1884 ANEROID BAROMETER: ITS CONSTR jCTION AND OSb, R Z V NL V \ORK : D. VAN NOSTBANT) COMPANY, 23 MURRAY AND 27 WARREN C REET. 1893. THE VAN NOSTRAND SCIENCE SERIES 18mo, Green Boards. Price 50 Cents Each. Amply Illustrated when the Subject Demands. No. 1. CHIMNEYS FOR FURNACES, FIREPLACES ANI STEAM BOILERS. By R. Armstrong C. E. & Edition, with an Essay on High Chimneys, b 1 Pinzger. No 2. STEAM BOILER EXPLOSIONS. By Zerah Colburn No. 3. PRACTICAL DESIGNING OF RETAINING WALLS By Arthur Jacob, A. B. No. 1 -PRO PORTIONS OF PJNS USED IN BRIDGES By Charles Bender, C. E. No 5 VENTILATION OF BUILDINGS. By W. F. Butler Edited and Enlarged by Jas. L. Greenleaf. 2t Edition. No. G. ON THE DESIGNING AND CONSTRUCTION Of STORAGE RESERVOIRS. By Arthur Jacob, A.B No. 7. -SURCHARGED AND DIFFERENT i ORMS OF RE- TAINING WALLS. By Jas. S. Tate, C. E. No. 8. -A TREATISE ON THE COMPOUND ENGINE. B> John Turnbull, Or. 2d Edition. With Additions by Prof. S. W. Robinson. No. 9. FUEL. By C. William Siemens, D. C L., to which is appended the VALUE OF ARTIFICIAL FUEL^ AS COMPARED WITH COAL. By John Wor maid, C. E. No. 10.-COMPOUND ENGINES. Translated from the French of A. Mallet With Results ot American Practice, by R. H. Buel, C. E. 2d Edition. No. 11. THEORY OF ARCHES. By Prof. W. Allan. No. 12.-A THEORY OF VOUSSOIR ARCHES. By Prof. W. E. Cain. No. 13. -GASES MET WITH IN COAL MINES. By J. J. Atkinson. 3d Edition, Revised. To which is added THE ACTION OF COAL DUSTS. By Ed. H. Williams, Jr., E. M. No. 14.-FRICVION OF AIR IN MINES. By J. J. Atkinson. No. 15. -SKEW ARCHES. By Prof. E. W. Hyde, C. E. No. 16. A GRAPHIC METHOD FOR SOLVING CERTAIN ALGEBRAICAL EQUATIONS. By Prof. Geo. L. Vose. No. i7. WATER AND WATER SUPPLY. By Prof. W. fl. Corfield, M. A. No. 18.-SEWERAGE ANL- SEWAGE UTILIZATION. By Prof. W. H. Corfield. No. 19. STRENGTH OF BEAMS UNDER TRANSVERSE LOADS. By Prof. W. Allan. No. 20. BRIDGE AND TUNNEL CENTRES. By John B. McMasters, C. E. No. 21. SAFETY VALVES. By Richard H. Buel, C. E. THE VAN NOSTRAND SCIENCE SERIES. No. 22. HIGH MASONRY DAMS. By John B. McMaster. No. 23.-THE FATIGUE OF METALS UNDER REPEATED STRAINS, with various Tables of Results of .Ex- periments. From the German of Prof. Ludwig Spangenberg. With a Preface by S. H. Shreve. No. 24. A PRACTICAL TREATISE ON THE TEETH OF WHEELS, with the Theory of the Use of Robin son's Odontograph. By Prof. S. W* Robinson. No. 25. -THEORY AND CALCULATIONS OF CONTINU- OUS BRIDGES. By Mansfield Merriman, C. E. No. 26.-PRACTICAL TREATISE ON THE PROPERTIES OF CONTINUOUS BRIDGES. By Charles Bender. JSo. *7. ON BOILER INCRUSTATION AND CORROSION- By F. J. Rowan. No. 28.-ON TRANSMISSION OF POWER BY WIRE ROPES. By Albert W. Stahl. No. 29. -INJECTORS; THEIR THEORY AND USE. Trans- lated from the French of M. Leon Pouchet. No. 30. TERRESTRIAL MAGNETISM AND THE MAGNET- ISM OF IRON SHIPS. By Prof. Fairman Rogers. No. 81. THE SANITARY CONDITION OF DWELLING HOUSES IN TOWN AND COUNTRY. By George E. Waring. Jr. No. 32.-CABLE MAKING FOR SUSPENSION BRIDGES, as exemplified in the construction of the East River Bridge . By Wilhelm Hildenbrand , C. E . No, 33. MECHANICS OF VENTILATION. By George W. Rafter, C. E. No. 34.-FOUNDATIONS. By Prof. Jules Gaudard, C. E. Translated from the French. No. 35. THE ANEROID BAROMETER; Its Construction and Use. Compiled by Prof. G. W. Plympton. 3d Edition. No. 36. MATTER AND MOTION. By J. Clerk Maxwell . No. 37.-GEOGRAPHICAL SURVEYING . Its Uses, Methods and Results. By Frank De Yeaux Carpenter. No. 38.-MAXIMUM STRESSES IN FRAMED BRIDGES. By Prof Wm. Cain. No. 39. A HANDBOOK OF THE ELECTRO-MAGNETICS TELEGRAPH. By A. E. Loring, a Practical Tel- egrapher. 2d Edition. No. 40. TRANSMISSION OF POWER BY COMPRESSED AIR. By Robert Zahner, M. E. No. 41. STRENGTH OF MATERIALS. By William Kent. No. 42.-VOUSSOIR ARCHES, applied to Stone Bridges, Tun- nels, Culverts and Domes. By Prof. Wm. Cain. No. 43. WAVE AND VORTEX MOTION. By Dr. Thomas Craig, of Johns Hopkins University THE ANEROID BAROMETER: ITS CONSTRUCTION AND USE. > THIKD EDITION. REVISED AND ENLAROED. NEW YORK: D. VAN NOSTRAND COMPANY, 23 MURRAY AND 27 WARREN STREET. 1890. COPYRIGHT, 1884, BY D. VAN NOSTRAND. CONTENTS. PAGE. CHAPTER I. Th e Atmosphere 5 CHAPTER II. Barometric Measurements of Altitudes 27 CHAPTER III. Aneroid Barometers : Their Construction 39 CHAPTER IY. The Use of Aneroid Bar- ometers i . x .v . * 52 CHAPTER V. Suggestions in Regard to the Selection and Systematic Use of an Aneroid 77 TABLE L Prof . Airy's Table of Altitudes. 88 TABLE II. Logarithmic Table 106 TABLE III Metric Altitude Table 121 TABLE IV Corrections for Mercurial Bar- ometer 125 TABLE V. Boiling Point of Water cor- responding to Different Barometric Pressures... . 126 PREFACE TO SECOND EDITION. THE fact that the first edition of this little manual is entirely exhausted is a sufficient indication that it supplied a want. As the use of the Aneroid Bar- ometer is on the increase, the presump- tion is that there will be a further demand for this book of tables and in- structions. It has been thought advisable to re- arrange the matter and to increase it by fuller descriptions of different in- struments ; and what is of more im- portance to the novice in measuring altitudes, to add a number of ex- amples. Another table has also been added to the collection of the previous edition. THE ANEROID BAROMETER; ITS CONSTRUCTION AND USE. CHAPTEK I. TH*E ATMOSPHERE. The gaseous envelope which surrounds oar globe, and to which we give the name of atmosphere, is subject to many and varied changes. In the relative amount of the two gases which chiefly compose it, it remains marvelously con- stant; yielding upon analysis the same ratio of oxygen to nitrogen for all lati- tudes and all altitudes. It is only within a few restricted and generally confined areas where the natural chemical pro- cesses of respiration, combustion or fer- mentation are active, that the free oxy- gen is found to be notably deficient, and the product, carbonic dioxide, which ex- ists normally to the extent of one twen- G ty-fifth of one per cent., is, to a corre- sponding extent, in excess. When, however, we regard the condi- tions which arise from its physical prop- erties, no such constancy is observable. Indeed, it seems the most fitting type of a transitory state, and whether we regard the temperature, the moisture, the press- ure resulting from its weight, or the di- rection and velocity of its motions, we can only acquaint ourselves with the lire its within which these conditions have been known to vary. The nature of the changes within these limits we can- not, in the present state of our knowl- edge, assume to predict for the future, except for very limited periods; and even then the prediction is set forth only as a "probability." Certain average conditions are noticea- ble as belonging to certain areas or zones of the earth, and differing somewhat among themselves, especially as to greater or less range in temperature, moisture, etc. To such general condi- tions we apply the term climate. The department of science which re- gards the physical phenomena arising from these varying conditions is called meteorology. The instruments employed with which to indicate or measure the extent of these changes, are of various kinds. Thus the thermometer indicates the relative temperature, the hygrometer the humidity, the anemometer the force or the velocity of the wind, and the bar- ometer the pressure of the air which arises directly from its weight. It is with the last of these instruments that we are especially concerned in the present essay. It has two quite distinct uses : One to indicate the varying press- ures of the air at some fixed point for meteorological purposes, and the other to indicate difference in altitude of points to which the instrument is carried by af- fording a measure of the greater or less amount of atmosphere above it. Before using the instrument to measure alti- tudes it is important to become some- what familiar with its use as a stationary instrument. The barometer most fre- 8 quently employed for such use is the one invented by Tcricelli in 1643. It is too well known to require description here. It will be sufficient to say that it meas- ures the varying pressure of the air by the varying length of a column of mer- cury which balances the pressure. When the barometer is employed for the purposes of meteorology only, the following facts are taken into considera- tion. We quote from Buchan's " Handy Book of Meteorology." Variations of the Jlarometer. The variations observed in the pressure of the air may be divided into two classes, viz., periodical and irregular ; the peri- odical variations recurring at regular in- tervals, whilst the irregular variations observe no stated times. The most marked of the periodical variation is the daily variation, the regularity of which in the tropics is so great that, according to Humboldt, the hour may be ascer- tained from the height of the barometer without an error of more than 15 or 17 minutes on the average. This horary oscillation of the barometer is masked in Great Britain by the frequent fluctuations to which the atmosphere is subjected in these regions. It is, however, detected by taking the mean of a series of hourly observations conducted for some time. The results show two maxima occurring from 9 to 11 A.M. and from 9 to 11 P.M., and two minima occurring from 3 to 5 A.M. and from 3 to 5 P.M. (See Table, page 10.) The maxima occur when the tempera- ture is about the mean of the day, and the minima when it is at the highest and lowest respectively. This daily fluctuation of the barometer is caused by the changes which take place from hour to hour of the day in the temperature, and by the varying quantity of vapor in the atmosphere. The surface of the globe is always divided into a day and night hemisphere, separated by a great circle which revolves with the sun from east to west in twenty- four hours. These two hemispheres are thus in direct contrast to each other in 10 H 3 fc $ < i O? OQ t^ CO ^ji lOOit J3 oooooo ooo * I a I I I I I I I I I t> cuO-tfCOOlO^OOC q j=30opooooo<: ++++++++ I GO __ CO CO T-H rH GO O ^ ^_ O O :ii .r- w Qi JH ^-i ^> 11 respect of heat and evaporation. The hemisphere exposed to the sun is warm, and that turned in the other direction is cold. Owing to the short time in which each revolution takes place, the time of greatest heat is not at noon, when the sun is in the meridian, but about two or three hours thereafter ; similarly, the period of greatest cold occurs about four in the morning. As the hemisphere under the sun's rays becomes heated, the air, ex- panding upwards and outwards, flows over upon the other hemisphere where the air is colder and denser. There thus revolves round the globe from day to day, a wave of heat, from the crest of which air constantly tends to flow towards the meridian of greatest cold on the opposite side of the globe. The barometer is influenced to a large extent by the elastic force of the vapor of water invisibly suspended in the at- mosphere, in the same way as it is influ- enced by the dry air (oxygen and hydro- gen). But the vapor of water also exerts a pressure on the barometer in 12 another way. Vapor 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 vapor is accumulated or pent up in the lower stratum of the atmosphere, and being impeded in its ascent its elastic force is increased by the reaction, and the barom- eter consequently rises. When the air falls below the temperature of the dew- point, part of its moisture is deposited in dew, and since some time must elapse before the vapor of the upper strata can diffuse itself downwards to supply the deficiency, the barometer falls most markedly at 10 P.M., when the deposition of dew is greatest. Hence, as regards temperature, the barometer is subject to a maximum and minimum pressure each day the maxi- mum occurring at the period of greatest cold, and the minimum at the period of greatest heat. And as regards vapor in the atmosphere, the barometer is subject to two maxima and minima of pressure 13 the maxima occurring at 10 A.M., when, owing to the rapid evaporation, the accu- mulation of vapor near the surface is greatest, and about sunset, or just be- fore dew begins to be deposited, when the relative amount of vapor is great ; and the minima in the evening, when the deposition of dew is greatest, and before sunrise, when evaporation and the quan- tity of vapor in the air is least. Thus the maximum in the forenoon is brought about by the rapid evaporation arising from the dryness of the air and the increasing temperature. But as the vapor becomes more equally diffused, and the air more saturated, evaporation proceeds more languidly ; the air becomes also more expanded by the heat, and flows away to meet the diurnal wave of cold advancing from the eastwards. Thus the pressure falls to the afternoon minimum about 4 P.M. From this time the temperature declines, the air ap- proaches more nearly the point of satu- ration, and the pressure being further increased by accessions of air from the 14 warm wave, now considerably to the westward, the evening maximum is at- tained. As the deposition of dew pro- ceeds, the air becomes drier, the elastic pressure of the vapor is greatly dimin- ished, and the pressure falls to a second minimum about 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 fluc- tuation is 0.125 inch, 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 maxi- mum at 9 A. M. Since the whole column of the at- 15 mosphere, from the sea-level upwards, expands during the heat of the day, thus lifting a portion of it above all places at higher levels, it is evident that the after- noon minimum at high stations will be less than at lower stations, especially when the ascent from the one to the oth- er is abrupt. Thus, at Padua, in Italy, the afternoon minimum is 0.014 inch, but at Great St. Bernard it is only 0.003 inch. Annual Variation. When it is sum- mer in the one hemisphere, it is winter in the other. In the hemisphere where summer prevails, the whole air being warmer than in the other hemisphere, expands both vertically and laterally. As a consequence of the lateral expansion there follows a transference of part of the air from the warm to the cold hemi- sphere along the earth's surface ; and, as a consequence of the vertical expansion, an overflow in the upper regions of the at- mosphere in the same direction. Hence, in so far as the dry air of the atmosphere is concerned, the atmospheric pressure 16 will be least in the summer and greatest in the winter of each hemisphere. But the production of aqueous vapor by evap- oration being most active in summer, the pressure on the barometer will be much increased from this cause. As the aque- ous vapor 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 vapor brought with it from the warm hemisphere will remain, thus tending to increase the pressure. In the neighborhood of the equator there is little variation in the mean press- ure from month to month. Thus, at Cayenne, the pressure in January is 29.903 inches, and in July 29.957 inches. At Calcutta, 22 36 ' N. lat., the press- ure is 29.408 in July, and 30.102 in Jan- uary, thus showing a difference of 0.694; tind at Bio de Janeiro, 22 57' S. lat., it is 29.744 in January (summer), and 29.978 in July (winter), the difference being 17 0.234. The large annual variation at Calcutta is caused jointly by the great heat in July, and by the heavy rains which accompany the south-west mon- soons at this season ; while in January the barometer is high, owing to the north-east monsoons, by which the dry cold dense air of Central Asia is con- veyed southward over India. At places where the amount of vapor in the air varies little from month to month, but the variations of temperature are great, the difference between the summer and winter pressures are very striking. Thus, at Barnaul and Irkutsk, both in Siberia, the pressures in July are respect- ively 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 Siberia during summer causes the air to expand and flow away in all directions, and the diminished pressure is not compensated for by any material accessions being made to the aqueous vapor of the atmosphere ; and, on the other hand, the great cold and 18 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 Moscow, St. Petersburg, and Vienna. At Reykjavik, in Iceland, the pressure in June is 29.717, and in December 29.273; at Sandwich, Orkney, 29.77 ~. and 29.586; and at Sitcha, in Russian America, 29.975, and 29.664. In all these places the distribution of the press- ure is just the reverse of what obtains in Siberia, being least in winter and great- est in summer. The high summer press- ures are due to the cool summer tem- peratures as compared with surrounding countries, thus causing an inflow from these region*, and to the large amount of vapor in the atmosphere, thus still fur- ther raising the barometric column. On the other hand, the low winter pressu are due to the comparatively high winter temperatures causing an outflow towards adjoining countries, and the large winter rainfall which, by setting free great quan- 19 '8 of latent heat, still farther aug- ments and accelerates the outflow. The variations in mean pressure are very slight, and not marked by any very 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 vapor and rainfall are at no time much in excess or defect, but are more equally distrib- uted over the different months of the year. At the Great St Bernard, 8174 feet above the sea, the pressure in summer is --' :*64 inches, while in winter it is only 22.044. At Padua, there is scarcely any difference in the pressure between sum- mer and winter. The increase in the summer pressure at the Great St Ber- nard is no doubt due to the same cause already referred to in art. 65 viz., the expansion of the air upward during the warm summer months, thus raising a larger portion of it above the barometer 20 at the highest station. But at St. Fe de Bogota, 8615 feet high, near the equator, and where, consequently, the difference between the temperature in July and January is very small, the difference in the pressures of the same months is also very small, being only 0.035. Distribution of Atmospheric, Press- ure over the globe, as determined by the Annual Means. Though much addi- tional observation is required, especially in Africa, Asia, and South America, be- fore the isobarometric lines can be laid down on a map of the world, yet many important conclusions regarding the mean barometric pressure have been ar- rived at from the results already obtained. We have seen that the daily and monthly variations of pressure observed at differ- ent places are modified by the variations of the temperature of the air, the amount of vapor, and the rainfall. Since these are in their turn greatly modified by the unequal distribution of land and water on the earth's surface, we should expect to find the pressure, and the variations 21 in the pressure, most regular in the southern hemisphere. Accordingly, there is a remarkable regularity observed in the distribution of the pressure from about 40 N. lat. southwards to the Ant- arctic Ocean, with the exception of the region of the monsoons in Southern Asia. The mean pressure in the equatorial regions is about 29.90; at 20 N. lat. it rises to 30.00, and at 35 N. lat. to 30.20, from which northwards the pressure is diminished. The same peculiarity is seen south of the equator, but it is not so strongly marked. At 45 S. lat. it falls to 29.90, and from this southwards it continues steadily and rapidly to fall to a mean pressure of 28.91 at 75 S. lat. This extraordinary depression of the barometer in the Antartic Ocean, being one inch less than at the equator and 1,326 inches less than at Algiers, is per- haps the most remarkable fact in the meteorology of the globe. The pressure in the north temperate and frigid zones is in striking contrast to the above. From Athens, in a north- 22 eastern direction, a high isobarometric line traverses Asia, passing in its course Tim's, Barnaul, Irkutsk, and Yakutsk. To the east of the northern part of this area of high mean pressure, around the peninsula of Kamtschatka, there is a region of low barometer, the mean press- ure being only 29.682. There is another remarkable area of low pressure around Iceland, the center being probably in the south-west of the island near Reykjavik, where the mean is 29.578. As observa- tions are more numerous in Europe and North America, the dimensions of this depression may be defined with consider- able precision by drawing the isobaro- metric of 29.90, which is about the mean atmospheric pressure. This line passes through Barrow Straits in North Amer- ica, thence south-eastward toward New- foundland, then eastward through the north of Ireland, the south of Scotland, and the south of Sweden, whence it pro- ceeds in a north-easterly direction to Spitzbergen. The following mean annual pressures will show the nature of the de- 23 pression : New York, 30.001 ; Paris, 29.988; London, 29.956; Glasgow, 29.863; Orkney, 29.781; Bergen, 29.804; Spitz- bergen, 29.794; Keykjavik, 29.578; God- thaab, in S. Greenland, 29.605; Uperna- vik, in N. Greenland, 29.732 ; and Mel- ville Island, 29.807. A depression also occurs in India, where the mean is only about 29.850, whereas in the same lati- tudes elsewhere it is about 30.100. There are thus four areas of low press- ure on the globe, the extent of each being nearly proportioned to the depth of the central depression viz., Antarctic Ocean, the least pressure being 28.910 ; Iceland, 29.578 ; Kamtschatka, 29.682 ; and India, 29.850 ; and three areas of high pressure, one lying between latitudes 20 and 40 N., another between 15 and 35 S., and the third in Central Asia, from south- west to north-east. These low mean ' pressures are by no means constant in all cases during the months of the year. In the Antartic Ocean they are nearly con- stant during the months, with perhaps a slight tendency to an increase in winter. 24 In the region of low pressure around Ice- land the pressure is a little less than elsewhere in summer; but in winter, when the rainfall is heaviest, it is very much less, being 0.251 inch less in winter than in summer at Reykjavik, and 0.189 at Sandwich, in Orkney. Similarly at Petropaulovski, in Kamtschatka, the pressure in winter is 0.323 less than in summer. Hence the low mean annual pressures in the North Atlantic and the North Pacific are chiefly brought about by the low pressure during the cold months of the year, and are doubtless caused by the copious rainfall during that season. On the other hand, in Southern Asia, the lowest pressures occur in sum- mer. Thus, at Calcutta it is 29.408 in July, while in January it is 30.102 the average pressure for that degree of north latitude. Hence, in Hindostan, the low mean annual pressure arises from the very low pressure in summer caused by the heavy rains falling at that season, particularly on the south slope of the Himalayas. Generally the pressure is 25 low wherever a copious rainfall prevails over a considerable portion of the earth's surface, owing to the large quantity of caloric set free as the vapor is condensed into rain. It is scarcely necessary to point out how important it is to keep in mind these facts of the pressure of the atmosphere, it being evident, for instance, that a press- ure of 29.00 in the North Atlantic would portend stormy winds, while the same pressure south of Cape Horn, being the mean pressure there, would indicate set- tled weather. The readings of the mercurial barome- ter are subjected in nice observations to several corrections : 1st. To 32 F. allowance being made for expansion of both mercury and scale for all observations above that temperature. A baro- metric pressure of thirty inches at 32 would be indicated by a height of 30 T V inches at 70. 2d. For decrease of gravitation at sta- tions above the level of the sea, 26 acting on both the mercury and the air. 3d. For increase of gravity with in- crease of latitude. 4th. For temperature of air ; the den- sity decreasing as temperature rises. 5th. For humidity of the air which also influences its density. 6th. For capillary attraction of the tube. 27 CHAPTEE II. BAROMETRIC MEASUREMENTS OF ALTITUDES. THE text books in physics present formulas for computing heights from barometric observations, based on physi- cal laws which we will briefly give. If the density of the air were constant throughout, the measurement of heights would be a problem of the simplest character; for as mercury weighs 10,500 times as much as air at the sea level, the mercurial column would fall one inch for every 10,500 inches of ascent above the sea. But air is compressible, and, in accordance with Boyle's law, its density varies with the pressure to which it is subjected. Now suppose the atmosphere divided into layers of uniform thickness, but so thin that the density may be considered uniform throughout. 28 Let A=the thickness of each layer. W= weight of a cubic foot of air at pressure H. W, = weight of a cubic foot of air at H. , H H 1? &c. pressures measured in' inches of mercury. Then the pressure upon the unit of surface of any layer is greater than that upon the surface of next higher layer, by the weight of a volume of air whose base is the unit of surface and whose height is the thickness of the layer. If one foot be the unit of surface, then this quantity would be AW. And to express it by height of mercury column, it is 30 necessary to multiply by 3 2157 But W : W : : H : 30. W being the weight of a cubic foot air at the level of the sea (=.0807 at 32F). We have from the above Wx 30= W X H, and the above expression for dimi- AW H nution may be written . 29 If H H t H 2 represent the pressures at the surfaces of the successive layers, we shall have AWH AWH / AW H :n-H n _t(i- 21577 Multiplying these equations and sup- pressing common factors, we get H _ H I H n -H p_ If A be taken at one foot then n would represent the number of feet vertically between two stations at which the baro- metric pressures are H n and H respect- ively. By substituting for W its value and taking logarithms we have H , / 2157 whence n=60135.4xlog.=r 9 . i 'X. 30 For use in accurate observations, cor- rections are required for temperature, humidity and variation in the force of gravity. La Place's formula which includes terms derived from the consideration of these conditions is obtained as follows : Suppose a portion of the atmosphere included between two stations at differ- ent altitudes to be divided into very thin laminae. Let z be the distance of one of these from the surface of the globe and dz its thickness. Let P be the pressure upon a unit of surface upon the lower side of this layer ; and W the weight per cubic meter of the air at this pressure. Then the pressure on the upper side will be less than P by an amount equal to the weight of a column of air whose base is a unit and height is equal to dz. Whence Ut as h is always small compared with H this correction may be neglected. But there is another of more import- ance which should be taken into account. On account of the spheroidal form of the globe weight varies with the lati- tude. If G represent the weight of a body at latitude 45, then at any other latitude Z, its weight, is found by multi- plying G by 1-. 00265 cos. 2 I This factor is to be applied to W in the formula. This is accomplished by multiplying the above value of z by 1 + 00265 cos. 2 I. In order to simplify the expression we will substitute for 6 the mean between the temperatures of the upper and lower stations, designated by t Q and t. The factor 1 + aO then becomes since =.004; and the value of z may be written 34 (1 + . 00265 cos. 2 I) If M be used to represent the modulus of the Napierian logarithms we may write 0.76 2 = MW I 1000 ) A 2Mz ] (1 + 0.00265 cos. 21) in which the logarithms are of the com- mon kind. This is La Place's formula, h in the expression is not the barometric height directly observed at the upper station, but this height reduced to the tempera- ture of the lower station. 7fi The value of MW has been determ- ined by trial of the formula upon known altitudes. Kamond in his survey of the Pyrenees determined its value to be 18336. 35 The unknown term z in the second member is determined by successive ap- proximations. The first value being */ = 18336. log. j- (meters) This being substituted, we may have -_- 2(*. + O s * 2 ^ 1000 l ' Finally, these being substituted in the above value of z we get .,=1888610**-+^ 4-4t.00966.oo8.lI + (z a + 2M. 18336)^ The terms of this formula are gener- ally reduced to tabular form for practi- cal use. Guyot's formula which is derived from this, reducing meters to feet and the con- stants depending on temperature being changed to accord with Fahrenheit's scale, is 2=60158.6 log. - 36 900 (1 + .00260 cos. 21) / z + 52252 I ' 20886860^104434307 The three terms after the first are the corrections. The first being that for the temperature at the two stations. The second is the correction for the force of gravity depending on the latitude. The third contains, first the correction for action of gravity on the mercury column at the elevation z, and second a correction required for decrease in densi- ty of air owing to decrease in action of gravity at the greater elevation. The factor s being the approximate difference in altitude of the stations. Plantamour's formula, which has been much used, differs slightly from Guyot's. The first coefficient is 60384.3. The de- nominator of temperature term is 982.26 and a separate correction is used for humidity of the air. To use either of these formulas tables are necessary, of which those prepared 37 by Lieut. Col. Williamson* are the most ' elaborate. For the Aneroid in ordinary practice, formulas of much less complexity may be profitably used. The corrections de- pending upon the gravity of the mercury column would, in any case, be omitted. The other corrections may in very nice work be retained. But a correction de- pending on the effect of changes of tem- perature on the metallic work of the instrument , should be carefully remem- bered. First-class Aneroids claim to be compensated, but a greater portion will need a correction which the purchaser can determine for himself, by subjecting the instrument to different temperatures while the pressure remains constant. A modification of Guyot's formula adapted to aneroid work was suggested in an excellent paper on the use of the aneroid, read before the American Society of Civil Engineers, in January, 1871 * The use of the Barometer on Surveys and Recon- noisances. By R. S. Williamson. New York : D. Van Nostrand. London : Trubner & Co. 38 It is D=60000 (logH-log/o(l+ D is the difference of altitude in feet. H and A are the barometric readings in inches. T and t are the temperatures of the air at the two stations. Table II is prepared for the use of this formula. Other formulas will be given in another chapter. 39 CHAPTER III. ANEROID BAROMETERS: THEIR CONSTRUCTION. THE general principle of construction of all aneroids is the same. A box with flexible sides, hermetically sealed, the air having been first exhausted, changes its form as the pressure of the atmosphere varies. The chief differences in the various kinds lie in the mechanical devices, by which the motions of the box are ren- dered apparent to the eye, and also meas- sured in such a manner as to allow the corresponding pressures to be expressed in inches of mercury. The aneroid was invented about the beginning of this century, but was first made of a serviceable form by Vidi, in 1848. It is substantially the form most used to-day. The vacuum box is a thin low cylinder, and the motion of the thin flexible head of the cylinder is conveyed 40 by suitable mechanism to the index hand. Vidi's aneroid is shown in Fig. 1. D is the vacuum box, supporting the up- right pillar M upon its center. As M; rises or falls, a corresponding motion is given to the plate C. A counter pressure 41 is afforded by the spiral spring S. The motion of C is conveyed by the links 1 and 2 to a little rocker shaft, shown in the figure. An arm, 3, attached to this shaft is connected by a minute chain with the shaft which carries the index pointer. It is kept wound to the proper tension about this shaft by a fine spiral hair spring. 42 A modification of this is shown in Figs. 2 and 3. (See, also, frontispiece). Fig,3 This is Naudet's aneroid, and is the one chiefly employed now. It differs from Vidi's in the substitution of the thin 43 laminated spring (B in frontispiece) for the spiral spring (S in Fig. 1). One of the oldest forms of box barom- eter and the one to which the name Fig. 4. aneroid is restricted by some writers, is represented in Fig. 4. A rectangular tube, from which the air has been per fectly exhausted, is sealed hermetically, 44 and, having been bent into the form rep- resented in the figure by cbd, is made fast at the middle point b. The varying pressure of the atmosphere causes the extremities c and d to approach or recede from each other. This motion is con- verted into a to-and-fro traverse of the index, by a mechanism sufficiently well exhibited by the diagram. c This is known as Bourdon's form. It is not now employed for delicate work. The forms of Vidi and Naudet are, by some writers, designated the holosteric barometers. The graduation of these instruments is made to correspond with the height of the mercurial barometer, and is expressed as inches or millimeters. The difficulties to be met by the maker, in securing accuracy of working, are those which arise chiefly from the varying elas- ticity of the several metallic elements under change of temperature. Greater simplicity of construction might be pre- sumed to be attended with a smaller lia- bility to a kind of error, for which it it 45 exceedingly difficult to compensate. This is the theory of the Goldschmid Aneroid. The instrument designed for ordinary engineering use is represented by Fig. 5. The size recommended by the present makers for this service is 3J inches in diameter and 2J- inches high. The construction is exhibited by Fig. 6. The vacuum box, constructed as be- fore described, is shown at aa. The mo- tions of the box, caused by variations of atmospheric pressure, are conveyed di- rectly to the lever, whose fulcrum is at e", and whose free end is at e. This end, projecting through the side of the cas- ing and working freely through a slot, is observed with a magnifying lens, and the reading on the index ff taken. But it is evident that the lever, working with proper ease on its fulcrum, must be sup- plied with a certain amount of counter- pressure. This is ingeniously done by aid of the delicate spring e', which is at- tached to the lever near the fulcrum. Bearing on the spring is the point of the micrometer screw M, whose head is grad- 46 uated to hundredths and forms the top of the case. Both lever and spring are furnished at their extremities with bright 47 metal heads, whose end surfaces lie in the same plane. The head e' is, under ordinary conditions, higher than e, as shown in Fig. 6. When a reading is to be taken the top of the case is turned until e' and e are side by side ; the hori- zontal marks borne on the metallic heads being brought to an exact coincidence by aid of a lens (P in Fig. 5). The reading of the Inches is taken from the scale ff^ and of the hundredths from the divisions on the scale around the top of the box T ; a fixed point c being marked on the cylinder. In figure 7 the indices exhibit a reading of 29.75 inches. The thermometer F is an important part of the instrument. In some of these instruments the scale ff bears no reference to the inches of the mercurial barometer, but is of an arbi- trary character, and is different for dif- ferent instruments. The value of the divisions is determined by comparison with standard instruments, and is care- fully expressed in tabular form on the cover of the box 48 Some corrections for temperature and pressure are required in the use of these instruments which, although desirable in the more common forms of aneroid, have not heretofore been considered necessary. In the latter instruments, however, when of the best construction, a compensation has been effected which renders a correc- tion for temperature unnecessary. In the Goldschmid aneroids no compensa- tion is attempted, but each instrument is furnished with a table^ of corrections which have been prepared from observa- tion on standard instruments. Thus, aneroid No. 3187, imported last year, bears on the cover the follow- ing: CORRECTION TABLE. For Division. For Temperature. 26.0"= -0.02 28 to 48= 26.5" = -0.03 52=: +0.01 27.0"=-0.03 56= +0.015 27.5 =-0.02 60= +0.025 28.0 = 64= +0.035 28.5 = +0.03 68= +0.04 29.0 = +0.06 72= +0.05 49 For Division. For Temperature. 29.5"=: +0.10 76= +0.07 30.0 = + 0.14 80 =+0.09 30.5 =+0.19 84 =+0.11 31.0 =+0.25 88 =+0.13 92= +0.15 The temperatures are, of course, taken from the thermometer that forms a part of the instrument, and which, when the latter is carried slung from the shoulder, may exhibit a temperature considerably higher than that of the air. A smaller and ruder instrument called the Pocket Aneroid is made by the Zurich manufacturers. It is only 1J inches in diameter and 1^ inches high. A bar fastened to the top of the vacuum box takes the place of the lever in the larger instrument. A larger size is also made in which the movements of the vacuum box are di- rectly observed with a compound micro- scope. There is no doubt that all aneroids need a careful comparison with standard instruments or a series of trials upon 50 known altitudes, in order to determine the proper corrections. Such trials .> o should be made at different temperatures and under different conditions as to ris- ing or falling at the time of observation. 51 The tables of corrections furnished by the maker cannot well be substituted for those made by a careful observer deduced from systematic work. The air pump, the hot chamber and the freezing box are convenient, but inadequate substi- tutes for a large number of trials under normal conditions. 52 CHAPTEK IV. THE USE OF ANEROID BAROMETERS. The Aneroid, like the Mercurial bar- ometer may be used either as a weather indicator or in the measurement of alti- tudes. When used in the former capa- city, the Aneroid, especially at sea, pos- sesses some obvious advantages. Aside from its superior compactness of form and its portability, it responds more readily to the changes in atmospheric pressure than the Mercury column, and thereby serves more efficiently to warn the mariner of sudden tempests. The words Rain Change Fair seen stamped or engraved on the dial of many barometers have, of course, no special significance, and are now rarely seen on first-class instruments of either kind. The probable changes of weather indicated by changes of the barometer are briefly set f crth in the following : 53 KULES FOE FORETELLING THE WEATHER. A Rising Barometer. A " rapid " rise indicates unsettled weather. A " gradual " rise indicates settled weather. A " rise " with dry air, and cold in- creasing in summer, indicates wind from Northward ; and if rain has fallen better weather is to be expected. A "rise" with moist air, and a low temperature, indicates wind and rain from Northward. A " rise " with southerly wind indi- cates fine weather. A Steady Barometer. With dry air and seasonable tempera- ture, indicates a continuance of very fine weather. A Falling Barometer. A "rapid" fall indicates stormy weather. A "rapid" fall, with westerly wind, indicates stormy weather from North- ward. 54 A " fall," with a northerly wind, indi- cates storm, with rain and hail in sum- mer, and snow in winter. % A " fall," with increased moisture in the air, and the heat increasing, indicates wind and rain from Southward. A " fall " with dry air and cold increas- ing (in winter) indicates snow. A "fall" after very calm and warm weather indicates rain with squally weather. It does not require the highest quality in the mechanism of an Aneroid to serve the purpose indicated in the ab^ove rules. For the accurate measurement of dif- ferences of altitude, however, the best skill in construction and the most care- ful adjustment of the parts is indispens- ably necessary. The use of an Aneroid of even medium quality will frequently lead to considerable errors in estimating heights. It may also be added here that instruments of the best manufacture in the hands of observers unacquainted with the principles involved, will often lead to 55 erroneous conclusions. This is owing in many cases to a method adopted by some makers of adding a circle marked feet outside of the common graduation to inches of mercury. Many tourists carry Aneroids of the pocket size, and consult them frequently while traveling, relying upon a single observation of the index for the deter- mination of their altitude. If such a circle of feet be engraved on the dial plate with the zero mark made to correspond with 30 inches of the mercury column, of course every estimate of alti- tude made as above mentioned assumes that at the moment of observation ; the barometer at the level of the sea would stand exactly at 30 inches ; a condition only realized occasionally. And the fur- ther condition is also assumed, that the temperature of the air is of no account in estimating heights; an assumption equally at variance with fact. It is only an inferior class of Aneroids that bear a fixed graduated circle of feet, with the zero of altitude corresponding to 30 inches of pressure. 56 Prof. Airy, the former Astronomer Royal of Great Britain, prepared a table for the use of barometer makers a scale from which is now engraved on many English Aneroids. It places the zero of altitude at 31 inches of pressure. This affords such large numbers for slight elevations that the proper use of the rule is sug- gested to the observer. He is led to subtract the two readings of feet to get difference in height. But this again as- sumes that the average temperature is 50 F. Table I exhibits Prof. Airy's series of heights. Some makers, designing to improve upon the simple construction just de- scribed, have engraved the outer circle of feet on a movable ring encircling the dial, so that when an observer is at any locality whose height is known, he may bring the proper mark of the altitude scale against the index pointer. Then if the observer travels about over a section of country, the pointer will indicate with fair approximation for some hours the altitude of the new positions. FIELD'S ENGINEERING ANEROID. (For description, see page 57.) 57 This device is convenient to a skilled observer who only requires rapid and approximate results, but to the novice it is misleading in two ways ; first, because the temperature is left out of the calcula- tion, and furthermore, such a use of the movable scale will, at times, involve a large error, as it is not a scale of equal parts. Mr. Eogers Field, C. E., in 1873, ap- plied the movable scale to the Aneroid, so as to convert it from a source of inaccu- racy into an aid towards accuracy. He employs the altitude scale proposed by Sir G. Airy for temperature 50, but he makes it movable so as to adjust it for any other temperature. The shifting of the scale into certain fixed positions, is made to answer the same purpose as if the original scale were altered to suit various temperatures of the air. In the Journal of the Meteorological Society for 1874, January, Mr. Field says : " The object aimed at in designing this improved form of Aneroid was, to sim- plify the correct determination of alti- 58 tudes in cases such as ordinarily occur in England, and the instrument is therefore arranged to suit moderate elevations, say of 2000 feet and under, and is not in- tended for more considerable heights. " The Aneroid is graduated for inches in the usual way on the face, but the graduation only extends from 31 inches to 27 inches so as to preserve an open scale. The outer movable scale is grad- uated in feet for altitudes, and this grad- uation is laid down by fixing the movable scale with the zero opposite 31 inches. This is the normal position of the scale and it is then correct for a temperature of 50. For temperatures below 50 the zero of the scale is moved below 31 inches; for temperatures above 50, the zero of the scale is moved above 31 inches. The exact position of the scale for different temperatures has been determined partly by calculation and partly by trial, and marked by figures engraved on the out- side of the Aneroid. In order to insure the altitude scale not being shifted, after it has once been set in its proper position 59 there is a simple contrivance for locking it in the various positions. This consists of a pin, which fits into a series of notch- es on the outside of the ring carrying the glass. By slightly raising the glass it is freed from this locking pin, and can be turned until the figures corresponding to the air temperature are opposite to the pin, when the glass should be depressed so as to relock it, and the scale becomes correct for that temperature. The alti- tudes are in all cases determined by tak- ing two readings, one at each station, and then subtracting the reading at the lower station from that at the upper. " It will be seen from the foregoing description that the movable sdale of the instrument requires to be set for tem- peratures before taking any observations, and must not be shifted during the prog- ress of the observations. " This may appear at first sight as a defect, inasmuch as the temperature of the air may alter during the progress of the observations ; but practically it will not be found to be any drawback in the 60 case of moderate altitudes, as small vari- ations of temperature will not appreciably affect the result. A variation of 5 of temperature gives only about 1 per cent, variation in the altitude, an amount that would under ordinary circumstances be inappreciable, so that as long as the tem- perature does not vary during the course of the observations more than 5 from that at which the instrument is set, the results may be accepted as correct, and, generally speaking, even a greater varia- tion than this, say 6 or 8, would be practically of no importance. Of course, if it should be found at any time that the temperature has varied considerably, during the course of the observations, from that at which the instrument was set, this variation can be allowed for by calculation in the usual way." The principle of allowing for variation of temperatures of the air by shifting the altitude scale is not theoretically accurate, but sufficiently so for practical purposes. For altitudes within the range of the in- strument (say 3000 feet and under) and 61 temperatures between 30 and 70, the maximum error from usin~ the shifted scale, instead of the calculation, is only 2 feet, which is inappreciable on the scale. The same principle might even be applied to altitudes up to 6000 feet, as the maximum error would be only 10 feet. For considerable elevations, how- ever, the variations of the temperature between the base and the summit would interfere with the application of the prin- ciple. Nevertheless, the best plan is to dis- pense with altitude scales, whether fixed or movable, and to calculate the heights. Simple rules, giving more reliable results than the attached scales, are at the ser- vice of those who need easy processes. Among these are the following : Note the rise or fall of the barometer in hundredths of an inch, in passing from one station to the other multiply by 9. The product is the difference of altitude in feet. This is for ordinary temperatures and pressures. If the pressure is below 26 62 inches or the temperature above 70, use 10 for a multiplier. A higher degree of accuracy is obtained by using the multiplier obtained from the following table prepared by Mr. G. J. Symons : Mean temperature. . . 30 40 50 60 70 80 Mean presssure, 27in. 28in. 9.7 9.8 9.910.1 9.5 9.8 10.3 10.0 10.6 10.2 10.8 10.4 29in. 9.09.2 9.4 9.6 9.8 10.0 30in. 8.78.9 9.1 9.3 9.5 9.7 To find the difference in height be- tween two stations : Find the mean pressure; also the mean temperature. The number in the table corresponding to these two means, if multiplied by the difference of the barometric pressures in hundredths of an inch^ mil give the dif- ference in altitude very nearly. In the absence of a table to aid in computation, but having an Aneroid with the scale of feet, use the formula, D=55000; H-A H+X 63 adding -%^ of the estimated altitude for every degree, the average temperature is above 55, and subtracting a like amount when it is below. D, is the difference of altitude in feet; H and h are the read- ings in feet from the Aneroid scale. This gives fair approximations up to 3000 feet. For accurate results use one of the following methods : Having Airy's table (Table 1) and an Aneroid carefully grad- uated to inches ; Take the reading in inches of the baromteric scale at both lower and upper stations ; also the tem- perature at both stations. Find from the table the heights in feet correspond- ing to the barometer readings. Subtract them and multiply the remainder by \ 1000 The complete formula is T and t are the observed temperatures ; H and h are the heights in feet taken from the table. 64 In the absence of this table, but with a table of logarithms at hand, the baro- metric heights in inches are to be taken, and the following formula used : D=60000 (log. B-log. b) 900 B and b are the barometric readings in inches ; D, T and t as in the other for- mulas. (See Table II.) To avoid error from the constant changes in barometric pressure, the ob- servations should be simultaneous. This is accomplished in the best manner by using two instruments, and requires, when the distance between the stations is considerable, two observers. With one instrument only, large errors are avoided by repeating the observation at the first station after taking that at the 2d station, and assuming that any change in barometric pressure that has occurred has been gradual during the absence. When it is impracticable to repeat the observation at the first station, the error 65 which, in case of a changing pressure, might be a large one, may be reduced if the observation at the 2d station be con- tinued for an hour or two, or until the rate of change can be estimated and a proportionate correction applied. Many Aneroids marked "compensated" exhibit a sensible change when the tem- perature is varied ; such instruments may be serviceable and quite accurate if allowance be made for the error of the instrument. This correction the owner had better determine by experiment. It is easy to subject the Aneroid to such variation of temperature as shall embrace the range at which it is likely to be used, and the movement of the index for each 10 or 20 of temperature recorded. Aneroids require to be compared from time to time with a good mercurial baro- meter. While making such comparisons, it is well to remember that the mercurial column and the scale by which it is measured both require correcting, and that during times of rapid changes, in atmospheric pressure, the Aneroid shows 66 such changes more readily than the mercurial barometer. (See Table IV.) In measuring heights with the Aner- oid care should be taken that the instru- ment is not influenced by the heat of the hand nor by the direct rays from the sun. The instrument should always be tap- ped gently with the finger at the moment of taking an observation. It should also be held in the same position for both observations ; preferably with the face horizontal. Considerable care is also required to determine exactly where the index points. It is best accomplished by sight- ing along the pointer, using one eye only for the purpose. The following example will illustrate the use of the tables. Barometer at Station A 30. 04 Thermometer 78 B 28.68 " 65 From Table I we find height corre- sponding to reading at A is 857 feet. The height for B is 2120 feet. The approximate height is 2120857 67 = 1263 feet ; but the sum of the tempera- tures is 143. An additional correction of T ff -g- is, therefore, to be applied to the above difference; this is 54 feet. The total estimated difference of altitude is then 1263 + 54=1317 feet. The formula directly applied is = 1317.21 Applying the logarithmic formula we have: Log. B 30. 04= 1.477700 " b 28.68 = 1.457579 Log. B Log. 5=0.020121 78 + 65-60\ ( 1 900 / feet. As before remarked, the Goldschmid Aneroid requires that both the tempera- ture of the air and of the instrument be carefully taken. Two examples of alti- tudes taken with the instrument prev- iously referred to (No. 3187) will serve to show the kind, of correction necessary, 68 and as both examples apply to the same mountain (Kiarsarge of Conway, N. H.,) they will together indicate the character of the instrument. Ex. I. JFLY 9-TH, 1881. Station. ^ Temp. Correct :> ^ _ Time. c. = - ."- ^ir. 6. 00 AM. 29.51 66 66 -.04 ^.1029.65 Mt. Kiar- sarge.. l.OOp.M 26.75 74 74 +.06 -.0: Ex. II. AUGUST 9xH, 1881. bi Temp. Corm-:':-> ^ ^ Station. Time. J^>:_ f S ^ FrveVg. 7.00A.M. 29.3460 65 -.03 -.09 39.46 Mt' Kiar- sarge. 1.20P.M. 26.4S65" 75' 4--06 .03 26.51 In both these examples another read- ing would have been taken at Erveburi: on the return, if the better alternate 69 securing hourly readings of a stationary barometer at Fryeburg had not been fol- lowed. On July 9th there was no change in the Fryeburg barometer. On August 9th the following readings were taken at Fryeburg: 7 A. M. 29.53 1 P. M. 29.40 8 " 29.52 2 29.455 10 u 29.515 3 u 2940 12 " 29.46 As this set of observations indicates a fell of .07 in the interval between the base and summit readings, it becomes necessary to make another correction to the last column. Correcting the first reading to accord with the fall indicated by the stationary barometer, we get after all corrections: Fryeburg, 29.39. Mt. Kia: -'"'.51. The logarithmic formula for estimating heights from barometric observations is / T f 60 \ D=60000(log. B-log. - . ( 1 - ' ) in which 70 D = difference in altitude in feet. B= height of barometer in inches at lower station. b = height of barometer in inches at upper station. T and t are the temperatures of the air in Fahrenheit degrees. Applying this formula to our first ex- ample we have: D=60000(1.47202- 1.42781) The second example gives : D=60000(1.46820 - 1.42341) As the station at Fryeburg is 434 feet above the sea, the estimated total height of Kiarsarge would be, in one case, 3321 feet, and in the other 3315 feet. Prof. Airy's table gives 3319 and 3314 from the same data. The instrument employed in the above measurements has been used in many other cases of altitudes from 3000 to 71 4000 feet. An error of about 2 per cent, in excess has been detected in those cases where the altitude has been measured by more accurate means. It seems likely that the special correction table needs some slight revision. The following measurement was made with an aneroid only 1J inches diameter, made by Casella. Neversink, Sullivan Co., N. Y., and Slide Mountain, Ulster Co. Time. Bar. Readings T. Ht. Tab. I. Neversink 7 A.M. 28 64 6i 2158 Fly Club Camp. Slide Mountain. 11 " 4 P.M. 27.92 25.87 78 69 2853 4931 = (4931 -2158) 61 + 69-100\ 1000 / = 2773x1.03=2856 feet. As Neversink had been satisfactorily determined to be 1350 feet above the sea, the total height of Slide Mount- ain is estimated from this observation to have an altitude of 4206 feet. 72 (NOTE). Beturn observations were made only at the camp of the Fly Club. Between 11 A. M. and 9 p. M., no change occurred in the barometer. The Tribune report, however, indi- cates a rise on this date of .07 between 7 and 11 A. M. If such a change was felt in this region, then the calculated height of the mountain is too low by at least 60 feet. On the other hand, a height given by railway survey in this vicinity, (Johnson's Mill) near the camp, seems to confirm the figures given here. Also, the height of Helsinger Notch, taken incidentally on this excursion, was estimated at 2660 feet. Guyot makes the Notch 2677 and the summit of Slide Mountain 4205 feet. The height of the base at Neversink was established by four observations, between New York Bay and this base, and was confirmed by comparison with the height of the railway track at Lib- erty, six miles southwest. 73 Neversink to Blue Mountain, August 18, 1880. Time. Bar. Rd'g. T. Cor. Rd'g Ht. Tab. I. Neversink Blue Mt.. Neversink 1030P.M. 3 PM. 6 28.90 27.47 28.85 60 60 64 28.87 27.47 1941 3295 60 + 62-100 1000 Diff. = (3295- 1941 ) --=1354x1.022 1384 feet above Neversink or 2734 feet above the sea. The corrected reading would be 28.875, if the second reading had been midway in point of time between the first and last. This mountain is in Ulster Co., N. Y. Long. 74 35 "W.. and Lat. 41 52 N. Neversink and (Casella Aneroid). Denman Mountains September 11, 1880. Time. Bar. Rd'g T. Cor. Rd'g Ht. Tab.I. Neversink 1). Mt.... Neversink 12. 30 A M. 4.30 " 9 28 86 27.13 28.82 70 63 55 28.84 27.13 1969 3634 74 = 1665x1.026 =1708 feet above Neversink or 3058 feet above the sea. This mountain is S. S. W. of Slide Mountain, and near Claraville. Long. 74 28'; Lat. 41 53' N. Fryeburg, Me., and Kiarsarge Mount- ain, N. H. Fryeburg base 434 feet above the sea, July 9th, 1881. (Casella Aneroid] Time. Bar. Readings rp ! Jit. Tab.L Fryeburg. . . Kiarsarge. . 6 A. M. .... IP. M. 29.63 26.83 66 1233 74 3938 (Note) Barometer at Fryeburg re- mained stationary. =2813 feet or 3247 feet above the sea. 75 Fryeburg, Me., and Mt. Kiarsarge, N. H. (second survey) August 17th, 1881. ( Casella A nero id. ) Time. Bar. | T Readings Ht. Tab. I. Fryeburg 9 A.M, 29.70 59 1169 Mt. Kiarsarge. . . 3P.M. 26.81 53 3958 (Note) Barometer at Fryeburg sta- tionary till 4 P. M. Diff. = 2,789x1.012=2822 feet. Total ht.= 3256 feet above the sea. Height of this summit according to the Geological Survey is 3251 feet. Liberty Hill, N. H. (near Laconia), and Mt. Belknap. The base station was at Mr. Howe's 1130 feet above the sea, July 9th, 1878. (Casella Barometer.} Bar. Readings. T. Ht. Tab. I. Liberty Hill. .... lit. Belknap 28.75 27.53 82 78 2054 3235 76 As the interval between the observa- tions was very short, and the general pressure sensibly stationary, no record was made of the time nor the return reading. 82 + 78-100 Diff. = (3235 -2054)(l + * 1000 = 1252 feet or 2382 feet above the sea. (Note) An average of three measure- ments of this mountain gave 2392 feet. The other observations yielding 2369 and 2425 ft. respectively. The height given in the Guide Books quoted from the Geological Survey is 2394 feet. 77 CHAPTER Y. SUGGESTIONS IN REGARD TO THE SELECTION AND SYSTEMATIC USE OF AN ANEROID. Dealers in good aneroids are generally prepared to testify in regard to the per- formance of their instruments when tested by the air pump. Comparison tables frequently accompany first-class instruments which show the differences between the aneroid referred to and a standard mercurial barometer submitted to the same exhaustion. The buyer may reasonably ask, there- fore, that such a .test may be made if it has not been previously done. The best English aneroids are now marked compensated, and are presumably free from error arising from changes of temperature in the instrument itself. Whether such be the case can readily be determined, by the owner of the instru- ment subjecting it to the action of a 78 freezing mixture and then of a drying oven, while the normal pressure remains the same. A thermometer should be placed beside the aneroid during the trial. A range of temperature from 15 F. to 175 F, may easily be produced, and a co- efficient of correction if the in- strument is not compensated, may be determined. The graduations of a good instrument are neatly engraved on the dial. The divisions corresponding to the inches and fractions of a mercurial bar- ometer are the only essential ones. The circle of feet, whether movable or fixed, is a convenience of secondary import- ance; If an aneroid bears a fixed circle of feet with the zero mark corresponding to the 30-inch point of the other scale, the probabilities are that the instrument is not from one of the best makers. Excellent aneroids are now made with dial plates only 2^- inches in diameter. The Casella barometer referred to in the examples has a diameter of only 1^ 79 inches. Of course the smaller fractions of an inch are more easily read on dials of 4 inches in diameter ; but the porta- bility of the smaller instruments recom- mends them for the use of the topogra- pher, and the medium size, which is from 2J to 2^- inches, is now most in demand for surveyor's work. The aneroids in any considerable collection will be found to be vari- ously graduated ; some of them capable of indicating a fall of pressure to 20 inches, corresponding to a height of over 11,000 feet, while many are designed for continual use below 3,000 feet of alti- tude. In two instruments of the same diameter, but differing as above, it is clear that the latter will have the larger scale divisions, and will, therefore, be the better instrument to use at the lower altitudes. It should be carefully remembered that all aneroids vary in their readings, with the position in which they are held; reading always a little higher with the dial horizontal (face uppermost), than 80 when it is vertical. The difference is clearly owing to the direct weight of the mechanism exerted on the vacuum box. There is no objection to allowing this weight to be always added, but the prac- tice of the observer should be uniform, and to read from the horizontal dial is probably the most convenient practice. A tap with the finger just before tak- ing the reading is required to bring the springs to their proper bearing. Also, in case of rapid ascents, as some aneroids will not, at the moment of attaining an altitude, indicate the entire fall of press- ure, a few minutes' delay is necessary. The pointer should be fine and very close to the graduated scale, and the reading should be taken by looking along the direction of the pointer. For ordinary work it should not be considered important to adjust the aneroid to an absolute agreement with the mercurial barometer. The difference between the readings may be noted, but to force the aneroid to an agreement by 81 aid of the adjusting screw is a question- able practice. Whenever comparison with the mer- cury column is made, the reduction for the latter by Table 4 should be carefully observed. In the use of either form of Aneroid, whether it has been furnished with a correction table or not, the observer should take early means to become ac- quainted with its limits of error under various conditions of temperature or pressure. Repeated measurements of a known altitude afford good data for such information, but direct comparisons, for a long time, with a standard cistern barometer will yield, with a minimum of labor, the greatest number of compari- sons. For the method of dealing with such data to determine correction coefficients, the reader is referred to the larger treati- ses, the most exhaustive of which, prob- bly, is " Die Aneroide," by Josef Holt schl (Alfred Holder, Vienna, 1872). For ordinary use of a single instru- 82 ment, however, the corrections, if any are necessary, are determined with suffi- cient accuracy by the exercise of ordi- nary skill and patience ; skill here imply- ing, also, systematic trial. Some of the sources of error in meas- uring altitudes, which are not to be elimi- nated by any adjustment or correction of instruments, are clearly stated by Prof. Elias Loomis, in a paper read before the National Academy of Sciences, April 19, 1881. "The Laplace formula assumes* that the atmosphere has attained a condition of equilibrium, and in such a case it gives the reduction to sea level with tolerable accuracy. The average of a long series of observations represents approximate- ly such a condition of equilibrium ; but in the daily observations this equilibrium is very much disturbed. The mean be- tween the temperatures at the upper and lower stations does not represent the average temperature of the intermediate column of air ; and when the atmos- phere is in rapid motion the downward 83 pressure is modified by the earth's rota- tion, in a manner not represented by the Laplace formula. There is no doubt that the formulae of reduction now em- ployed may be considerably improved ; but it does not seem possible that any single formula, with constant coefficients, , should provide for the immense variety of conditions which prevail in the neigh- borhood of mountain stations ; and we may be compelled for each mountain re- gion to adopt tables founded upon a di- rect comparison of observations made at stations of different elevations and not very remote from each other." The following remarks bearing upon the same subject are from an article by J. Allan Brown, F. K. S., on " Periodic Oscillations of Barometric Pressure,*' published in Nature in April, 1881 : Sedgwick has said : [" To explain dif- ficulties in these questions " (relating to pressure and temperature) "the atmos- pheric strata have been shuffled in accord- ance with laboratory experience."] " If we suppose that the attraction of gravity is not the only attraction which affects the pressure of the atmosphere, but that this pressure varies through some other attracting force such as an electric attraction of the sun depending upon the varying humidity of the air, and this again depending on its tempera- ture, we should find another method of relating the two variations which does not exist if gravitation alone is employed. It is quite certain that many physicists will not admit the idea of an electric at- traction on our atmosphere in the present state of our knowledge, hence the efforts to make expansion, and a shuffling of the atmospheric strata suffice. We must not, however, in our ignorance, attempt to force conclusions in opposition to facts, and if these can be satisfied more easily and with greater probabilities in its favor by the aid of the hypothesis of an electric attraction of the sun, that hypothesis will have a better claim to acceptance than the other. I shall here note a few facts which cannot be explain- ed by thermic actions. 85 " 1. I have shown that, on the average of many years' observation in our latitudes, the mean pressure diminishes at the rate of 0".038 of mercury for every one hun- dred miles we proceed toward the north. This has been called a gradient from the the similar term used in railway slopes: but it is no slope, it is a level of a sur- face of equilibrium like that of the sea. It is the mean heights of the barometer at the sea level which indicate the form, if we may so say, of the equilibrating at- mosphere. " 2. In India we have seen that the at- mospheric pressure oscillates at each station even when these are quite near to each other, independently of the known laws of equilibrium of gases. When we "turn to the semi-diurnal oscillation of the barometer we are only amused at the attempts made to explain it by shuffling the atmospheric strata. Nothing can be more certain than that the theories of expansion, or resistance to expansion and overflow, are the vain efforts to make the laws of nature agree with a theory. Over 86 the great ocean within the tropics, where the diurnal variations of temperature are small and the air. is absolutely without perceptible currents for days together, the barometer rises and falls a tenth of an inch twice in twenty -four hours with the regularity of the solar clock. The action of the sun on the whole atmos- phere which produces this movement varies chiefly during the day hours at in- land stations with the temperature oscil- lation, so that, as in the case of the annual variation, the fall of the barometer at 4 P. M. is greater in the same latitude as the temperature is higher. This variation occurs during the most com- plete calms; the smoke rises vertically from the plain of Tinnevelly ; no current is visible in the motion of the clouds; yet the barometer falls at four in the morn- ing as it did at four in the afternoon, only it falls less." It seems probable that the use of the Aneroid will soon become more widely extended, and that engineers, when made familiar with the qualities of well-made 87 instruments, will welcome so valuable an aid in preliminary surveys. The condi- tions of satisfactory work with baro- meters are certainly peculiar, and to field workers familiar only with the level and transit, may seem unique. But when the conditions are fully understood, the engineer may easily take precautions which will avoid too large errors, and conduct surveys in hilly regions with acelerity not heretofore attained. 88 TABLE I. FOR ESTIMATING HEIGHTS BY THE ANEROID. Take readings of the barometer and thermom- eter at both stations ; find in the table the heights corresponding to the barometric readings, and subtract them. Multiply the T and t being - remainder by 1+ J the temperatures, the product will be the difference in altitude. Barometer Readings. Heights. Barometer Readings. Heights. Inches Feet. Inches. Feet. 31.00 00 30.81 168 30.99 9 30.80 177 80.98 18 30.79 186 80.97 27 30.78 195 30.96 85 30.77 203 80.95 44 30.76 212 30.94 53 30.75 221 30.93 62 30.74 230 30.92 71 30.73 239 30.91 80 30.72 247 30.90 88 30.71 256 30.89 97 30.70 265 30.88 106 30.69 274 30.87 115 30.68 283 30.86 124 30.67 292 30.85 133 30.66 301 30.84 142 30.65 310 30.83 151 30.64 318 30.82 160 30.63 827 89 Barometer TT . , , Readings. He 'S Qts - Barometer TT K+ Readings. i He 'S hts - Inches. Feet. Inches. Feet. 80.62 336 30.30 622 30.61 345 30.29 631 30.60 354 30.28 640 30.59 363 30.27 649 30.58 372 30.26 658 30.57 381 30.25 667 30.56 390 30.24 676 30.55 399 30.23 685 30.54 407 30.22 694 30.53 416 30.21 703 80.52 425 30.20 712 30.51 434 30.19 721 30.50 443 30.18 730 30.49 452 30.17 740 30.48 461 30.16 749 30.47 470 30.15 758 30.46 479 30.14 767 30.45 488 30.13 776 30.44 497 30.12 785 30.43 506 30.11 794 30.42 515 30.10 803 30.41 524 30.09 812 30.40 533 30.08 821 30.39 542 30.07 830 30.38 551 30.06 839 30.37 559 80 05 849 30.38 569 30.04 857 30 35 578 30.03 866 30.34 587 30.02 875 30.33 596 30.01 884 30.32 605 30.00 893 30.31 613 29.99 903 90 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 29.98 911 29.66 1205 29.97 920 29.65 1214 29.96 929 29.64 1224 29.95 938 29.63 1233 29.94 947 29.62 1242 29 93 956 29.61 1251 29.92 965 29.60 . 1260 29.91 97(5 29.59 1269 29.90 985 29.58 1278 2). 89 994 29.57 1287 29.88 1002 29.56 1296 29.87 1012 29.55 1305 29.86 1021 29.54 1314 29.85 1030 29.53 1824 29.84 1039 25.52 1333 29.83 1049 29.51 1342 29.82 1058 29.50 1352 29.81 1067 29.49 1361 29.80 1076 29.48 1370 29.79 1085 29.47 1379 29.78 1094 29.46 1389 29.77 1103 29.45 1398 29.76 1113 29.44 1408 29 75 1122 29.43 1417 29.74 1132 29 42 1426 29.73 1141 29.41 1435 29.72 1150 29.40 1445 29.71 1159 29.39 1454 29.70 1169 29.38 1464 29 69 1177 29.37 1473 29.68 1186 29.36 1482 29.67 1195 29.35 1491 91 Barometer Readings. Heights. Barometer Readings. Heights. Inches Feet. Inohes. Feet. 29.34 1500 29.02 1799 29.33 1509 29.01 1809 29.32 1519 29.00 1818 29.31 1528 28.99 1827 29.30 1537 28.98 1837 29 29 1546 28.97 1846 29.28 1556* 28.96 1856 29.27 1565 28.95 1865 29.26 1574 28.94 1875 29.25 1583 28.93 1884 29.24 1593 28.92 1894 29.23 1603 28.91 1903 29.22 1612 28.90 1913 29.21 1621 28.89 , 1922 29.20 1630 28.88 * 1931 29.19 1639 28.87 1941 29.18 1649 28.86 1950 29 17 1658 28.85 1960 29.16 1668 28.84 1969 29.15 1677 28.83 1979 29.14 1687 28.82 1988 29.13 1696 28.81 1998 29.12 1706 28.80 2007 29.11 1715 28.79 2016 29.10 1725 28.78 2026 29.09 1734 28.77 2035 29.08 1743 28.76 2044 29.07 1752 28.75 2054 29.06 1762 28.74 2063 29.05 1771 28.73 2073 29.04 1781 28.72 2082 29.03 1790 28 71 2091 92 Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 28.70 2101 28.38 2407 28.69 2111 28.37 2416 28.68 2120 28.36 2426 28.67 2129 28.35 2435 28.66 2139 28.34 2445 28 65 2148 28 33 2455 28.64 2158 28.32 2464 28.63 2168 28 31 2474 28.62 2177 28.30 2483 28.61 2186 28.29 2493 28.60 2196 28.28 2503 28.59 2205 28.27 2512 28.58 2215 28.26 2522 28.57 . 2224 28.25 . 2531 28.56 2234 28.24 2541 28.55 2243 28.23 2551 28.54 2253 28.22 2561 28.53 2263 28.21 2570 28.52 2272 28.20 2580 28. ni 2282 28.19 2590 28.50 2291 28.18 2600 28.49 2301 28.17 2609 28.48 2310 28 16 2619 28.47 2320 28.15 2628 28.46 2329 28.14 2638 28.45 2339 28.13 2648 28.44 2349 28.12 2658 28.43 2358 28.11 2667 28.42 2368 28.10 2677 28.41 2378 28.09 2687 28.40 2387 28.08 2696 28.39 2397 28.07 2706 i 93 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet, Inches. \ Feet. 28.06 2715 27.74 3029 28.05 2726 27.73 3039 28.04 2735 27.72 3048 28.03 2745 27.71 3058 28.02 2755 27.70 3068 28 01 2765 27.69 3078 28.00 2774 27.68 3087 27.99 2784 27.67 3097 27.98 2794 27.66 3107 27.97 2804 27.65 3117 27.96 2813 27.64 3126 27.95 2823 27.63 3136 27.94 2833 27.62 3146 27.93 2843 27.61 3156 27.92 2853 27.60 3166 27 91 2863 27.59 3176 27 90 2873 27.58 3186 27.89 2882 27.57 3196 27.88 2892 27.56 3206 27.87 2901 27 55 3216 27.86 2911 27.54 3225 27.85 2921 27.53 3235 27.84 2930 27.52 3245 27.83 2940 27.51 3255 27.82 2950 27.50 3265 27.81 2960 27.49 3275 27.80 2969 27.48 3285 27.79 2979 27.47 3295 27.78 2989 27.46 3305 27.77 2999 27.45 3315 27.76 3009 27.44 3325 27.75 3019 27.43 3335 94 "Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet, 27.42 3345 27.10 3665 27.41 3355 27.09 3675 27.40 3365 27.08 3685 27.39 3375 27.07 3695 27.38 3384 27.06 3705 27.37 3394 27.05 3715 27.36 3404 27.04 3725 27.35 3414 27.03 3785 27.34 3424 27.02 3745 27.33 3434 27.01 3755 27.32 3444 27.00 3765 27.31 3454 26.99 3775 27.30 3464 26.98 3785 27.29 3474 26.97 3795 27.28 3484 26.96 3806 27.27 3494 26.95 " 3816 27.26 3504 26.94 3826 27.25 3514 26.93 3836 27.24 3524 26.92 3846 27.23 3534 26.91 3856 27.22 3544 26.90 3866 27.21 3554 26.89 3876 27.20 3564 26 88 3886 27.19 3574 26.87 3897 27.18 3584 26.86 3907 27 17 3594 26.85 3917 27.16 3604 26.84 3927 27.15 3614 26.83 3038 27.14 3624 26.82 3948 27.13 3634 26.81 3958 27 12 3644 26.80 , . 3068 27.11 3654 26.79 3978 , 95 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet, Inches. Feet. 26.78 3988 26.46 4315 26.77 3999 26,45 4326 25.76 4009 26.44 4336 26 75 4019 26.43 4347 26.74 4030 26.42 4357 26.73 4040 26.41 431J8 26.72 4050 26.40 4378 26. 7L 4060 26.39 4388 26.70 4070 26.38 .4399 26.69 4081 26.37 4409 26.68 4091 26.36 4419 , 26.<)7 4101 26.35 4430 26.66 4111 26.34 4440 26.65 4122 26.33 4450 26.64 4132 26.32 4461 26.63 4142 26.31 4472 26.62 4152 26.30 4482 26.61 4163 26.29 ' 4492 26 . (50 4173 26.28 4502 26.59 4183. 26.27 4513 26.58 4193 26.26 4523 26.57 4203 26.25 4533 26.56 4213 26.24 4544 26.55 4223 26.23 4554 26.54 4233 26.22 4565 26.53 4244 26.21 4575 26.52 4254 26.20 4585 26.51 4264 26.19 4596 26.50 4274 26.18 4606 26.49 4284 26.17 4617 36 . 48 4294 26.16 4627 26.47 4304 26.15 4638 96 Barometer H . , Readings. Iei hts - Barometer Readings. Heights. Inches. Feet. Inches. Feet, 26.14 4648 25.82 4983 26.13 4658 25.81 4994 26.12 4669 25.80 5004 26.11 4679 25.79 5014 26.10 4690 25.78 5025 26.09 4700 25.77 5036 26.08 4711 25.76 5046 26.07 4721 25.75 5057 26.06 4731 25.74 5067 26.05 4742 25.73 5078 26.04 4752 25.72 5088 23.03 4763 25.71 5099 28.02 4773 25.70 5110 26.01 4784 25.69 5121 26.00 4794 25.68 5132 25.99 4805 25.67 5142 25.98 4815 25.66 5153 25.97 4826 25.65 5164 25.96 4836 25.64 5174 25.95 4847 25.63 5185 25.94 4857 25.62 5195 25.93 4868 25.61 5206 25.92 4878 25.60 5216 25,91 4889 25.59 5227 25.90 4899 25.58 5237 25.89 4910 25.57 5248 25.88 4920 25.56 5259 25.87 4931 25.55 5270 25.86 4941 25.54 5281 25.85 4952 25.53 5291 25.84 4962 25.52 5302 25.83 4973 25.51 5312 97 Barometer Readings. TT . -. . i Barometer Hei - rhts ' Readings. Heights. Inches Feet. Inches. Feet. 25.50 5323 25.18 5668 25.49 5333 25.17 5679 25.48 5344 25 16 5689 25.47 5355 25.15 5700 25.46 5365 25.14 5711 25.45 5376 25.13 5722 25.44 5387 25.12 5733 25.43 5397 25.11 5744 25.42 5408 25.10 5754 25.41 5419 25.09 5765 25.40 5429 25.08 5776 25 39 5440 25.07 5787 25.38 5451 25.06 5798 25.37 5462 25.05 5809 25.36 5473 25.04 5820 25.35 5483 25.03 5831 25.34 5494 25.02 5842 25.33 5505 25.01 5853 25.32 5516 25.00 5863 25.31 5527- 24.99 5874 25.30 5537 24.98 5885 25 29 5548 24.97 5896 25.28 5559 24.96 5907 25.27 5570 24.95 5918 25.26 5581 24.94 5929 25.25 5592 24.93 5940 25.24 5602 24.92 5950 25.23 5613 24.91 5962 25.22 5624 24.90 5972 25.21 5635 24.89 5983 25.20 5646 24.88 5994 25.19 5657 24.87 6005 98 I Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 24.86 6016 24.54 6368 24.85 6027 24.53 6379 24.84 6038 24.52 6390 24.83 6049 24.51 6401 24.82 6060 24.50 6412 24.81 6071 24.49 6424 24.80 6082 24.48 6435 24.79 6093 24/47 6446 24.78 6104 24.46 6458 24.77 6115 ' 24.45 6469 24.76 6126 24.44 6480 24.75 6137 24.43 6491 24.74 6148 24.42 6503 24,73 6159 24.41 6514 24.72 6170 24.40 6525 24.71 6181 24.39 6536 24.70 6192 24.38 6547 24.69 6203 24.37 6559 24.68 6214 24.36 6570 24.67 6225 24.35 6581 24.66 6236 24.34 6592 24.65 6247 24.33 6603 24.64 6258 24.32 6615 24.63 6269 24.31 6626 24.62 6280 24.30 6637 24.61 6291 24.29 6648 24.60 6302 24.28 6659 24.59 6313 24.27 6671 24.58 6324 24.26 6682 24.57 6335 24.25 6693 24.56 6346 24.24 6705 24.55 6357 24.23 6716 99 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 24. 22 6727 23.90 7090 24.21 6738 23.89 7101 24.20 6750 23.88 7113 24.19 6761 23.87 7124 24.18 6772 23.86 7135 24.17 6783 23.85 7146 24.16 6795 23.84 7157 24.15 6806 23.83 7168 24.14 6817 23.82 7180 24.13 6828 23.81 7191 24.12 6840 23.80 7203 24.11 6851 23.79 7214 24.10 6862 23.78 7226 24.09 6873 23.77 7237 24.08 6885 23.76 7249 24.07 6896 23.75 7261 24.06 6907 23.74 7272 24.05 6919 23.73 7283 24.04 6930 23.72 7294 24.03 6941 . 23.71 7305 24.02 6953 23.70 7316 24.01 6964 23.69 7327 24.00 6976 23.68 7339 23.99 6987 23.67 7350 23.98 6999 23.66 7362 23.97 7010 23.65 7374 23.96 7022 23.64 7386 23.95 7033 23.63 7398 23.94 7045 23.62 7409 23.93 7056 23.61 7421 23.92 7068 23.60 7433 23.91 7079 23.59 7445 [ 100 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 23.58 7456 23.26 7829 23.57 7468 23.25 7841 23.56 7480 23.24 7853 23.55 7492 23.23 7865 23.54 7503 28.22 7876 23.53 7515 23.21 7888 23.52 7527 23.20 7900 23.51 7539 23.19 7912 23.50 7550 23.18 7923 23.49 7562 23.17 7935 23.48 7574 23.16 7946 23.47 7585 23.15 7958 23.46 7597 23.14 7969 23.45 7609 23.13 7981 23 44 7621 23.12 7092 23.43 7633 23.11 8004 23.42 7644 23.10 8015 23.41 7656 23.09 8027 23.40 7667 23.08 8039 23.39 7679 23.07 8051 23.38 7690 23.06 8063 23.37 7702 23.05 8075 23.36 7713 23.04 8086 23.35 7725 23.03 8098 23.34 7736 23.02 8110 23.33 7748 23.01 8122 23.32 7759 23.00 8134 23.31 7771 22.99 8146 23.30 7782 22.98 8158 23.29 7793 22.97 8170 23.28 7805 22.96 8182 23.27 7817 i 22.95 8194 101 Barometer Reading?. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 22.94 8206 22.62 8591 22.93 8218 22.61 8603 22.92 8-^30 22.60 8615 22.91 8242 22.59 8627 22.90 8254 23.58 8638 22.89 8266 22.57 8650 22.88 8278 22.56 8661 22.87 8290 22.55 8673 22.86 8302 22.54 8685 22.85 8314 22.53 8697 22.84 8326 22.52 8709 22.83 8338 22.51 8721 22.82 8350 22.50 8733 22.81 8362 22.49 8745 22.80 8374 22.48 8757 22.79 8386 22.47 8769 22.78 8398 22.46 8781 22.77 8410 22.45 8793 22.76 8422 22.44 8806 22.75 8434 22.43 8818 22.74 8446 22.42 8830 22.73 8458 22.41 8842 22.72 8470 22.40 8855 22.71 8482 22.39 8867 22.70 8495 22.38 8879 22.69 8507 22.37 8891 22.68 8519 22.36 8904 22.67 8531 22.35 8916 22.66 8543 22.34 8928 22.65 8555 22.33 8941 22.64 8567 22.32 8953 22.63 8579 22.31 8965 102 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 22.30 8977 21.98 9372 22.29 8090 21.97 9384 22.28 9002 21.96 9397 22.27 9014 21.95 9410 22.26 9026 21.94 9422 22.25 9039 21.93 9435 22.24 9051 21.92 9447 22.23 9063 21.91 9460 22.22 9075 21.90 9472 22.21 9088 21.89 9485 22.20 9100 21.88 9497 22.19 9113 21.87 9510 22.18 9125 21.86 9522 22.17 9138 21.85 9535 22.16 9150 21.84 9547 22.15 9162 21.83 9560 22.14 9174 21.82 9572 22.13 9187 21.81 9585 22.12 9199 21.80 9597 22.11 9212 21.79 9610 22.10 9224 21.78 9622 22.09 9236 21.77 9635 22.08 9249 21.76 9647 22.07 9262 21.75 9660 23.06 9274 21.74 9672 22.05 9286 21.73 9685 22.04 9298 21.72 9697 22.03 9311 21.71 9710 22.02 9323 21.70 9722 22.01 9336 21.69 9735 22.00 9348 21.68 9747 21.99 9360 21.67 9760 103 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 21.66 9772 21.34 10176 21.65 9785 21.33 10189 21.64 9797 21.32 10202 21.63 9810 21.31 10214 21.62 9822 21.30 10228 21.61 9835 21.29 10241 21.60 9848 21.28 10253 21.59 9861 21.27 10266 21.58 9873 21.26 10278 21.57 9886 21.25 10291 21.56 9898 21.24 10304 21.55 9911 21.23 10317 21.54 9923 21.22 10330 21.53 9936 21.21 10343 21.52 9949 21.20 10355 21.51 9962 21.19 10368 21.50 9974 21.18 . 10381 21.49 9987 21.17 10394 21.48 9999 21.16 10407 21.47 10012 21.15 10420 21.46 10025 21.14 10432 21.45 10088 21.13 10445 21.44 10050 21.12 10458 21.43 10063 21.11 10471 21.42 10075 21.10 10484 21.41 10088 21.09 10497 21.40 10101 21.08 10509 21.39 10114 21.07 10522 21.38 10126 21.06 10535 21.37 10139 21.05 10548 21.36 10151 21.04 10561 21.35 10164 21.03 10574 104 Barometer TT ^ f Readings. Hel S bts - Inches. 21.02 21.01 21.00 20.99 20.98 20.97 20.96 20.95 20.94 20.93 20.92 20.91 20.90 20.89 20.88 20.87 20.86 20.85 20.84 20.83 20.82 20.81 20.80 20.79 20.78 20.77 20.76 20.75 20.74 20.73 20.72 20.71 Feet. 10587 10600 10613 10627 10640 10654 10667 10681 10694 10707 10720 10733 10746 10759 10772 10785 10798 10811 10824 10837 10850 10863 10876 10889 10902 10915 10928 10941 10954 10967 10980 10993 Barometer "Readings Heights. Inches. Feet. 20.70 11006 20.69 11019 20.68 11032 20.67 11045 20.66 11058 20 65 11071 20.64 11084 20.63 11097 20.63 11110 20.61 11123 20.60 11136 20.59 11149 20.58 11163 20.57 11176 20.56 11190 20.55 11204 20.54 11217 20.53 11230 20.52 11243 20.51 11257 20.50 11270 20.49 11284 20.48 11297 20.47 11311 20 46 11324 20.45 11338 20.44 11351 20.43 11364 20.42 11377 20.41 11391 20.40 11404 20.39 11418 105 Barometer Readings. Heights. Barometer Readings. Heights. Inches. Feet. Inches. Feet. 20.38 11431 20.18 11700 20.37 11444 20.17 11714 20.36 11457 20.16 11727 20.35 11470 20.15 11741 20.34 11483 20.14 11754 20.33 11496 20.13 11768 20.32 11509 20.12 11781 20.31 11523 20.11 11795 20.30 11536 20.10 11808 20.29 11550 20.09 11821 20.28 11563 20.08 11835 20.2? 11577 20.07 11859 20.26 11591 20.06 11863 20.25 11605 20.05 11877 20.24 ! 11618 20.04 11891 20.23 11632 20.03 11905 20.22 11645 20.02 11918 20.21 11659 20.01 11932 20.20 11673 20.00 1'1945 20.19 11687 1 - ..." - fa 3 ' Z i 106 The following table is to be used when applying the modified formula of chapter II: D=60000(log.B-log.)(l+ RULE. Find in the table the loga- rithms of the barometer readings to hundredths of an inch. Subtract these logarithms and multiply the remainder by 60000. The product is the approx- imate difference in altitude between the two stations. To apply the corrections for temperature, add the temperatures of the two stations and subtract 60. Increase the above approximate value by -g^ of itself for each degree of excess above 60. If the sum of the tempera- ture is less than 60 diminish the value by a like amount. 107 TABLE II. Bar. Height. Log. Bar. Height. Log. 2200 3.34242 2231 3.34850 01 .34262 32 .34869 02 .34282 33 .34889 03 .34301 34 .34908 04 .34321 35 .34928 05 .34341 36 .34947 06 .34361 37 .34967 07 .34380 38 .34986 08 .34400 39 .35005 09 .34420 40 .35025 10 .84439 41 .35044 11 .34459 42 .35064 12 .34479 43 .35083 13 .34498 44 .35102 14 .34518 45 .35122 15 .34537 46 .35141' 16 .34557 47 .35160 17 .34577 48 .35180 18 .34596. 49 .35199 19 .34616 50 .35218 20 .34635 51 .35238 21 .34655 52 .35257 22 .34674 53 .35276 23 . 34694 54 .35295 24 .34713 55 .35315 25 .34733 56 .35334 26 .34753 57 .35353 27 . 34772 58 .35372 28 .34792 59 .35392 29 .34811 60 .35411 30 .34830 61 .35430 108 Bar. Height. Log. Bar. Height. Log. 2262 3.35449 2295 3.36078 63 .35468 96 i .36097 64 .35488 97 .36116 65 .35507 98 .36135 66 .35526 99 .36154 67 .35545 2300 .36173 68 .35564 01 .36192 69 .35583 02 .36211 70 .35603 03 .36229 71 .35622 04 .36248 72 ' .35641 05 .36267 73 .35660 06 .36286 74 .35679 07 .36305 75 .35698 08 .36324 76 .35717 09 .36342 77 .35736 10 36361 78 .35755 11 .36380 79 .35774 12 .36399 80 .35793 13 .36418 81 .35813 14 .36436 82 .35832 15 .36455 83 .35851 16 .36474 84 .35870 17 .36493 85 .35889 18 .36511 86 .35908 19 .36530 87 .35927 20 .36549 88 .35946 21 .36568 89 .35965 22 .36586 90 .35984 23 .36605 91 .36003 24 .36624 92 .36021 25 .36642 93 .36040 26 .36661 94 .36059 27 .36680 109 Bar. Height. Log. Bar. Height. Log. 2328 3.36698 2361 3.37310 29 .36717 62 .37328 30 .36736 63 .37346 31 .36754 64 .37365 32 .36773 65 .37383 33 . 36791 66 =37401 34 .36810 67 .37420 35 .36829 68 .37438 36 .36847 69 .37457 37 .36866 70 .37475 38 .35884 71 .37493 39 .36903 72 .37511 40 .36922 73 .37530 41 .38940 74 .37548 42 .36959 75 .37566 43 .36977 76 .37585 44 .36996 77 .37603 ' 45 .37014 78 .37621 46 .37033 79 .37639 47 .37051 80 .37658 48 .37070 81 ,37670 49 .37088 82 .37694 50 .37107 83 37712 51 .37125 84 .37731 52 .37144 85 .37749 53 .37162 86 .37767 54 .37181 87 .37785 55 .37199 88 .37803 56 .37218 89 .37822 57 .37236 90 .37840 58 .37254 91 .37858 59 .37273 92 .37876 60 .37291 1 93 .37894 110 Bar. Height. Log. Bar. Height. Log. 2394 3.37912 2427 3.38507 95 .37931 28 .38525 96 .37949 29 .38543 97 .37967 30 .38561 98 .37985 31 .38579 99 .38003 32 .38596 2400 .38021 33 .38614 01 .38039 34 .38632 02 .38057 35 .38650 03 .38075 36 .38668 04 .38093 37 .38686 05 .38112 38 .38703 06 .38130 39 .38721 07 .38148 40 .38739 08 .38166 41 .38757 09 .38184 42 .38775 10 .38202 43 .38792 11 .38220 44 .38810 12 .38238 45 .38828 13 .38256 46 .38846 14 .38274 47 .38863 15 .38292 48 .38881 16 .38310 49 .38899 17 38328 50 .38917 18 .38346 51 .38934 19 .38364 52 .38952 20 .38382 53 .38970 21 .38399 54 .38987 22 .38417 55 .39005 23 .38435 56 .39023 24 .38453 57 39041 25 . 38471 58 .39058 26 .38489 59 .39076 Ill Bar. Height. 1 Bar. Height. 2460 3.39094 2493 3.39672 61 .39111 94 .39690 63 .39129 95 .39707 63 .39146 96 .39724 64 .39164 97 .39742 65 .39182 98 .39759 06 .39199 99 .39777 67 .39217 2500 .39794 68 .39235 01 .39811 69 .39252 02 .39829 70 .39270 03 .39846 71 .39287 04 .39863 72 .39305 05 .39881 73 .39322 06 .39898 74 .39340 07 .39915 75 .39358 08 .39933 76 .39375 09 .39950 77 .39393 10 .39967 78 .39410 11 .39985 79 .39428 12 40002 80 .39445 13 .40019 81 .39463 14 .40037 82 .39480 15 .40054 83 .39498 16 .40071 84 .39515 17 .40088 85 | .39533 18 .40106 86 .39550 19 .40123 87 .39568 20 .40140 88 .39585 21 .40157 89 .39602 22 .40175 90 .39620 23 .40192 91 .39637 24 .40209 92 .39655 25 .40226 112 1 Bar. Height. 1 Bar. Height. Log. 2526 3.40243 255J 3.40807 27 .40261 60 .40824 28 .40278 61 .40841 29 .40295 62 .40858 an .40312 63 .40875 31 .40329 64 .40892 32 .40346 65 .401)0:; 33 .40364 66 .40926 34 .40381 67 .40943 35 .40398 68 .40960 36 .40415 69 .40976 37 .40432 70 .40993 38 .40449 71 .41010 39 .40466 72 .41027 40 .40483 73 .41044 41 .40500 74 .41061 42 .40518 75 .41078 & .40535 76 .41095 44 .40552 77 .41111 45 .40569 78 .41128 46 .40586 79 .4114') 47 .40603 80 .41162 48 .40620 81 .41179 49 .40637 82 .41196 50 .40654 83 .41212 51 .40671 84 .41229 52 .40688 85 .41246 53 .40705 86 .41263 54 .40722 87 .41280 5) 40739 88 .41296 56 .40756 89 41313 57 .40773 90 .41330 58 .40790 91 .41347 113 Bar. Height. Log. Bar. Height. Log. 2592 3.41364 2625 3.41913 93 .41880 26 .41929 94 .41397 27 .41946 95 .41414 28 .41963: 96 .41430 29 .4197$ 97 .41447 30 .41996- 98 .41464 31 .42012 99 .41481 32 .42029' 2600 .41497 33 .42045. 01 .41514 34 .420621 02 .41531 35 .4207$ 03 .41547 36 .42095 04 41564 37 .42111 05 .41581 38 .42127 06 .41597 89 .42144 07 .41614 40 .42160 08 .41631 41 .42177 09 41647 42 .42193: 10 .41664 43 .42210 11 .41681 44 .42226 12 .41697 45 .42243: 13 .41713 46 .42259 14 .41731 47 .42275 15 .41747 46 .42292 16 .41764 49 42308 17 ,41781 50 .42:',25 18 .41797 51 42341 19 .41814 52 .42357 20 .41831 53 , 42374 21 .41847 54 .42390 22 .41863 55 .42406 23 .41880 56 . 42423 24 41896 57 42439 114 "Rar Height. L S' I )< 1 1 . Height. Log. 2658 3.42455 2691 3.42991 59 .42472 92 43008 60 .42488 93 .43024 - 61 .42504 94 .43040 62 .42521 95 .43056 63 .42537 96 .43072 64 .42553 97 .43088 65 .42570 98 .43104 66 .42586 99 .43120 67 .42602 2700 .43136 68 .42619 01 .43152 69 .42635 02 .43169 70 .42651 03 .43185 71 .42667 04 .43201 72 .42684 05 .43217 73 .42700 06 .43233 74 .42716 07 .43249 75 .42732 08 .43265 76 .42749 09 .43281 77 .42765 10 .43297 78 .42781 11 .43313 79 .42797 12 .43329 80 ,42813 13 .43345 81 .42830 14 .43361 82 .42846 15 .43377 83 ,42862 16 .43393 84 42878 17 .43409 85 .42894 18 .43425 86 .42911 19 .43441 87 .42927 20 .43457 88 .42943 21 .43473 89 .42959 22 .43489 90 .42975 23 .43505 115 Bar. Height. Log. Bar. Height. Log. 2724 3.48521 2757 3.44044 25 .43537 58 .44059 26 .43553 59 .44075 27 .43569 60 .44091 28 .43584 61 .44107 29 .43600 62 .44122 30 .43616 63 .44138 31 .43632 64 .44154 32 .43648 65 .44170 33 .43664 66 .44185 34 .43680 67 .44201 35 .43696 68 .44217 36 .43712 69 .44232 37 .43727 70 .44248 38 .43743 71 .44264 39 .43759 72 .44279 40 .43775 73 .41295 41 .48791 74 .44311 42 .43807 75 .44326 43 .43823 76 .44342 44 .43838 77 .44358 45 .43854 78 .44373 46 .43870 79 .44389 47 .43886 80 .44404 48 .43902 81 .44420 49 .43917 82 .44436 50 .43933 83 .44451 51 .43949 84 .44467 52 .43965 85 .44483 53 ,43981 86 .44498 54 .43996 87 .44514 55 .44012 88 .44529 56 .44028 89 .44545 1 116 Bar. Height. Log. Bar. Height. Log. 2790 3.44560 2823 3.45071 91 .44576 24 .45086 92 .44592 25 .45102 93 .44607 26 .45117 94 .44623 27 .45133 95 .44638 28 .45148 96 .44654 29 .45163 97 .44669 30 .45179 98 .44685 31 .45194 99 .44700 32 .45209 2800 .44716 33 .45225 01 .44731 34 .45240 02 .44747 35 .45255 03 .44762 36 .45271 4 .44778 37 .45287 5 .44793 38 .45301 06 .44809 39 .45817 07 .44824 40 .45332 08 .44840 41 .45347 09 .44855 42 .45362 10 .44871 43 .45378 11 .44886 44 .45393 12 .44902 45 .45408 13 .44917 46 .45423 14 .44932 47 .45439 15 .44948 48 | .45454 16 .44963 49 .45469 17 .44979 50 i .45484 18 .44994 51 .45500 19 .45010 52 .45515 20 .45025 53 .45530 21 .45040 54 .45545 22 .45056 55 .45561 117 Bar. Height. Log. Bar. Height. Log. 2856 3.45576 2889 3.46075 57 .45591 90 .46090 58 .45606 91 .46105 59 .45621 92 .46120 60 .45637 93 .46135 61 .45652 94 .46150 62 .45667 95 .46165 63 .45682 96 .46180 64 .45698 97 .46195 65 .45712 98 .46210 66 .45728 99 .46225 67 .45743 2900 .46240 68 .45758 01 .46255 69 .45773 02 .46270 70 .45788 03 .46285 71 .45803 04 .46300 72 .45818 05 .46315 73 .45834 06 .46330 74 .45849 07 .46344 75 .45864 08 .46859 76 .45879 09 .46374 77 .45894 10 .46389 78 .45909 11 .46404 79 .45924 12 .46419 80 .45989 13 .46434 81 .45954 14 .46449 82 .45969 15 .46464 83 .45984 16 .46479 84 .46000 17 .46494 85 .46015 18 .46509 86 .46030 19 .46523 87 .46045 20 .46538 88 46060 21 .46553 118 i Bar. Height. Log. Bar. Height. Log. 2922 3.46568 2955 3.47056 23 .46583 56 .47070 24 .46598 57 .47085 25 .46613 58 .47100 26 .466^7 59 .47114 27 .46642 60 .47129 28 .46657 61 .47144 29 .46672 62 .47159 30 .46687 63 .47176 31 .46702 64 .47188 32 .46716 65 .47202 33 .46731 66 .47217 34 .46746 67 .47232 35 .46761 68 .47246 36 .46776 69 .47261 37* .46790 70 .47276 38 .46805 71 .47290 39 .46820 72 .47305 40 .46835 73 .47319 41 .46849 74 .47334 42 .46864 75 .47349 43 .46879 76 .47363 44 .46894 77 .47378 45 .46909 78 .47392 46 .46923 79 .47407 47 .46938 80 .47422 48 .46953 81 .47436 49 .46967 82 .47451 50 .46982 83 .47465 51 .46997 84 .47480 52 .47012 85 .47494 53 .47026 86 .47509, 54 .47041 87 .47524^ 119 Hefght. L S- Bar. Height. Log. 2988 3.47538 3021 3.48015 89 .47553 22 .48030 90 .47567 23 .48044 91 47582 24 .48058 92 .47596 25 .48073' 93 47611 26 .48087 04 .47625 27 .48101 95 . 47640 28 .48116 96 .47654 29 .48130 97 .47669 30 .48144 98 .47683 31 .48159 99 .47698 32 .48173 3000 .47712 33 .48187 01 .47727 34 .48202 03 47741 35 .48216 03 47755 36 .48230 04 . 47770 37 .48244 05 . 47784 38 .48259 06 .47799 39 .48273 07 .47813 40 .48287 08 .47828 41 .48302 09 . 47842 42 .48316 10 . 47857 43 .48330 11 .47871 44 .48344 12 .47886 45 .48359 13 .47900 46 .48373 14 .47914 47 .48387 15 .47929 48 .48402 16 .47943 49 ,48416 17 .47958 50 48430 18 .47972 51 ,48444 19 47986 52 .48458 20 ,48001 53 .48473 120 Bar. Height. Log. Bar. Height. | Log. 3054 3.48487 3078 3.48827 55 .48501 79 .48841 56 .48515 80 .48855 57 .48530 81 .48869 58 .48544 82 .48883: 59 .48558 83 48897 60 .48572 84 .48911 61 .48586 85 .48926 62 .48601 86 .48940 63 .48615 87 .48954 64 .48629 88 .4896$ 65 .48643 89 . 48982 66 .48657 90 .48996 67 .48671 91 .49010 68 .48686 92 .49024 69 .48700 93 49038 70 .48714 94 1 . 49052 71 .48728 95 .49066 72 .48742 96 . 49080 73 .48756 97 .49094 74 .48770 98 .49108 75 .48785 99 .49122 76 .48799 3100 .49136 77 .48813 121 TABLE III. BAROMETRIC READINGS IN MILLIMETERS. ALTITUDES IN METERS. This is from Radau's table. The formula for calculation of difference of altitude of two stations is D=(hh') 11+ - + I in which D is the difference of height in meters, h and h f arc barometer readings in millimeters and I and t' are the temperatures in centigrade degrees. Mill. Meters. j| Mill. Meters. Mill. Meters. 500 3365.4 519 3067 4 538 2780.0 501 3349.4 520 3052 539 2765.2 502 3333.5 521 3036.6 540 2750.4 503 3317.6 \ 522 3021 3 541 2735.6 504 3301 7 523 3006 542 2720.9 505 3285.9 524 2990 7 543 2706.1 506 3270.1 525 2975.5 544 2691.4 507 | 3254.3 526 2960.3 545 2676.8 508 3238.5 527 2945 1 546 2662.1 509 3222.8 528 2930 547 2647.5 510 3207 1 529 2914 9 | 548 2632.9 511 3191.5 530 2899 8 549 2618.3 512 3175.9 531 2884.7 550 2603.8 513 3160.3 532 2869.7 551 2589.3 514 3144.7 533 2854.7 552 2574.8 515 3129.2 534 2839.7 553 2560.3 516 3113.7 535 2824.7 554 2545 9 517 3098.2 536 2809.8 555 2531.5 518 3082.8 537 2794.9 556 2517.1 i 122 Mill. Meters. Mill. Meters. Mill. Meters. 557 2502.7 591 2029 4 625 1582.6 558 2488.4 592 2015 9 626 1569.8 559 2474 1 593 2002 4 627 1557.1 560 2459.8 594 1989.0 628 1544.4 561 2445.6 595 1975.5 029 1531.7 562 2431 4 596 1962 1 630 1519.0 563 2417.2 597 1948.7 631 1506.3 564 2403.0 598 1935.4 632 1493.7 565 2388.8 ! 599 1922.0 633 1481.0 566 2374.7 600 1Q08.7 034 1468.4 567 2360.6 601 1895.4 635 1455.8 568 2346 5 602 1882.1 636 1443.3 5(59 2332.5 603 1868.8 637 1430.7 570 2318.4 604 1855.6 638 1418.2 571 2304 4 605 1842.4 639 1405.7' 572 2290.4 606 1829.2 640 1393.2 573 2276.5 607 1816.0 641 1380.7 574 2262.6 608 1802.9 642 1368.3 575 2248.7 609 1789.8 643 1355.8 576 2234.8 610 1776.7 644 1343.4 577 2220.9 611 1763.6 645 1331.0 578 2207.1 612 1750.5 646 1318.7 579 2193.3 613 1737.5 647 1306.3 580 2179 5 614 1724.4 648 1294.0 581 2165.7 615 1711.4 649 1281.7 582 2152.0 616 1698.5 650 1269.4 583 2138.3 617 1685.5 651 1257.1 584 2124.6 618 1672.6 652 1244.8 585 2110.9 619 1659.7 653 1232.6 586 2097.3 620 1646.8 654 1220.4 587 2083.7 621 1683.9 655 1208.2 588 2070.1 622 1621.0 656 1196.0 589 "2056.5 623 1608.2 657 1183.8 590 2042.9 624 1595.4 658 1171 7 123 Mill. Meters. Mill. Meters. Mill Meters. 659 1159.5 693 757.8 727 375.4 6GO 1147.4 694 746.3 728 ! 364.4 661 1135.3 695 734.8 729 353.5 662 1123.3 696 723.3 730 842.5 663 1111.3 697 711.9 731 831.6 664 1099.2 698 700.4 732 820.7 665 10b7.2 699 689.0 733 309.8 666 1075.2 700 677.6 734 298.9 667 1063.2 701 666.2 735 288.0 668 1051 2 702 654.8 736 277.2 669 1039.3 703 643.4 737 266.3 670 1027.3 704 632.1 738 255.5 671 1015.4 705 620.7 739 244.7 672 1003.5 706 609.4 740 233.9 673 991.7 707 598.1 741 223.1 674 979.8 708 586.8 742 212.3 675 968.0 709 575.6 743 201.6 676 956.1 710 564.3 744 190.8 677 944.3 711 553.1 745 180.1 678 932.6 712 541 8 746 169.4 679 920.8 713 530.6 747 158.7 680 909.0 714 519.5 748 148.0 681 897.3 715 508.3 749 137.4 682 885.6 716 497.1 750 126.7- 683 873.9 717 486.0 ! 751 116.1 684 862.2 718 474.8 i 752 105.5 685 850.5 719 463.7 j 753 94.9 686 838.9 720 452.6 754 84.3 687 827.3 721 441.6 ! 755 73.7 688 815.6 722 430.5 756 63.1 689 8C4.0 723 419.4 757 52.6 690 792.5 724 40S.4 758 42.0 691 780.9 725 397.4 759 31.5 692 769.3 726 386.4 760 21.0 124 Mill. Meters. Mill. Meters. Mill. Meters. 761. 10.5 768 - 62.6 775 -135.0 762 769 - 73.0 776 -145 3 763 -10 5 770 - 83.4 777 -155 6 764 -20 9 771 - 93.7 778 -165.9 765 -31 4 772 -104 1 779 -176.1 766 -41 8 773 -114 4 780 -186.4 767 -52.2 774 -124.7 125 In comparing the Aneroid with a Mercurial Barometer, correct the latter by the following table, subtracting the corrections. TABLE IV. Reduction of Mercurial Column to 32 Fahr. Brass scale to barometer correct at 62 Fahr. Temp. 30" 25" 20" 32 .009 .008 .006 35 .017 .015 .012 40 .031 .026 .021 45 .044 .037 .030 50 .058 .048 .038 55 .071 .059 .047 60 ..084 .070 .056 65 .098 .082 .065 70 .111 .093 .074 75 125 .104 .083 80 .138 .115 .092 85 .151 .126 .101 90 .164 .137 .110 95 .178 .148 .118 100 .191 .159 .127 126 TABLE Y. BAROMETRIC PRESSURES CORRESPONDING TO BOILING WATER TEMPERATURES. Whole Deg. .0 Tenths of each Degree. .2 s -4 .6 .8 in. in. in in. in. 183 16.317 16 389 16.461 16.533 116.605 184 16 618 16 752 16.826 16.900 16.974 185 17 048 17 122 17.197 17.272 17.348 186 17 423 17 499 17.575 17.652 17.729 187 17 806 17.883 17.961 18.039 18.117 188 18 195 18.274 18.353 18.432 18.512 189 18 592 18.672 18.753 18.833 18.914 190 18 996 19.077 19.159 19.241 19.324 191 19 407 19.490 19.573 19.657 19.741 192 19 825 19.910 19.995 20.080 20.166 193 20 251 20.338 20.424 20 511 20.598 194 '20 685 20.773 20.861 20 949 21.038 195 21.126 21.216 21.305 21.895 21.485 196 21 . 576 21 . 666 21.758 21.849 21.941 197 22 . 033 22.125 22.218 22.311 22.404 198 22 498 22 592 22.686 22.781 22.876 199 22 971 23 067 23.163 23.259 23.356 200 23 . 453 23 550 23.648 23.746 23.845 201 23 . 943 24 042 24.142 24.241 24.341 202 24 442 24.542 24.644 24.745 24.847 203 24 949 25 051 25.154 25.257 25 361 204 25 465 25 569 25 674 25.779 25.884 205 25 990 26 096 26.202 26.309 26.416 206 26 523 26 . 631 26.740 26.848 26.957 207 27 066 27.176 27.286 27.397 27.507 208 27.618 27.730 27.842 27.954 28.067 209 28 180 28.293 28.407 28.521 28.636 210 28.751 28.866 28.982 29.098 29.215 211 29.331 29.449 29.566 29.684 29 803 212 29.922 30.041 30.161 30.281 30.401 * Any book in this Catalogue sent free by mail on receipt o/ VALUABLE SCIENTIFIC BOOKS PUBLISHED BY D. VAN NOSTRAND COMPANY, 23 MURRAY STREET AND 27 WARREN STREET, N. Y. ADAMS (J. W.) Sewers and Drains for Populous Districts. Embracing Rules and Formulas lor the dimensions and construction of works of Sanitary Engineers. Second edi- tion. 8vo, cloth $2 50 ALEXANDER (J. H.) Universal Dictionary of Weights and Measures, Ancient and Modern, reduced to the standards of the United States of America. New edition, enlarged. 8vo, cloth 350 ATWOOD (GEO.) Practical Blow-Pipe Assaying. I2mo, cloth, illustrated 2 OO AUCHINCLOSS (W. S.) Link and Valve Motions Simplified. Illustrated with 37 wood-cuts and 21 lithographic plates, together with a Travel Scale and numerous useful tables. 8vo, cloth 300 AXONf (W. E. A.) The Mechanic's Friend : a Collection of Re- ceipts and Practical Suggestions Relating to Aquaria- Bronzing Cements Drawing Dyes Electricity Gilding Glass-working Glues Horology Lacquers -Locomo- tives Magnetism Metal-working Modelling Photogra- phy Pyrotec^ny Railways Solders Steam-Engine Tel- egraphy Taxiuermv Varnishes Waterproofing, and Mis- cellaneous Tools, Instruments, Machines, and Processes connected with tne Chemical and Mechanic Arts. With nu- merous diagrams and wood-cuts. Fancy cloth ..... .. I 50 &ACON (F. W ) A Treatise on the Richards Steam-Engjne Indicator, with directions for its use. By Charles T. Por- ter. Revised, with notes and large additions as developed by American practice ; with an appendix containing useful formulae and rules for engineers. Illustrated. Third edi- tion. i2mo, cloth: ...... oo 2 D. VAN NOSTRAND S PUBLICATIONS. BARBA (J.) The Use of Steel for Constructive Purposes Method of Working, Applying, and Testing Plates and Brass. With a Prelace by A. L. Holley, C.E. 12010, cloth.$i 50 BARNES (Lt. Com. J. S.. U. S. N.) Submarine Warfare, offen- sive and defensive, including a discussion of the offensive Torpedo System, its effects upon Iron-Clad Ship Systems and influence upon future naval wars. With twenty litho- graphic plates and many wood-cuts. 8vo, cloth 5 oo BE1LS TEIN (F.) An Introduction to Qualitative Chemical Analysis, translated by I. J. Osbun. i2mo, cloth 75 BENET (Gen. S. V., U. S. A.) Electro-Ballistic Machines, and the Schultz Chronoscope. Illustrated. Second edition, 410, cloth 300 BLAKE (W. P.) Report upon the Precious Metals : Being Sta- tisiic.il Notices of the principal Gold and Silver producing regions of the World, represented at the Paris Universal Exposition. 8vo, cloth 200 Ceramic Art. A Report on Pottery, Porcelain, Tiles, Terra Cotta, and Brick. 8vo, cloth 2 oo BOW (R. H.) A Treatise on Bracing, with its application to Bridges and other Structures of Wood or Iron. 156 illustra- tions. 8vo, cloth i ;o BOW SLR (Prof. E. A.) An Elementary Treatise on Analytic Geometry, embracing Plane Geometry, and an Introduc- tion to Geometry of three Dimensions. I2mo, cloth I 75 - An Elementary Treatise on the Differential and Integral Calculus. With numerous examples. I2mo, cloth 225 BURGH (N P.) Modern Marine Engineering, applied to Pad- dle and Screw Propulsion. Consisting of 36 colored plates, 259 practical wood-cut illustrations, and 403 pages of de- scriptive matter, the whole being an exposition of the pre- sent practice of Tames Watt & Co., J. & G. Rennie, R. Na- pier & Sons, and other celebrated firms. Thick 410 vol., cloth 3 10 oo Hail morocco , 15 oo BUR f (W. A.) Key to the Solar Compass, and Surveyor's Com- panion ; comprising all the rules necessary for use in the held : also description of the Linear Surveys and Public Land Astern of the United States, Notes on the Karome- ter, -.tgestions for an outfit for a survey of four months, etc. .second edition. Pocket-book form, tuck 2 50 BUTLER (Capt. J. S., U. S. A.) Projectiles and Rifled Cannon. A Critical Discussion of the Principal Systems of Rifling and Projectiles, with Practical Suggestions for their Im- provement, as embraced in a Report to the Chief of Ord- nance, U. S. A. s6plates 410, cloth 6 oo D. VAN NOSTRAND 7 S PUBLICATIONS. 3 CAI N (Prof. WM ) A Practical Treatise on Voussoir and Solid and Braced Arches. i6mo, cloth extra $j 75 CALDWELL (Prof. GEO. C.) and BRENEMAN (Prof. A. A.) Manual of Introductory Chemical Practice, for the use of Students in Co leges and Normal and High Schools. Third edition, revised and corrected. 8vo, cloth, illustrated. New and enlarged edition I 50 CAMPIN (FRANCIS). On the Construction of Iron Roofs. 8vo, with plates, cloth . . . . 2 oo CHAUVENET(Prof. W.) New method of correcting Lunar Distances, and improved method of finding the error and rate of a chronometer, by equal altitudes. 8vo, cloth 200 CHURCH (JOHN A.) Notes of a Metallurgical Journey in Europe. 8vo, cloth 2 oo CLARK (D. KINNEAR, C.E.) Fuel: Its Combustion and Economy, consisting of Abridgments of Treatise on the Combustion of Coal and the Prevention of Smoke, by C. W. Williams ; and the Economy of Fuel, by T S Pri- deaux. With extensive additions on recent practice in the Combustion and Economy of Fuel : Coal, Coke, Wood, Peat, Petroleum, etc. I2mo, cloth I 50 A Manual of Rules, Tables, and Data for Mechanical Engineers. Hased on the most recent investigations. Illus- trated with numerous diagrams. 1,012 pages.' 8vo, cloth... 7 50 Half morocco 10 oo CLARK (Lt. LEWIS, U. S. N ) Theoretical Navigation and Nautical Astronomy, illustrated with 41 wood-cuts. 8vo, cloth I 50 CLARKE (T. C.) Description of the Iron Railway Bridge oyf r the Mississippi River at Quincy, Illinois. Illustrated with 21 lithographed plans. 410, cloth 7 50 CLEVENGERfS. R.) A Treatise on the Method of Govern- ment Survexing, as prescribed by the U S. Congress and Commissioner of the General Land Office, with complete Mathematical, Astronomical, and Practical Instructions for the use of the United States Surveyors in the field. i6mo, morocco 2 50 COFFIN (Prof J. H. C ) Navigation and Nautical Astrono- my. Prepared for the use of the U. S. Naval Academy. Sixth edition. 52 wood-cut illustrations. I2mo, cloth.. 3 50 COLBURN (ZERAH). The Gas-Works of London. I2mo, boards 60 COLLINS (JAS. E) The Private Book of Useful Alloys and Memoranda for Goldsmiths, Jewellers, etc. i8mo, cloth... 50 4 D. VAN NOSTRAND'S PUBLICATIONS. CORNWALL (Prof. H. B.) Manual of Blow Pipe Analysis, Qualitative and Quantitative, with a Complete System 01 Descriptive Mineralogy. 8vo, cloth, with many illustra- tions. N. Y., 1882 $250 CRAIG (B. F ) Weights and Measures. An account of the Decimal System, with Tables of Conversion for Commer- cial and Scientific Uses. Square 32mo, limp cloth 50 CRAIG (Prof. THOS.) Elements of the Mathematical Theory of Fluid Motion. i6mo, cloth 125 DAVIS (C. B.I and RAE (F. B.) Hand-Book of Electrical Dia- grams and Connections. Illustrated with 32 full-page illus- trations. Second edition. Oblong 8vo, cloth extra ....... too DIED RICH (JOHN). The Theory of Strains : a Compendium lor the Calculation and Construction of Bridges, Roofs, and Cranes Illustrated by numerous plates and diagrams. 8vo, cloth 5 00 DIXON (D. B.) The Machinist's and Steam-Engineer's Prac- tical Calculator. A Compilation of useful Rules, and Prob- lems Arithmetically Solved, together with General Informa- tion applicable to Shop-Tools, Mill-Gearing, Pulleys and Shafts, Steam-Boilers and Engines. Embracing Valuable Tables, and Instruction in Screw-cutting, Valve and Link Motion, etc. i6mo, full morocco, pocket form ...(In press) DODD (GEO.) Dictionary of Manufactures, Mining, Ma- chinery, and the Industrial Arts. I2mo, cloth 150 DOUGLASS 'Prof S. H.) and PRESCOTT (Prof. A B.) Qual- itative Chemical Analysis. A Guide in the Practical Study of Chemistry, and in the Work of Analysis. Third edition. 8vo, cloth 3 50 DUBOIS (A. T.) The New Method of Graphical Statics. With 60 illustrations. 8vo, cloth i 150 EASSIE (P. B.) Wood and its Uses. A_ Hand-Book for the use of Contractors, Builders, Architects, Engineers, and Tim- ber Merchants. Upwards of 250 illustrations. 8vo, cloth, i 50 EDDY (Prof. H. T.) Researches in Graphical Statics, err'dac- ing New Constructions in Graphical Statics, a New General Method in Graphical Statics, and the Theory of Internal Stress in Graphical Statics. 8vo, cloth i ), per vol $2 50 FANNING (J. T.) A Practical Treatise of Water-Supply En- gineering. Relating to the Hydrology, Hydrodynamics, and Practical Construction ol Water- \V orks in North America. Third edition. With numerous tables and 180 illustra- tions, 650 pages . 8vo, cloth 5 oo FISkE (BRADLEY A., U.S. N.) Electricity in Theory and Practice. 8vo, cloth , . . . 2 50 FOSTER (Gen. J. G., U. S. A.) Submarine Blasting in Boston Harbor, Massachusetts. Removal ot Tower and Corwin Rocks. Illustrated with seven plates. 410, cloth 3 50 FOYE (Prof. T. C.) Chemical Problems. With brief State- ments of the Principles involved. Second edition, revised and enlarged. i6mo, boards 50 FRANCIS (JAS. B., C E.) Lowell Hydraulic Experiments: Being a selection from Experiments on Hydraulic Motors, on the Flow of Water over Weirs, in Open Canals of Uni- form Rectangular Section, and through submerged Orifices and diverging Tubes. Made at Lowell, Massachusetts. Fourth edition, revised and enlarged, with many new ex- periments, and illustrated with twenty-three copperplate engravings. 410, cloth = , 15 oo FREE-HAND DRAWING. A Guide to Ornamental Figure and Landscape Drawing. By an Art Studeiu. l8mo, boards go GILLMORE (Gen. Q. A.) Treatise on Limes, Hydraulic Ce- ments, and Mortars. Papers on Practical Engineering, U. S. Engineer Department, No. 9, containing Reports or numerous Experiments conducced in New York City during the years 1858 to 1861, inclusive. With numerous illustra- tions. 8vo, cloth 4 OO Practical Treatise on the Construction of Roads, Streets, and Pavements. With 70 illustrations. I2mo, cloth 2 OO Report on Strength of the Building Stones in the United States, etc. 8vo, illustrated, cloth 250 Coignet Beton and other Artificial Stone. 9 plates, views, etc. 8vo, cloth 2 50 GOODEVE (T. M.) A Text-Book on the Steam-Engine. 143 illustrations. I2mo, cloth V ? oo GORDON (J. E. H.) Four Lectures on Static Induction. lamo, cloth 80 6 D. VAN NOSTRAND'S PUBLICATIONS. GRUNER (M. L.) The Manufacture of Steel. Translated from the French, by Lenox Smith, with an appendix on the Bessemer process in the United States, by the translator. Illustrated. 8vo, cloth $350 xxALF-HOURS WITH MODERN SCIENTISTS. Lectures and Essays. By Professors Huxley, Barker, Stirling, Cope, Tyndall, Wallace, Rpscoe, Hvfgina, Lockyer, Youi.g, Mayer, and Reed. Being the University Series bound up. With a general introduction by Noah Porter, President of Yale College. 2 vols izmo, cloth, illustrated 2 50 HAMILTON (W. G.) Useful Information for Railway Men Sixth edition, revised anu enlarged 562 pages, pocket form. Morocco, gilt 200 HARRISON (W. B.) The Mechanic's Tool Book, with Prac- tical Rules and Suggestions for Use of Machinists, Iron- Workers, and others. Illustrated with 44 engravings. I2mo, cloth i 50 HASKINS (C. H.) The Galvanometer and its Uses. A Man- ual for Electricians and Students. Second edition. I2mo, morocco i 50 HENRICI (OLAUS). Skeleton Structures, especially in their application to the Building of Steel and Iron Bridges. With folding plates and diagrams, fcvo, cloth I 50 HEWSON (WM.) Principles and Practice of Embanking Lands from River Floods, as applied to the Levees of the Mississippi. 8vo, cloth 2 oo HOLLEY (ALEX. L.) A Treatiseon Ordnance and Armor, em- bracing descriptions, discussions, and professional opinions concerning the materials, fabrication, requirements, capa- bilitie, and endurance of European and American Guns, for Naval, Sea-Coast, and Iron-Clad Warfare, and their Rifling, Projectiles, and Breech-Loading ; also, results of experiments against armor, from official records, with an appendix referring to Gun-Cotton, H&oped Guns, etc., etc. 948 pages, 4Q3 engravings, and 147 Tables of Results, etc. evo, half roan 10 oo Railway Practice American and European Railway Practice in the economical Generation of Steam, including the Materials and Construction of Coal-burning Boilers, Combustion, the Variable Blast, Vapoiization, Circulation, Superheating, Supplying and Heating Fetd-wster ? etc., and the Adaptation of Wood and Coke-burning Engines to Coal-burning; and in Permanent Way, including Road-bed, Sleepers, Rails, Joint-fastenings, Street Railways, etc., etc. Witn 77 lithographed plates. Folio, cloth ..12 o HOWARD (C. R.) Earthwork Mensuration on the Basis of the Prismoidal Formulae. Containing simple and labor- saving method of obtaining Prismoidal Contents directly D. VAN NOSTRAND S PUBLICATIONS. 7 from End Areas. Illustrated by Examples, and accom- panied by Plain Rules for Practical Uses. Illustrated. 8vo, cloth $l 50 INDUCTION-COILS. How Made and How Used. 63 illus- trations. i6mo, boards 50 ISHERWOOD (B. F.) Engineering Precedents for Steam Ma- chinery. Arranged in the most practical and useful manner for Engineers. With illustrations. Two volumes in one. 8vo, clolh 230 JANNETTAZ (EDWARD). A Guide to the Determination of Rocks: being an Introduction to Lithology. Translated from the French by G. W. Plympton, Professor of Physical Science at Brooklyn Polytechnic Institute. I2mo, cloth.... i 50 JEFFERS (Capt. W. N., U. S. N.) Nautical Surveying. Illus- trated with 9 copperplates and 31 wood-cut illustrations. 8vo, cloth 500 JONES (H. CHAPMAN). Text-Book of Experimental Or- ganic Chemistry fo- Students. i8mo, cloth I oo JOYNSON (F. H.) The Metals used in Construction: Iron, Steel, Bessemer Metal, etc., etc. Illustrated. iamo, cloth. 75 Designing and Construction of Machine Gearing. Illus- trated 8vo, cloth , 2 oo KANSAS CITY BRIDGE (THE). With an account of the Regimen of the Missouri River, and a descnption of the methods used for Founding in that River. By O. Chanute, Chief-Engineer, and George Morrison, Assistant-Engineer. Illustrated with five lithographic views and twelve plates of plans. 410, cloth 6 OO KING (W. H.) Lessons and Practical Notes on Steam, the Steam-Engine, Propellers, etc., etc , for young Marine En- gineers, Students, and others. Revised by Chief-Engineer J. W. King, U. S. Navy. Nineteenth edition, enlarged. 8vo, cloth 2 oo KIRKWOOD (JAS. P.) Report on 'the Filtration of River Waters for the supply of Cities, as practised in Europe, made to the Board of Water Commissioners of the City of St. Louis. Illustrated by 30 double-plate engravings. 410, cloth 1500 LARRABEE (C. S.) Cipher and Secret Letter and Telegra- phic Code, with Hogg's Improvements. The most perfect secret code ever invented or discovered. Impossible to read without the key. i8mo, cloth I oo LOCK (C. G.), WIGNER (G W.), and HARLAND (R. H.) Sugar Growing and Refining. Treatise on the Culture of Sugar- Yielding Plants, and the Manufacture and Refining of Cane, Beet, and other sugars. 8vo, cloth, illustrated 12 oo 8 D. VAN NOSTRAND'S PUBLICATIONS. LOCKWOOD (THOS. D.) Electricity. Magnetism, and Elec- tro-Telegraphy. A Practical Guide for Students, Operators, and Inspectors. 8vo, cloth , $2 s,o LORING (A. E.) A Hand-Book on the Electro-Magnetic Tele- graph. Paper boards 50 Cloth 75 Morocco I oo MACCORD (Prof. C. W ) A Practical Treatise on the Slide. Valve by Eccentrics, examining by methods the action of the Eccentric upon the Slide-Valve, and explaining the prac- tical processes of laying out the movements, adapting th* valve for its various duties in the steam-engine. Second edi- tion Illustrated, ato, cloth 250 McCULLOCH (Prof. R S.) Elementary Treatise on the Me- chanical Theory of Heat, and its application to Air and Steam Engines. 8vo, cloth 3 50 MERRILL (Col. WM. E , U. S. A.) Iron Truss Bridges for Railroads. 1 he method of calculating strains in Trusses, with a careful comparison of the most prominent Trusses, in reference to economy in combination, etc., etc. Illustrated. 4to, cloth ; 500 MICHAELIS (Capt. O. E., U. S. A.) The Le Boulenge Chronograph, with three lithograph folding plates of illus- trations. 410, cloth 3 O MICHIE (Prof. P. S.) Elements ot Wave Motion relating to Sound and Light. Text-Hook for the U.S. Military Acade- my. 8vo, cloth, illustrated 5 MINIFIE rWM.) Mechanical Drawing. A Text-Book of Geo- metrical Drawing for the use of Mechanics and Schools, in which the Definitions and Rules of Geometry are familiarly explained ; the Practical Problems are arranged, from the Illustrated with over 200 diagrams engraved on steel. Ninth edition. With an Appendix on the Theory and Application of Colors. 8vo, cloth 4 oo "It is the best work on Drawing that we have ever seen, and is especially a text-book of Geometrical Drawing for the use of Me- chanics and Schools. No youn? Mechanic, such as a Machinist, Engineer, Cabinet-maker, Millwright, or Carpenter, should be with- out it." Scientific American. . Geometrical Drawing. Abridged from the octavo edi- tion, for the use of schools. Illustrated with forty-eight steel plates. Fifth edition. i2mo, cloth 2 oc U. C. BERKELEY LIBRARIES 44. -TURBINE WHEELS. No. 45. THERMODYNAMICS. T. P. Trov By Prof H. T. Eddy. BY t . Ji. No. Tl.-DYNAMICTIDECTjvix^^Y. By John Hopki J. A. Schoolbred and R. E. Day. TH1-J JNiVEFSTTY SERIES. 01-: THE PHYSICAL BASIS OF LIFE. By Prof. T. H. T rcTjET T PHYSICAL FORCES. By Prof. GEO RGB F. BARK^: , ?1.D., of Yale College. 36 pp. Paper Covers. Price 25c, III. AS REGARDS PROTOPLASM, in relation to Prof. Huxley's Physical Basis of Life. By J. HUTCHISON STIRLING, F.R.C.S. pp. 72. Price 25 cents. IV. ON THE HY PC "HI SIS OF EVOLUTION Physical and Ketay, */#ical. 1 Prof ^DVARD D. COPE, 12mo., 7P> pp. Papt r Cc ers. Fi^a *35 co ts. V. SCIENTIFIC _,1>DH?TSES: 1. Oa 'V tfe tnods and Tendencies rf Physical li<,i*e*i r i . {>; Ua?-e and Dubl. 3. 6 & the Scientific Che of , , A-/,,, nvtim. By Prof, JC-.N TYN^AI-L, F.R.S. i*Jm<. ?4 pp. .Oaper Covers. Pi if 6 2f cents. Flex Cioth. 5U cts. ^O. VI. NATJif M SELECTION AS /.PPLIED TO My .K. B^ AL: CED RUSSELL WALLACE. This ; t.Kita ,!) of the Development of Human ur ;' sr fc" .e law of selec uon ; (2 ) the limits of Nat- i ral Se . T^ as applied to man. 54 pp Price 25 cents. NO VII.- 31 J ECTBUM ANALYSIS. Three lee- tares by Profb. Roscoe, Huggics, and Locky,.r. Fine- ;| ly ill D.SI . 4ted. ''85: P.^-er Covers. Price 25 cents. Hnr^jhlp' 4 , 5i^j|L/x ^ s1ietc - hL oi " *^ present ^ta' . i <. . tC o}- Jii>>n d ^ sgsrih tbi ^ocJ - , with ^ observaticL- PY 7 f. C. A. YOUNCV 1 ^ , of Da mouth College. 5(5^,.., Paper Covert* K. < 3 2< NO. ix.- THE EARTH'A GPT .T MAGFET. ] A. H. MAY ^ Ph.D., of Stevens JustL'ite. A profo:mdl3 r iate T esting lecture on the subject of nil netLm. ?!3 pp. Paper Covers. Frice ^5 ce its. Fl| ible Oloth, 50 cents. tfO. X.M!"STERIES Ojb' r>1 HE VO JE A" EAR, By Pi of. O. N. ROOD, Columbia College, ^ York. Oii^ of the most interest! A ;^ leetu*",. on erer delive . . ^ Original disco yeri as, brilliant exo< mectu Beautifully illus. 38 pp. r a^oi Covers 25 <