocity, direction, season, and latitude. According as trades, anti- 
 trades, monsoon or anti-monsoon, prevail (1) at different places at the same 
 reason ; (2) at the same place at different seasons, so will specifically distinct effects 
 arise both from the amount of vapour brought, and its conditions of precipita- 
 tion, to determine which, not only the general conditions introduced by latitude 
 and season, but the local and meteorological functions of the region must be 
 -carefully studied. The anti-trade, which in its seasonal shifts north and south 
 traverses the entire temperate zone, should give signs of a secular change in 
 intensity and humidity, corresponding according to the hypothesis, inversely 
 with the sun's spots.. 
 
 Broun, J. Allan. 
 
 (Page 126.) Herschel cites Humboldt's statements that the clearing away of 
 -clouds was well known to the seamen and pilots of Spanish America. Barnardin de 
 St. Pierre, in his ' Voyage a 1'He de Reunion,' says : ' I remarked constantly that 
 the rising of the moon dissipated the clouds in a marked way. Two hours 
 .after rising the sky is perfectly clear' (April 1768). Faye says the moon has 
 no such effect, supporting his conclusion by the Vigevano register by Serafini, 
 who, however, records the condition of the sky between morning and evening 
 only. M. Schiaparelli finds from this register that the sky was clearest in the 
 first quarter of the moon. Faye's conclusion was faulty owing to the one-sided 
 character of the evidence, and from his neglecting the observations of Madler 
 and Kreil, Park Harrison and Balfour Stewart. The moon's heat cannot be 
 (Page 127) the cause of the phenomenon, as the moon gives no heat, so that 
 it must be explained in some other way 
 
 404 
 
AQUEOUS VAPOUR 1878. Lockyer. NOTES. 
 
 King, Samuel. Symons's Meteorol. Mag., vol. xiii. (rsp.) 
 
 (Page 176.) He refers to dense fogs at Elswick Lodge. The ponds and ditches 
 were covered with a greyish scum, which seems to indicate the fog was not 
 entirely composed of watery particles. The wind had blown from the north for days. 
 
 Lockyer, J. "N. 
 
 (Page 224.) I would ask whether during the night the molecules of aqueous 
 vapour which absorb the blue have not been driven into higher forms, dew 
 being one of them, owing to the reduction of temperature. This would explain 
 the generic differences between sunrise and sunset colours, as also the golden 
 instead of red sunsets which accompany the formation of cloud. 
 
 Murray, A. E. Symons's Meteorol. Mag., vol. xiii. (rsp.) 
 [No. for November. It is a newspaper insertion opp. p. 160.] 
 Col. 3. [There is no numbering in the original.] The clouding which occurs 
 in the front of a barometric depression usually commences in the west, and 
 the clouds at first often assume the appearance of streamers. [His statement 
 is general, but he seems to have W. Europe in his mind.] An attempt was 
 made to test if the moon influences the cloud, by means of observations made 
 at Hastings. [It was assumed that if the thermometer on the ground was 
 not very different from one 4 feet above ground that the sky was cloudy ; if there 
 was a great difference that the sky was clear] . For the year 1876 I picked 
 out all the days of full moon, new moon, first and last quarters, and found 
 that the difference between the thermometers was in the following proportions : 
 Full, 24-7; last quarter, 39'3 ; new, 41'0; first quarter, 46'6 ; showing 
 that for that year there was most cloud at full moon, and least at the first 
 quarter. I then combined one day on each side, and obtained the following 
 figures : Full, 91-9; last quarter, 108; first quarter, 116'3 ; new moon, 
 151 '5; giving least at new moon, most at full. For 1877 the results were, 
 for one day : First quarter, 38'9 ; new, 431 ; full, 49'9 ; last quarter, 52'5 ; 
 giving most to the first quarter, least to the last quarter. Including one day 
 on each side, First quarter, 130'1 ; new moon, 137'5 ; last quarter, 150' 1 ; 
 full moon, 158'3 ; giving most to first quarter, least to the full. The two years are 
 utterly at variance, and the impression I arrived at was that the different years 
 would neutralize each other, and that the amount of cloud would prove to 
 be on the average the same for all ages of the moon. 
 
 nsr., j. H. 
 
 (Page 672.) Boussingault (' Ann. de Chimie,' xii., p. 289) finds from the average 
 of fourteen experiments that the hourly loss of water by evaporation of the leaves 
 of a healthy Jerusalem artichoke for every square metre of foliage is 65 grammes 
 in sunshine, 8 in shade, and 3 during the night. Mint gave off 82 grammes 
 in sunshine and 36 in shade. A grape vine gave off 35 grammes in sunshine, 
 11 in shade, and 5 during the night. The whole plant had about 138 square 
 metres of foliage, and in sunny weather would lose in 21 hours 48 kilogrammes 
 of water. An acre of beets, it was calculated, could lose in 24 hours between 
 (Page 673) 8,000 and 9,000 kilogrammes. Plants that have lost much of their 
 constitutional water may absorb water from an atmosphere saturated with 
 aqueous vapour. 
 
 Thomson, Sir C. W. 
 
 (Page 449.) There is a vast mass of cold ocean water which flows from the 
 south far into the north hemisphere. The explanation of this is simple. For 
 
 E E 405 
 
AQUEOUS VAPOUR 1878. Nature. NOTES. 
 
 some cause, not fully understood, evaporation is greatly in excess of precipita- 
 tion in the northern portion of the land hemisphere, while over the water 
 hemisphere, and particularly its southern portion, the reverse is the case ; thus 
 one part of the general circulation of the ocean is carried on through the 
 atmosphere, the water being raised in vapour in the northern hemisphere, hurried 
 by the upper wind currents to the zone of low barometric pressure in the 
 south, where it is precipitated in the form of snow or rain, and welling thence 
 northward in the deepest channels on account of the high specific gravity dependent 
 on its low temperature, it supplies the place of the water which has been removed. 
 
 Nature. 
 
 Page 385.) In Plante's experiments the electric current in presence of aqueous 
 vapour yields a series of phenomena altogether analogous to the various phases 
 of polar aurorse. If the positive electrode of the secondary pole of the secondary 
 battery is brought into contact with the sides of a vessel of salt water, we 
 observe, according to the distance of the film from the liquid, either a corona 
 of luminous particles arranged round the electrode (fig. 8*), an arc bordered 
 with a fringe of brilliant rays (fig. 9), or a sinuous line, which rapidly folds 
 and refolds on itself (fig. 10). This undulatory movement in particular forms a 
 complete analogy with what has been compared in aurorse to the undulations 
 of the serpent, or to those of drapery agitated by the wind. [If so, then notes 
 on aurorse would afford some information as to the distribution of aqueous 
 vapour in the higher regions]. Plante explains the slow movement or stoppage 
 (Page 386) of globular lightning by the movement or repose of the column 
 of moist air strongly electrified and invisible, which serves as electrode. Almost 
 (Page 436) every known portion of the south hemisphere (March 28th) has been 
 suffering from a severe and protracted drought. 
 
 Nature. 
 
 (Page 288.) If the upper currents depicted by the Rev. W. C. Ley in his 
 paper are to be regarded as tolerably close approximations to the movements 
 of the cirrus-cloud of a cyclone, it follows that the region of the cirrus occupies 
 a much higher level over the front portion of a cyclone than it does over 
 its rear, notably than over its north-west quadrant, a point of prime import- 
 ance in relation to the theory of storms. Professor Loomis supposes that in 
 great storms the inflowing ajr escapes by an ascending current, carrying with 
 it a large amount of vapour, which, as it is cooled, is condensed into cloud 
 and rain, and that the heat thus liberated further expands the air. Montigny 
 (Page 292) shows that approaching moist weather increases the intensity of scin- 
 (Page 352) tiUation of stars (Acad. Sci. Paris', July 16th). Crova observed that 
 solar radiations were weakest with S. or S.W. winds, and strongest with N. or 
 N.W. winds, the former increasing, the latter diminishing the vapour in the 
 (Page 680) air. Dr. Hellmann (in the 30th report of the Royal Meteorological 
 Institute of Prussia) finds that the daily maximum of cloud occurs at Crefeld 
 about, or a little before, sunrise from September to April, whereas from May 
 to August the maximum is from about 11 A.M. to 3 P.M. The monthly maximum 
 which holds also for all hours of the day is December, while the month 
 with clearest skies is September. 
 
 These figures are not reproduced here. 
 
AQUEOUS VAPOUR. 1878. Nature. NOTES. 
 
 Nature. 
 
 (Page 178.) Rev. W. Clement Ley : Cloud observation requires a special train- 
 ing of the eye. The classification and nomenclature is highly unsatisfactory, having 
 been framed at a time when the relation of wind and weather to the distribu- 
 tion of barometric pressure was unknown ; and with this relation the form 
 and movements of the cloud are intimately connected. As regards configuration, 
 clouds seem naturally divisible into two groups those which arrange themselves 
 in layers, whose vertical diameter is small as compared with its horizontal, 
 and those which assume spherical or hemispherical shapes, and this division 
 is related to certain physical conditions of the atmosphere, and of the earth's 
 surface beneath the clouds. The movements of the upper clouds afford most 
 valuable information concerning the distribution and movement of the areas 
 of high and low barometric pressure. It may be sufficient to explain that in 
 the front of an advancing barometric depression there usually extends a bank 
 of the halo-producing cirro-stratus, the exterior edge of which is, roughly 
 speaking, a parabola, the focus of which lies in the line about to be traversed 
 by the centre of the depression. On the right hand of the centre this bank 
 or sheet is abruptly broken, and is succeeded in the rear by local shower-clouds. 
 On the left hand the sky commonly continues overcast, but the cloud-plane 
 gradually descends until little is to be seen but low stratus. A backing of 
 the upper current takes place until after the centre of the depression has 
 passed. In whatever direction a depression is advancing the same characteristic 
 phenomena are observed. Thus changes in the clouds indicate to us probable 
 alterations of wind and weather. While the nimbus which exists in the front 
 of a depression first makes its approach evident by changes in the higher cloud- 
 strata, the process of nubefaction is the converse of this in those local showers 
 which commonly occur on the right hand and in the rear of a centre of depression, 
 and therefore when the barometer is rising, or just about to rise. These latter are 
 developed in an upward direction through the formation of cumulus. The pre- 
 cipitation which occurs in them always preceded by a change of appearance 
 in the domes of clouds, which assume a soft and cirriform aspect is attri- 
 buted to the neutralization of electricities as the summit of the cloud passes into 
 a higher region ; but there are important differences between those cumuli 
 which are likely, and those which are unlikely, to undergo this transformation. 
 A physical explanation is given of the ordinary weather signs derived from 
 the colours of the sky, from visibility, and from unusual refraction. Attention 
 is invited to some unusual types of clouds, especially to a very elevated turreted 
 stratus often erroneously termed cirro-cumulus, occurring with high temperature 
 on the S.W. borders of anti-cyclones, a forerunner of thunderstorms. The forma- 
 tion of the low level stratus, and of the fog which usually prevails in our 
 winter anti-cyclones, seems to be due to a downward movement of the air at a 
 time when the earth's surface is colder than the atmosphere at a slight eleva- 
 tion above it. 
 
 Symons's Meteorol. Mag., vol. xiii. (rsp.) 
 [No. for May.] 
 
 (Page 55.) Alluard's hygrometer is essentially an improved Regnault's. By an 
 arrangement of tubes ether is made to evaporate when wished, so as to cool a flat 
 brass plate. The thermometer beneath the plate indicates the temperature at which 
 dew is observed to form. This is made easier by having an annular surface near, 
 which is not cooled. It is probably the best condensing hygrometer as yet 
 introduced. 
 
 407 
 
AQUEOUS VAPOUR 1879. Hind. NOTES. 
 
 [No. for July.] 
 
 (Page 91.) The questions proposed for discussion at the International Meteoro- 
 logical Congress include the following : Influence of cultivation, of grassing, and of 
 replantation upon the production of dew, on the amount of rain-fall, and on its 
 discharge from the surface of the earth. Origin and nature of dry fogs. 
 
 [No. for December.] 
 
 (Page 167.) In Blandford's theory of cyclones, an essential condition is that the 
 cyclonic area be supplied with an indraught of a saturated current from the S.W. or 
 W.S.W. [His remarks refer to North India, so that this would fee also a warm 
 quarter. His theory is in the main the same as Espy's.] 
 
 (Page 169.) Dr. Koppe's per cent, hygrometer is a Saussure's hygrometer with an 
 arrangement for adjusting the index to the true reading. 
 
 1879. 
 
 Erskine, St. Vincent, Journ. Roy. Geog. Soc., vol. xlviii. (1879). Read January 28th 
 
 1878. (Vs.) 
 
 (Page 28.) At Muxango's Kraal [in South Mozambique] in 21 2' S. the mornings 
 and evenings were calm and clear, and a sea breeze generally prevailed during the 
 day laden with cumuli. 
 
 Hind, J. R. 
 
 (Page 189.) In B.C. 44 Plutarch and Dion Cassius record that fora whole year the 
 sun was paler than usual, and gave less heat, the air continuing cold and misty. 
 
 Ley, Rev. W. C., in Modern Meteorology, 1879. (rv.) 
 
 (Page 102-103.) Very little progress has been made on the subject of clouds and 
 (Page 103) weather signs. Aratus and Virgil were almost as advanced as some 
 modern meteorologists. But this science is capable of great ultimate achievements. 
 (Page 104.) Cloud observation is, in a very great measure, an incommunicable art. 
 Keenness of sight, coupled with the habit of observing phenomena, are the first 
 requisites ; to this must be added a training of the eye by practise. By practise, I 
 can now, when only the summit of a cloud forty miles away is visible above the 
 distant horizon, state, with unfailing certainty, whether or not rain is falling from 
 (Page 105) the under-surface of that cloud. Similarly, I can detect motions in 
 cirri imperceptible to most observers. Inaccuracy in cloud observations, as regards 
 distance or relative height, is the rule. For example, when cirrus or cirro-cumulus, 
 at a great altitude, is moving in a rapid under-current, while thin clouds nearer to 
 the earth's surface are stationary, or nearly so, most persons say the first-named 
 (Page 106) cloud is the lower of the two strata. Forster made this mistake. 
 Artists seldom paint clouds right, so that there is no way of referring to the 
 (Page 107) objects by way of illustration except directly. Observers have not 
 settled upon a reliable classification, and the nomenclature is faulty. Every classifi. 
 (Page 108) cation must fail which does not take into account the intimate connection 
 between the forms and movements of clouds with other elements. The behaviour 
 of clouds is evidently controlled to a great extent by atmospheric electricity, but 
 we know little about this. A thorough knowledge of all these is essential before we 
 can make a good cloud classification. Clouds may be grouped in two divisions : 
 (Page 109) first, those tending to arrange themselves in a horizontal layer, the 
 components of which may be either fibrous and interlacing (which is commonly 
 noticeable when the bed is at a great elevation), or more compactly welded (which is 
 more common when the bed is near the earth's surface), but whose vertical diameter 
 is in any case very small as compared with its horizontal ; second, the clouds of 
 408 
 
AQUEOUS VAPOUR 1879. Ley. NOTES. 
 
 massive spherical or hemispherical shapes, and having a plane base when in the 
 inferior regions. Both exist at all altitudes at which clouds are visible. The first 
 of these divisions comprises essentially the clouds of the night, and the second those 
 (Page 110) of the day. Again, clouds of the first division are those of winter, those 
 of the second, clouds of summer. But this rule applies with much fewer exceptions 
 to the lower than it does to that of the higher portion of our hemisphere. Finally 
 (but this rule has many exceptions), clouds of the first division are more common 
 over the sea than over the land. On the west coast of Norway, for example, I have 
 often seen the mainland covered with massive piles of cumulus, while over the sea 
 were only a few streaks of linear cloud. Each little island had a little cumulus 
 poised above it, a larger island a larger cumulus, and so on, the size of the cloud 
 being almost exactly proportional to that of the land surface beneath it. It is even 
 said that a reef when covered with shallow water often has its position marked by a 
 solitary cloud of the cumulus form above it. I here adopt the term stratus for 
 clouds of the first division, and cumulus for those of the second. The most valuable 
 weather signs are derived, not from the former, but from the direction of motions 
 (Page 111) of clouds of different levels. Movements of the highest clouds afford 
 information of the highest value concerning the distribution and movements of the 
 (Page 112) areas of barometric pressure existing at the time of observation. Here 
 I apply the term ' cirrus ' only to the ' curl clouds/ or * mares' tails,' which float at 
 a high elevation ; cirro-stratus to the halo-producing sheet ; cirro-cumulus to the 
 (Page 113) small white nebulae which float at the same level as the cirrus and 
 cirro-stratus. 
 
 [He then points out how the movements of clouds indicate the positions of areas 
 of high and low pressure ; these details more pertinently appertain to barometric 
 pressure and wind, but those which bear upon the distribution of aqueous vapour 
 are given here.] 
 
 (Page 115.) There commonly exists in front of an advancing barometric depression 
 a great bank of the frozen moisture in the high regions of the atmosphere which we 
 call cirro-stratus. Synchronous observations show that the edge of this bank is 
 commonly curved, and that the curve is, roughly speaking, a parabola, the focus 
 of which lies nearly in the line along which the centre of the depression is about to 
 travel. We do not, however, commonly see this curve in looking at the cloud. 
 What we do see are longitudinal threads, or filaments of thin cloud, at an altitude 
 (Page 116) of between 25,000 and 40,000 feet above the earth, and so arranged as to 
 be parallel to each other. Outlying streaks of this cloud often form from twenty to 
 one hundred miles in advance of the main pack, the pioneers of the coming army, and 
 can be examined without difficulty. These threads of ice crystals terminate in most 
 attenuated points which are often curled more or less outwards or upwards, 
 being kept asunder by electric repulsion, the whole thread acting as a horizontal 
 conductor of electricity. As the actual bank comes over us the threads which 
 compose it are seen to be more or less reticulated, forming a filmy sheet or canopy, 
 the structure of which becomes less and less discernible. This is the form of cloud 
 which produces halos. Occasionally, indeed, even from the first appearance of the 
 sheet, we can scarcely discern any structure in it at all ; the sky seems simply to 
 become gradually overspread with a milky-looking film of whitish cloud matter. 
 In this latter case we infer that the upper regions are especially humid, and that 
 the crystals being less insulated, consequently do not arrange themselves in definite 
 threads. In any case, as the bank becomes more fully over our station its under 
 surface becomes lower, and is at the same time rendered indistinct by the formation 
 of visible cloud matter in the lower regions of the atmosphere. The commencement 
 of this stage usually coincides with that of the fall in mercurial column, for the 
 (Page 117) barometer is often either rising or stationary under the outlying threads 
 
 409 
 
AQUEOUS VAPOUR 1879. Ley. NOTES. 
 
 already described. The rain-bringing wind now begins slowly to make itself felt at 
 the earth's surface, the upper clouds cease to be visible at all, for the sky becomes 
 totally covered by a composite mass of condensed vapour, and more or less precipi- 
 tation at once sets in. I will now describe the movements of that upper current 
 which has brought this canopy over our heads. I will suppose, then, first, that 
 (Page 118) depressions are travelling from S.W. to N.E. (which is with us their 
 most common direction), an anti-cyclone lying to the S.E. of our district. First, let 
 us imagine ourselves to be situated actually upon the line which is to be traversed 
 by the centre of the disturbance. Cirrus thread will first appear upon the south- 
 west horizon, and parallel to that horizon. When some of them have arrived at the 
 zenith we shall find them to travel from some point between W.S.W. and W.N.W. 
 A little later, when an easterly wind has sprung up beneath, and when the cloud- 
 bank is getting thick, we shall, if we can catch an opportunity of seeing the higher 
 clouds, find that their current has backed ; that is to say, is now from a rather more 
 southerly point. By-and-by, when the barometer has reached, or nearly reached, its 
 minimum, if we can see the clearing of the sky, we shall find that this upper current has 
 backed so much as to be then moving from a south-easterly point. The cirri will then 
 (Page 119) be ranged in lines from S.E. to N. W. Their appearance will, at the same 
 time, have greatly altered ; they will have become much more massive, and their 
 threads or tufts will commonly be seen to point in a more or less downward direction, 
 indicating that a cold and drier atmosphere is setting in below. Now let us imagine 
 that the advancing depression is passing considerably to the N.W. side of our station- 
 In this case the bank of cirro-stratus or its outlying threads have first been visible 
 on the W. or W.N.W., and parallel to that horizon, and the upper current is found 
 to travel from some N.W. point. As the bank spreads over us, while the south- 
 westerly wind springs up beneath, we observe the upper cloud to be less thick and 
 watery-looking than in the description given before. Cirro-cumulus in this case 
 often takes the place of cirro-stratus, which is probably an indication that no great 
 conduction is going on aloft. The rain, if any, falls in spasmodic showers, and 
 when the sky clears it does so far more gradually than at more central stations. 
 Here, too, we shall find that the upper current has backed, but only to a W. or S.W. 
 point, so that when the wind at the earth's surface has veered to W., clouds of 
 every level over our heads will be found to move from nearly the same quarter. 
 (Page 120) Again, suppose a depression in going N.E. is leaving us upon its left. 
 In this instance the cirro-stratus bank first shows itself on the S.S.W. horizon, and 
 its motion is from some point between W.S.W. and S. In this case, after the sky 
 has thickened, and a north-easterly wind has freshened with a falling glass, we very 
 rarely get an opportunity of seeing the upper clouds at all ; but when we do, at the 
 time that the centre of the disturbance is nearest to us, we usually observe the 
 upper current to have backed so as to come from S.E. The rain, in this 
 instance, if it extends so far north as our station, is cold, thick, and continuous. 
 As it ceases the clouds remain for a little while low and dreary, the clearing of the 
 sky is very gradual, and when the wind is gone round to N. and the barometer 
 is rising, we commonly see that the main vapour-plane has greatly descended, and 
 that in lieu of the cirro-cumulus, and shower-clouds which are being experienced 
 farther south, we have irregular but level stratus occupying the middle or rather 
 lower beds of the atmosphere. Now, suppose we are in the rear of a disturbance, 
 the central part of which has passed fairly off to the N.E. The sky is either clear 
 or contains fragmentary cumulus and perhaps a few local shower-clouds. Such 
 (Page 121) upper clouds as are seen are here commonly either masses or threads of 
 somewhat curly cirrus ; if threads, they stretch from N.W. to S.E., and their motion 
 is, in any case, nearly from that direction, and this coincides, or nearly so, with the 
 line of the isobars. It is a very rare thing to experience a N.W. wind (except 
 
AQUEOUS VAPOUR 1879. Ley. NOTES. 
 
 immediately after it has veered to that point) which does not extend to the highest 
 regions of the cloud-bearing atmosphere. When depressions are passing over or 
 near us, the general distribution of high and low barometer is not always such as I 
 have described. But the same rules apply, the winds being shifted. Thus if the 
 depressions are going S.E., we must veer our words eight points or shift our diagram. 
 I shall give one or two illustrations of what I mean. In weather in which we 
 (Page 122) know from the previous changes of wind, and better still from our study 
 of the daily maps, that the depressions or areas of rainy weather are travelling 
 from S. to N., the appearance of a thick bank of cirro-stratus in the S.E., 
 moving from some point between S.W. and S. after an interval of fine weather, 
 is often an indication of coming rain, probably heavy, and accompanied by 
 a muggy N.E. wind. On the other hand, if under the same circumstances the 
 first threads of cirrus or cirro-stratus are observed in the W., but are found to 
 travel from the S. W., the rainfall is not likely to reach our station, at least in more than 
 one or two passing showers. Again, let the weather be such as we frequently have 
 in spring, and occasionally in autumn and winter, winds backing and veering 
 between W.S.W. and N., and the weather map showing us that areas of bad weather 
 are travelling from the Scottish coasts towards Holland and Denmark. Let a fine 
 day be succeeded by a watery bank of cirro-stratus in the N.W. travelling from 
 N. or N.KE., hard weather is to be expected; a blustering westerly wind ac- 
 companied by composite cloud-bank will probably veer to a cold N. or N.E. gale. 
 On the other hand, under the same circumstances, let the cirrus appear first 
 in the N.N.E., and travel from a northerly point, we are not then likely to 
 experience more than a few slight showers of sleet or snow, with only a moderate 
 (Page 123) backing or veering of the wind. The whole subject is one of great 
 importance in making forecasts. Howard called every cloud from which rain falls 
 a nimbus, but he appears to indicate a twofold division ; but neither he nor his 
 successors have told us much of this division. The symptoms of the extensive 
 rainfall become first apparent, as a general rule, in the higher regions of our atmo- 
 sphere ; the cloud-bank begins at a high level, and is succeeded by a composite 
 (Page 124) cloud at a lower level. The formation of passing showers is commonly 
 the converse of this process. Almost every one must have observed the forma- 
 tion of a cumulus cloud, probably in the earlier hours of a showery day. 
 Loose shreds of irregular cloudy matter begin to appear, here and there, 
 under the bright blue. They are at first near the earth's surface, commonly 
 in what has been the vapour plane of some stratus in the preceding night. Gradually, 
 as rapid evaporation goes on under tli3 increasing power of the sun's rays, the 
 rising vapour forces upwards the particles above it, which are condensed by the cold 
 of the higher regions into more and more mountainous masses. The under-surface 
 remains level, reposing on the vapour-plane that is precisely at that altitude above 
 the earth at which water passes from the gaseous state to that of mist. Below the 
 cumulus the vapour is rising, but in the invisible state. The general shape of the 
 cumulus is a hemisphere or cone with a surface formed of rounded protuberances. 
 If you look at these you often see them continually tumbling back into the main 
 body of the cloud, which yet continues to swell gradually upwards and outwards. 
 That the older meteorologists were right in attributing this process principally to 
 (Page 125) electric disturbance I cannot doubt. The cloud is now an insulated body, 
 more or less highly charged. It repels the opposite electricity from the particles in 
 its neighbourhood, and attracts them to itself, and an invisible rain of such particles is 
 perpetually pouring probably upon all parts of its surface, the general charge of the 
 cloud beingretained partly by reason of its spherical surface. Similar clouds have been 
 simultaneously forming in other parts of the heavens, and a thunder clap is heard on 
 the distant horizon. We see in the quarter from which it has proceeded a cumulus or 
 
 41] 
 
AQUEOUS VAPOUR 1879. Ley. NOTES. 
 
 body of cumuli, the upper surface of which has put on quite a different appearance. It 
 is spreading outwards and upwards in very thin cirrus-like filaments. It has, in fact, 
 risen to such a height as to approach a stratum of gas intensely electrified, and with 
 an electricity opposite to its own, and it is disposing the ice-prisms in innumerable 
 threads, or feelers, spreading their attenuated points through the lofty regions of 
 highly-rarefied air. We look again at the cumulus which we have watched before. 
 Its glowing summit is undergoing a similar metamorphism, becoming softer and 
 more downy than the lower portions of the cloud. Exactly at the same time that 
 this change is taking place, we notice the atmosphere beneath our cloud to begin to 
 be dimmed by the falling rain. The neutralisation of the electricities aloft has per- 
 mitted the particles of water, hitherto kept asunder by repulsion, to unite and be 
 discharged to the earth in rain. By-and-by little will be seen by the melting 
 (Page 126) cloud save a certain amount of cirrus disposed above, and some loose flecks 
 of scud or of soft cumulus beneath. This is the first formation of the typical shower. 
 We have showers and showers ; showers which have been formed a long way off, and 
 showers, too, which are so embedded in other cloud forms, that we fail to get a 
 glimpse of their cirriform summits, or even to distinguish the outlines of their sides 
 or base. Showers of thick small rain even fall, in some circumstances, from low 
 clouds of the stratus type, but these clouds also, just before their precipitation com- 
 mences, lose their definiteness of outline as regards their upper surface, always 
 looking as if they were discharging rain or snow in an upward as well as in a down- 
 ward direction. But the formation that I have described is decidedly that most 
 distinctive of the local shower in contrast to the widespread rain. Now we all know 
 that the first steps of the formation which I have described are often discernible with- 
 out being followed by any shower atall. In fine weather, especially in the spring arid 
 summer, we often see cumulus forming day after day, attaining its greatest dimen- 
 sions about the hour of highest temperature, and either dissolving altogether about 
 (Page 127) sunset or subsiding into the loose-spread stratus which is scattered at 
 nightfall through the vapour-plane. The colours of the sky are, in many instances, 
 related to the advance or retreat of the extensive nimbus. When cumulus begins 
 to form under those other circumstances which lead us to suspect coming showers, 
 watch its formation and appearance with great care. A very rapid upward develop- 
 ment of the cloud while the outline is hard and the base very level is a bad sign, 
 which is intensified if the protuberances of the upper surfaces are seen to toss and 
 roll with much activity. When, as is very commonly the case, there are clouds of 
 other species in the sky, notice these particularly. If there is a good deal of loose 
 (Page 129) stratus, the remains of night cloud, around the base of the cumuli, and 
 the latter are forcing their domes far above them, and gradually absorbing or repel- 
 ling them beneath, the occurrence of showers before nightfall is probable. On the 
 other hand, if there is stratus at a moderate altitude and cumuli are formed still 
 lower down, and the summits of the latter seem inclined to spread out and blend 
 with the stratus as they reach it, while the base of the cumuli become ill-defined and 
 appear gradually melting, the weather is pretty sure to remain dry. In the latter 
 case there is a sort of second cloud-plane in the middle region of the atmosphere, 
 namely, that occupied by the stratus, which serves both to impede the evaporation 
 from the earth's surface by checking the solar rays, and also to conduct horizontally 
 the electricities of the cloud at a very early stage of their formation. The stratus is 
 sometimes of a special kind, never or hardly ever seen before rain. The bold level 
 (Page 130) based cumulus is often the precursor of a hail or thunderstorm. It is a 
 very common thing on those occasions, when there is what I have called a second 
 cloud plane at no very great altitude, to see cumulus when its summit reaches the 
 plane, spreading out in very thick opaque folds. To the inexperienced eye these 
 clouds have a somewhat stormy and formidable appearance, probably because they are 
 
AQUEOUS VAPOUR 1879. Ley. NOTES. 
 
 rather similar in shape to those far loftier shower clouds whose summits have spread 
 outwards into the cirrus regions of the atmosphere, and the untrained eye recognizes 
 forms far more readily than distance. Yet clouds of this kind rarely or never pro- 
 duce a shower. They may be seen at all times of the year, but especially in spring, 
 particularly in the eastern parts of an anti-cyclone. They are most commonly ac- 
 companied with a good deal of haze, and associated with a dry and harsh atmosphere. 
 Luke Howard seems to have intended his term cumulo-stratus to apply to the cirrus- 
 (Page 131) crowned cumulus. There is a particular kind of cloud distinctive of 
 special, though rather uncommon, types of weather which would by many be called 
 cirro-cumulus. It is a very high stratus, having numerous protuberances emanating 
 from its upper surface. There is no cirrus about it. Their altitude is rarely less 
 ( Page 132) than 14,000 feet. They hardly ever occur in our islands, except in sum- 
 mer, and rarely then, unless the temperature is above the mean. They are rather 
 more prevalent in the inland districts than elsewhere. They are usually seen near 
 the western and south-western limits of an anti-cyclone when there happen to be one 
 or more shallow depressions to the southward. They seem to be associated with 
 vast electrical disturbances in the higher regions of the atmosphere, and they are 
 very commonly the precursors of our grandest thunderstorms. This is especially 
 the case when they move with great velocity from a south-easterly or southerly 
 point, while clouds a little below them are flying from N.E. or E. Under 
 these circumstances a single fragment of the cloud of this type, however minute, 
 occurring in a bright sky, will enable an accurate observer to prognosticate thunder. 
 These clouds sometimes disappear before the occurrence of a thunderstorm ; the 
 latter then takes place in the daytime, and is formed from the cumulus type already 
 described. But there is a remarkable class of thunderstorms which come on with 
 this kind of cloud. This cloud resembles ordinary stratus in one respect, that it 
 glories in the night. Soon after sunset in a summer evening it often thickens and 
 (Page 199) darkens in the S. and S.W., its under- surf ace being disposed in 
 numberless wavy folds, through which, here and there, shine the highly-reflecting 
 sides of its broken but cumulus-like turrets. Presently the sheet lightning begins 
 to illumine the southern sky, while a light easterly or northerly breeze is felt below. 
 In a few hours the storm is raging. Those of our summer thunderstorms which 
 occur during the night are, with very rare exceptions, of this sort. When passing 
 into the form which produces a shower, this cloud behaves like the ordinary shower- 
 producing cumuli. Their summits run up so as to inosculate in some cases with 
 cirrus at no great distance above them ; in other cases their summits become spon- 
 taneously cirriform ; and this change, probably accompanied by a neutralisation of 
 electricities, is, so far as I have observed, the essential requisite of their precipitation 
 (Page 134) in rain. The types of cloud opposite to the rain-bringing clouds are 
 signs of fine weather. One cloud may be particularly mentioned as indicative of no 
 rain. In summer the centres of anti-cyclones often comprise cloudless skies. A little 
 stratus occurs at night, on some occasions at an elevation of from 4,000 to 10,000 
 feet, and this is developed into cumulus of moderate dimensions during the day. 
 At a great elevation cirrus may often be seen in conoid tufts whose movement is 
 extremely slow. In winter, on the other hand, neither cirrus nor cumulus is common 
 near the centre parts of anti-cyclones, but the sky is rarely clear. A bed of nearly 
 stationary stratus often covers the heavens for many nights and days in succession. 
 This bed is frequently of vast extent, but of very small vertical thickness. Where 
 gaps occur in it we observe a sky totally devoid of every species of upper cloud. 
 Now we infer that there is over every anti-cyclonic area a slight general downward 
 movement of the atmosphere. In the summer the sun's rays dissolve the stratus, 
 (Page 135) and the rapid evaporation taking place during the long and hot days 
 sends up the local or scattered patches of cumulus or cirrus. In winter this does 
 
 413 
 
AQUEOUS VAPOUR 1879. Lucas. NOTES. 
 
 not take place. The vapour in the very high regions of the atmosphere is carried 
 by the descending current towards the surface of the earth ; it probably, therefore, 
 experiences a rise of temperature, and consequently does not pass from the gaseous 
 into the visible form. The surface of the earth is, however, losing heat by radiation, 
 and at an altitude of about 3,000 feet or less (often much less) above that surface a 
 temperature is encountered which is low enough to condense the gas into a level 
 sheet of vapour. The remarkable continuity of this sheet I imagine to be due to the 
 fact that wherever a break in it occurs the earth beneath loses more heat by 
 radiation, and the sheet is consequently speedily reformed. The air below is some- 
 times clear, sometimes foggy. Occasionally over a great expanse of country, and 
 especially in the neighbourhood of our large towns, the atmosphere is obscured by 
 thick fog, and the densest and darkest fogs of London are commonly those which 
 occur beneath this anti-cyclonic stratus ; these fogs being, possibly, due not only to 
 the want of horizontal motion in the air, but partly also to the descending currents 
 which accelerate the downward movement of the now water-laden particles of smoke. 
 (Page 136) Although strati are usually more prevalent over sea than land, this stratus 
 is much more continuous over the land than over the sea. It is also noticeable 
 that the breaking up of one of these bands of stratus is usually the first sign of a 
 change from settled to unsettled weather. The explanation offered accounts for 
 both these facts. The relative warmth of the atmosphere over the sea in winter 
 prevents the formation of stratus ; and again, the cessation of the general descend- 
 ing currents, or the commencement of the ascending currents, necessarily attends 
 the breaking up or the passing off of the an ti- cyclone. 
 
 Lucas, Joseph. Symons's Meteorol. Mag., vol. xiv. (rsp.) [Abstract of a paper 
 read to the British Association.] 
 
 [No. for October.] 
 
 (Page 147.) Changes of temperature in the soil must act upon the contained 
 moisture in the same way as they do on the air above, thereby tending to cause 
 evaporation, or to produce percolation. In an abstract of more than 100,000 
 observations upon the temperature of the soil, made in the gardens of the Royal 
 Botanic Society, London, 1871-1876, Mr. G. J. Symons observes that the heat- 
 wave commences in March, and spreads downwards till the whole four feet of 
 observation is warmer than the air in September and October, the effect of the 
 preceding cold wave disappearing at four feet by the end of August. In November 
 the cold wave commences, and moves down till the whole four feet is colder than 
 the air by the end of February, when the heat wave begins again. 
 
 Morgan, E. D. Journ. Roy. Geog. Soc., vol. xlviii. (1879) (r*.). 
 
 (Page 306.) Along the Urun-daria the atmosphere is so damp, that over the 
 whole region there is a vegetation, consisting of saksaul (Anabasis saxaul), tamarisk, 
 brambles, and, where the moisture is still greater, willows and reeds. 
 
 Moseley, H. M". (B.) 
 
 (Page 45.) On many mountains the distribution of plants is mainly dependent 
 on the gradual increase of moisture with height (above sea level), as in St. Vincent 
 (Page 226) and Ascension. In high Arctic latitudes there is little cooling at night, 
 owing to clouds and mists preventing radiation. 
 
 Skertchley, J. A. Journ. Roy. Geog. Soc., vol. xlviii. (rs.}. 
 
 (Page 281.) In Wassaw the dry season commences from the end of August, and 
 lasts till November. From December to May there is a short dry season. 
 414 J J 
 
AQUEOUS VAPOUR 1879. Symons. NOTES. 
 
 Symons, G. J., in Modern Meteorology (1879) (rv.). 
 
 (Page 138.) Each cubic foot of the air in the tropics may be said to contain 
 roughly eight grains of vapour at the temperature of 76. If that air be transferred 
 to these islands, and be reduced to their average temperature of 50, it must part 
 with nearly half its vapour. When one substitutes for grains and feet, tons and 
 miles, there is no difficulty in understanding why winds from those regions deposit 
 rain on all colder countries over which they blow. 
 
 Symons, G-. J. Symons's Meteorol. Mag., vol. xiv. (rsp.) 
 
 [No. for November.] 
 
 (Page 163.) A lovely spot, embowered in trees and encircled by hills, is usually 
 characterized by a damp, misty, cold, and stagnant atmosphere. These conditions 
 (Page 164) are not adapted for vigorous health. Evaporation data would be ser- 
 viceable in computing the yield of storage reservoirs. Data as to the amount of 
 evaporation would be very useful in connection with sewage irrigation, for it ought, 
 evidently, to be most successful where the air absorbs the largest amount of surplus 
 moisture. Hygrometry is almost identical with the measurement of evaporation, 
 but not quite, because hygrometry considers the amount of moisture in the air at 
 rest, and evaporation is the resultant of the average of a variable number of miles 
 of air of a variable hygrometric condition over a water surface. It is the business 
 of hygrometers to tell us how much water [in the state of aqueous vapour] there is 
 in the air. It is never very great ; fifteen grains of water [in the state of vapour] 
 in a cubic foot of air is the extreme, perhaps a trifle beyond the extreme, which 
 ever occurs in this country [England], while it may run down to one grain per 
 cubic foot. 
 
 Nature. 
 
 (Page 269.) Eliot has discovered that a cyclonic vortex when generated in the 
 middle of the Bay of Bengal always travels towards that part of the coast where 
 the wind velocity for the time being is least in comparison with the average velocity 
 for the same place and time of year. This law lends a great deal of support to the 
 theory that a cyclonic vortex is developed through the accumulation, concen- 
 tration, and condensation of aqueous vapour over a region of comparative calm. 
 (Page 299.) Dr. Mann at Society of Arts, January 21st, stated that when solar spots 
 were abundant, more solar energy was thrown out, and this caused a larger amount 
 of the water of the earth to be raised in vapour, which condensed to a greater 
 (Page 326) rainfall. Montigny comes to the conclusion that it is the presence of 
 water in greater or less quantity in the atmosphere that exerts the most marked 
 influence on scintillation, and which most modifies the character of it, either when 
 the vapour is dissolved in the air, or when it falls to the surface of the ground in the 
 liquid state, or in the solid state in the form of snow. Prof. Asa Gray in Am. Journ. 
 (Page 327) Sd. showed how the distribution of forests is mainly dependent on 
 the distribution of moisture, and thus explained the great difference which exists in 
 this respect between the eastern and western United States. Afterwards he shows how 
 the distribution and nature of the North American forests are dependent mainly 
 (Page 548) on moisture and temperature. Acad. Sci., Paris, March 31st. Colladon : 
 In large hail storms the cumuli forming them are divided into several distinct 
 groups, insulated electrically from each other by sections of cold air resembling smoke 
 columns from several chimneys. The columns of hail the author conceives as a 
 huge descending piston ; hence the violent whirling movements of wind near the 
 ground, and the descent of cold, dry, highly-electrified air from the upper regions. 
 (Page 523.) Meteorol. Soc., March 19th. Dew, mist, and fog, by George Dines. 
 
 415 
 
AQUEOUS VAPOUR 1879. Nature. NOTES. 
 
 He used watch glasses of known area and weight, and exposed them on grass, slate, 
 and a deal board ; the two latter were raised a few inches above the grass. A 
 minimum thermometer was placed beside each glass. It is only on rare occasions 
 that an amount of dew exceeding '01 inch in depth has been deposited upon the 
 measuring glasses, and out of 198 observations in only three has that amount been 
 exceeded. Fifty-eight observations gave the amount of from '01 in. to '005 in. ; 
 107 from '005 in. to '001 in. ; 22 less than '001 in. ; and eight observations gave no 
 dew at all. Dines thinks it may be fairly assumed that the average annual deposit 
 of dew upon the surface of the earth falls short of 1/5 in. There are two kinds of 
 mist, the morning and evening ; the morning mist is caused by the evaporation 
 from the water and the moist ground taking pl&ce faster than the vapour is taken 
 away ; the air becomes saturated, but this does not stop evaporation ; the vapour 
 continues to rise into the air, is there condensed, and forms mist, which gradually 
 spreads over a wider surface. The evening mist is produced as follows. The cold 
 on the grass caused by radiation lowers the temperature of the air above it ; the 
 invisible vapour of water previously existing in the air is in excess of that which 
 the air can retain when the air temperature is lowered, the surplus is condensed, 
 becomes a mist cloud, and floats in the air just above the surface of the grass. 
 Taken either separately, or combined, the mists appear to be totally and altogether 
 inadequate to account for those dense fogs which at times overspread the country. 
 Dense fogs near the earth are often accompanied by a clear sky above. Dines 
 would attribute these to some cause unknown, by which the whole body of air to 
 some distance above the earth is cooled down, and as a consequence, part of the 
 vapour in that air is condensed, and forms an ' earth cloud.' 
 
 Nature. 
 
 (Page 116.) Meteorol. Soc., May 21st. G. M. Whipple finds that at Kew the 
 amount of sky covered with clouds varies inversely as the barometric pressure 
 between the limits of 29'0 in. and 30'3 in., the variation being most rapid between 
 29*8 and 30 '1 in. Also that above 30*3 in. cloud increases with increasing pressure, 
 attaining the mean about 30'5, and rising above it at 30'6 in. Loomis (Am. Jouiii. 
 (Page 270) Sci., July 1879) examines the paths of storms advancing from the north 
 and from the south. They present different characteristics. In those moving from 
 the south, the southerly winds which accompany them are marked by a greater 
 humidity and velocity, and excessive rainfall. The facts presented by these favour 
 the idea that in a great storm the condensation of vapour is an efficient cause which 
 controls the movements of the winds. The central depression of the barometer 
 seems to be the result of a circulating system of winds, the most frequent cause of 
 which is two or more areas of high pressure at considerable distances, often 1,400 
 miles from each other differences of humidity and temperature being important 
 agents in producing, but more especially in maintaining such a system of winds. 
 We require then, to know what are the causes which bring about those areas of 
 high pressure round a region of lower, though still high pressure, and the concen- 
 tration of moister and warmer air over this region. 
 
 Symons's Meteorol. Mag., vol. xiv. (rsp.) 
 
 (Page 89). A. Cruickshank selected six elevated points at distances of about 
 (Page 90) 5, 10, 20, 30, 40, and 50 miles from his station, and by means of these 
 estimated the extreme limits of view in the middle of each day for twenty-one years. 
 The paper concludes with the deductions drawn from the observations. The mean 
 daily distance seen is only twenty-live miles. The mean number of days in the year 
 on which a distance of fifty miles can be seen is ninety. The greatest mean daily 
 
AQUEOUS VAPOUR 1880. Aitken. NOTES. 
 
 distance seen increases for each month from January to July, and then decreases 
 again from July to January. This monthly increase and decrease in the greatest 
 mean daily distance seen corresponds respectively with the monthly decrease and 
 increase in the humidity of the air. There is no regular relation between the 
 monthly variations in the mean distance seen and the mean monthly amount of cloud 
 in the sky. 
 
 [No. for September. 
 
 (Page 122.) Dr. Grabham, in a paper read before the British Association, 
 observes that the sirocco wind in Madeira is sometimes very dry ; the temperature 
 being 84 and the dew-point below freezing. 
 
 (Page 124.) H. Courtenay Fox, in a paper read before the British Association, 
 concludes from the discussion of the observations at Greenwich that in the winter 
 (Page 125) months cold tends to be synchronous with dryness, warmth with large 
 rainfall ; in the summer months cold tends to be accompanied by much rain, warmth 
 by dryness ; and that years of drought tend to assume an average temperature. 
 
 1880. 
 Aitken, J. 
 
 (Page 196.) Vapour must have some solid or liquid body on which to condense ; 
 the dust particles usually form the nuclei required. When there is much dust 
 in the air, but little vapour condenses on each particle, and they become but little 
 heavier, and easily float in the air. If there are few dust-specks each gets more 
 vapour, is heavier, and falls more quickly. When the air is nearly pure, and only 
 a few dust-particles present, then only a few cloud-particles form, and they are 
 heavy, and fail like tine rain. He concludes that if there was no dust in the air 
 there would be no clouds and no mists, and that the supersaturated air would 
 convert every object on the surface of the earth into a condenser on which it would 
 deposit. When there are many dust-particles they give rise to the light form of 
 condensation which constitutes a fog, and therefore whatever increases the amount 
 of dust in the air tends to increase fogs, and when the dust-particles are not so 
 numerous the cloud-particles are larger, and settle down more quickly. The dust- 
 motes seen in a beam of sunlight are not the active nuclei of fog and cloud-particles, 
 but those which are smaller and invisible. The large motes may be active nuclei, 
 but their number is too small to have any important effect. The products of com- 
 bustion of gas and fire have great fog-producing power. The products from a clear 
 fire and a smoky one give about equal fogging. Common salt when burned gave 
 an intensely fog-producing atmosphere, but burned sulphur was the most active 
 (Page 197) substance experimented on. Smoke descends during a fog because the 
 smoke-particles are good radiators and soon get cooled, and form nuclei on which the 
 water-vapour condenses. Falling smoke indicates a saturated condition of the 
 air. 
 
 Archibald, E. D. 
 
 (Page 394.) [He gives tables showing the variations from mean of cloud for the 
 year, summer and winter at various places]. The tables show that with few 
 exceptions 1. The annual amount of cloud is below the mean at the epochs of the 
 crests of the heat waves, and above the same at those of cold waves ; 2. That the 
 relation is of the same kind, but more marked when the results for the summer 
 season alone are compared ; 3. That the results for the winter show, in several cases, 
 a tendency to vary in the opposite manner. The dates of the crests of the hot and 
 cold waves, as given by Professor Smyth, coincide with and include the principal 
 critical epochs of cloud variation. It would seem that the waves both of heat and of 
 
 417 
 
AQUEOUS VAPOUR 1880. Blanford. NOTES. 
 
 cold were partially dependent upon watery vapour and its transformations, the heat 
 wave being in part the effect of an excess of sunshine, and the cold wave of an excess 
 of cloud. 
 
 Blanford, H. F. 
 
 (Page 482.) The following is a possible explanation of the alternating oscillation 
 of pressure between the Indo-Malayan region and the Russian plains. Among the 
 best established variations in meteorology which conform to the sun-spot cycle are 
 those of tropical cyclones, and the general rainfall of the globe, both of which imply 
 a corresponding evaporation and the condensation of vapour. Now this variation 
 of pressure evidently has its seat in the higher (probably the cloud-forming) strata 
 of the atmosphere. It is then a reasonable inference that the principal agency in 
 producing the observed reduction of pressure at the epoch of sun-spot maximum is 
 the more copious production and ascent of vapour which may operate in three 
 different ways : First, by displacing air, the density of which is three-eighths greater; 
 second, by evolving latent heat in its condensation ; and thirdly, by causing ascending 
 currents, The first and second of these processes do not directly reduce the pres- 
 sure, but only the density of the air-stratum while they increase its volume. In 
 order, therefore, that the observed effect may follow, a portion of the higher atmo- 
 sphere must be removed, and this will necessarily flow away to regions where the 
 production of vapour is at a minimum viz., the polar and cooler portions of the 
 temperate zones, and more especially those where a cold, dry land surface radiates 
 rapidly under a winter sky, such as the great plain of European Russia and Western 
 Siberia. 
 
 Burder, G. "Ft Symonss Meteorol, Mag., vol. xv., 1880. 
 
 (Page 29.) A rather remarkable hoar frost was observed here [Clifton] on the 
 last two days of January and February 1st. Generally hoar frost is caused by the 
 cooling of the ground below the temperature of the air by radiation. In this case 
 the relatively low temperature of the ground was evidently occasioned by the slow- 
 ness with which the earth, cooled by a long frost, became affected by the thaw then 
 prevailing. This hoar frost differed also from others in the situations in which it 
 was found, being scarcely less abundant on the roadways, pavements, and gravel- 
 walks than on the grass. The roads were so white as to give the impression of a 
 thin covering of snow. It was also deposited thickly on the perpendicular faces of 
 walls. Another point noticed was its persistence during the day, notwithstanding 
 maximum temperatures of 43 and 48. The crystals were remarkable for their scale- 
 lik orm. 
 
 Croll, James. 
 
 (Page 521.) But for the sea there would probably be no aqueous vapour, and 
 consequently nothing to protect the earth from losing its heat by radiation. The 
 surface of the ground would then fall to the temperature of stellar space if deprived 
 (Page 522) of solar heat. The lowering of the temperature tends to diminish the 
 amount of aqueous vapour contained in the air, and this in its turn tends to lower 
 the temperature by allowing of freer radiation into space. 
 
 Croll, James. 
 
 (Page 191.) The reason why snow at great elevations does not melt is owing to the 
 fact that the heat received from the sun is thrown off into stellar space so rapidly by 
 radiation and reflection that the sun fails to raise the temperature to the melting 
 point. At low elevations where the snowfall is probably greater and the amount of 
 heat less than at the summits, the snow melts and disappears. This is probably due 
 
 418 
 
AQUEOUS VAPOUR 1880. Dines. NOTES. 
 
 to the influence of aqueous vapour. At high elevations the air is dry, and allows 
 the heat radiated from the snow to pass into space ; but at low elevations a very 
 considerable amount of the heat radiated from the snow is absorbed in passing 
 through the air into space. A considerable portion of this intercepted heat is 
 radiated back into the snow, and being of the same quality as that which the snow 
 itself radiates, is on this account absorbed by the snow. This heat accumulates in 
 the snow till melting takes place. Were the amount of aqueous vapour possessed 
 by the atmosphere sufficiently diminished, perpetual snow would cover our globe 
 down to the sea shore. The air is warmer at the lower level than the higher, 
 mainly owing to the influence of aqueous vapour ; were this reduced the difference 
 would not be so great. The lower descent of the snow-line on the south side of the 
 Himalayas, and on the east side of the Andes, which are the moister sides, is owing 
 to the fact that the snow-fall is much greater on the moister side. Other things 
 equal the snow would melt at a higher elevation on the moist than on the dry side. 
 The dryness of the air will, in a great measure, account for the present accumulation 
 of snow and ice on Greenland and on the Antarctic continent. These regions are 
 covered with snow because the quantity melted is small, and this is owing to its 
 being prevented from rising to the melting point, owing to the dryness of the air. 
 (Page 192) In places like Fuego and South Georgia, perennial snow and ice are 
 caused by the sun's heat being cut off by clouds and dense fogs. The upper surface 
 of the clouds reflects the sun's rays into stellar space, while one-half of the heat 
 which they do absorb is radiated upwards ; the other half which reaches the ground 
 is insufficient to clear off the winter's accumulation. 
 
 Dines, Q-. Symons's Meteor ol. Mag., vol. xir. (rsp.) 
 
 [No. for January.] 
 
 (Page 191.) From observations with the microscope on slightly cooled brass 
 surfaces during fogs or mists, I conclude that a good deal of the moisture occurring 
 on surfaces is really a very fine rain, and that the annual deposit of real dew upon 
 the surface of the earth does not exceed one inch. Can any correspondent give a 
 definition of dry fogs ? Are they caused by smoke, by some combination of the 
 temperature of the air with vapour, or do they only differ in degree from other 
 fogs. 
 
 Ley, Rev. W. C. Aids to the Study and Forecast of Weather, 1880. (rv.) 
 
 (Page 3.) The points of cirri frequently point downwards, especially in dry 
 weather. When increasing, these clouds form an interlacing network or sheet of 
 filmy ice-mist, which is often seen over one side of the sky, while the other remains 
 (Page 4) temporarily clear. True cirro-cumulus at the highest level often 
 accompanies dry and warm weather. The more massive cloud-forms commonly 
 degenerate into the stratiform descriptions soon after sunset. A peculiar modifica- 
 tion of stratus is common under certain conditions. It arranges itself in parallel, 
 but ill-defined, bars transverse to the meridian, which often coalesce so as to over- 
 spread the sky. It only occurs with a somewhat tranquil atmosphere, and rarely 
 with a very high or extremely low temperature, and it may be further distinguished 
 by its uniformly sober tints, in which a bluish-grey predominates. It may be 
 distinguished as ' dry weather stratus.' Cumuli may be regarded as a sign of great 
 (Page 5) cold in the region above them. Fine weather cumulus has a moderate 
 elevation, and a well-defined rounded surface. Its formation and dissipation is 
 governed greatly by the temperature of the day, the cloud frequently beginning to 
 show itself soon after sunrise, increasing till the hottest part of the day, then 
 gradually diminishing, and eventually disappearing about sunset. This form of 
 
 419 
 
AQUEOUS VAPOUR 1880. Ley. NOTES. 
 
 cumulus is comparatively uncommon over the surface of the sea in our latitudes, 
 and it may often be seen from a great distance, marking the position of a coast- line 
 or even of small islands. Showery weather cumulus is remarkable for the rapidity 
 of its formation and disappearance, and for the readiness it displays to pass into 
 other cloud forms. Large and well- developed cumuli are usually called thunder- 
 clouds, from their prevalence in periods of electrical disturbance ; but it is worthy 
 of observation that electrical discharges never appear to take place in any form of 
 cloud until its summit has begun to spread outwards or upwards in a more or less 
 cirriform shape, and has exchanged its hard for a soft outline. When cumulus has 
 thus attained a great size it becomes a shower-cloud. In this state it is commonly 
 called nimbus, a term applied to this kind of cloud, as also to the extensive composite 
 cloud-banks, and, indeed, to all forms of rain-cloud. Here the term nimbus will be 
 restricted to the great banks of composite rain-cloud. Other descriptions of clouds 
 have similar modifications to the pocky form of cumulus. Thus cirro-stratus not 
 unfrequently exhibits pendulous banks or wreaths on its under-surface when the 
 temperature of the lower region of the atmosphere is falling, and a colder wind is 
 setting in beneath. Detached fragments of cumulus, particularly when near the 
 earth, are often as irregular in contour on their lower surface as on their upper 
 (Page 6) surfaces. Unusual clearness of the atmosphere is commonly taken as a 
 token of impending rain or storm. Now, the removal of the dust particles with 
 which the atmosphere, in settled, and therefore somewhat calm and dry weather, is 
 much charged, is an early indication that either condensation of vapour, or rapid 
 movements of air, or both, has begun to occur in regions immediately to the 
 windward of the observer, and consequently that the latter is nearly within a system 
 (Page 7) of atmospheric disturbance. It is commonly said that a rosy sky at sunset 
 presages fine weather. This generalization will fail if taken as a rule ; but if we 
 take pains to draw an inference as to the distribution of aqueous vapour in the 
 atmosphere from the colour of the sky, we shall find that the latter frequently 
 furnishes us with information which may be employed as subsidiary to our 
 principles, with much practical utility. The redness of the sun when near the 
 horizon is due to diffraction. Particles suspended in the air, whether dust, smoke, 
 or very minute globules of water, give a red colour to transmitted light. This is 
 the reason why in large towns the sun, both rising and setting, nearly always 
 appears red. In the country the red colour which the rays acquire in passing 
 through a long stratum of air is probably, in large measure, due to water globules 
 forming an extremely fine mist. At sunset, after the evaporation which has taken 
 place during the day, these globules are usually present in large quantity at the 
 time when the air is rapidly becoming cooler, and the sun, therefore, usually appears 
 somewhat red. During the further cooling which occurs in the night, many of the 
 particles are commonly deposited in dew, fewer remain suspended in the air, and 
 the rising sun is therefore less usually red. A red sunrise indicates that after this 
 precipitation the atmosphere still contains a large quantity of water-particles which, 
 after the evaporation about to occur in the next few hours, is likely to form rain- 
 clouds. A grey sky in the evening is commonly caused by the presence of an 
 amount of cloud in the west, which is sufficient to stop the direct rays of the sun, 
 and to allow nothing but diffused light to pass. The behaviour of secondary 
 (Page 25) barometric depressions after they have reached the front of an advancing 
 cyclone, seems to be ordinarly determined by the general atmospheric conditions of the 
 district into which they have thus penetrated. If the barometric pressures in front 
 are generally high, and the atmosphere dry, they become filled up, and disappear. 
 (Page 26) If, on the other hand, the conditions are less favourable to their ulterior 
 development, they commonly advance as independent cyclonic systems. It is 
 (Page 27) probable that an ascending current of atmosphere occurs in the cyclonic 
 420 
 
AQUEOUS VAPOUR 1880. Ley. NOTES. 
 
 observations, and that this ascending current originates in the simultaneous con- 
 densation of water- vapour over an extensive area. The district in which this 
 condensation is most active occupies the point of the cyclone. A little consideration 
 will show that over the north temperate zone, it is on the eastern side of a cyclone 
 that this condition will in ordinary cases occur, since it is on this side that we have 
 southerly winds, while these winds, in moving from warm to colder regions, ex- 
 perience a diminution in their capacity for holding aqueous vapour. A cyclone 
 must, therefore, be regarded as an eddy of spirally ascending air, which eddy is 
 being constantly reproduced on one side of its original position. An anti-cyclone, 
 on the other hand, represents the position of a downward movement of the air, 
 which has lost the greater part of the water vapour in previous cyclonic circulations. 
 In the districts, therefore, near the central calm of an anti-cyclone, the currents 
 take up, instead of precipitating, vapour. This explains why there is no principle 
 of progressive development in an anti-cyclone, and why the cyclones, in their 
 onward course, are not drawn towards the centres of the. anti-cyclones, but skirt 
 (Page 28) round the extreme exterior of the latter, for it is only the exterior 
 currents of the anti-cyclones which have taken up sufficient water vapour to 
 maintain the cyclonic disturbances. The same hypothesis accounts for the ex- 
 ceptional fact, already noticed, that in our region of the globe, a cyclone on the 
 southern side of an anti-cyclone rarely moves westward, since in this instance the 
 surface winds drawn into the cyclone from the anti-cyclone have not only been 
 descending currents, but have also come from higher latitudes, and are there- 
 fore especially cold and dry. The tendency of the cyclones to skirt coast-lines 
 rather than to travel towards inland districts is probably, in some measure, due to 
 the fact that the vapour on which their maintenance depends is drawn principally 
 from the seas. A secondary depression, according to this hypothesis, has its origin 
 in a somewhat local nimbus, or in a local intensification of the general nimbus, and 
 its in-flowing and ascending current is only an imperfect spiral. Again, the same 
 hypothesis throws some light on the tendency which the cyclonic systems exhibit 
 to run in a series a fact which is difficult to explain, if a cyclone is regarded 
 simply as a revolving disc. When the atmosphere over an extensive district of the 
 globe, say over a portion of the North Atlantic to the westward of our islands, is 
 much charged with water-vapour, the formation of a large nimbus is sufficient to 
 originate a cyclonic system, but a considerable portion of the atmosphere whfrch is 
 drawn into the circulation never reaches the front of the cyclone at all, being left 
 behind, as the cyclone is rapidly developed over another part of the earth's surface ; 
 this part of the atmosphere, therefore, falls calm before it has parted with its 
 aqueous vapour, and is in the condition favourable for the propagation of another 
 system. Other and converging lines of evidence in favour of this theory of cyclone 
 and anti-cyclone may be drawn from the behaviour of these phenomena in other 
 parts of the world, but the whole subject may be dismissed with one important 
 observation, that neither the dampness of the atmosphere, as measured by the 
 hygrometer, nor the amount of water collected in a rain-gauge, affords an adequate 
 measure of the amount of cyclonic disturbance which attends a nimbus. The 
 former instrument tells us nothing of the humidity of the atmosphere in general 
 (Page 29), and the latter tells us nothing of the thickness of the atmosphere from 
 which the water has been drawn. It is not surprising, therefore, that some of our 
 shallowest cyclones are accompanied by as heavy and general a rain as the deeper 
 systems, especially when it is observed that during sluggish circulations at the 
 earth's surface rapid currents often exist in the higher cloud regions. An objection 
 to the condensation theory of cyclones is occasionally drawn from the fact that, in 
 some cases, both heavy and extensive rainfall is found to occur in the immediate 
 rear of a centre of depression, when travelling eastwards. This may arise from the 
 
AQUEOUS VAPOUR 1880. Ley. NOTES. 
 
 inclination of the axis of the cyclone, from which it will occasionally happen that 
 over the wind which blows in the rear of a depression, currents flow in nearly an 
 opposite direction to that wind. These latter currents consequently precipitate 
 their water through the lower stratum of relatively dry air ; the condensation being 
 due to the fact that they are chilled not only by travelling from lower into higher 
 latitudes, but by contact of their under-surfaces with air which is simultaneously 
 (Page 30) travelling from still higher latitudes. In the front of a large depression 
 (Page 31) at its extreme exterior there commonly stretches a great bank of cirro- 
 stratus. The outside edge of the bank is pretty definite, and its outline in most 
 cases is in rough correspondence with the contour of the advancing isobars. 
 The movement of the upper current which carries the outlying parts of this 
 elevated cloud-bank is often nearly tangential to the edge of the cloud-bank, 
 and nearly opposite to the direction of the wind, which is presently about 
 to spring up at the earth's surface, and in nearly all cases it makes a greater 
 angle than 90 with this wind. As the sheet extends over us the upper current 
 backs very quickly, and continues to do so over the whole of the front half of the 
 advancing system. As the centre advances towards us we commonly observe 
 composite cloud (nimbus), the rain or snow being accompanied by the new current 
 of air belonging to the depression. This cloud bank extends in most instances 
 nearly over the whole front half of the system, both on the right hand and left hand 
 of the centre's path ; but its character differs very considerably on the two sides. 
 If the centre is passing so as to leave our station on its right, the nimbus usually 
 continues until the centre has almost reached its nearest point to us. Then usually, 
 after a sudden precipitation, the sky clears, the cirro-stratus terminating in an upright 
 line, while the wind at the earth's surface begins to veer. The appearance of the 
 sky in the rear of the disturbance, but still on the right side of the centre's course, 
 is usually very unlike that in the front. Comparatively few upper clouds are 
 observed, and the movement of these is commonly observed to be nearly the same 
 with that of the current on the earth's surface. In lieu of cirro-stratus we see 
 fleecy cumulus. Shower-clouds are also common over this district. These latter, 
 in summer, especially in our more inland regions, often take the form of local 
 thunderstorms. In winter, passing squalls of rain, snow, and hail are common. It 
 ehould be remarked that these showers in the rear of a depression are far more 
 extensive and persistent on exposed coasts and in hilly districts than in inland and 
 more level countries. The atmosphere in this part of the disturbance is in most cases 
 (Page 32) clearer or more devoid of haze than in the front. Suppose the barometric 
 minimum leaves the station to the left of its course. Here the nimbus extends over 
 ITS, and the wind after springing up commences to back, and continues to do so 
 throughout the passage of the disturbance. On this side we rarely experience an 
 abrupt change from a rainy to a clear sky. As the centre passes the higher cloud- 
 forms degenerate into banks of dreary stratus, often attended with an increase 
 rather than a diminution of haze. As the rear of the system approaches us on this 
 side the bolder forms of cumulus are rarely seen, and in place of shower-clouds we 
 commonly notice gloomy-looking banks of condensed vapour in the middle and 
 lower levels of the atmosphere, while cirrus has usually almost or altogether 
 disappeared. In the actual centre of a large depression the sky is often com- 
 paratively clear. Shower-clouds are frequently visible, but these have usually here 
 a thin and disintegrated aspect, while cumulus tends to spread itself into stratus, 
 and cirrus lies in broken, though watery-looking patches. The above description 
 cannot be applied without considerable modifications to the smaller or more local 
 systems. These latter are commonly characterized by a more unbroken cloud-bank, 
 gloomy skies (often with rain or snow) prevailing over the central calm, and even 
 to some extent over the extreme rear of the system. The secondaries are especially 
 
AQUEOUS VAPOUR 1880. Ley. NOTES. 
 
 marked in most cases by very copious precipitation. In summer local depressions, 
 especially if they are secondaries travelling northwards, are usually associated with 
 heavy thunderstorms. In the front of these last-mentioned systems the cirro-stratus 
 is commonly accompanied, and sometimes almost replaced, by the turreted stratus. 
 {Page 33) In summer brilliant weather usually accompanies anti-cyclones, the dry air 
 permitting the sun's rays to have full power. In the central districts particularly, 
 the sky is often nearly or totally devoid of cloud ; at other times light fleecy cirrus, 
 whose motion is extremely slow, is the principal cloud visible. Near the exterior 
 of the system, and especially on its eastern and south-eastern sides, stratus and 
 fine weather cumulus, often accompanied by haze, are the prevailing cloud-forms. 
 At the extreme \vestern and northern borders cirro-cumulus and cirrus are very 
 common beneath which there is fog, occasionally at the sea coast, but rarely at the 
 inland stations. Near the south-western limit of a large and well-formed summer 
 anti-cyclone remarkably cloudless weather often prevails. In winter the aspect of 
 the sky is different. Dry-weather stratus is now the most 'common form of cloud, 
 occasionally covering nearly the whole of the anti-cyclonic system with an unbroken 
 canopy, the perpendicular thickness of which is very small, though its extent is so 
 immense. Above this, in the higher regions of the atmosphere, there is, in such 
 instances, a remarkable absence of cloud ; while beneath it dense ground-fogs very 
 commonly prevail at the inland stations. In some cases, however, the sky is almost 
 devoid of cloud, or the ground-fog alone prevails. Near the extremity of the 
 system the atmospheric currents usually break up, to a great extent, the canopy of 
 cloud and land-fog. On the eastern and south-eastern limits of the system the 
 appearance of the clouds is often very similar to that which prevails in the same 
 district of an anti-cyclone in the summer ; but banks of the dry stratus are even 
 here more common than true cumulus. Occasionally, however, we experience, as 
 in summer, an exceedingly clear sky on the south-western side of a large anti. 
 cyclone, which in winter is accompanied by intense frost. It may be said generally 
 that the occurrence in any marked degree of the form of cloud which has been 
 distinguished as dry- weather stratus is commonly an indication of an anti-cyclonic 
 movement of the air, arid a thoroughly well-trained cloud observer can, in many 
 instances, tell by a glance at the sky whether the wind at his station is anti-cyclonic 
 or cyclonic in character. The following are examples of forecasts based on records 
 of actual conditions : 1. Winter. In the rear right hand of a depression travelling 
 to E. or N.E. Barometers moderately low, rising rapidly ; brisk or moderate N.W. 
 wind ; clear sky between passing showers ; very transparent atmosphere. No 
 tendency to the formation of banks of stratus ; little or no cirrus. As depressions 
 commonly follow each other in a series, and as the direction taken by the last, as 
 well as the absence of the more anti-cyclonic forms of clouds indicates the absence 
 of any distinct anti- cyclone in the west, we expect the N.W. current shortly to fall 
 calm, and to be followed by a fresh bank of cirro-stratus, decline of pressure, wind 
 and rain. 2. Winter. After a day of chilly N. or N.W. winds, depression in the 
 N.E. ^taking a S.E. course. Wind W. or W.S.W., brisk or moderate ; atmosphere 
 mild ; barometer about the mean or below it, falling rapidly ; cloudy, with flying 
 scud, rough-looking composite cloud-bank, or dense cirro-stratus. The rapid 
 decrease of pressure, in conjunction with the aspect of the sky, and with the 
 previous weather, makes it probable that the right-hand segments of a cyclonic 
 circulation travelling S.E. is about to pass over the station ; N.W. to N. or even 
 N.N.E. gale is, therefore, to be apprehended, with a great fall of temperature, and 
 brisk recovery of pressure. 3. Summer. After moderately dry weather with westerly 
 winds, and barometer about or rather above the mean (northern limit of an anti- 
 cyclone). Barometer about the mean, and steady, or falling but little ; wind S.W. 
 or W.S.W., moderate or light ; overcast, with much low cloud ; temperature about, 
 
 423 
 
AQUEOUS VAPOUR 1880. Ley. NOTES. 
 
 or a little above the mean, for the season. The right-hand portion of a depression 
 taking a N.E. direction is probably passing over the station ; no rain, or but slight 
 (Page 35) drizzling showers, may be expected ; the wind will most probably veer a 
 little shortly, with a clear sky. 4. Winter. Extreme rear right hand of a large 
 depression going E. or N.E. Calm, clear, and cold ; N.W. wind having died down, 
 and cumuli and shower-clouds disappeared quickly ; sheet of cirro-stratus on S. 
 horizon, edge travelling from W. or S.W. ; barometer below mean, rising, but rise 
 checked somewhat. If the new cirrus-bank had appeared farther in the W. , and its 
 edge had moved from a more northerly point, the fresh depression which is probably 
 approaching might have been expected to follow nearly in the wake of the previous 
 system. As it is, however, there is risk of its centre passing on the S. side of the 
 observer, causing a temporary easterly wind, perhaps gale on exposed coasts, with 
 overcast skies, and probably some sleet or snow. 5. Winter. After light winds and 
 dull weather. Barometer much above mean ; totally overcast with low, tranquil 
 stratus, and nearly calm. As this is the central portion of an anti-cyclone no 
 immediate change can be anticipated. 6. Summer. Barometer near its mean, but 
 falling somewhat ; E. or N. breeze ; turreted stratus above, with some cirrus 
 travelling rather briskly from a southerly point. A shallow depression is probably 
 about to pass northerly over the station ; thunder and rain may be anticipated, 
 followed by a light wind from some westerly point. 7. Summer. After westerly 
 winds, with temperature and pressure near the mean. Decided rise of barometer, 
 and very high temperature ; extremely clear and brilliant sky, with very few, 
 and those only very low, soft clouds. Very light W. or N.W. breeze. The 
 central part of an anti-cyclone moving slowly N.E. is likely to pass over the 
 station. A further increase of temperature may be expected, followed probably 
 by bright and hot easterly winds. 8. Winter. Extreme rear of depression moving 
 to S.E. Steady rise of barometer; wind veering from N.W. to N.N.E. ; hazy, 
 with some dry-looking broken stratus, and no cirrus. An anti-cyclonic system 
 may be surmised to exist over the W. or N.W. Fine and cold, though cloudy 
 weather, may, therefore, be expected, with light winds. 9. Winter. After a period 
 of disturbed weather, with cyclonic disturbances going easterly. Barometer about, 
 or rather above the mean, scarcely falling ; continuous calm for some hours, with 
 persistent and rather heavy rain. The observer seems to be near the centre of a 
 very shallow depression, whose course is not distinctly towards E. or N.E. There 
 is, therefore, a probability that anti-cyclonic currents are forming in the N. 
 Much drier weather with a high barometer may consequently be, with some 
 probability, anticipated. 
 
 Ley, W. Clement. 
 
 (Page 207.) Professor Poey was one of the first to appreciate the importance of 
 the terminology of clouds being based on the physical conditions to which the 
 varieties are related ; but we know so little of these physical conditions that no 
 (Page 210) satisfactory classification can be thus formed. That two distinct t^ds of 
 clouds the one at a high and the other at a low level frequently exist when rain 
 is falling, there is abundant evidence to show ; and perhaps this is especially the 
 case during extensive intra-tropical rains. But observers are at least equally agreed 
 as to the fact that a bed of cirrus may co-exist with a layer of low clouds, either 
 with or without one or more intermediate layers, without the occurrence of rain or 
 snow. And it is equally certain thab the majority of passing showers are produced 
 in a single mass of clouds, not necessarily, and perhaps never, homogeneous in 
 structure in the portions near the earth, and in those which extend into the higher 
 regions of the atmosphere, but certainly not divided into two ocularly distinguish- 
 able strata. 
 
 424 
 
AQUEOUS VAPOUR 1880. Parfitt, NOTES. 
 
 Parfitt, Edward. 
 
 (Page 324.) Professor Sayce states that the Accadians supposed all kinds of 
 astronomical phenomena to have an influence upon the clouds. 
 
 Rolleston, George. Journ. Roy. Geog. Soc., vol. xlix. (1880) (rsp.) 
 (Page 320.) Robert Rawlinson, in a lecture on Meteorology delivered in 
 November 1868, said that evaporation has only an indirect and incidental reference 
 to the land, its real dependence being in the great ocean and still greater sun. The 
 powers of man can never seriously modify cloud in reference to the world at large. 
 (Page 348) Professor Koch, following Ebermayer, says a great deal has been 
 written on the evaporation of plants, of which much is intrinsically self -contradic- 
 tory. Unger says water gives off three times as much vapour as a tree ( ? surface 
 for surface) ; Schleiden that the tree gives off thrice as much as water. Koch says 
 such observations and results are of no scientific value ; but I consider they are 
 valuable as they are reducible to weight and measure ; and also that they have a 
 distinctly appreciable practical value and applicability. Professor Wellington 
 (Page 349) Gray tells us that 3,000 square metres of cabbage leaves will give off as 
 much as a pint of water per diem. It may be objected that the rate of evaporation 
 observed in an isolated mass of leaves or in a single isolated tree does not give us a 
 measure of the rate at which the same process will go on in a wood when the ex- 
 posed and evaporating surface is relatively so much smaller ; and this difficulty, 
 which lies in the geometrical nature of the case, may account for the great discre- 
 pancies in the estimates which various writers have given of the amount of watery 
 vapour given off by masses of wood. Pfaff gives 120 kilogrammes as the entire 
 amount evaporated by an oak with 70,000 leaves, each of a square surface of 2,325 
 millimetres during the period from May 18th to October 24th. Yaillant gives the 
 amount of watery vapour given off by an oak of 21 metres height, and 2 '63 metres 
 girth at a height of 1 metre above the ground, as 2,000 kilogrammes on a fine day. 
 Hartig calculates that a German morgen ( = 2'3895 acres), carrying a thousand trees of 
 nine different sorts of conifers and broad-leaved trees of twenty j ears' planting, 
 exhale daily during the period of vegetation at least 3,000 Ib. weight of water. 
 Professor Prestwich (Water-bearing Strata, 1851 p. 118), gives as an estimate. for the 
 amount of watery vapour given off by leaves of a tree of average size 2J gallons per 
 diem. Lawes, in Journ. Hort. Soc. y vol. v. (1858), states that three plants of wheat 
 or barley gave off 1| gallons, 250 grains of water for every grain of solid residuum 
 in the adult plant. Hellriegel gives as his estimate that for the production of 1 Ib. 
 of dry barleycorns, 700 Ibs. of water, inclusive of the water evaporated from the 
 soil, are all that is necessary, and that other cerealia have their demands limited 
 within somewhat similar proportions. It must, however, be allowed that the cases 
 (Page 350) of the drying up of springs as a consequence of cutting down trees are 
 more numerous and better established than the increase of springs by this operation. 
 The explanation of this apparently self-antagonizing or capricious operation of the 
 same primary cause is not far to seek. When a tree is cut down the area once 
 protected by its leaves is exposed to the uncounteracted action of the summer sun, 
 and rainfall may run off it when hardened, just as it runs off an imperfectly thawed 
 surface in the spring, or it may sink away underground by fissures caused by the 
 exposure, and under favourable conditions may give rise to a lake. Generally, one 
 or more of the conditions favourable for this are wanting, and then the diminution 
 of wood goes hand in hand with the diminution of water. Yiollet le Due notices 
 the marked influence of forest destruction in bringing about a diminution of glaciers 
 (Page 351), but is unable to say what the connection is. I think the loss of the 
 trees as evaporating agencies is the true cause of the diminution. The cerealia, with 
 their deep roots, are quantitatively pre-eminent for the amount of aqueous vapour 
 
 425 
 
AQUEOUS VAPOUR 1880. Smyth. NOTES. 
 
 they give off. An area of wood must give off much more vapour than an area of 
 glacier, and would, by the vapour it set free into the atmosphere, save the glacier 
 from wasting. In mountains the influence of forests in increasing rainfall may 
 count for something considerable, whilst in the plains, howsoever well wooded, 
 trees can act only, as do other good radiators, in the way of precipitating, not wind- 
 borne, moving vapour, but simply dew. Any one may observe in a mountainous 
 district how 
 
 ' The swimming vapour slopes athwart the glen, 
 Puts forth an arm, and creeps from pine to pine, 
 And loiters slowly drawn.' 
 
 TEXNYSON: (Enone. 
 
 The term ' Rauchen der Walder ' is used for the smouldering of the clouds amongst 
 trees. In a lowland or other country frost hangs on such a tree as the birch long 
 {Page 353) before it has begun to whiten the ground round it. What is the source 
 of the larger amount of vapour above pines than broad-leaved trees? Does it 
 come from the soil ; is it the result of evaporation from the leaves ; or is it due in 
 the coniferae to the action of thousands of points which the whorls of their leaves 
 develop every year 1 This is a complex question which the present data do not 
 enable us to answer. It is clear the transpiration of the leaves cannot by itself pro- 
 duce this phenomenon, since the transpiration in coniferse is less active than it is 
 in broad-leaved trees. It follows, then, that if the vapour of water dissolved in such 
 great abundance in the atmosphere enveloping the pines was the result of the 
 evaporation of the trees, this phenomenon ought to be much more striking over the 
 mass made up by the broad -leaved trees than in that made up by the coniferse, 
 whilst observation shows that exactly the contrary is the actual fact. We must, 
 therefore, ascribe to the soil and to other unknown causes this remarkable property 
 which pines have of attracting watery vapour. If it had appeared from M. Fautrat's 
 tables that this excess of watery vapour was more marked in rainy than in dry 
 times, it would have been easy to explain the fact by figuring to ourselves, the all but 
 infinite area which the fine films of water clothing every needle-shaped leaf of a 
 coniferous tree would make up and offer for evaporation. For the leaves of our 
 common coniferae wet readily ; and it is owing to this property I apprehend that 
 they intercept as much as one-half the rain which falls upon them before it reaches 
 (Page 354) the ground, whilst broad-leaved trees intercept but one-third. But, as 
 it appears the coniferae possess the hygrometric advantage independently of the 
 rainfall, the phenomenon does require some additional information, and may per- 
 haps find it in the theory of the cause of rain proposed by J. A. Rowell in 1839 viz., 
 that electricity increases the buoyancy of aqueous vapour particles. A good con- 
 ductor would cause rain or dew or mist by drawing off the electricity from the 
 particles ; the pointed pine-leaves would very much favour the action. 
 
 Smyth, Piazzi. (See Biby.) 
 
 (Page 194.) Angstrom showed that some of the dark lines at the red end of the 
 
 sky-spectrum were due to watery vapour. He has found that these lines increase 
 
 in darkness according to the quantity of vapour present in the atmosphere. This 
 
 (Page 195) band precedes D. A sudden darkening in it denotes a large amount of 
 
 xtra moisture, which is likely to be deposited in rain. The spectroscope is then a 
 
 ready means for detecting rapid changes in the amount of aqueous vapour in the 
 
 This can be done with the smallest spectroscope. With larger ones the group 
 
 called 'little a, and its preliminary band,' with its myriads of black lines, forms a 
 
 still more powerful rain -band 
 
 426 
 
AQUEOUS VAPOUR 1880. Tait. NOTE 
 
 Tait, (See%.) 
 
 (Page 340.) Seen from a distance, the mass of cloud belonging to a thunderstorm 
 usually presents a most peculiar appearance, quite unlike any other form of cloud. 
 It seems to boil up from below, and to extend through miles of vertical height. The 
 estimated height, at its lower surface, above the ground varies within very wide 
 limits. Saussure has seen it as much as three miles, and in one case noticed by 
 De 1'Isle it may have been as much as five. On the other hand, at Pondicherry and 
 (Page 438) Mandli it is scarcely ever more than half a mile. Ordinary auroras are 
 thought to be due to the condensation of aqueous vapour in far less quantity, but 
 through far greater spaces, than the quantities and spaces involved in thunder- 
 storms. 
 
 Woeikoff, A. (SeeJB%.) 
 
 (Page 250.) I think I have proved that, as to what we call the temperature 
 of the air (really that of fche lowest stratum), it is, on the equator and a few 
 degrees north and south of it, far more influenced by the yearly distribution 
 of clouds and rain than by the amount of heat received from the sun. The 
 result would be different if we knew the temperature of the whole stratum of 
 air. The heating of the whole surface of the clouds by the sun, and especially 
 the heat liberated by the condensation of water, must give to the higher strata 
 a superior temperature than that they had in the dry season ; in other words, the 
 decrease of temperature with elevation is much slower where the sky is cloudy 
 and rain is abundant in the greater part of the year ; so that in such regions 
 the temperature of the whole air may be higher than in drier climates. I consider 
 water to be the only direct cause of the mildness and uniformity of equatorial 
 temperatures, and this in three ways : (1) By the great heat capacity of water ; 
 (2) by the clouds which interpose a screen between the sun and the surface of the 
 earth ; and (3) by the evaporation of rain-water by the soil and plants. The two 
 latter are especially powerful on the land, even very far from the sea. If it was 
 not for the clouds and evaporation how could we explain, for example, the absence of 
 great heat (hottest month 78'6) at Iquitos on the Amazon in 4 S., and more than 
 1,000 miles from the Atlantic ? Where the sky is clear and humidity and rain 
 deficient very high temperatures of the air are attained even at great distances 
 from the equator (10 to 30), notwithstanding the prevalence of winds from colder 
 regions. 
 
 Nature. (See Biby.} 
 
 (Page 220.) Acad. Sci., Paris, December 15th, 1879. On the influence of rain 
 currents traversing them, and the affinity of pines for vapours, by M. Fautrat. On 
 an average the weight of aqueous vapours contained in 1 cubic metre above pines is 
 8'66 grammes, and on bare ground at the same height 7'39 grammes, showing T27 
 grammes in favour of the pines. Above leafy trees the corresponding numbers are 
 8-46 grammes and 8'04 grammes ; difference in favour of leafy trees 42 grammes. 
 
 Nature. (SeeB%.) 
 
 (Page 355.) There are fogs and fogs from the one extreme of the dry fog of 
 continental meteorologists which merely blur the sky with a bluish-tinted mist and 
 shears the sun of its brilliancy as it nears the horizon, so that the eye can look on 
 its disc undisturbed, to the other extreme of our London fogs. Fogs appear under 
 (Page 356) widely different conditions. The last touch in the character of fogs is 
 contributed by smoke, as explained by Sir John Herschel, whereby each particle of 
 soot, acting as as insulated radiant, collects dew on itself, and sinks rapidly through 
 the fog as a heavy body, thus giving to London fogs their yellow, thick consistency, 
 and the suffocating and unwholesome sensation experienced in breathing them. 
 
 427 
 
AQUEOUS VAPOUR 1880. Nature. NOTES. 
 
 Nature. (See Biby.) 
 
 (Page 363.) Meteorol. Soc., January 21st, Report. The great local differences 
 in humidity require to be more accurately ascertained than they are at present, not 
 only at seaside places, but in inland districts in their relation to hills and valleys- 
 The council have decided to establish a third set of stations, to be called climato- 
 logical, at which observations of humidity, clouds, etc., are taken daily at 9 A.M. 
 C. Greaves advocated a more attentive inquiry into the subject of hygrometry. The 
 appearance and disappearance of vapour, its diffusion, its origin in and withdrawal 
 from the vapourous forms, were matters which could now be readily denned through 
 (Page, 503) the increased supply of good observations. Loomis finds that storms 
 advancing from the Rocky Mountains to the Atlantic pass from a drier to a more 
 humid atmosphere ; whereas in Europe those going east pass from a humid to 
 a drier atmosphere. 
 
 Nature. (See Biby.} 
 
 (Page 594.) Loomis finds that dry air, even when greatly heated, has but little 
 ascensional force, and that the violent uprising of heated air so frequently witnessed 
 in moist climates is mainly due to the large amount of aqueous vapour with which 
 it is charged. Buchan (Journ. Scot. Meteorol. Soc.) remarks that the maximum 
 daily period of the summer thunderstorms in Scotland coincides with the hour when 
 the ascending columns of heated air from the earth's surface are in full activity, and 
 the result is, no doubt, largely due to the circumstance that these ascending masses 
 of heated air develop a charge of electricity as their moisture condenses into cloud. 
 The period of maximum frequency of the winter thunderstorm occurs some hours 
 before and some hours after midnight, or during those hours of the day when the 
 vapour-laden wind of the Atlantic approaches to and reaches its diurnal maximum 
 temperature, and when, consequently, the condensation of the vapour may be expected 
 to reach its daily maximum. 
 
 Nature. (See Biby.) 
 
 (Page 48.) Acad. Sci., Paris, November 2nd. Faye says that in paroxysmal 
 eruptions the enormous amount of steam ejected causes volcanic thunderstorms. 
 (Page 96) Meteorol. Soc., November 17th. 'Table of Relative Humidity,' by 
 (Page 204) Edward F. Dymond. Lister s experiments show that a single drop of 
 ram develops organisms in sensitive solutions which would otherwise have remained 
 unaltered. Hence germ-producing matter, or the germs themselves, form at least a 
 part of the cloud- and fog-producing dust. 
 
 m f -G, , Symons's Meteorol. Mag., vol. xv. 
 
 [.No. for February.] 
 
 (Page 2.) Signor Capello finds that the mean of the rain gauges on a tower seventy- 
 
 t high, one on the windward, and the other on the leeward side, is almost 
 
 ame as that collected by a gauge in an open space five feet above the ground. 
 
 icludes that the difference between the higher and lower gauges depends on 
 
 the force and direction of the wind. 
 
 (Page 3.) Prof. Poey first suggested his new classification of clouds at a meeting 
 
 of t] e Acad. des Sci. at Paris, in 1863 ; a fuller paper was read before the 
 
 i ; , anC6; translate <* ^to Spanish, and published in Mexico, 
 
 en developed and printed in English in two or three publications in the United 
 
 ) then appeared in the Report of the Smithsonian Institution for 1870, 
 
 devJ I A v, r Classification of Clouds.' Two years after it was further 
 
 developed and published in the Annales Hydrographies with the title ' Nouvelle 
 
 OD UageS/ and n W * a PP ears as 'Comment on observe les 
 
 428 
 
AQUEOUS VAPOUR 1880 Symons's Met. Mag. NOTES. 
 
 [No. for March.] 
 
 (Page 19.) At the Australian Meteorological Conference in November 1879, 
 it was proposed that the mean humidity curve be derived from the means of maxi- 
 mum and minimum of wet and dry bulb thermometers. In this country [= England] 
 maximum and mininum wet bulbs are scarcely ever used, because the maximum 
 of the dry bulb and of the wet bulb not being necessarily synchronous, the difference 
 between them is not always, if indeed, often a true indication of the actual 
 (Page 20) difference between the dry and wet at any given instant, and the same 
 argument applies to the minimum. In the absence of self-recording dry and wet 
 thermometers we should have preferred to take the mean of the humidity at 3 A.M., 
 9 A.M., 3 P.M., and 9 P.M., obtaining the former from one of Nigretti's turnover 
 hygrometers. 
 
 The Conference resolved to consider and report on observations to determine the 
 difference in humidity by self-registering maximum and minimum thermometers, 
 and by other methods ; and as to the best method of determining spontaneous evapo- 
 ration. 
 
 [No. for April.] 
 
 (Page 40.) M. Masure read a }>aper at the Easter meeting of scientific men at 
 the Sorboniie in 1880, entitled, ' Observations on the Evaporation of Water, and 
 on the Transpiration of Plants.' He remarked that even when air was damp (say 
 the humidity not above 80) moisture is often deposited on the earth, that the 
 consumption of water by plants is not wholly due to evaporation from their leaves ; 
 that the true amount of evaporation is at present badly determined, but that [it] 
 is really merely a question of the interchange of vapour between the clouds and the 
 earth, dependent on their respective temperatures. This view the author developed 
 in a formula, by which he said that the amount of evaporation could be computed 
 from ordinary meteorological readings. The velocity of the wind is not included 
 in the formula. 
 
 [No. for May.] 
 
 (Pages 49-51. ) [Gives criticisms on the skies depicted in pictures at the Salon, 
 Paris, and Royal Academy, London. The artists' names are intentionally not given, 
 the pictures being indicated by numbers and title. The criticisms seem to give 
 very little meteorological information, and to relate rather to artistic success or 
 failure in depicting skies and clouds. Hence the notes are here considered to belong 
 to Art and not to Climate.] 
 
 [No. for December.] 
 
 (Page 160.) If water, or matter containing water, be warmer than the dew- 
 point of air resting upon it, the water will evaporate ; and if the air be colder than 
 the water the vapour in the air may become saturated with invisible vapour, and 
 may, in addition, contain globules of water too minute for their weight to cause 
 them to fall to the earth as rain, and which globules, breaking up the transparency 
 of the atmosphere, produce what is called mist or fog. Similarly, but inversely, if 
 warm saturated air passes over ground which is much colder than itself, its capacity 
 (Page 162) for retaining, in an invisible form, all the water in it is lessened by its 
 own loss of heat, and the water which it cannot hold invisibly changes into the 
 globular form, and so again we have the transparency of the air destroyed. This 
 second explanation carries with it the identity of cloud and fog, and accords with 
 the cloud formation known as ' pennants ' from many isolated mountain peaks, 
 and with the ' table-cloth ' of the Cape of good Hope. So much for fogs in general, 
 the damp white normal fog of all parts of the world where fogs exist at all. 
 
 429 
 
AQUEOUS VAPOUR 1881. Aitken, NOTES. 
 
 1881. 
 
 Aitken, John. (See Biby.) 
 
 (Page 312). Mr. Russell's difficulty with regard to fogs in large towns is due to 
 his not taking into account the amount of vapour in the air. The atmospheres of 
 the towns which do not have fogs are drier than that of London. 
 
 Aitken, John. (See Biby}. 
 
 (Page 384). He describes Coulier's experiments by which he discovered the part 
 (Page 385) played by dust in the condensation of vapour. Coulier found the 
 products of combustion to be active as condensers of vapour. This he attributed 
 to unconsumed carbon. He found air after rain and storms less active, and the 
 air of summer less active than that of winter. Coulier also made experiments 
 rendering inactive gases active by means of combustion. He concludes that the 
 explanation of these phenomena has to be found ; but seemed to attribute the 
 activity to the heating of the air. 
 
 Broun, J. A. (See Biby). 
 
 (Page 558.) Aqueous vapour cannot explain the annual oscillation of pressure, 
 since it is just when the tension of vapour is greatest that the barometric weight is 
 least. The introduction of more vapour into the atmosphere does not make 
 the whole lighter, but heavier ; and when we subduct the vapour pressure from 
 the barometric height, we find the oscillation to be greater, not less, than 
 before. It is not easy to determine the vapour pressure from the indica- 
 tions of the dry and wet bulb thermometers ; but its amount will not explain 
 the annual law, nor will it explain the independent oscillations in question. I 
 have, however, suggested that the humidity of the air may be in question, and as 
 the oscillations of drynoss or humidity of the lower mass are probably related to 
 (Page 559) the temperature, the oscillations of pressure may be related to them. 
 I would suggest that the pressure of the atmosphere is affected by gravitation and 
 some other attracting force, such as the electric attraction of the sun, depending 
 upon the varying humidity of the air, and this again depending on the temperature. 
 
 Capron, J. R. Symons's MeteoroL Mag., vol. xvi. (rsj).) 
 
 (Page 181.) I began daily records of observations with the spectroscope on the 
 rain-band on July 1st, 1880, and have continued them till now (November). The 
 history of the rain-band may be said to date from the time when Angstrom's maps 
 of the solar lines were found to present different aspects according to the conditions 
 (Page 182) of moisture of the atmosphere at the time of observation, and when that 
 pioneer of spectroscopy proved the presence and absence of certain lines forming 
 bands in the spectrum, more especially a set near D to depend on that condition. 
 No practical meteorological result followed, however, until, as Prof. P. Smith tells 
 us, the subject was first presented to him as a marked feature in sky spectrum at 
 Palermo before and after a sirocco in 1872. [References are made to Smyth's 
 papers on the subject.] In February 1878, appeared vol. xiv. of the Edinburgh 
 Astronomical Observations, 1870-77, in which the subject is fully treated. He 
 has contributions in Nos. li., lii. of the Journ. of the Scot. Meteor ol Soc. 
 McClean's star spectroscope is a useful instrument for these observations. 
 (Page 183) Having obtained the instrument, close the slit, and adjust the focus till 
 the lines in the spectrum are sharp and clear. This should be done on a bright part 
 of the sky. Then point the instrument to the. quarter of the heavens which it is 
 desired to examine, and note results, especially as to lines D and their neighbour- 
 hood. I generally observe thus at 9 A.M. daily from my laboratory window (looking 
 towards the south) ; but if time and opportunity allow, three observations at 9 A.M., 
 1 A.M., and 5 A.M., would be better, varying the parts of the sky tested ; and 
 
 4:30 
 
AQUEOUS VAPOUR 1881. Capron. NOTES. 
 
 I examine with the spectroscope elevated about 13. Prof. Smyth recom- 
 mends to point as low as you can to the horizon, provided you get transmitted 
 light, and to obsene when the sun is neither high nor low. I find in 
 practice 9 A.M. a good time to make observations when only a single one is taken 
 daily, and also that if I get too low on the horizon I am apt to have a false band , 
 due to earth moisture. In observing you will soon remark change in the character 
 of some of the spectrum lines as compared with those seen on a blue sky, with an 
 elevated spectroscope, and moreover, bands of varying intensity are found added 
 to the low spectrum not seen in the higher one. The lines and bands that change 
 their character, or are variable in their appearing, are telluric ; either rain-bands or 
 lines, called by Prof. Smyth ' a function of moisture and temperature,' or low sun- 
 bands and lines, distinguished by him as ' a function of dry air and low sun.' The 
 true solar bands remain unchanged. For meteorological purposes generally it will 
 suffice if examination is confined to the principal band on the red side of D. In enu- 
 meration of the darkness of the band for the purpose of record, I use from Nos. 1 to 
 5, as under : 1, means faint ; 2, faint to moderate ; 3, moderate ; 4, moderate to strong ; 
 5, strong. Prof. Smyth uses the enumeration 1 to 10 ; but I have found a difficulty 
 in distinguishing when so many degrees are used, especially when the intensity of 
 the light varied. Simultaneous observations of the other meteorological instru- 
 ments should be made, and the circumstances of sun, sky, and clouds noted. 
 Drawings are given of the rain-band as seen by the spectroscope [but are not 
 reproduced here]. They are thus described : 1. Spectrum as seen upon a pure 
 high sky. 2. Spectrum observed January 17th, 1881, 8 A.M. Morning dull, red 
 sunrise ; low sun-bands and lines strong ; no rain-band. 3. Spectrum observed 
 24th August, 1881, 8 A.M., showing moderate low sun-bands and lines, and a faint 
 rain-band and lines weak. Rain-band moderate. 5. Spectrum seen December 9th, 
 1880,8A.M. Sun shining through watery clouds ; low sun-lines strong. Rain-band 
 strong. 6. Spectrum seen July 6th, 1881 : Rain-band everywhere and excep- 
 tionally strong, stretching nearly half-way between and D. Whole spectrum 
 darkened, and obscured. The rain-band's action is hygrometric, and involves the 
 general principle that according to the amount of suspended moisture in the air 
 so [is] its appearance and strength. A faint, or faint to moderate rain-band, may, 
 in some cases only, show an amount of moisture which will remain suspended for 
 some time. A moderately strong, or strong rain-band, represents an excess of 
 suspended moisture which, before long, is sure to descend [as rain]. Prof. Smyth 
 mentions instances, and 1 have met with several myself where an apparently perfect 
 (Page 185) transparent sky showing rain-band has, on a change of temperature, 
 condensed, as it were, into clouds which have poured. A little while since (August) 
 I observed only a faint, or at most a faint to moderate, rain-band , on a beautiful blue 
 sky, studded with white cauliflower innocent-looking cumuli. I predicted wet, and 
 at mid-day meal was twitted with the sunshine and brightness ; but sure enough 
 in the afternoon down came the rain. On the other hand, it will sometimes be 
 raining, and yet only a slight, perhaps no, rain-band shows ; an effect generally 
 connected with a cold wind, north or east. No rain -band is also sometimes observed 
 when the wet and dry bulb readings only slightly differ ; but the explanation of this 
 may be that low earth moisture affects the bulbs, which is not recognised in the 
 sky-directed instrument looking through a thin stratum of it: [He gives some 
 diagrams and observations which show the relation noticed between the rain-bands 
 and rainfall during several periods.] 
 
 Groneman, H. J. H- (See Biby.) 
 
 (Page 337.) Messrs. Ooulier and Mascart obtained the same results as Aitken in 
 1875 (Naturforscher, p. 400 ; Journ. of Pharm. [4] xxii., p. 165). In my 'Throne 
 
AQUEOUS VAPOUR 1881. Preece. NOTES. 
 
 cosmique de 1'Aurore polaire,' I have pointed out the importance of these results 
 on the relation between aurora and clouds. If the invisible aqueous dust is able 
 to reach much higher regions than terrestrial dust, and if aurorae are in close 
 connection with cosmical matter in a state of extreme division, this cosmical matter 
 is without any doubt enabled to form aqueous clouds in a much higher than the 
 usual level. In Gcea, in 1873, it was noticed that the dispersed iron and other 
 vapours derived from combustion in the higher regions must form on cooling a fine 
 precipitate, and may form conducting channels for the aurorse. Secchi, in 1872, 
 noticed the peculiar structure of the cirrus seen during the auroral display, 
 particularly their orientation, which indicated the possibility of such position 
 being due to their magnetic qualities. Microscopic meteorites often occur in 
 hailstones (Comptes Rendus, 1872, p. 683). 
 
 Preece, W. H. (See Biby.} 
 
 (Page 336.) A confirmation of Aitken's theory of fog occurred in a friend's house 
 at Streatham, on the occasion of the place being filled with steam from the bursting 
 of a boiler. Wherever a cold surface was found the vapour condensed, and left 
 behind it black carbon dust. Nowhere else was this dust found. The snow of 
 London in thawing becomes dirty, owing to the dust and carbon being left behind. 
 
 Russell, R. (See 5%.) 
 
 . (Page 267.) According to Mr. Aitken's theory, fogs should be common wherever 
 large quantities of fuel are burnt ; and all large towns should have urban fogs. 
 Before coal was used Paris did not have more fog than the surrounding country. 
 (Page 268) Philadelphia, which burns anthracite, rejoices in a transparent atmo- 
 sphere. The great coal and iron districts of South Wales are free from fog. A humid 
 atmosphere is not necessary for the production of mist and haze. The frequent 
 long-continued prevalence of blue haze over the whole country, not excepting the 
 east coasts, in the driest east winds of spring, would be a subject deserving inves- 
 tigation. They sometimes extend to a height much above the tops of our highest 
 mountains. 
 
 W hippie, G. M. Symom's Meteorol. Mag., vol. xvi. (rsp.~) 
 
 (Page 39.) F. N. Shaw is now conducting an investigation on hygrometry and 
 hygrometers on behalf of the Meteorological Society. He adopts Schwtickhofer's 
 hygrometer as his standard of reference. Schwackhofer concludes that the only 
 correct way of estimating the amount of aqueous vapour in the atmosphere is by 
 chemical methods. Of these methods there are two : analysis by weight, and 
 analysis by volume. Hitherto the first has been the only plan Adopted, but it 
 involves much trouble, and gives the average humidity for a kugthened period of 
 time, not the humidity for any given moment. The volumetric method is free 
 from this objection, and may be worked with a comparatively simple apparatus, kept 
 ready to hand, and capable of giving the desired result with accuracy in a few 
 minutes. As to the degree of delicacy required it may be remarked that as O'l mm. 
 (Page 40) (0'039 in.), of vapour tension represent about 0'013 per cent, of the 
 volume of aqueous vapour in the air, the apparatus should indicate with certainty 
 the change of one-hundredth per cent, or one ten-thousandth part in the volume of 
 air measured. Although Schwackhofer first constructed his instrument for the 
 particular purpose of determining the humidicy of the air at different levels in 
 forests, and comparing it with air at similar heights in the open country, yet he 
 considers that it may be equally well employed in place of the ordinary pschycro- 
 meters [= psychrometers] for daily observations at meteorological stations, since 
 it is always ready for immediate use, and without much calculation will give the 
 humidity, the operation occupying ten minutes or a quarter of an hour. The 
 
 432 
 
AQUEOUS VAPOUR 1881. Nature. NOTES. 
 
 principle is to measure the volume of air, and repeat the measurement, after the air 
 has had its moisture abstracted by means of sulphuric acid, under the same con- 
 ditions. In the case of fog the air is slightly heated before it is passed into the 
 apparatus, so that the watery vesicles may be converted into vapour. [A sketch and 
 description of the apparatus is given, and details as to how it is worked. ] 
 
 Nature. (SeeJ5%.) 
 
 (Page 260). Acad Sci., Paris, January 3rd. ' Facts for the Study of the Forma- 
 tion of Fogs,' by M. Andre. A high barometer was observed to sink suddenly (with 
 rain) while a fog present disappeared. With a slow rise of the barometer the fog 
 (Page 370) reappeared. The report of the Government Gardens at Rangoon and the 
 attempt made at West African settlements indicate that the vegetation of tropical 
 (Page 398) Australia will not thrive in a humid climate. Dines (Zeits. f. MeteoroL, 
 xv., p. 381) estimates the annual dew formation to be about 35'5 millimetres (on 
 grass 26 mm.) ; at the best 38 mm. Average nightly on grass '07 mm. Meteorol Soc., 
 (Page 427) February 16th. ' Relative Humidity,' by C. Greaves. The term frequently 
 leads to misunderstanding. He suggests other tables with a more correct denomina- 
 tion. Roy. Soc. Edinburgh, February 7th. Aitken communicated further experi- 
 ments on the formation of fogs. He found the same results were obtained at very 
 low temperatures (down to 8 F.) as at higher ones. In dry fogs that is, fogs formed 
 in non-saturated air certain kinds of fog-forming dust were much more efficient in 
 their action than others. Some, in virtue of their deliquescent properties, formed 
 clouds in non-saturated air ; others only acted in saturated air ; while a third class 
 (Page 490) required the air to be super-saturated. At Mexico the hottest time of the 
 year is the driest, the mean relative humidity for April and May for 1878 and 1879 
 being only 42. 
 
 Symons's MeteoroL Mag., vol. xvi. (rsp.) 
 
 [No. for May.] 
 
 (Page 65.) At the Annual Reunion des Socie'tes Savantes in Paris Prof. 
 Alluard suggested that Saussure's hair-hygrometers should be graduated in accord- 
 ance with the indications of the dew-point by one of Alluard's hygrometers occupy- 
 ing the same space. M. Garban read a paper on the rate of evaporation. He 
 experimented with a series of vessels filled with various earths and regularly 
 weighed. The evaporation from chalk was less than that from sand ; in fact, the latter 
 appeared to collect most dew and vapour, and also to yield its vapour more readily 
 than any other variety of earth. M. Hebert considers that the foahn and sirocco 
 are produced when, under the influence of a great Atlantic storm, a current of warm 
 humid air moving rapidly impinges on a chain of mountains which compels it to 
 dilate and to become cooler, and therefore to produce a larger fall of rain. When 
 the air reaches the top cf the mountain it contains only the quantity of vapour 
 necessary to saturate it at the low temperature to which it fell during its ascent, arid 
 falling down the other slope with a circular or spiral motion, it becomes warmed 
 by the compression, and as much drier as it is warmer. When the point of the 
 system reaches the plain the gyratory descending motion and the centrifugal force 
 jointly produce a diminution of pressure, which gives rise to an internal gyratory as- 
 cending current of considerable force, which produces the low pressure found in the 
 centre of the storm. A complete storm ihus consists of two parts : an interior region 
 of low pressure, where the air is ascending in conical spirals, and an external area 
 of high pressure and descending spirals. The air in the cyclones becomes rapidly 
 more damp, and thus, while commencing with a very dry air, they finish with 
 (Page 57) violent winds and torrential rains. He traces these features in all the 
 cyclones and great storms which occur in the best-known storm regions. 
 
 433 
 
AQUEOUS VAPOUR 1882. Boerner. NOTES. 
 
 M. Masure read a paper on ' New Researches on the Evaporation of Water and on 
 the Transpiration of Plants. 3 The abstract supplied by himself differs much from 
 the notes we took. According to the abstract, arable lands influence evaporation 
 mainly by the manure they contain, which renders them more retentive of water. 
 According to our notes he stated that the amount of evaporation could be deter- 
 mined by a formula containing values for (a) temperature of the water ; (6) tempera- 
 ture of the air ; (c) temperature of solar radiation ; (d) humidity of the air ; (e) 
 velocity of the wind. He then exhibited one of a series of fifty -one charts, 
 on each of which he had placed curves giving hourly observations of all the 
 meteorological instruments which he possessed. The air temperature was 
 taken by a thermometer swung round in the air, and the same thermometer 
 was subsequently used to ascertain the temperature of the water in the evaporators. 
 His observations were made in a garden rather full of plants. He found the tem- 
 perature of the water at sunrise always below that of the air. He considered that 
 the temperature of stagnant water was different from that in a river where it was 
 tossed about. During the early morning hours he not infrequently found that, 
 instead of evaporating, condensation had taken place on the surface of the water in 
 his evaporators. He found the range of temperature of the water in one day as 
 much as from 49 to 85 F. or 36 F. He had also made experiments as to the 
 amount of evaporation from a tobacco-plant, and found that the hourly amount 
 (Page 68) passing off was markedly less when the sky was overcast ; the life and 
 breathing of the plant were, in fact, checked by want of sunshine, the influence of 
 which was greater even than that of heat. 
 
 [No. for October.] 
 
 (Page 155.) Baldwin Latham, in a paper read before the British Association, 
 noticed that the levels of springs rose or fell inversely with the barometric, pressure 
 (Page 156), and did not seem to be influenced by the hygrometric state of the air, as 
 was suggested by Prof. Hughes. 
 
 1882. 
 
 Boerner, C. G-. (See 5%.) 
 
 (Page 482.) Evaporation commences at sunrise, and continues until the diurnal 
 temperature has attained its maximum, between 2 and 4 P.M. As the decrease of 
 terrperature progresses more rapidly from 4 to 9 P.M., than during the remainder of 
 the night, it is evident that a large proportion of the vapour suspended in the heated 
 air during the day is precipitated as evening dew, and frequently by 10 P.M., the 
 deposit on the foliage of trees becomes so copious that it may be heard falling in 
 drops from leaf to leaf. Another period in which dew is copiously deposited is 
 after midnight and at the dawn of day. After 9 P.M. the rate of decrease in 
 atmospheric temperature is considerably retarded, but when the temperature has 
 arrived at its minimum the deposition of dew is augmented. The appearance of 
 dew only in the morning proves that the temperature of the evening was not re- 
 duced to the temperature of the dew-point. A hazy atmosphere, or a large amount 
 of invisible vapour, will retard radiation ; hence serene cloudless nights, without 
 deposition of dew, are regarded as indications of coming rain. According to the 
 (Page 483) theory of Prof. Henry, the deposition of dew depends upon the stillness 
 of the atmosphere. 
 
 Finley, John P, (See Biby.) 
 
 (Page 4.) The place of origin of cyclones is between the belt of calms and the 
 
 ith limit of the trade winds, or say, briefly, in the vicinity of 10 N. 50 W. This 
 
 region coincides with the zone of constant rainfall, where evaporation is very rapid, 
 
 cloud formation exceedingly brisk, the air almost constantly saturated with 
 
AQUEOUS VAPOUR 1882. Finley. NOTES. 
 
 moisture, and heavy condensation a regular feature of the day. Typhdons form 
 south of the Tropic of Cancer, and in the vicinity of the Philippine islands. The 
 same remarks apply to this region as in the case of cyclones. The general direction 
 of movement of the tornado-cloud is invariably from a point in the S.W. quadrant 
 to a point in the N.E. quadrant. The tornado-cloud assumes the form of a funnel, 
 the small end drawing near to or resting upon the earth. This cloud, or the moving 
 air of which it is the embodiment, revolves about a vertical axis with inconceivable 
 rapidity, and always in a direction contrary to the movement of the hands of a 
 watch. The destructive violence of the storm is sometimes confined to the 
 immediate path of the cloud, as when the small or tail end just touches the earth. 
 While, on the other hand, as the body of the cloud lowers, more of it rests upon the 
 earth, the violence increases, and the path widens to the extreme limit. The tornado 
 (Page 5), with hardly an exception, occurs in the afternoon just after the hottest 
 part of the day, and generally disappears before the going down of the sun. The 
 (Page 6) hour of greatest frequency is between 3 and 4 P.M. When I speak of the 
 formation of a water-spout at a considerable height in the air, I mean that the 
 (Page 7) embodiment of the whorl, or the revolving current of the air, first appears 
 in a dark cloud of minutely divided particles of water, the result of rapid condensa- 
 tion of course in the air, and therefore in the water. Hailstorms are characterized 
 by a strange cloud-formation, and a peculiarity of precipitation unlike any other 
 formation in the category of storms. The cloud from which the hail falls is basket- 
 shaped, with a dark and portentous exterior, a ragged and ominous-looking 
 opening at the bottom ; and within a whirling conglomeration of snowflakes, 
 pellets of snow and ice, partly formed, and perfect hailstones. The hail-cloud forms 
 between the currents of the upper and lower regions of the atmosphere, and moves 
 forward in the plane of these currents, either within or just above the upper limit 
 of the lower atmospheric regions, where it finally disappears, and the deposition of 
 (Page 9) hail ceases. The tornado is preceded by the formation of a large baro- 
 metric trough, with a prevalence of northerly and southerly winds at each end. 
 Carefully study cloud development, colour as well as form, also manner and 
 direction of approach. The approach of a cirrus-cloud (perhaps at a height of six 
 to eight miles) from the S. W. is very significant, and is the evidence of the gradual 
 but certain advance of the upper south-west current, which eventually plays so 
 important a part in the development of the tornado-cloud. Clouds are but the 
 embodiments of air currents, yet they are full of meaning. A study of the upper 
 currents of the atmosphere would be impossible without their manifestations, and 
 that, too, in a variety of forms. Wind direction, temperature, and clouds are the 
 proper subjects of observation and thought by the isolated observer [of tornadoes]. 
 (Page 10) While the conditions preceding a tornado are forming, the winds north 
 and south of the main axis of the trough cause an increasing contrast of tempera- 
 ture. This contrast increases with rapidity, and the formation of cloud commences 
 in earnest. Huge masses of dark and portentous appearance bank up in the N.W. 
 and S.W. with amazing rapidity. The struggle for mastery in the opposing 
 currents is thus indicated by the gathering cloud formations. The condensation 
 of vapour from the extremely humid southerly currents by contact with the 
 augmenting cold of their struggling opponents continues. It increases rapidly. 
 Finally, when the tenacious hold upon a stable equilibrium can no longer be main- 
 tained (which is controlled by the rapidity and extent of condensation), the opposing 
 forces are, as it were broken asunder, followed by the upward rush of huge volumes 
 of air. The outward indication of this event is first shown in the whirling, dashing 
 clouds over the surface of the heavy bank of condensed vapour forming the back- 
 ground. The next stage is the gradual descent of the funnel-shaped cloud from a point 
 apparently just beneath the position of the enactment of the first scene. One pre- 
 435 
 
AQUEOUS VAPOUR 1882. Finley. NO TE 
 
 (Page 11) monitory sign is excessive sultriness of the air. Other signs equally impor- 
 tant and reliable may be found in the development and peculiar formation of the 
 clouds in the western horizon. Sometimes these peculiar clouds extend from the S.W. 
 through the W. by the N. to N.E. More frequently they form in the N.W. 
 and S.W., sometimes commencing first in the former quarters, and then again in 
 the latter ; but in either case they are equally significant. The marked peculiarity 
 of the cloud is found to occur not only in the form, but in the colour and character 
 of development. The sudden appearance of ominous cloud, first in the S.W. and 
 then almost immediately in the N.W. or N.E. (perhaps the reverse in the order of 
 their appearance), generally attracts attention. In almost all cases these premonitory 
 clouds are unlike any ordinary and usual formation. If they are light their 
 appearance resembles smoke issuing from a burning building or straw-stack, rolling 
 (Page 12) upwards in fantastic shapes to great heights. Again like a fine mist, or 
 quite white, like fog or steam, Some persons describe these light clouds as at times 
 apparently iridescent, or glowing, as if from their irregular surfaces a pale, whitish 
 light was cast. The dark clouds at times present a deep greenish hue, which fairly 
 fOTbodes the greatest evil. Again they appear jet black from centre to circum- 
 ference, or in a change of form this deep- set colour may only appear at the centre, 
 gradually diminishing in intensity as the outer edges of the cloud or bank of clouds 
 are approached. Sometimes these dark clouds, instead of appearing in solid and 
 heavy masses, roll up lightly, but still intensely black, like the smoke from an 
 engine or locomotive burning soft coal. They have been described as of a purple 
 or bluish tinge, or at times possessed of a strange lividness. Frequently dark 
 green, again an inky blackness. One observer . says : ' The clouds seemed to be 
 boiling up like muddy water, the upper surface of the cloud reminding me of the 
 incessant eddies or whirls seen in the muddiest portions of the Missouri river.' 
 Others thus : ' I saw two whirling circles of lightish-grey clouds in the west ; they 
 were acting independent of each other, and moved slowly inward toward each other 
 from opposite directions. The clouds were very low, seemed to be on the earth, 
 the wind in contrary directions across the face of the western sky, and surrounding 
 clouds in great profusion.' * I saw a green-looking cloud in the N.W., surrounded 
 by others not so deep set in colour. Under the cloud from the S. W. there came a large 
 number of little thunder heads, some very dark, but others as white as steam. They 
 seemed to be separated, and running very low. I never saw clouds so low before. Pretty 
 soon they began to go in all directions some up, some down, right and left, back- 
 wards and upwards. I next saw a cloud that looked even all over in colour, and very 
 white, the edges pretty even. It moved remarkably steady, and seemed to be right 
 under the edge of the cloud from the S.W.' ' Two clouds, one from the N.W. and 
 the other from the S.W., seemed to meet, and after meeting passed still lower. Above 
 (Page 13) their place of meeting black smoke appeared in very peculiar shape.' The 
 peculiar action of the clouds while they are forming is another interesting and 
 significant feature, which should be carefully watched. There seems to be some 
 strange connection between the almost simultaneous appearance of clouds in the 
 S.W. and N.W. As they approach from opposite directions, they are suddenly 
 thrown into the greatest confusion, breaking up, as it were, into small portions, 
 which dash pell-mell over each other, and in every direction, now darting towards 
 the earth, now rushing upward to considerable heights like the ascension of a sky- 
 rocket, or at moderate elevations rolling over each other in a well-developed whirl. 
 An observer in describing the approach of the clouds from the S.W. and N.W. 
 stated that they ' came together with a terrific crash, as if thrown from the mouths 
 of cannons.' Generally, following closely upon the existence of this condition, the 
 funnel-shaped tornado-cloud appears against the western sky, moving boldly to the 
 front from without this confused mass of flying clouds. As the tornado cloud 
 436 
 
AQUEOUS VAPOUR 1882. Schwedoff. NOTES. 
 
 advances these scuds continue to play about its top and sides, constituting a 
 {Page 15) characteristic feature of the scene. The tornado cloud is, generally speak- 
 ing, funnel-shaped ; that is to say, the lower end is always the smallest. It may 
 appear to be balloon-shaped, basket-shaped, egg-shaped, like a kite or a bulb, or 
 an elephant's trunk, etc. The major axis may be inclined to the perpendicular, but 
 is usually upright. Sometimes it is hour-glass-shaped, and then the tornado is 
 extremely violent. The variations of form are important in a critical study of 
 the tornado. They depend upon the peculiar whirling movements of the air. 
 
 Schwedoff, Theodore. Symons's Meteorol. Mag., vol. xvii. (rsp.} Paper read before the British 
 
 Association. 
 [No. for November.] 
 
 (Page 149.) Hail comes from very characteristic clouds, sometimes dark, almost 
 black ; at other times very bright, but always dense, with clear cut and agitated out- 
 lines ; we recognize them amongst storm clouds. The same character of clouds is 
 repeated in the falls of meteorites. It is suggested that hail is of extra-terrestrial 
 origin. 
 
 Symons's Meteorol Mag., vol. xvii. (rsp.) 
 
 Notice of Professor Poey's ' Les Courants Atmospheriques,' etc. A translation is 
 given of a portion of Chapter I., from which the following remarks are selected: 
 
 (Page 99.) We proved in a previous volume that the form of clouds is due to 
 their integral structure, which is inseparable from the physical constitution of the 
 various layers of the atmosphere, where the action of weight, pressure, heat, and 
 humidity undergo constant changes, indicated by the presence of special formations 
 of clouds ; that there are two characteristic types of cloud, the cirrus, formed of 
 frozen particles, and the cumulus, formed of watery ones ; all other forms are 
 evolved from these two types ; that there exists in the evolution of qlouds a scale of 
 complication or increasing speciality from the upper region of the cirrus down to 
 the fracto-cumulus near the surface ; that one may regard the atmosphere in a 
 vertical sense as divided into two great regions, each having physical characteristics 
 and meteorological products quite distinct ; that usually the Pallio-fractus forms 
 the boundary between these two layers. It is at this intermediate layer, where the 
 watery particles are changing into snow or ice, that the meteorological manifestations 
 are developed. In the regions below this are produced thunderstorms, rain, snow, 
 hail, the easterly trades, surface winds, and optical phenomena dependent on re- 
 flection, such as rainbows and coronse. The general movements of the atmosphere 
 have their origin in the upper regions, as have also equatorial storms, the westerly 
 trades, and optical phenomena dependent on refraction, such as haloes, parhelise, 
 and paraselense. Accordingly heat and moisture prevail in the lower regions, cold 
 and dryness in the upper ; and hence the formation and structure of the clouds. 
 In the upper regions the vapour of water is precipitated in the form of ice needles, 
 and in the formation of cirrus ; in the middle region in that of snow crystals and 
 cirro-cumulus ; and in. the lowest region in that of watery particles and of cumulus. 
 The atmosphere may therefore be regarded as consisting of a series of concentric 
 beds of constantly varying properties, and in which the clouds are modified from 
 the cirrus or cumulus to an extent corresponding with their altitude. From the 
 altitude alone it is therefore possible to determine the physical constitution of the 
 stratum and the characteristic forms of cloud, and vice versa. The elements are all 
 intimately related, and the knowledge of any one enables us to deduce the others. 
 When observers are thoroughly persuaded of the truth of these facts they will have 
 a powerful guide in their observations of clouds, they will recognize the importance 
 of employing a nomenclature in harmony with the present state of science, and per- 
 haps they will adopt that which we have proposed. 
 
 GG 437 
 
AQUEOUS VAPOUR 1883. Crosby. NOTES, 
 
 [To this the reviewer adds] : 
 
 (Page 102.) Is it possible that the reason that shepherds and fishermen are such 
 good weather prophets is that they study the form and character of the clouds, and 
 that in their rough way they get a truer insight than do those excellent observers 
 who determine that the mean amount of cloud at 9 A.M. is 67, and at 9 P.M. 7*1 ? 
 
 [No. for August.] 
 
 (Page 104. ) It seems to follow from the figures given by M. Fautrat that the 
 degree of saturation of the air by moisture is much greater over masses of leafed 
 species of trees than others. [See under 1880 Nature, xxi., Notes.] The leafage 
 and branches of leafed trees intercept one-third, and those of resinous trees the 
 half of the rain-water which afterwards returns to the atmosphere by evaporation. 
 On the other hand, these same leaves and branches restrain the evaporation of the 
 water which reaches the ground, and that evaporation is nearly four times less under 
 a mass of leafed forest than in the open, and two and one-third times only under a 
 mass of pines. 
 
 1883. 
 Abercromby, Hon. Ralph. Symons's Meteorol. Mag., vol. xviii. (rsp.) 
 
 [No. for February.] 
 
 (Page 11.) There are what are called good and bad hours for clearing ; that is to 
 say, that if during a rainy day the sky breaks about 11 A.M. or 2 P.M., the improve- 
 ment will not last, so that these are bad hours. If, on the contrary, the break 
 occurs about noon or 4 P.M., it is expected that the weather will clear permanently ; 
 and these are called good hours of clearing. These are the hours which hold good 
 (Page 12) in Scotland, but perhaps they vary in different parts of the country. 
 
 Backhouse, T. W. Symons's Meteorol. Mag., vol. xviii. (rsp.) 
 
 (Page 58.) Since 1858 I have registered foggy weather, using as a gauge the 
 distance at which objects can be seen. The scale is as follows : 
 
 Distance visible, 32 miles Fog, 4 
 
 8 8 
 
 2 ., 16 
 
 880 yards 32 
 
 220 6t; 
 
 and so on in inverse ratio to the square root of the distance visible. The objects 
 observed are any solid bodies in the daytime, and at night ordinary gas-lights. The 
 visibility depends on the distance, not upon the angle subtended by the object ; 
 (Page 59) size and colour have little influence on visibility. A good deal depends 
 upon height, since the atmosphere is usually clearer high up than low down. I 
 therefore select objects which are approximately of the same height. I found a 
 difficulty in deciding upon a scale. Distance alone would not do, nor a scale of 
 simple inverse ratio, since then there would be no perceptible difference between a 
 moderately clear day and a very clear day. Perhaps a logarithmic scale would be 
 fairer than any, such as : 
 
 Distance visible, 32 miles Fog, 6 
 
 16 7 
 
 and so on. 
 
 Crosby, W. O. AjyalacJiia, vol. iii., No. ii. (1883). Head December 13th, 1882 (r). 
 
 (Page 132.) In East Cuba the sky is usually clear till the sea breeze or N.E. 
 trade-wind strikes the mountains in the middle of the forenoon. Then the watery 
 
 138 
 
AQUEOUS VAPOUR 1883 Gladstone. NOTES. 
 
 vapour is condensed, and clouds (usually cumuli) begin to appear. The cloudiness 
 increases until a continuous cloud-belt is formed, extending east and west as far 
 as the eye can see, but always of very limited breadth. From any moderate 
 eminence, or from a mile or two off the north coast, it can be distinctly seen that 
 the clouds do not extend far south of the summit of the range, enveloping the high 
 peaks and ridges, while through the low passes clear sky appears beyond ; but 
 towards the north the cloud-belt may cover the shore, or extend several miles out 
 to sea. On many days, especially in the dry season, the clouds do not form a 
 distinct and continuous belt, and their development is not followed by rain. When 
 the land breeze sets in at night the cloud-belt is carried out to sea, and may often 
 be seen in early morning resting on the northern horizon before it is dissipated 
 (Page 133) by the advancing sun. Except during the prevalence of general storms 
 the precipitations take place on the north sides of the mountains, the clouds rapidly 
 disappearing in invisible vapour as they are carried by the trade wind over the 
 heated southern slope. 
 
 Dines, W. Symons's Meteorol. Mag., vol. xviii. (rsp.) 
 
 (Page 107.) I have had a meter in use since January. I send a specimen of the 
 results obtained with it : 
 
 TENSION. 
 
 Dry bulb. "Wet bulb. By calculation. By meter. 
 
 60-5 [degrees] 57-8 [degrees] '439 [inches] -302 [inches] 
 
 64-5 58-8 -418 '263 ,. 
 
 64-0 57-4 '387 '249 n . 
 
 64-0 ., 56-6 -367 ,, -223 
 
 64-8 56-5 -355 ,. '205 
 
 The method is to take a given volume of air, extract the vapour by means of 
 sulphuric acid, restore the air to its original volume and temperature, and note the 
 loss of pressure. The tension thus obtained is less than that given by the tables ; 
 and I have no doubt that further investigation will show that the tension of vapour 
 mixed with air, and not in the presence of water, is less than is generally supposed. 
 
 Gladstone, J. H. Symons's Meteorol. Mag., vol. xviii. (rsp.) 
 
 [This paper is regarded as belonging to 1883. It, of course, strictly belongs to 
 1863, and when the paper is read in the original publication, it is possible some 
 facts not given here would be entered on account of priority of statement.] 
 
 (Page 19. ) The paper is based on observations on fogs made at about 250 
 stations. Prof. Tyndall denned a cumulus as the visible capital of an invisible 
 column of saturated air. When on the summit of the Righi one morning last 
 summer [=1862], there lay in the valley of the Reuss a mist like a white sheet on 
 the ground, but as the sun began to exert his power, and a light breeze to spring 
 up, the uniform layer began to break into regular masses, and soon far beneath us 
 there stretched a cirrus-cloud, identical in aspect with those one often sees in the 
 (Page 20) highest regions of the atmosphere. It is difficult to draw a line of 
 distinction between fog and mist. The value of meteorological returns depends on 
 this, and it appears that what one observer calls fog another describes as mist or 
 haze. Mr. Cunningham suggests that when a pole, painted vermilion, placed at 
 100 yards distance, is rendered invisible by mist, such mist should be called a fog. 
 Some months are marked by fogs more than others. For instance, along the south 
 coast of England, February and September are comparatively free, while January 
 and June are foggy months. November is notorious for fogs in London, but does 
 not seem to deserve that character elsewhere. Some years are much more visited 
 by fogs than others. For instance, 1861 was freer than 1858 along most parts of 
 
 439 
 
AQUEOUS VAPOUR . "1883. Tomlinson. NOTES. 
 
 . . ** J ''I ._. . 
 
 " "i ' 
 
 the coast. England does not ^deserve that pre-eminent character for mistiness 
 
 which is attributed to it "by the popular imagination of the Continent. A fog 
 is more uniformly distributed over the surface of the sea than on the adjoining 
 coasts. 
 
 Robie, David. Symons's Meteor ol. Mag., vol. xvii. (rsp.) 
 [No. for January.] 
 
 (Page 184.) In past generations it was the common opinion that the rain-clouds 
 were supplied with their water from neighbouring seas. The old agricultural 
 reporters of the counties often spoke of a certain quantity of rain coming with the 
 west or south-westerly wind from the Atlantic Ocean, and again so much being 
 brought by an east wind from the German Ocean. They obviously attached 
 little significance to what is termed a drying wind or a sunny day, or perhaps 
 thought that the evaporation from the soil in the shape of aqueous vapour passed 
 into space. The washerwoman, though a capital judge of a drying day when 
 suspending her wet clothes, would take no account of what became of the moisture 
 which disappeared in the process of drying. From observations with rain and 
 (Page 185) Dalton gauges made at Bedford in 1882, I find that the water in the rain 
 gauge measured 28'42 in., while the amount in the Dalton gauge, representing the 
 amount which percolates the soil, was 14'50 inches. Hence almost one-half of the 
 rainfall passed upwards into the atmosphere in an imperceptible form. The 
 percentage which the percolation amounts bore to the rainfall in the several months 
 was January, 83 ; February, 50 ; March, 68 ; May, 54 ; June, 20 ; July, 51 ; 
 August, 8 ; September, 40 ; October, 46 ; November, 67 ; and December, 94. 
 (Page 186) Dalton gauges of various depths are in operation at Rothamsted, from 
 which it is found that the moisture in the soil is drawn up from considerable 
 depths. One gauge is five feet deep. 
 
 Tomlinson, Charles. Symons's Meteorol. Mag., vol. xviii. 
 
 (Page 117.) Pictet made observations on the temperature at 5 feet and 79 feet 
 (Page 118) above the ground in 1779. He found that the lower thermometer marked 
 a lower temperature than the upper during the night. The difference was observed 
 at all seasons during moderate and in cloudy weather ; only in the last case the 
 effect was much less appreciable. When the sky was completely clouded or fog 
 prevailed the difference disappeared, both thermometers reading alike. Prevost, in 
 1772, correctly expounded the action of clouds in limiting radiation. 
 
 Symons's Meteorol. Mag., vol. xviii. 
 
 (Page 18.) We regret that no systematic records have been kept of the amount 
 of fogs. We can only recall three short papers on fog distribution two in the 
 British Association Reports for 1861 and 1862 and the abstract of Dr. J. H. Glad- 
 stone's lecture to the Royal Institution on < Fogs and Fog Signals.' [The latter is 
 reprinted and notes from it are given separately under Gladstone.] What is the 
 (Page 21) best mode of determining the density of a fog 1 Dr. Gladstone mentions 
 Mr. Cunningham's suggestion of a vermilion- coloured post. Why vermilion ? 
 Purely black and white would be a better contrast. The visibility of the pole will 
 depend upon the background. The background should be uniform. Hence we 
 think a broad board painted with stripes would be better than a pole. Further, the 
 pole should face the south at all stations. In towns a distance of 100 yards may 
 not be available and we do not think so great a distance is needed. It appears to 
 be desirable and practicable to obtain something more precise than a mere record 
 of fog or no fog, according as one special object is or is not visible, and we should 
 like to see an apparatus which by day or by night would indicate no fog, slight fog, 
 
AQUEOUS VAPOUR 1883. TomHnir c : ^ Ofc^S. NOTES. 
 
 moderate fog, dense fog. Mr. Cunningham's pole Va^nnot oe\assumad to be more 
 than 4 in. in diameter, and such a pole at the distaSsje/o^j^ vafdfe'wpuld subtend 
 the very small angle of 3' 49". The measure of obscu^*i(QJi^pej^W on the angle 
 subtended by the object, and a black line 0'4 in. broad on a white board at a 
 distance of 30 feet would subtend the same angle of 3' 49". As Dr. Gladstone says 
 that such a pole as has been proposed seems to correspond with the ordinary defini- 
 tion of fog, we might accept its equivalent or (0'27 in.) in. at 20 feet as the breadth 
 of No. 1 on the fog scale ; and the subsequent numbers might be multiples of it 
 viz., , ^, 1, 2, and 4 in. Our board would be horizontal, so that all parts of the 
 (Page 22) scale should be under identical conditions, and it should, we think, never 
 be less than 5 nor more than 10 feet above the ground. The scale figures should 
 be painted above the lines. At night fogs may be gauged by street lamps or by 
 means of small lanterns fitted with a composite candle and having a groove into 
 which from one to four thicknesses of coloured glass could be dropped. In the 
 densest fog such a light without any glass would be invisible at about 30 feet (per- 
 haps at 20 feet, but we are not sure), and the density of the fog would be determined 
 by placing the lamp at a distance of 20 feet with all the thicknesses of glass super- 
 posed, and removing them one by one until the light becomes visible ; e.g., if when 
 all four were in the light could be seen, there would be no fog ; with three in it 
 would be No. 1 ; with two, No. 2 ; with 1, No. 3 ; with none in, No. 4 ; and if 
 the naked light could not be seen, it would be a maximum fog, or No. 5. Of course 
 (Page 38) all the lanterns must be alike and the glasses of equal tints. The Rev. 
 W. C. Ley has issued a circular of a scheme for the observation of the upper clouds, 
 in which he suggests the outlines of a cloud classification. He objects to the terms 
 cirro-stratus and cirro-cumulus as leading to confusion. In point of structure the 
 clouds usually called cirro-cumulus belong essentially to the higher strati forms, 
 consisting of nubecules separate or partly coalescing, occupying a layer of atmo- 
 sphere of very small vertical thickness, but of very great horizontal extent, and they 
 are not formed in nature by the processes which are productive of clouds either of 
 the cirrus or of the cumulus type. The different varieties of cirriform clouds are 
 described, with the symbols proposed for their designation. By means of a regular 
 staff of observers information may be obtained as to the forms of the higher clouds, 
 which will double the value of existing storm warnings ; enable an isolated observer 
 to plot out the general distribution of atmospheric pressure, and of the weather 
 existing in the British Islands at the time of observation ; form a forecast of what 
 such distribution and the weather will be in the ensuing twenty-four hours ; 
 and furnish early information of coming storms. Mr. Ley's nomenclature seems to 
 be too complicated for cloud observers. 
 
 441 
 
AQUEOUS VAPOUB, 
 
 BIBLIOGRAPHY. 
 
 1875. 
 
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AQUEOUS VAPOUR 
 
 18791880. 
 
 BIBLIOGRAPHY. 
 
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 Zeits. f. Meteorol., xiii. 1878. 
 
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 scintillation of the stars. Nature, xviii., p. 
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 1879. 
 
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 logy." 1879 (rv). 
 
 16. Symons, G. J Symons's Meteorol. 
 Mag., vol. xiv., pp. 163164. 1879 (rs). 
 
 17. Volland. Ueber Verdunstung und 
 Insolation. Ein Beitrag zur bessern Kennt- 
 niss d. Hochgebirgsklimas. 8vo. Basle. 1879. 
 T6 marks. 
 
 18. Nature, xix., pp. 269, 299, 326, 327, 
 523, 548 (rv) ; xx., pp. 116, 270 (rv). 1879. 
 
 1 9. Symons's Meteorol. Mag., vol. xiv.,pp. 89, 
 90, 122, 124, 125 (rs). 1879. 
 
 1880. 
 
 I. Aitken, J. On dust, fogs, and clouds. 
 Nature, xxiii., pp. 195 197. 1880 (rv). [Read 
 to Roy. Soc. Edin., December 20th.] 
 
 v. Anderson, A. R. A dry period. 
 Symons's Meteorol. Mag., vol. xv. (No. for 
 May), p. 57 (rs). [Refers to rainfall near 
 Liverpool.] 
 
 3. Archibald, E. D. Nature, xxi., p. 394. 
 1880 (rv). 
 
 4. Bicknell, P. The dry period. Symons's 
 Meteorol. Mag., vol. xv. (No. for July), p. 92 
 (rv). [Refers to rainfall at Beckenham.] 
 
 5. Blanford, H. F, Nature, xxi., p. 482. 
 1880 (rv). 
 
 6. Burder, Geo. F. A variety of hoar 
 frost. Symons's Meteorol. Mag., vol. xv. (No. 
 for March), p. 29 (rs). 
 
 7. Byng, Rev. John. A dry period. 
 Symons's Meteorol. Mag., vol. xv. (No. for 
 April), p. 48 (rs). [Refers to rainfall at 
 Colchester.] 
 
 8. Cantoni, G. On the temperature and 
 humidity of the air and the formation of dew 
 in the neighbourhood of great lakes. Ren- 
 diconti Lombard., vol. xii. 1880. 
 
 9. Croll, James. Nature, xxi., pp. 521 
 522. 1880 (rv) ; xxii., pp. 191192. 1880 (rv). 
 
 10. Dines, G. Symons's Meteorol. Mag., 
 vol. xiv., p. 191 (rs). 
 
 II. Fordham, H. Geo. A dry period. 
 Symons's Meteorol. Mag., vol. xv. (No. for 
 May), p. 57 (rs). [Refers to rainfall at 
 Royston.] 
 
 12-. Griffith-Boscawen, B. T. Dry 
 January. Symons's Meteorol. Mag., vol. xv. 
 (No. for February), p. 8. [Refers to rain- 
 fall at Wrexham.] 
 
 13. Harvey, Rev. E. W. A travelling 
 fog. Symons's Meteorol. Mag., vol. xv. (No. 
 for February), p. 8 (rs). [Refers to a London 
 fog at Buntingford.] 
 
 14. King, S. A dry period. Symons's 
 Meteorol. Mag., vol. xv. (No. for May), p. 56 
 (rs). [Refers to rainfall at Garstang.] 
 
 15. Ley, Rev. W. C. Aids to the study 
 and forecasts of the weather. 1880 (rv). 
 
 16. Ley, Rev. W. C. Nature, vol. xxii., 
 pp. 207, 210. 1880 (rv). 
 
 17. Miller, H.E. A dry period. Symons's 
 Meteorol. Mag., vol. xv. (No. for May), p. 57 
 (rs). [Refers to rainfall at Lowestoft.] 
 
 18. Farfltt, Edward. Nature, vol. xxi., 
 p. 324 (rv). 
 
 448 
 
AQUEOUS VAPOUR 
 
 18811883. 
 
 BIBLIOGRAPHY. 
 
 19. Poey, A. Comment on observe les 
 nuages pour prevoir le temps. 3rd Ed. 1879. 
 Noticed in Symons's Meteorol. Mag., vol. xv., 
 pp. 25. 1880 (rs). 
 
 20. Kobie, David. The dry period. 
 Symons's Meteorol. Mag., vol. xv. (No. for 
 June), p. 71 (rs). [Refers to rainfall at 
 Bedford.] 
 
 21. Smyth, C. Piazzi. Nature, vol. xxii., 
 pp. 194, 195 (rv). 
 
 22. Tait, P. G. Nature, vol. xxii., pp. 340, 
 438. 1880 (rv). 
 
 23. WoeikofF, A. Nature, vol. xxii., p. 
 250. 1880 (rv). 
 
 24. Nature. Fogs, vol. xxi., pp. 355356. 
 1880 (rv). 
 
 25. Nature, vol. xxi., pp. 220, 363, 503. 
 1880 (rv) ; xxii.. p. 594. 1880 (rv) ; xxiii., pp. 
 48, 86, 204. 1880 (rv). 
 
 26. Symons's Meteorol. Mag., vol. xv., pp. 2, 
 3, 19, 20, 40, 4951, 160, 162. 1880 (rs). 
 
 1881. 
 
 1. Aitken, John. Dust and fogs. Nature, 
 vol. xxiii., pp. 311312. 1881 (rv). 
 
 2. Aitken, John. Dust, foge, and clouds. 
 Nature, vol. xxiii., pp. 384385. 1881 (rv). 
 
 3. Aitken, J. Note de M. Aitken sur la 
 formation de brouillard. Ann.- Soc. Meteorol. 
 France. 1881. 
 
 4. Broun, J. A. Nature, vol. xxiii., pp. 
 558559 (rv). 
 
 5. Capron, A, Rand. A plea for the 
 rainband. Svmons's Meteorol. Mag., vol. xvi. 
 (No. for December), pp. 181190 (rs). 
 
 6. Chatel. Dust, fogs, and smoke. Nature, 
 vol. xxiii., p. 436. 1881 . [Refers to London.] 
 
 7. Dymond, E. E. Tables of relative 
 humidity. Q. Journ. Meteorol. Soc., vii., pp. 
 13, January 1881. [Read to Meteor. Soc., 
 November 17th, 1880.] 
 
 8. Greaves, Charles. Relative hu- 
 midity. Q. Journ. Meteorol. Soc., vii., pp. 132 
 135 (No. for April). [Read to Meteor. Soc. 
 February 16th.] 
 
 9. Groneman, H. J. H. On dust, fogs, 
 and clouds. Nature, vol. xxiii., p. 337. 1881 
 (rv). 
 
 10. Preece. W. H. On dust, fogs, and 
 clouds. Nature, vol. xxiii., pp. 336337. 1881 
 (rv). 
 
 11. Richter, A. Zug der oberen Wolken 
 n Verhaltniss zur unteren Druck-und War- 
 
 mevertheilung. Zeits. f. Meteorol. Bd. xv. 
 1881. 
 
 12. Russell, R. Dust and fog. Nature, 
 vol. xxiii., pp. 2672(58. 1881 (rv). 
 
 13. Whipple, G. M. Schwackhofer's 
 Hygrometer. Symons's Meteorol. Mag., vol. 
 xvi. (March), pp. 3941 (?*). 
 
 14. Nature, xxiii., pp. 260, 370, 398, 427, 
 451, 490. 1881 (rv). 
 
 15. Symons's Meteorol. Mag., vol. xvi., pp. 
 65, 67, 68, 155, 156. 1881 (?*). 
 
 1882. 
 
 1. Boerner, Prof. C. G. The forma- 
 tion of dew. 1882 (rd). 
 
 2. Finley, John P. Tornadoes. 1882 
 (ra). 
 
 3. Poey, A. Les courants atmospheriques 
 d'apres les nuages au point de vue de la pre- 
 vision du temps. 8vo. Paris. 1882. [Noticed 
 in Symons's Meteorol. Mag., vol. xvii. (August), 
 pp. 99102 (rs). 
 
 4. SchwedofF, T. Symons's Meteorol. 
 Mag., vol. xvii., p. 149 (rs). 
 
 5. Symons's Meteorol. Mag., vol. xvii., pp. 
 99, 102, 104 (ra). 
 
 1883. 
 1. Abercromby, Hon. R. Symons's 
 
 Meteorol. Mag., vol. xviii., pp. 11, 12 (rs). 
 
 3, T. W. 
 ioro 
 5859 (rs). 
 
 2. Backhouse, T. W. Fog gauge. 
 Symons's Meteorol. Mag. , vol. xviii. (May), pp. 
 
 3. Crosby, "W. A. Appalachia, vol. iii pp. 
 132 133 (rs). 
 
 4. Dieulefait, M. Evaporation de 1'eau 
 de mer dans le sud de la France et en par- 
 ticulier dans le delta du Rhone. Comptes 
 Rendus, xevu (Juin 18), pp. 1787 1790. 
 
 5. Dieulefait, M. Evaporation des eaux 
 marines et des eaux douces dans le delta du 
 Rhone et a Constantine. Comptes Rendus, 
 xcvii., pp. 500582 (Aout 13). 
 
 6. t Dines, W. H. Vapour tension. 
 Symons's Meteorol. Mag., vol. xviii. (August), 
 p. 107 (rs). 
 
 7. Gladstone, J. H. On fogs and fog- 
 signals. Symons's Meteorol. Mag., vol. xviii. 
 (March), pp. 1821 (rs). [Reprint from Proc. 
 Roy. Inst., 1863.] 
 
 8. Lalanne. Note on paper by Salles. 
 Comptes Rendus, xcvii., pp. 349 350. 
 
 9. Luroth. On measuring the height of 
 clouds. Symons's Meteorol. Mag., vol. xviii. 
 (November), pp. 149 150. [Abstract of paper 
 read to Brit, Association. ] 
 
 10. Robie, David. Symons's Meteorol. 
 Mag., vol. xvii., pp. 184186 (rs). 
 
 11. Salles, A. Experiences sur 1'evapora- 
 tion faites a Aries pendant les annees 1876 a 
 1882. Comptes Rendus, xcvii. (July 30), pp. 
 347349. 
 
 12. Tomlinson, Charles. Symons's 
 Meteorol. Mag., vol. xviii., pp. 117 118 (rs). 
 
 13. Symons's Meteorol. Mag., vol. xviii., pp. 
 17 22. Fog gauges (rs). 
 
 14. Symons's Meteorol. Mag., vol. xviii. 
 (April), pp. 38 iO. Scheme for the observa- 
 tion of the upper clouds (rs). 
 
 15. Symons's Meteorol. Mag., vol. xviii., pp. 
 18, 21, 22, 38 (rs). 
 
 444 
 
INDEX. 
 
 B. denotes Bibliography. N. denotes Notes. The figures refer to pages. 
 
 AIR : transparency. Seidel, B. 183 : Vaillant, 
 B. 185. 
 
 as a weather sign. Ley, N. 420. 
 AQUEOUS VAPOUR : 
 
 Abercromby, B. 444; Archibald, B. 442, 
 443 ; Armand, B. 183 ; Blanford, B. 442, 443 ; 
 Bonavia, B. 442 ; Broun, B. 442 444 ; C. H., 
 B. 442 ; Croll, B. 443 ; Crosby, B.444 ; Dines, 
 B. 443 ; Erskine, B. 443 ; Hill, B. 442 ; Hind, 
 B. 443 ; Ley, B. 442, 443 ; Lockyer, B. 443 ; 
 Lucas, B. 443 ; Mann, B. 443 ; Moritz, B. 186 ; 
 Moseley, B. 443; Murray, B. 442, 443; 
 Nature, B. 442444 ; Parfitt, B. 443 ; Eagona, 
 B. 185 ; Robie, B. 444 ; Schwedoff, B. 443, 
 444; Secchi, B. 183; Skertchley, B. 443; 
 Smyth, B. 442, 444; Symons, B. 443, 444; 
 Tait, B. 444 ; Thomson, B. 443 ; Tomlinson, 
 B. 182 ; Woeikoff , B. 444. 
 
 action of dust as condenser. Aitken, N. 430. 
 
 action of hills. Buchan, B. 344. 
 
 action on air. Hopkins, B. 182. 
 
 action on pendulum. Squire, B. 179. 
 
 and barometric pressure. Dauiell, N. 292 
 294 ; Saul, N. 189191. 
 
 and clouds. Hobbes's view, N. 189. 
 
 electricity. Quetelet, B. 182. 
 
 polarization of air. Buchan. N. 368. 
 
 and radiant heat, N. 344 ; Ainsworth. N. 286 ; 
 Flammarion, B. 185; Harrison, B. 185, 186, 442 ; 
 Neumayer, B. 184 ; Soret, B. 184 ; Strachey, 
 B. 184 ; Thomson, N. 364 ; Tyndall, B. 183 
 185 ; Wild, B. 185. 
 
 and its relation to air. Airy, N. 333; Bloxam, 
 N. 334336 ; Laniont, N. 341344. 
 
 and its relation to barometric pressure. 
 Herschel, N. 317, 322325 ; Monck, N. 388 ; 
 Richter, B. 444. 
 
 and its relation to cyclones and anti-cy- 
 clones. Ley, N. 420, 421. 
 
 as a cause of blueness of sky. Sorby, N. 
 363. 
 
 as a regulator of cyclones. Parish, N. 312. 
 
 as a regulator of storm tracts, N. 416. 
 
 as a regulator of temperature. Buchan, N. 
 360, 361 ; Croll, N. 418. 
 
 as indicated by date palm. Barns, N. 394. 
 
 as indicated by wheat. Brumham, N. 390 ; 
 Stow, N. 391. ' 
 
 as the motive power in air currents, N. 428. 
 
 as the motive power in cyclones. Maury. 
 N. 394, 395. 
 
 ascent of. Eason, B. 178. 
 
 condensation of, by dust. Aitken, N. 430 ; 
 Oronemann, N. 431, 432; Preece, N. 432. 
 
 condensation on ice. Dufour and Forel, B. 
 1S6, 187. 
 
 condensation on snow. Dufour, B. 186. 
 
 daily period. Austin, N. 309 ; Elias, N. 396 ; 
 Erskine, N. 408 ; Mann, N. 370, 371. 
 
 daily and seasonal period. English Cyclo- 
 pedia, N. 313. 
 
 AQUEOUS VAPOUR continued. 
 
 distribution in air. Dujardin, B. 185 ; Eng- 
 lish Cyclopaedia, N. 313, 314; Findlay, N. 
 299 ; Maclaren, N. 309. 
 
 distribution as regulated by evaporative 
 and rainy areas. Hopkins, N. 309312. 
 
 distribution as regulated by plants. 
 Becquerel, N. 345. 
 
 importance of a knowledge of tension dis- 
 tribution. Stewart, N. 388. 
 
 in air. Aubuisson, B. 178 ; Bolthauser, B. 
 18G ; Dalton, N. 215217 ; Daniell, B. 179 ; 
 N. 217219, 241265, 277285, 289298 ; 
 Dove, B. 179, 181 ; Espy, B. 182 ; Flammarion, 
 B. 185 ; Grey,N. 314 ; Hare, B. 180; Herschel, 
 N. 316330; Hopkins, B. 181 ; Hunt, B. 182; 
 Ladame, B. 181 ; Lament, B. 183, 184 : 
 Monck, B. 187 ; Prestel, B. 186 ; Simons, B. 
 179 ; Stewart, B. 186 ; Strachey, B. 183 ; 
 Stratingh, B. 179 ; Suerman, B. 179, 180 ; 
 Symons, N. 415 ; Topfer, B. 188 ; Tralles, B. 
 178 ; Vogel, B. 185. 
 
 in connection with auroras, N. 330, 331, 406. 
 
 in connection with barometric pressure. 
 Blanford, N. 418 ; Broun, N. 430 ; Buchan, 
 N. 349, 350, 366, 367, 369, 370, 386. 
 
 in connection with consumption and brain 
 diseases. Buchan, N. 346. 
 
 in connection with plants. Bidie, N. 377 
 379; Buchan, N. 344346; English Cyclo- 
 paedia, N. 313. 
 
 in connection with snowline. Senienof, N. 
 347. 
 
 in connection with sunset colours. Lockyer, 
 N. 405. 
 
 in connection with sun-spot frequency. 
 Archibald, N. 404. 
 
 in connection with temperature. Wrede, 
 B. 180 ; Richter, B. 444. 
 
 in connection with thunderstorms, N. 428. 
 
 in connection with transparency of air, N. 
 402 ; Abercromby, B. 442 ; Cruickshank, B. 
 443 ; Wild, N. 375. 
 
 in connection with wind. Dove, B. 179. 
 
 in connection with cylones, N. 408, 433. 
 
 in connection with cyclones and tornadoes. 
 Finley, N. 434437. 
 
 in connection with cyclonic vortexes, N. 415. 
 
 in connection with shifting of monsoons. 
 Broun, N. 406. 
 
 influence on barometer. Renny, B. 182 ; 
 Soldner, B. 178. 
 
 influence on light. Spottiswoode, N. 391. 
 
 influence on radiant heat, N. 403 ; Mark- 
 ham, N. 396 ; Russell, N. 362, 363 ; Stow, N. 
 397. 
 
 influence on snow-line. Croll, N. 418, 419. 
 
 influence on wind. Buchan, N. 367, 368. 
 
 its pathways. Somerville, N. 381, 382. 
 
 relation to plants and animals. Somerville, 
 N. 383, 384. 
 
 445 
 
INDEX. 
 
 AQUEOUS VAPOUR continued. 
 
 relation to colour of skin. Brine, N. 394 ; 
 Grant, N. 394. 
 
 meter for measuring tension. Dines, N. 
 439. 
 
 method of gauging vertical and horizontal 
 distribution. Stewart. N. 373, 374. 
 
 observations required. Hildebrandsson, B. 
 443. 
 
 on rivers. Murray, B. 179. 
 
 pressure. Bloxam, B. 184. 
 
 rainband spectroscopic observations. Ca- 
 pron, N. 430, 431 ; B. 444 ; Smyth, B. 442. 
 
 reduction of observations. Stewart, B. 177. 
 
 retention by soil. Schomburgk, N. 289. 
 
 seasonal changes. Barker, N. 298 ; Davis, 
 N. 299; FitzRoy, N. 299; Gregory, N. 
 316; G-utzlaff, N. 299; Hunt, N. 298; 
 Parkyns, N. 299 ; Strachey, N. 300 ; Wallin, 
 N. 299. 
 
 seasonal and geographical distribution. 
 Somerville, N. 382383. 
 
 seasonal period. Allen, N. 288 ; Bacon, N. 
 288 5 Christopher, N. 289 ; Forbes, N. 346 ; 
 Grant, N. 312 ; Mann,N. 370, 371 ; Palgrave, 
 N. 346 ; Skertchley, N. 414 ; Speke, N. 347 j 
 Thomson, N. 397 ; Wilson, N. 397. 
 
 spectroscopic bands. Smyth, N. 426. 
 
 tension. Dines, B. 444. 
 
 tension increases with scintillation of stars, 
 N. 400, 406, 415. 
 
 theory of vapour pressure. Airy, B. 183 ; 
 N. 333 ; Bloxam, B. 183 ; N. oo4 336 ; 
 Lamoiit, B. 183 j N. 341344. 
 
 tide. Bellingharn, B. 183 ; N. 315. 
 
 upper. B. 444. 
 
 ARID COUNTRIES. Hopkins, B. 182. 
 ATMOMETER. Miller, B. 442. 
 CHEMICAL ACTION: organized in- 
 quiry into the speed of, 337. 
 CLEARNESS OF MORNINGS. Eng- 
 lish Cyclopaedia, N. 314. 
 
 CLOUDS : Aitken, B. 443, 444 ; Anon, 215 ; 
 Dalton, N. 184186; Duponchel, B. 183; 
 Flammarion, B. 185; Fritsch, B. 185, 186; 
 Goethe, B. 179, 180; Haidinger, B. 184; 
 Herschell, N. 318, 330; Howard, B. 443: 
 Mottez, B. 187 ; Miihry, B. 188 ; Oliver, N. 
 182; Prestel, B. 187; Tyndall, B. 186; 
 Varley, B. 178 ; Wiillerstorf-Urbair, B. 188. 
 
 action on air. Reye, B. 184. 
 
 and aurorae. Blake, B. 183 ; N. 333 ; Pratt, 
 B. 183; Zollaer, B. 187. 
 
 and barometric pressure, B. 188, N. 301 
 304, 416 ; Buchan, N. 345 ; Ley, N. 407. 
 
 and dust. Gronemann, B. 444 ; Preece, B. 
 
 and electricity. Barber, B. 188 ; Schbnbein, 
 B. 182 ; Zantedeschi, B. 185, 186. 
 
 and radiant heat. Tomlinson, N. 440. 
 
 and rising air currents. Abercromby, N. 398. 
 
 and solar radiation. Harrison, B. 442. 
 
 and storms. Blasius, B. 442. 
 
 and sun-spot periods. Klein, B. 188. 
 
 and temperature. Archibald, N. 417418 ; 
 Mtihry, B. 187 ; Tomlinson, N. 440 ; Watson, 
 B. 443. 
 
 and terrestrial magnetism. Groth, B. 184. 
 
 and weather, N. 437438 ; Buchan, N. 355 
 360, 368. 
 
 and wind, N. 331 (air currents) ; Bucchich, 
 B. 184185; Home, N. 373 (whirlwinds); 
 Karaczay, N. 288289. 
 
 as weather indicators, N. 401 ; Ley, N. 
 446 
 
 CLOUDS continued. 
 
 408 414,419 424 ; B. 443 ; Mitchell, N. 346, 
 347 ; Poey, B. 183, 443, 444. 
 
 attracted by land. FitzRoy, N. 287. 
 
 cirri of remarkable character. Haviland, 
 K 391. 
 
 classification. N. 428 (Poey's), 441 ; Fritsch, 
 B. 187 ; Mann, B. 187 ; Poey, B. 186188. 
 
 colour. Sorby, B. 185 ; Buchan, N. 368 (in 
 connection with weather). 
 
 condensation. Kuhn, B. 185. 
 
 consequent on explosion. N. 385. 
 
 constitution of rain clouds. N. 388. 
 
 cumuli and hailstorms. N. 415. 
 
 daily period. N. 406 ; Bell, N. 315 ; Bonavia, 
 N. 401 ; Calvert, N. 361 ; Erskine, N. 380 : 
 H. N. 870 ; Page, N. 288 ; Richardson, N. 288 ; 
 in mountainous areas, Crosby, 1ST. 438, 439. 
 
 distribution in cyclones. N. 403. 
 
 distribution in cyclones and anti-cyclones, 
 Abercromby, N. 403, 404. 
 
 during fife. Bache, B. 181. 
 
 during hailstorms. Schwedoff, N. 427. 
 
 during storms. Silbermann, B. 184. 
 
 during thunderstorms. B. 181 ; Hann, B. 
 188 ; Perkins, B. 184 ; Tait, N. 427. 
 
 during tornadoes. Finley, N. 435437. 
 
 forecasting of, a guess. Strachan, N. 374. 
 
 formation. Ansted, N. 375, 376 ; Rozet, 
 B. 181. 
 
 formation by radiation. Thomson, N. 363, 
 3G4. 
 
 formation by means of dust. Aitken, N. 
 417. 
 
 geographically distributed. Poey, N. 380, 
 381. 
 
 good and bad hours of clearing. Aber- 
 cromby, X. 438. 
 
 height. Feussner, B. 187 ; Luroth, B. 444 ; 
 Prestel, B. 188 ; Rozet, B. 182 ; Saul, N. 191 ; 
 Wartmann, B. 181 ; Whewell, B. 181. 
 
 height (great) of cirri. Glaisher, N. 316. 
 
 height (observations wanted). N. 393. 
 
 influence of astronomical phenomena. Par- 
 fitt, N. 425. 
 
 influence of moon. Broun, N. 404 ; Ellis, 
 B. 185 ; Gritton, N. 375 ; Harrison, B. 185 ; 
 Murray, N. 405. 
 
 influence of mountains. N. 371. 
 
 influence on temperature. Woeikoff, N. 
 427. 
 
 influence on pictures. N. 429. 
 
 in S. Africa. N. 287. 
 
 Leipzig Conference recommendation to ob- 
 servers. N. 396. 
 
 new form. Poey, B. 187 ; (Poey's) Scott, 
 B. 188. 
 
 movements of cirri in connection with cy- 
 clones. N. 406. 
 
 observations of higher forms. N. 441. 
 
 orange-coloured before wind. Luck, N. 370. 
 
 periodicity. Buchan, N. 344 ; Klein, B. 187. 
 
 prevalence of constant cloud zone. Eng- 
 lish Cyclopaedia, N. 313. 
 
 relation of pocky cloud to thunderstorms. 
 Burder, N. 396. 
 
 suspension. B. 179 ; Pengelly, B. 185 j 
 Raillard, B. 184 j Rowell, B. 181 j Vaillant, 
 B. 184. 
 
 weather proverbs. N. 392, 393. 
 COMMITTEE OF BRITISH AS- 
 SOCIATION : on erratic blocks, 222 ; on 
 underground temperature, 223 ; underground 
 waters, 222. 
 
INDEX. 
 
 CONTAGIOUS DISEASES OF ANI- 
 MALS : experimental inquiry, 337. 
 DEW. B. 180 ; N. 399, 400, 403, 433 ; Dalton, 
 N. 180 ; Dines, B. 186, N. 419 ; Fusinieri, B. 
 181 ; Gersten, B. 177 j Hudson, B. 186 ; Ma- 
 jocchi, B. 181 ; Prevost, B. 178 ; Prieur, B. 
 178 ; Roosbroeck, B. 180 ; Spandri, B. 181 ; 
 Tyndall, B. 184 j Webster, B. 178 ; Wells, B. 
 179, 185, N. 187205, 209215 ; Zantedeschi, 
 B. 181184. 
 
 diurnal period. Boerner, N. 434. 
 formation. Boerner, B. 444. 
 formation near lakes. Cantoni, B. 443. 
 formulas for calculating. Everett, N. 386. 
 heavy. Wilson, N. 397. 
 in Somali country. Cruttenden, N. 298. 
 preventive causes. N. 371. 
 theory. Cantoni, B. 443. 
 Wells's claim to theory. Tomlinson, B. 183. 
 DEWBOW. Rankine, B. 183. 
 DEWPOENT. Bloxam, B. 184 ; Dalton, N. 
 377 ; Dines, B. 187 j Espy, B. 180 ; G-albraith, 
 B. 182 ; Miller, B. 182 ; Prideaux, B. 180. 
 at sea. Laughton. N. 361. 
 vertical distribution. Glaisher, N. 316. 
 DIPHTHERIA: inquiry circular. 388340. 
 DROUGHT. B. 180; Anderson, B. 443; 
 Byng, B. 443 ; Cotte, B. 178 j Fordham, B. 
 443 ; Griffith-Boscawen, B. 443 ; King, B. 443 ; 
 Miller, B. 443 ; Robie, B. 444 ; Volta, B. 179 ; 
 Whitmee, B. 443. 
 
 1858. Watson, B. 182. 
 1864-5. Fournet, B. 184. 
 1868. Hutchinson, B. 187, 188 ; Michie, B. 
 187. 
 
 1870, and its causes. N. 384, 385. 
 animals characteristic of dry regions. 
 Frere, N. 386. 
 
 as pre-indicated by leafing of oak. Home, 
 N. 364. 
 
 Brumham's rules. 
 N. 374. 
 
 caused by sirocco. N". 403. 
 heat indications of. Brumham, N. 372. 
 lunar indications of. Brumham, 1ST. 372. 
 DROUGHTS : periodicity. Brumham, N. 
 
 347, 348 ; Steinmetz, N. 364. 
 DRY AREAS THE PRODUCERS 
 
 OF WIND. Somerville, N. 381. 382. 
 DRYNESS OF SIROCCO WIND. 
 N. 417. 
 
 of summer, prognostics for. N. 366. 
 of wind injurious. Mitchell, N. 362. 
 EVAPORATION. N. 365, 3G6, 400, 429; 
 Cantoni, B. 443 ; Dieulefait, B. 444 ; Humber, 
 B. 442 ; Lalanne, B. 444 ; Salles, B. 444 ; 
 Garban's experiments, N. 433 ; Masure's ex- 
 periments, N. 434 ; observations by Dines, N. 
 415, 416 ; Ansted, N. 376 j Aubuisson, B. 178; 
 Beardmore, B. 183 ; Buchan, N. 350352 ; 
 Buist, B. 182 ; Castellon, B. 181 ; Clerk, B. 
 182 ; Dalton, B. 178, N. 184186 ; Daniell, B. 
 179 ; Dines, B. 186, N. 379, 380, 385, 386, 389, 
 390 ; Drian, B. 182 (negative) ; Dufour and 
 Forel, B. 186, 187 ; Espy, B. 180 j Fritsch, B. 
 187 ; Geddes, B. 177 ; Herschel, N. 316318, 
 325 ; Hoffmann, B. 187 ; Home, N. 346 ; Hud- 
 son, B. 187, N. 387, 388, 391 ; Lamont, B. 186 ; 
 Lyell, N. 361 ; Mann, B. 187 ; Maverley, B. 
 181; Meikle, B. 179; Miller, N. 391; Mott, 
 N. 395 ; Murphy, N. 399 ; Oliver, N. 192 ; 
 Pfaff, B. 187 ; Rosen and Hildebrandsson, B. 
 184; Rowell, B. 181; Saul, N. 191, 192; 
 Tacchini, B. 185 ; Tate, B. 183 ; Yalle's, B. 
 
 Ryves, N. 473 ; Stow, 
 
 EVAPORATION continued. 
 
 182 ; Yassalli-Eandi, B. 179 ; Vivenot, B. 184, 
 185 ; Watts, N. 346 ; Williams, N. 183, 184 ; 
 Wistar, B. 178 ; Wrede, B. 178. 
 
 and electricity. Mascart, B. 443 ; Rowell, 
 B. 181 ; Volpicelli, B. 188. 
 and lakes. Somerville, N. 381. 
 and magnetic fluctuations. Norton, N. 298. 
 and ocean currents. Ansted, N. 375 ; Mur- 
 ray, N. 399 ; Somerville, N. 391 ; Thomson, 
 N. 405, 406. 
 
 and soil temperature. Lucas, N. 414. 
 and solar spots, N. 415. 
 and water supply. Leslie, B. 187. 
 as influenced by vegetation. Markham, N. 
 362. 
 
 at sea. Laidley, B. 181. 
 defects in measurement. Symons and 
 Field, N. 374, 375. 
 
 dependent on radiation. Blanford, N. 398. 
 drawing action on soil water. Robie, N. 440. 
 from damp and wet ground. Vogel, B. 186. 
 from forest-covered land. N. 438. 
 from lake. Hajech, B. 186. 
 from land. Risler, B. 186 ; Vogel, B. 185. 
 from moss. Buchan, N. 367. 
 from oak. Pfaff, B. 186. 
 from plants. Deherain, B. 186 ; Hartog, B. 
 184 ; Knop, B. 183, N. N. 405 ; Nature, N. 
 392 ; Rauwenhoff, B. 185, 186 ; Risler, B. 186, 
 187 ; Rolleston, N. 425, 426 ; Vogel, B..185. 
 from rain gauges. Simmonds, B. 185. 
 from water surfaces. Buys-Ballot, B. 187 ; 
 Field and Symons, B. 186. 
 
 greatest in years of maximum rainfall. 
 Hill, N. 401. 
 
 in connection with desiccation of countries. 
 N. 393, 394. 
 
 in S. Africa. N. 286, 287. 
 in tropics. Baily, N. 289. 
 influence of temperature. Baumgartner, B. 
 442. 
 
 Leipzig Conference recommendations. N. 
 396. 
 
 observations on. Jackson, N. 286. 
 periodicity. Prestel, B. 183, 184. 
 EVAPORIMETERS : in South Kensing- 
 ton Museum loan collection. N. 400, 401. 
 Lamont's. Strachan, N. 384. 
 Prestel's. N. 393. 
 Wild, B. 442. 
 
 FOGS. N. 427, 429; Aitken, N. 430; B. 
 443 ; Backhouse, B. 444 ; Buchan, N. 353 
 355 ; Dines, N.419 ; Gladstone, B. 183, 444 ; 
 N. 439, 440 ; Harvey, B. 179, 443 ; Herschel, 
 N. 318; Hutton, B. 179; King, B. 443; 
 Ladame, B. 184 ; Miller, B. 443 ; Nature, B. 
 444 ; Peltier, B. 181 ; Selmonna, B. 184 ; 
 Symons's Met. Mag., B. 444. 
 Aitken's observations. N. 433. 
 and heat. Ladame, B. 184. 
 and dust. Aitken, B. 444 ; Chatel, B. 444 ;. 
 Groneman, B. 444 ; Preece, B. 444 ; Russell, 
 B. 444. 
 
 associated with rising barometer. N. 433. 
 independent of burning of fuel. RusselL 
 N. 432. 
 
 dry. Renou, B. 186; Roche, B. 184; Ser- 
 pieri, B. 187. 
 
 dry, 1863. Dufour, B. 184. 
 dry and aurora. Serpieri, B. 187. 
 E. Falkland Island. Parish, N. 286. 
 in 1871-2. Hirsch, B. 188. 
 method of measuring. N. 440, 441. 
 
 447 
 
INDEX. 
 
 FOGS continued. 
 
 method of registering. Backhouse, N. 438. 
 observations by Cruickshank. N. 416, 417. 
 
 scum connected with. King, N. 405. 
 
 seasonal distribution. Blakiston, N. 394. 
 
 seasonal occurrence. N. 364. 
 HAZE : Billeb, B. 180 ; Moore, N. 362 ; 
 Prestel, B. 185 ; Schiefferdecker, B. 185. 
 
 caused by particles in air. Anderson, N. 390. 
 
 prevalence in, B.C. 44. Hind, N. 408. 
 HILLS : influence in inducing rain. Eaton, 
 
 N. 314, 315. 
 HOAR-FROST. B. 180. 
 
 with high air temperature. Burder, B. 44d ; 
 N. 418. 
 
 HOUGHTON FARM EXPERI- 
 MENTS. 306308. 
 
 HUMIDITY. B. 181, 182; Ainsworth, N. 
 286 ; Buchan, N. 353 ; Hinds, B. 180 ; Lichten- 
 stein, B. 184 ; Prestel, B. 187 ; Regnault, B. 
 187 ; Russell, B. 177 ; Schiibler, B. 179 ; Ser- 
 pieri, B. 182. 
 
 absolute and relative. Herschel, N. 325. 
 
 action on plants. Toscani, B. 183. 
 
 and its relation to exceptional periods of 
 temperature. Bloxam, N. 333, 334. 
 
 and its relation to temperature during the 
 formation of dew. N. 399, 400. 
 
 and ozone. Ragona, B. 185. 
 
 and wind. Suhle, B. 187. 
 
 and woods. Maclaren, N. 309. 
 
 as demonstrated by spectroscope. L. N. 391. 
 
 as detected by spectroscope. Smyth, N. 398. 
 
 as indicated by coffee-plant. N. 402. 
 
 as indicated by heat. Lyell, N. 373. 
 
 as indicated by plants. Morgan, N. 414 j 
 Mosely, N. 414. 
 
 as indicated by rhododendron. Semenof, N. 
 347. 
 
 as indicated by steppes. N. 402. 
 
 as indicated by sugar-cane. Temple, N. 
 347. 
 
 as regulator of birds' habits. Ley, N. 402. 
 
 as regulator of distribution of forests. N. 
 415. 
 
 as regulator of path of barometric depres- 
 sions. Ley, N. 401, 402. 
 
 at 4, 22, and 50 feet. Glaisher, B. 187. 
 
 at different heights. B. 442. 
 
 at sea. Coupvent des Bois, B. 184. 
 
 average connected with rain. N. 398. 
 
 cases of extreme lowness. Compton, N. 
 379 ; Ryves, N. 397 ; Stow, N. 363 ; S.trachan, 
 N. 397 ; Symons, N. 363. 
 
 correction in electrical observations. Pal- 
 mieri, B. 183. 
 
 curve, coincident with that of temperature. 
 N. 371, 372. 
 
 curve, nearly the same as that of lightning 
 without thunder. Buchan, N. 373. 
 
 damp, stagnant air unhealthy. Symons, 
 JN 41o. 
 
 decrease with height. Hann, B. 188. 
 
 decreasing. Murphy, B. 442. 
 
 diurnal period. Chandless, N. 385 : Ruben- 
 son, B. 442. 
 
 in 1871. Dove, B. 187. 
 
 in 1875. Dove, B. 442. 
 
 in California. Coulter, N. 287. 
 
 in connection with Australian plants. N. 
 433. 
 
 in connection with squalls. Osborn, N. 313. 
 
 in connection with temperature N 417 
 Cantoni, B. 443. 
 
 448 
 
 HUMIDITY continued. 
 
 in connection with weather. Buchan, N. 
 358360. 
 
 increased by solar eclipse. N. 315. 
 
 in cyclones, partly due to condensation and 
 rarefaction of air. Abercromby, N. 398 ; B. 
 442 
 
 indicated by leafiness of trees. Livingston, 
 N. 309. 
 
 influence of dew on its diminution. N. 403. 
 
 influence of forests. 1ST. 403 ; Brown, B. 
 442 ; Fautrat, B. 442. 
 
 influence of moon. Emerson, B. 187. 
 
 influence of mountains. N. 402 ; Czerny, 
 N. 401. 
 
 in India, Africa, etc. Sykes, N. 300. 
 
 in town and country. Wislizenus, B. 183. 
 
 in local distribution. N. 428. 
 
 in Melville Island. Campbell, N. 28(5. 
 
 needles, dilute sulphuric acid, and leaves as 
 indicators of dry air. Wilson, N. 347. 
 
 of winds. N. 399. 
 
 of winds, changes slowly. FitzRoy, N. 
 315, 316. 
 
 of wooded areas. Hilhouse, N. 286. 
 
 over pines. N. 400. 
 
 over trees. N. 427, 438. 
 
 relative. N. 433. 
 
 relative tables. Dymond, B. 444 ; Greaves, 
 B. 444. 
 
 spring levels not influenced by. N. 434. 
 
 to heights of 1,000 feet. Glaisher, B. 186. 
 
 way to compute mean. Griffith, N. 373. 
 HYGROMETERS. B. 180 ; N. 429, 433 ; 
 Daniell, B. 179, 181 ; N. 295 297 ; Dines, N. 
 394 ; Franklin, B. 177 ; N. 192 ; Morris, B. 
 184; Pfeiffer, B. 188; Prinsep, B. 180; 
 Whitehouse, B. 188 ; Zylius, B. 178. 
 
 Alluard's. N. 407 ; B. 442. 
 
 Bogen's. Marriott, B. 442. 
 
 Chemical C. N. 390 ; Whipple, N. 392. 
 
 Daniell's. N. 392. 
 
 Koppe's. N.408. 
 
 Prestel's. Davis, K 390. 
 
 Schwackhbfer's. B. 442 ; Whipple, B. 444. 
 
 Snell's. N. 384. 
 
 error due to moisture. Kesteven, N. 373. 
 
 in South Kensington Museum loan collec- 
 tion. N. 400, 401. 
 
 realized in rope lifts. Fuller, N. 380. 
 HYGROMETRICAL MEANS AND 
 
 CONSTANTS. Capelli, B. 184. 
 HYGROMETRY. N. 365 ; Baumhauer, B. 
 186, 187 ; Bobe-Moreau, B. 178 ; Buchan, N. 
 348, 352, 353 ; Colson, B. 181 ; Daniell, B. 
 
 181 ; De Luc, B. 179 ; Espy, B. 180 ; Gough, 
 B. 178 ; Humboldt, B. 180 ; Kamtz, B. 180 ; 
 Koppe, B. 443 ; Majocchi, B. 181 ; Marriott, 
 B. 442; Prinsep, B. 179; Regnault, B. 181, 
 
 182 ; Renny, B. 182 ; Saussure, B. 177, 178 ; 
 Scharpenzeel-Thim, B. 181 ; Shortrede, B. 
 181; Symons, N. 415; Tabourin, B. 187; 
 Vogel, 182. 
 
 HYGROMETRY AND HYPSO- 
 METRY. Williamson, B. 185. 
 experimental observations. N. 402. 
 formulae. Everett, B. 187. 
 gradients required. Stevenson, N. 395. 
 observations at Kew. N. 385. 
 reliable instruments wanted. N. 395. 
 reliability of instruments. N. 395, 396. 
 tables. Glaisher, B. 18 L, 186, 442; Mar- 
 riott, B. 188; Russell, B. 185; Simmonds, B. 183. 
 volumetric method. Whipple, N. 432, 433. 
 
INDEX. 
 
 ICE : in connection with auroras. N. 330, 331. 
 INSECTS (injurious) : circular, 227230. 
 LUMINOUS COLOURED EFFECTS 
 AFTER SUNSET. 1 Blackmore, N. 347. 
 LUMINOUS SNOWFLAKES. Wald- 
 
 ner, N. 391. 392. 
 MIMICRY, 207, 208. 
 
 MISTS. Buchan, N, 353355 ; Herschel, N. 
 318. 
 
 daily period. Raimondi, N. 371. 
 seasonal occurrence. English Cyclopaedia, 
 N. 314. 
 
 MOISTURE OF GROUND, as indi- 
 cated by Mauritia. Schomburgk, N. 289. 
 PHRENOLOG-Y : circular, 226. 
 PSYCHROMETER. Becquerel, B. 185. 
 
 use in forecasts. Labrosse, B. 184. 
 PSYCHROMETRY Capelli, B. 183; 
 Echhardt, B. 180 ; Rubenson, B. 442.. 
 
 tables. Capelli, B. 185. 
 
 RAIN : drops increase by moisture rushing 
 into partial vacuum behind. Ingram, N. 391. 
 gives off vapour rather than condenses it 
 while falling. Stow, N. 389. 
 
 RAIN continued. 
 
 how induced by hills. Eaton, N. 314, 315 ; 
 
 English Cyclopaedia, N. 315. 
 RAINFALL : cause of greater amount at 
 
 lower levels. Chambers, N. 379. 
 circular, 223227. 
 same at all moderate heights above ground. 
 
 N. 428. 
 
 SCIENCE JOURNAL. 337. 
 SCIENTIFIC SOCIETIES : circular 
 
 issued by conference of delegates. 221 230. 
 report of conference of delegates, 1882. 
 
 267269. 
 SICKNESS AND DEATHS: systematic 
 
 study of causes of. Baker, 269, 276. 
 SKY : systematic observation of. N. 375. 
 STARS : scintillation. Montigny, B. 443. 
 SUNSET COLOURS as weather signs. 
 
 Ley, N. 420. 
 
 TORNADOES. Finley, 231239 ; B. 444. 
 "WEATHER : forecasts. Ley, B. 443. 
 YELLOWS OF PEACH TREE : ques- 
 tions. 307, 308. 
 
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