Q C 
 
 y ;p )ARD OF EDUCATION, SOUTH KENSINGTON. 
 
 UC-NRLF 
 
 S5S 
 
 ATALOGUE 
 
 OF THE 
 
 SCIENCE COLLECTIONS FOR TEACHING 
 AND RESEARCH 
 
 IN THE 
 
 VICTORIA AND ALBERT MUSEUM, 
 
 5 
 
 SOUTH KENSINGTON. 
 
 PHYSIOGRAPHY, PART II. 
 
 METEOROLOGY, INCLUDING TERRESTRIAL MAGNETISM 
 
 LONDON: 
 
 PRINTED FOR HER MAJESTY'S STATIONERY OFFICE, 
 BY WYMAN AND SONS, LIMITED, FETTER LANE, E.G. 
 
 And to be purchased, either directly or through any Bookseller, from 
 
 KYRE & SPOTTISWOODE, EAST HARDING STREET, FLEET STREET, E.G. ; o? 
 
 JOHN MENZIES & Co., ROSE STREET, EDINBURGH, and 
 
 90, WEST NILE STREET, GLASGOW ; or 
 HODGES, FIGGIS, & Co., Limited, 104, GRAFTON STREET, DUBLIN. 
 
 1900. 
 Price Four Pence Halfpenny, 
 
EXCHANGE 
 
BOARD OF iDFCA1IO^(|0UTH , KENSINGTON. 
 
 CATALOGUE 
 
 OF THE 
 
 SCIENCE COLLECTIONS FOR TEACHING 
 AND RESEARCH 
 
 IN THE 
 
 VICTORIA AND ALBERT MUSEUM, 
 
 \\ 
 
 SOUTH KENSINGTON. 
 
 PHYSIOGRAPHY, PART II. 
 
 METEOROLOGY, INCLUDING TERRESTRIAL MAGNETISM 
 f 
 
 LONDON: 
 PRINTED FOR HER MAJESTY'S STATIONERY OFFICE, 
 
 BY WYMAN AND SONS, LIMITED, FETTER LANE, E.G. 
 
 And to be purchased, either directly or through any Bookseller, from 
 EYRE & SPOTTISWOODE, EAST HARDING STREET, FLEET STREET, E.G. ; or 
 JOHN MENZIES & Co., ROSE STREET, EDINBURGH, and - 
 
 90, WEST NILE STREET, GLASGOW ; or 
 HODGES, FIGGIS, & Co., Limited, 104, GRAFTON STREET, DUBLIN. 
 
 1900. 
 Price Four Pence Halfpenny. 
 
PHYSIOGRAPHY, PART II. 
 
 METEOROLOGY, INCLUDING TERRESTRIAL MAGNETISM. 
 
 CONTENTS. 
 
 A. BAROMETERS Page 
 
 1. MERCURIAL - 1 
 
 2. ANEROID 6 
 
 B. THERMOMETERS 9 
 
 C. SUNSHINE- RECORDERS AND APPARATUS FOR MEASURING THE 
 
 HEATING EFFECTS OF THE DIRECT SOLAR RAYS 13 
 
 D. HYGROMETERS AND PSYCJHROMETERS 17 
 
 E. RAIN GAUGES AND EVAPORIMETERS 24 
 P. ANEMOMETERS 29 
 
 Gr. OZONOMETERS 38 
 
 H. MISCELLANEOUS METEOROLOGICAL APPARATUS - - 39 
 
 I, APPARATUS FOR THE OBSERVATION AND REGISTRATION OF THE 
 
 TERRESTRIAL MAGNETIC ELEMENTS - - - 43 
 
 456546 
 
A. BAROMETERS. 
 
 1. Mercurial. 
 
 1. Open Cistern Mercurial Barometer. Made by 
 Ramsden. (Imperfect.) 
 
 1893. Lent by the Royal Society. 
 
 In the description of the Royal Society's instruments by 
 Cavendish this barometer is referred to. See Philosophical 
 Transactions for 1776. 
 
 The internal diameter of the tube is given as about '25 inch, 
 the depression of the mercury from capillarity as '05 inch, and 
 the limit of the capacity error as about T ^ inch. 
 
 2. Open Cistern Mercurial Barometer. Made by 
 Newman under the direction of Sir H. Davy. 
 
 1893. Lent by the Royal Society. 
 
 Correction is made for capacity error by means of an iron 
 plunger which is of the same diameter as the interior of the 
 barometer tube, and is made to dip into the mercury of the 
 cistern. When the vernier is raised or lowered for taking 
 readings, the plunger is moved simultaneously, but in a contrary 
 direction, by the action of a pinion and a double rack. Thus 
 any decrease or increase in the amount of mercury in the cistern, 
 consequent on a rise or fall of the barometer, is compensated for 
 by the greater or less extent to which the plunger is immersed. 
 There is a thermometer attached to the case of the instrument, 
 its bulb being placed in the cistern. 
 
 3. Open Cistern Mercurial Barometer. Made by New- 
 man, under the direction of Dr. Daniell. (Imperfect.) 
 
 1893. Lent by the Royal Society. 
 
 The tube has a large bore (0'53 in.), hence the error from 
 capillarity is small. The correction to be applied for the 
 capacity of the cistern is T J^ of the distance above or below the 
 neutral point, which is given on the instrument as 30'576. A 
 scale, originally affixed to the case of the tube, enabled the 
 reduction of the readings to 32 F. to be readily effected. 
 
 The ivory float with marked stem shews the change of level 
 of the mercury in the cistern with the rise or fall of the 
 barometer. 
 
 The thermometer is marked with the Reaumur and 
 Fahrenheit scales, and its bulb dips into the mercury of the 
 cistern. See Meteorological Essays and Observations, by J. 
 Frederic Daniell, F.R.S., 18 C 23. Science Library, Victoria and 
 Albert Museum. 
 
 3179. Wt. 14948. 150010/00. Wy. & S. A 
 
3,-l.Vay 
 
 4. Marine Barometer by Bate. 
 
 1894. Lent by the Meteorological Council, 
 
 To prevent too rapid oscillations of the mercury during stormy 
 weather, the bore of the tube is contracted in the central part 
 and the whole instrument supported by a spring arm. 
 
 5. Mountain Barometers, old forms (2) by West and 
 Dollond respectively. 
 
 1893. Lent by the late G. J. Symons, F.R.S. 
 
 These instruments are contained in walking sticks, and have 
 screw adjustments for transferring the mercury from the cistern 
 to the tube, to render the barometers more portable. 
 
 6. Standard Barometer on Fortin's principle ; reads 
 by vernier to ^ J^ of an inch. 
 
 1885. Made by Elliott Bros. 
 
 The graduations in this instrument are made from the tip of 
 the ivory pointer in the cistern, which indicates the position of 
 the zero of the scale. 
 
 Before a reading is taken, the surface of the mercury is 
 brought into contact with this tip by means of a screw at the 
 bottom of the barometer, which, acting on an inner flexible base 
 of the cistern, raises or lowers the contents. Readings then 
 obtained give the height from the surface of the mercury in the 
 cistern, and capacity error is thus eliminated. 
 
 The barometer tube is supported by a bracket and supplied 
 with a ring and clamping screws, so that it can be readily fixed 
 in a vertical position. 
 
 7. Wallis's Barometer Adjunct for use with the 
 Fortin Barometer in adjusting the level of the mercury 
 in the cistern before taking a reading. 
 
 1893. Lent by L. Casella. 
 
 8. Portable Pediment Barometer, with rack-work 
 vernier to read to T ^ D in. Thermometer attached 
 to the front of the instrument with Fahrenheit and 
 Centigrade graduations. 
 
 1890. Lent by Elliott Bros. 
 
 9. Portable Pediment Barometer, with sliding vernier 
 to read to T^ in. 
 
 1888. Lent by P. Harris & Co. 
 
3 
 
 10. Stanley's Barometer, with tube of f in. bore. 
 Reads by rack-work vernier to T ^ in. A thermometer 
 is attached to the stand. 
 
 1893. Lent by W. F. Stanley. 
 
 11. Photograph of a Portable Barometer, made by 
 M. Herbst for the Topographical Department of 
 the Eussian General Staff, St. Petersburg, 1872. 
 
 1877. Given by the Pulkowa Observatory. 
 
 12. Drawing of a Normal Barometer and Manometer 
 of the Central Physical Laboratory, St. Petersburg, 
 after the design of Wild. Constructed by Brauer, 
 St. Petersburg. 
 
 1877. Given by Dr. H. Wild, Director of Central 
 Physical Observatory, St. Petersburg. 
 
 13. Barometer, Diagonal (about 1750) Watkinsand 
 Smith, London. 
 
 1876. Lent by the Hydrographic Department of the 
 Admiralty. 
 
 In this barometer, the tube is bent a little over half way 
 along its length through an angle of about 80. By this method 
 of construction an open scale is obtained, as any changes in 
 barometric pressure would be indicated by larger spaces in an 
 inclined than in a vertical tube. 
 
 A graduated scale, corresponding to a rise or fall of 3 inches, 
 is placed at the side of the upper part of the tube ; there is also 
 an index, capable of movement along a stiff wire, running parallel 
 to the tube. 
 
 Mounted on the same board is an alcohol thermometer, with 
 its scale graduated in degrees Fahrenheit. There is also an 
 index fixed to this similar to the one mentioned above. 
 
 The space between these two instruments is filled up with a 
 card headed " A perpetual Regulation, of Time." From this the 
 Days of the Month, Zodiacal Signs, Sun's Right Ascension, Decli- 
 nation, and time of Rising and Setting, High Water at London 
 Bridge, and Phases of the Moon, can be found. 
 
 14. Glycerine Barometer. 
 
 E. 218. 1877. Made by Jas. B. Jordan. 
 
 This instrument is designed for the purpose of affording a 
 delicate " weather glass," indicating small changes of pressure by 
 large oscillations of a fluid column, at the same time preserving 
 
 3179. A 2 
 
4 
 
 all the accuracy of the mercurial barometer. The fluid used is 
 glycerine, in a maximum state of purity, which has a specific 
 gravity of T26, or about one- tenth that of mercury. It has the 
 advantage of giving a vapour of very low tension in the Torri- 
 cellian vacuum from its high boiling point, and is therefore free 
 from the masking effect of back pressure which interferes with 
 the indications of a water barometer. The fluctuations of the 
 column are observed in a glass tube of 1 inch sectional area, or 
 100th that of the cistern. The tube forming the body of the 
 instrument is an ordinary composition gas pipe, J in. diameter 
 and 27 feet long, placed in the well of the staircase, between the 
 upper and lower galleries. The exposed surface of the glycerine 
 in the cistern is protected by a layer of paraffin oil, in order to 
 prevent absorption of moisture from the atmosphere. 
 
 The divided scale on the right hand side is in inches and tenths 
 in absolute measure, while that on the left shows the equivalent 
 values reduced to a column of mercury. 
 
 15. Syphon Barometer, with spiral connecting tube of 
 small diameter containing an air bubble. If the baro- 
 metric pressure falls half an inch the barometer falls a 
 quarter of an inch. The bubble moves as many quar- 
 ter inches as the sectional area of the vertical tube is 
 greater than that of the connecting tube. 
 
 1885. Lent by the late Professor F. Guthrie, F.R.S. 
 
 16. Photograph of the Barometrograph constructed 
 in the latter part of the 18th century by Fontana. 
 
 1877. Given by the Royal Institute of" Studii 
 
 Superior i" Florence. 
 
 Felice Fontana, a native of Boveredo in the Tyrol, was the 
 first Director of the Royal Museum of Physical Science and 
 Natural History, founded in Florence by the Grand Duke Pietro 
 Leopoldo. 
 
 A float on the surface of the mercury of a large barometer 
 transmits its motion to a cylinder about 70 mm. in diameter, 
 and covered with paper. Every hour an impression is made 
 upon this paper by a steel point set in motion by a clock. The 
 point itself advances a certain distance at each impression, so 
 that its indications end by drawing on the paper a curve of 
 the barometrical oscillations. 
 
 17. Milne's Barograph. Made by West ; clock sup- 
 plied by Schoof. 
 
 1894. Lent by the Meteorological Council. 
 
 ^ The record is obtained by a float placed on the mercury of the 
 cistern of a syphon barometer and connected with the short arm 
 
of a horizontal lever, the long arm of which carries a pricker. 
 A small hammer, actuated by the clock train, drives this pricker 
 every hour against a paper which travels along to receive the 
 record, and the series of indentations thus made shews the 
 fluctuations in barometric pressure. The paper is ruled for 
 tenths of an inch, and estimations of smaller amounts can be 
 readily made owing to the long range afforded by giving the 
 greater length to the recording arm of the lever. 
 
 18. Kreil's Barograph, formerly in use at the Kew 
 Observatory, for registering the movement of the 
 barometer. 
 
 1876. Lent by the Kew Committee of the Roy at Society. 
 
 An instrument employed at the Kew Observatory in 1845, 
 for the purpose of registering automatically the height of the 
 barometer. It consists of a syphon barometer, having a float 
 resting upon the surface of the mercury in the open end of the 
 tube. Immediately above the tube a lever is fixed horizontally, 
 and a cord, wrapped round a sector on the short arm, passes 
 down and is attached to the float. The other end of the lever 
 carries an ordinary pencil, which, being struck every five 
 minutes by a hammer moved by a clock, makes a dot upon a 
 sheet of paper fixed to a frame drawn in front of it by clock- 
 work. 
 
 19. Ronalds' Photo -Barometrograph, for registering 
 photographically the changes in the height of the 
 barometer, formerly erected at the Kew Observa- 
 tory. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
 An instrument for registering the variation in the height of 
 the barometer upon a daguerreotype plate ; constructed in 1847 
 by Mr. Francis Ronalds, afterwards erected at the Kew Observa- 
 tory, and described by him in the British Association Report 
 for 1851. 
 
 The light from an argand lamp, after passing through a 
 condensing lens, falls on a narrow slit cut in a metal plate 
 attached to a barometer tube, the mercury in which, by rising 
 or falling, varies the length of the slit illuminated. 
 
 An achromatic combination of lenses, by Voigtlander, throws 
 a magnified image of the bright slit upon an aperture in the 
 case, past which a daguerreotype plate is moved slowly by 
 clockwork,, and so registers the changes in the height of the 
 barometer. 
 
 The barometer itself, together with the cistern, which is of 
 large area, is suspended from an arrangement of levers and 
 zinc rods, on the principle of the gridiron pendulum, in such 
 
a manner as to render the indications unaffected by fluctuations 
 of temperature. 
 
 An improved form of this instrument, in which the photo- 
 graphic image is impressed upon paper, is in use at many 
 observatories. 
 
 20. Barograph, Mercurial. 
 
 E. 5. 1878. Made by M. Redier, Paris. 
 
 This has a syphon barometer, with a float resting on the 
 surface of the mercury in the cistern. The movement of the 
 float, with fluctuations of air pressure, is transferred by means 
 of a clock train and levers to a pencil which gives a magnified 
 record on the paper of the revolving cylinder of the variations 
 in height of the mercury. The method of action of the clock 
 train and levers is similar to that of the Regulator of Electric 
 Currents by M. Redier, described in the catalogue of the 
 Physical Section. 
 
 % 
 
 21. Drawing of a Balance Barograph, with tempera- 
 ture compensation according to a design by Wild. 
 Constructed by Hasler of Berne. 
 
 1877. Given by Dr. H. Wild, Director of Central 
 Physical Observatory, St. Petersburg. 
 
 In this instrument the recording is effected, at intervals of ten 
 minutes, by electrical action. 
 
 22. Chrono-Barometer, designed by W. F. Stanley. 
 The rise of 1 in. of mercury in the Barometer Pen- 
 dulum accelerates the clock about 949 beats per day. 
 
 E. 82. 1886. Made and given by W. F. Stanley. 
 
 The rise or fall of the mercury raises or lowers the centre 
 of gravity of the pendulum, thereby causing an acceleration 
 or retardation of its swing, and the change is indicated by 
 the dials. The registration during a day or for any period 
 of time of a high or low number of oscillations would represent 
 a high or low average for the height of the barometer for that 
 time. 
 
 2. Aneroids. 
 
 23. Aneroid Barometer, 8 inch, showing the mechanism. 
 Marked as a weather glass. 
 
 E. 219. 1877. Made by R. Deutschbein, Hamburg. 
 
 In this form of aneroid the action depends upon the changes 
 that take place, as the atmospheric pressure varies, in the form of a 
 
thin metallic vessel which is partially exhausted of air. This vessel 
 has its surface corrugated in concentric circles to make it yield 
 more easily to external pressure, and is furnished with a system 
 of springs, levers, &c., by which the movements of the surface, 
 resulting from variations in air pressure, cause an index to travel 
 round a dial. 
 
 24. Aneroid Barometer, 8 inch. Marked as a weather 
 glass. Visible movement. 
 
 1893. Lent by L. Casella. 
 
 Similar in principle to No. 23, but differs somewhat in the 
 mechanism by which the movements of the surface of the 
 metallic vessel are conveyed to the index. 
 
 25. Aneroid Barometer, 4J inch. Marked as a 
 weather glass. 
 
 1875. Lent by F. Barton & Co. 
 
 26. Aneroid Barometer, 5 inch, with altitude scale to 
 4,000 feet. For the use of surveyors. 
 
 1893. Lent by W. F. Stanley. 
 
 27. Aneroid Barometer (Field's Engineering), 2 inches 
 diameter ; reads to 4,500 feet. 
 
 1893. Lent by L. Casella. 
 
 This aneroid can be adjusted for changes in the density of the 
 air arising from variations of temperature. 
 
 It is set for observation by turning the altitude scale until the 
 number at the side of the case corresponding to the temperature 
 reading is brought into coincidence with the index above it. 
 
 28. Aneroid Barometer with dial of 1J metres. For 
 use at public buildings. 
 
 E. 3. 1878. Made by M. Redier, Paris. 
 
 The index of the dial is actuated by a small aneroid connected 
 through a lever with a clock having two trains which work in 
 reverse directions. When air pressure is stationary the fans of 
 the two trains are held fast by the cross piece of the levers, but 
 with a rise or fall of the pressure one or other of the fans is 
 released and its train thus freed to turn the index round the 
 dial. 
 
 29. Aneroid Barometer, 2 inch, compensated. 
 Altitude scale to 7,000 feet. 
 
 1893, Lent by L. Casella. 
 
8 
 
 30. Aneroid Barometer, 2| inch. Altitude scale to 
 8,000 feet. 
 
 1875. Lent by Pastorelli & Co. 
 
 31. Aneroid Barometers (2) ; with visible movement. 
 In these instruments the change of air pressure is 
 indicated by means of Bourdon's tubes. 
 
 E. 446 and 447. 1877. Made by E. Bourdon, Paris. 
 
 This is a modification, introduced by M. Bourdon in 1850, of 
 the ordinary form of aneroid, an elastic flattened tube, exhausted 
 of air and bent into the form of a circle, taking the place of the 
 metallic box. A tube of this form has the property of opening 
 out when air pressure is diminished and of closing up when 
 pressure is increased. This property is made use of to turn, with 
 the aid of suitable mechanical contrivances, an index round a 
 dial. 
 
 32. Sympiesometer for use at sea, 
 
 1893. Lent by L. Casella. 
 
 This is a Boyle's tube with bulbs at its extremities. It contains 
 a volume of hydrogen in the upper part of the longer branch, 
 and a liquid in this case coloured sulphuric acid in the lower 
 part and in the shorter branch. 
 
 Air has access to the lower bulb, and by the aid of its pressure 
 on the surface of the liquid both the weight of the column of 
 liquid and the pressure of the gas in the longer branch are 
 balanced. With a change of barometric pressure equilibrium is 
 disturbed, and a variation in the heights of the liquid in the two 
 branches takes place. Correction for temperature being made, 
 the height of the barometer can be found from the height of the 
 column in the longer branch. 
 
 In the sympiesometer, correction for temperature is effected 
 mechanically by a sliding scale to represent inches. This scale is 
 moved along the temperature graduations till its index is in line 
 with the number which corresponds with the reading given by 
 the thermometer; the graduation on the sliding scale in line 
 with the top of the column of liquid will then show the height 
 of the barometer. 
 
 The tube of the sympiesometer exhibited has its bore con- 
 tracted in the lower part to lessen the oscillations of the liquid in 
 stormy weather. 
 
 Hydrogen is used in preference to air for the contained gas as 
 giving a more open scale. 
 
 The revolving disc at the bottom of the case can be set to 
 record the pressure at each observation. 
 
B. THERMOMETERS. 
 
 33. Photographs of Old Thermometers ; a small 
 alcohol thermometer, with Florentine scale, and four 
 larger ones by Micheli clu Crest (1754). 
 
 1877. Given by Prof. Hagenbach-Bischoff, Director, 
 The Physical Institute in the Bernoullianum, 
 Basle. 
 
 In these alcohol thermometers, zero indicates the temperature 
 of the cellar under the Observatory of Paris, and 100 the 
 boiling point of water. 
 
 34. Rutherford's Maximum and Minimum Thermo- 
 meters. 
 
 1893. Lent by the Royal Meteorological Society. 
 
 These instruments, the invention of Dr. Rutherford, were 
 first described in the Transactions of the Royal Society of 
 Edinburgh for 1794. 
 
 35. Old Mercurial Thermometer by Adams of Fleet 
 Street. Scale 14 in. long, graduated from - 30 to 700 F. 
 The melting points and boiling points of various sub- 
 stances are shewn on the scale. 
 
 1893. Lent by the late G. J. Symons, F..R.S. 
 
 36. Old Mercurial Thermometer by Dollond. Scale 24 
 in. long, in two parts, graduated from 20 to 535 F. 
 
 1893. Lent by the Royal Society. 
 
 37. Old Mercurial Standard Thermometer by Trough- 
 ton and Simms. Brass divided scale, 15 in. long, 
 graduated from zero to 215 F. 
 
 1893. Lmt by the Royal Society. 
 
 38. BalloonThermometer.graduated from 10tol05F. 
 Made by L. Casella. 
 
 1 894. Lent by the Meteorological Council. 
 
 This thermometer was constructed with a view to extreme 
 sensitiveness, in order to obtain with it accurate records of the 
 temperatures of the layers of air through which a balloon might 
 be rapidly passing. 
 
 For this object the bulb, which is long and of narrow bore. 
 
10 
 
 was made of thin glass, and mounted fully exposed, to allow the 
 air free access to all sides of it. 
 
 Its delicacy of construction, however, renders this form of 
 thermometer very liable to damage from the bumping which 
 sometimes accompanies balloon descents, 
 
 39. Negretti and Zambra's Mercurial Minimum Ther- 
 mometer. (Imperfect.) 
 
 1893. Lent by the late G. J. Symons, F.R.S. 
 
 These instruments are made of more than ordinarily wide 
 bore, to allow a steel index pointed at both ends to move freely 
 in the tube. 
 
 When set for observation, the thermometer is put in an 
 upright position, and the index brought to the level of the 
 mercury. 
 
 With any contraction of the column, the index falls by its own 
 weight, but with expansion, it is forced to the side of the tube, 
 the mercury passing beyond it. The upper end of the index 
 indicates the temperature. 
 
 The magnet serves to bring the index into position ; the 
 bulb at the top of the tube is used as a receptacle for the 
 mercury, when, owing to the weight of the column, there is a 
 difficulty in moving the index. 
 
 40. Six's Thermometer, named after its inventor, Mr. 
 Six of Canterbury ; for registering extremes of tem- 
 perature. 
 
 1876. Lent by Dring and Page. 
 
 The indexes are little pieces of steel coated with glass which 
 are enabled to retain their position in the tube by means of a 
 hair fastened round them, and by this means the highest or 
 lowest temperature is recorded. 
 
 41. Six's Thermometer with a very flat bulb which 
 renders it as sensitive as an ordinary mercurial 
 thermometer. 
 
 1876. Lent by 8. G. Denton. 
 
 42. Phillips's Maximum Thermometer. 
 
 1893. Lent by L. Casella. 
 
 In these instruments the index is a portion of the mercurial 
 column which is separated from the remainder by an air bubble. 
 Of the two ends of the index, the further from the bulb indicates 
 the temperature. 
 
11 
 
 43. Minimum Thermometer, with flat bulb. 
 
 1876. Lent by Bring and Fage. 
 
 Constructed with a view to overcome the great drawback to 
 the use of spirit thermometers, sluggishness. The bulb is made 
 flat, so as to expose as large a surface as possible, while the glass 
 is made as thin as is consistent with a non-barometric action. 
 
 44. Minimum Alcohol Thermometer on Rutherford's 
 principle. 
 
 1893. Lent by L. Casella. 
 
 45. Minimum Alcohol Thermometer on Rutherford's 
 principle. Bulb forked to increase the sensitiveness of 
 the instrument. 
 
 1893. Lent by L. Casella. 
 
 46. "Thermometre Fronde." 
 
 1893. Lent by L. Casella. 
 
 The air temperature is ascertained by placing the thermo- 
 meter in its perforated case and swinging it round the head by a 
 cord. By this method more accurate results are obtainable than 
 by exposure on stands of ordinary construction. 
 
 Some notes by R. H. Scott on the use of the Thermometre 
 Fronde on board ship will be found in the Royal Meteorological 
 Society's Quarterly Journal, 3, 1877. 
 
 47. Symons's Earth Thermometer, and tube for 
 obtaining temperatures to any depth. 
 
 1893. Lent by L. Casella. 
 
 A pointed iron tube is driven into the ground to the depth 
 whose temperature is being ascertained, and a slow action 
 thermometer is suspended within it by a chain attached to the 
 copper cap of the tube. The thermometer, which reads from 25 
 to 95 F., is protected by a box- wood casing. 
 
 The usual sizes for the tubes are 6 inches, 1 foot, 2 ft., 3 ft., 4 ft., 
 6 ft., 10 fc. 
 
 48. Balfour Stewart's Fluctuation Thermometer. 
 1876. Lent by the late Prof. Balfour Stewart, F.R.S. 
 
 This is formed of two tubes of different bores connected by a 
 bulb in the centre. When set in a horizontal position, an increase 
 of temperature causes the mercury in the wider tube to 
 move from the bulb towards the end, but with a decrease of tem- 
 perature the mercury in the narrower tube moves towards the 
 
12 
 
 bulb. Thus with all changes there is a movement of the mercury 
 in the direction of the extremity of the wide tube. 
 
 Attached to the stand is a scale in two parts, graduated from 
 to 180, by means of which the amount of fluctuation for any in- 
 terval of time can be ascertained. The thermometer can be set 
 for observation by standing it on end. See Balfonr Stewart's 
 Elementary Treatise on Heat 
 
 49. Chrono-Thermometer, for registering tempera- 
 ture cumulatively. The expansion of the mercury by 
 1 F. accelerates the clock about 17*5 beats per day. 
 
 E. 83. 1886. Given by W. F. Stanley. 
 
 The rise and fall of the mercury in the thermometer pendulum 
 raises or lowers its centre of gravity, thereby causing an accelera- 
 tion or retardation of its swing, and the change is indicated by 
 the dials. The registration during the day or for any period of 
 time of a high or low number of oscillations would represent a 
 high or low average for the height of the thermometer for that 
 time. 
 
 50. Thermometer Screen for one minimum thermo- 
 meter. In use at stations belonging to the Norway 
 Meteorological Institute. 
 
 1876. Lent by Prof. H. Mohn, Christiania. 
 
 Made of sheet iron with double walls, suspended on a cylindri- 
 cal rod intended to pass through the window frame. The rod 
 has a handle inside, so that the screen with the thermometer can 
 be turned for " setting " in the same way as a thermograph. 
 
 The double walls prevent the rising of the thermometer even 
 in direct sunshine to more than a few degrees above that caused 
 by the air. The minimum thermometer was made by R. Grave 
 of Stockholm, and the screen was executed after the design of 
 Prof. H. Mohn. 
 
 51. Thermometer Screen for meteorological stations 
 of the 2nd order. In use at the stations of the Norway 
 Meteorological Institute. 
 
 1876. Lent by Prof. H. Mohn, Christiania, 
 
 Made of sheet iron. To be mounted outside a window and 
 kept in shade The screen contains one psychrometer (dry and 
 wet bulb), one minimum thermometer (both instruments made by 
 R. Grav r e of Stockholm), and one hair-hygrometer (made by 
 Herman and Pfister of Berne). The screen is constructed after 
 the designs of Prof. H, Mohn, 
 
13 
 
 52. Thermometer Screen for one single thermometer, 
 for obtaining the temperature of the air. In use at 
 stations belonging to the Norway Meteorological 
 Institute. 
 
 1876. Lent by Prof. H. Mohn, Christiania. 
 
 Made of sheet iron. To be mounted outside a window or on a 
 wall, and kept in shade. With thermometer, made by R. Grave 
 of Stockholm. Screen constructed after the design of Prof. H. 
 Mohn. 
 
 0. SUNSHINE-RECORDERS AND APPARATUS FOR MEASUR- 
 ING THE HEATING EFFECT OF THE DIRECT SOLAR RAYS. 
 
 53. The original Photographic Sunshine-recorder of 
 Prof. H. McLeod. 
 
 1885. Lent by Prof. H. McLeod, F.R.S. 
 
 The sunlight is reflected from the silvered bulb of a flask, 
 and then focussed by means of a double convex lens on the sen- 
 sitized paper contained in the camera. In taking observations, 
 the axis of the apparatus must be set parallel to the earth's, and 
 the recording paper adjusted in accordance with the sun's 
 declination. 
 
 This adjustment of paper is necessitated by alteration in the 
 position of focus caused by reflection of the sun's rays from 
 different parts of the bulb of the flask. 
 
 The record obtained is circular, and is marked for the hours, 
 when the position of the meridian line has been determined, by 
 drawing radial lines at intervals of 15. Ferroprussiate paper 
 is used for the records, which are fixed by placing them in water 
 for a few minutes. Examples of the traces, divided for the 
 hours, are exhibited with the instrument. For fuller informa- 
 tion, see Journal of the Physical Society, Vol. vi. p. 216. 
 
 (The McLeod Sunshine-recorder sold by dealers is a modified 
 form of that exhibited.) 
 
 54. Jordan's Single-cylinder Photographic Sunshine- 
 recorder. 
 
 1886. Made by Negretti and Zambra. 
 
 The dark chamber is a brass cylinder, mounted on a bronzed 
 stand having a latitude arc, and pierced with a small rectangular 
 aperture on each side to admit the sun's rays to act on the 
 sensitized paper within the cylinder. 
 
 When set for latitude and placed in the meridian, the mid-day 
 
14 
 
 rays of the sun passing through the two apertures should fall at 
 equal distances on each side of the 12 o'clock line of the 
 recording paper. 
 
 These papers are divided into hours and sixths, the cyanotype 
 process being used in sensitizing them. The record is fixed by 
 rinsing the chart in cold water for a few minutes. For fuller 
 description, see Quarterly Journal of Ike Royal Metereological 
 Society. Vol. xii. 
 
 55. Jordan's Twin-cylinder Sunshine-recorder. 
 1893. Made by Negretti and Zambra. 
 
 This is an apparatus for photographic registration and is an 
 improvement on Jordan's Single-cylinder Instrument. 
 
 It consists of two half-cylinders or chambers of brass, set with 
 their axial planes outwards at an angle of 60, and hinged to a 
 stand having a latitude arc. 
 
 At the sides are two small rectangular apertures, one in the 
 centre of each of the axial planes, for admitting the sun's rays. 
 One half cylinder is for the morning record, the other for the 
 afternoon. 
 
 When correctly placed in the meridian, the sun's rays at noon 
 should fall on the 12 o'clock line of the sensitized chart in each 
 chamber. 
 
 Amongst the advantages claimed for this instrument over the 
 Single-cylinder Recorder are : 
 
 1. The trace obtained is in a straight line at right angles to 
 the hour lines, and so can be readily measured. 
 
 2. The aperture is so placed in each chamber as to allow of 
 the admission of earlier and later rays. 
 
 3. The amount of diffused light admitted to the chamber is 
 reduced by having but one aperture. 
 
 56. Photographic Sunshine-recorder, designed by Dr. 
 J. Maurer. 
 
 1893. Made and lent by Th. Usteri-Reinacher, Zurich. 
 
 The dark chamber is a bronzed brass cylinder, with its top 
 oblique to the axis and pierced with a small rectangular hole. 
 The bottom of the cylinder is removable to allow of the 
 adjustment inside of the recording sensitized papers. A small 
 latitude arc is placed under the instrument and the whole is 
 supported on an iron stand. 
 
 If the cylinder be fixed with its axis adjusted for latitude 
 and its North-South line in the meridian, the sun's rays passing 
 through the hole at the top, leave a record of their course 
 on the sensitized paper. As this record is approximately a 
 straight line at right angles to the hour lines engraved on the 
 paper, the duration of sunshine for any particular day can be 
 readily ascertained. 
 
 The record should be placed in "water, after its removal from 
 the cylinder, for about ten minutes, in order to fix it. 
 
15 
 
 57. Campbell's bowls for sunshine recording, used at 
 the Kew Observatory 21st December, 1891 to 21st 
 June, 1892, and from June, 1892 to December, 1892. 
 
 1894. Lent by the Meteorological Council. 
 
 These bowls are made of mahogany, of as nearly as possible 
 the same quality, In the bowl is placed a spherical water or 
 glass lens, whose centre coincides with the centre of the cavity 
 in which the lens rests. 
 
 Through the concentration of the sun's rays, a record of its 
 course is burnt into the wood, the position of the record rising or 
 falling in the bowl according to the sun's declination. 
 
 A measurement of the amount of wood burnt out during 
 different periods gives the relative heating powers for these 
 periods. 
 
 The bowls exhibited show the difference in the sun's heat lor 
 the two halves af the year falling between the solstices. 
 
 58. Herschel's Actinometer. Used by Sir J. Hooker 
 in his investigations when travelling in the Himalayas. 
 
 E. 35. 1890. Given by Sir J. Hooker, F.R.S. 
 
 The Actinometer consists of a glass cylinder filled with 
 ammonio-sulphate of copper, to one end of which is connected a 
 tube with an arbitrary scale of equal parts, while to the other 
 end a screw is fitted which may be used to adjust the liquid in 
 the tube, the whole forming a delicate thermometer. Through 
 the screw is passed to the inside of the cylinder the bulb of an 
 alcohol thermometer, by which the temperature of the liquid is 
 ascertained. 
 
 By noting on the arbitrary scale the height of the liquid 
 immediately before and after the instrument has been exposed 
 to the sun's rays for a definite time, and also making similar 
 observations when it is set in the shade, a measure of the 
 heating effect of the sun's rays can be obtained. This can be 
 corrected for the unequal expansion of the liquid with the 
 aid of readings given by the alcohol thermometer. 
 
 Sir J. Herschel recommends that not less than three sun 
 observations and two intermediate shade observations should 
 be taken, the calculations to be made from the means of the 
 readings in each position. 
 
 The unit of solar radiation adopted in the ultimate reduction 
 of the observation was the Actine. By this is understood, 
 " that intensity of solar radiation which, at a vertical incidence 
 and supposing it wholly absorbed, would suffice to melt one 
 millionth part of a metre in thickness from the surface of a sheet 
 of ice horizontally exposed to its action per minute of mean 
 solar time." See the article on Meteorology by Sir J. Herschel 
 in the Admiralty Manual of Scientific Enquiry. Science 
 Library, Victoria and Albert Museum. 
 
16 
 
 59. Padre Secchi's apparatus for measuring the com- 
 parative intensity of the heat of the sun's rays. 
 
 1893. Lent by L. Casella 
 
 This is a metal vessel in the form of a hollow cylinder, 10 
 inches in length and of three inches diameter, filled with a liquid 
 at any desired temperature. 
 
 In three tubulures are inserted thermometers, the bulbs of two 
 of which are immersed in the liquid ; the bulb of the third is 
 passed through the vessel to the hollow centre of the cylinder. 
 
 For observation, the apparatus is placed on a stand and set so 
 that the sun's rays fall on the exposed bulb. It was found- that 
 the increase in the reading shewn by the thermometer was 
 independent of the temperature of the liquid surrounding it. 
 
 60. Pouillet's Pyrheliometer. Improved form Made 
 by L. Casella. 
 
 1893 Lent by the Rev. F. W. Stoiv,- M.A. 
 
 This consists of a thermometer whose bulb is immersed in the 
 mercury contained in a small cylinder of known capacity and 
 area of base. 
 
 When used, the base of the cylinder is turned for a definite 
 number of minutes alternately to and from the sun, and means 
 of the thermometer readings in each position are taken. 
 
 From these means can be determined the number of degrees 
 that the temperature of the volume of mercury in the cylinder 
 has been raised by the heat of the sun acting on a known area 
 for a fixed time. 
 
 The base should bo set so that the sun's rays fall perpendicu- 
 larly on it, and a paper disc is supplied to show by the position 
 of the shadow of -the cylinder when this is done. 
 
 The Rev. F. W. Stow's improvement is the outer cylindrical 
 case to protect the thermometer tube from wind, and rays other 
 than direct. 
 
 See TyndaWs Heat considered as a Mode of Motion. Science 
 Library, Victoria and Albert Museum. 
 
 61. Stanley's Copper Pyrheliometer. 
 
 1893. Lent by W. F. Stanley. 
 
 The thermometer in this instrument has its bulb enclosed in 
 a 1-4 inch copper ball, whose surface has been oxidised by heating. 
 For observations it is supported on a black polished slate slab at 
 a distance of about 2 in. from the surface, the s]ab being inclined 
 at an angle of 45. 
 
 It was found that readings obtained with this form of instru- 
 ment were lower than with the ordinary solar radiation 
 
17 
 
 thermometer, but results obtained with similarly constructed 
 instruments were uniform. 
 
 See Quarterly Journal of the Royal Meteorological Society, 
 April, 1885. 
 
 62. Southall's Helio-pyrometer. 
 
 1893. Lent by L. Casella. 
 
 This consists of a box lined with black cloth cushions, which 
 contains a maximum thermometer with blackened bulb, and is 
 closed by a glass lid. 
 
 If set so that the sun's rays fall perpendicularly on this lid, 
 the difference of the readings of the thermometer and those 
 obtained from a thermometer exposed in the ordinary way in 
 the shade, will give a measure of the heating power of the sun, 
 allowance being made for loss of heat by reflection from the 
 surfaces of the glass. 
 
 Mr. Southall recommends 11.30 to 12.30 as the most suitable 
 time for observations to be made, as then no change in the 
 position of the box will be necessary. 
 
 The advantages claimed for this method of exposure over that 
 ordinarily adopted with solar radiation thermometers are that 
 there is no lowering of the readings by air currents and by the 
 cooling resulting from evaporation from the soil. 
 
 With the apparatus a small vessel in which water is boiled by 
 the sun's rays is occasionally used. 
 
 D. HYGROMETERS AND PSYCHROMETERS. 
 
 63. Oat-beard Hygrometer. In brass case 1^ in. 
 diameter. 
 
 E. 2. 1893. Given by F. C. Bayard. 
 
 In this, the twining and untwining of the beard of the oat is 
 made use of to turn an index round a graduated dial. 
 
 One end of a short length of the beard is fastened to a plate 
 at the bottom of the case of the hygrometer, and the other is 
 secured to the index. 
 
 With humidity, by the untwining of the beard, the index is 
 turned round the dial in the direction of a clock hand ; with 
 dryness, by the twining, the movement is reversed. 
 
 The brass case is perforated to allow the air to act freely ^on 
 the beard, and is furnished at the back with a knob by which 
 the index can be set. 
 
 The invention of the Oat-beard Hygrometer is attributed by 
 some to Robert Hooke, and a description of it can be found 
 in his " Micrographia" published in 1667. Science Library, 
 Victoria and Albert Museum, 
 
 3179. B 
 
18 
 
 64. Kater's Hygrometer. Made by Kobinson. 
 1893. Lent by the Royal Society. 
 
 This instrument, which was invented by Capt. Kater, depends 
 for its action on the twining and untwining, with increased dry- 
 ness or dampness of the atmosphere, of the beard of the grass 
 Andropoyon contortum. 
 
 The beard is fastened to the cleft end of the axis of the index of 
 the larger dial and continued in a line to the back of the case, 
 where it is secured to a pin, which can be adjusted to give the 
 necessary tautnesss. 
 
 The larger dial is graduated in 100 parts; the smaller dial 
 serves to shew the number of revolutions of the index of the 
 larger. 
 
 The case is perforated to allow of free access of air. 
 
 This hygrometer was considered to be more sensitive than 
 that of Saussure. 
 
 A similar instrument is fully described in the Encyclopaedia 
 Britannica, 7th Edition, in the article on Hygrometry. Science 
 Library, Victoria and Albert Museum. 
 
 65. Nicolle's " Aqueous Meter." 
 
 1893. Lent by B. C. Wainwright. 
 
 A thin slab of wood is cut across the grain and placed in a 
 frame furnished with a graduated arc and an index. 
 
 The axis of the index is attached to the wood in such a way 
 that the lengthening and shortening of the slab by increase or 
 diminution of humidity of the air causes the index to move along 
 the arc. 
 
 The graduations range from to 100, the limit at one end 
 being "Desiccation," at the other " Immersion." 
 
 66. Single-hair Saussure's Hygrometer, in brass frame 
 with silvered scale. 
 
 1880. Lent by J. J. Griffin and Sons. 
 
 In this, the movement of the index depends on the changes, 
 caused by variations in the humidity of the atmosphere, of the 
 length of a hair. One end of the hair is secured at the top of 
 the frame, the other is passed round a pulley and kept taut by 
 a small weight. As the hair shortens the index rises to indicate 
 dryness ; when it lengthens the weight causes the index to fall, to 
 show increased humidity. 
 
 67. Eight-haired Saussure's Hygrometer, by Richer of 
 Paris, formerly the property of Mr. Francis Ronalds, 
 and used by him at the Kew Observatory in 1843. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
19 
 
 68. Klinkerfues' Bifilar Hygrometer, with percentage 
 scale of humidity. 
 
 E. 221. 1877. Prof. Klinkerfues, Gottingen. 
 
 A wisp of hairs is passed through holes at each end of the 
 small cross bar of the spindle which carries the index, and the 
 ends of the wisp are made fast to a plate in the upper part of the 
 case of the instrument. A second wisp of less length is also 
 passed, but in a contrary direction to the first, through the same 
 holes, crossed, and the ends secured to a bar near the bottom. 
 
 By these means a twist is given to the hairs acting on the 
 spindle and the index made to take up a position dependent 
 upon the balance of the torsions of the upper and lower wisps. 
 
 With a change in the humidity of the atmosphere this balance 
 IP disturbed, and the change made apparent by the movement of 
 the index towards one or other of the extremes of the scale. 
 
 A thermometer and reduction disc are supplied, by which air 
 temperature can be obtained and dew point calculated. 
 
 For an explanation of the theory on which the construction of 
 this instrument is based, see Klinkermes' " Theorie des Bifilar- 
 Hygrometers mit gleichtheiliger Prozent-Scala." 
 
 69. De Luc's Whalebone Hygrometer. Made by 
 U. F. Hausmann. (Parts wanting.) 
 
 1893. Lent by the late G. J. Symom, F.R.S. 
 
 A narrow strip of whalebone, cut transversely to the fibre, is 
 connected at one end with the bottom of the frame of the instru- 
 ment, at the other with the larger of two pulleys which turn on 
 the same axis as the index of the graduated circle. 
 
 Attached to the smaller of the two pulleys is a spring which 
 serves to keep the strip of whalebone taut. On the lengthening 
 of the strip by increased moisture, the spring carries the index 
 round ; on its shortening for dryness, the index is drawn by the 
 strip in a contrary direction. 
 
 De Luc claimed that this instrument was more uniform in its 
 action than the Saussure Hair Hygrometer. 
 
 70. DanielFs Hygrometer, graduated from to 130 F. 
 E. 44. 1886. Made by W. Ladd. 
 
 This is an instrument for determining the "dew-point," or 
 the temperature at which the aqueous vapour contained in 
 the air begins to be condensed. It consists of a glass siphon 
 connecting two bulbs. One of the bulbs is blackened, and 
 contains ether, into which dips a small thermometer for the 
 determination of the temperature of the liquid. The instrument 
 is mounted on a stand bearing another thermometer to take 
 the temperature of the surrounding air. The empty bulb is 
 covered with muslin tied tightly round it. To use the hygro- 
 
 3179. B 2 
 
20 
 
 meter, a little ether is poured upon the muslin, and the cold 
 produced by its rapid evaporation condenses the ether vapour 
 inside the empty bulb as fast as it is formed in the blackened 
 bulb. By this action the temperature in the blackened bulb is 
 lowered. As soon as the dew-point is reached, aqueous vapour 
 from the air condenses as dew on the black bulb, and at that 
 instant the readings of the two thermometers must be observed. 
 
 71. Daniell's Hygrometer, graduated from 20 to 
 120 F. Silvered bulb. 
 
 1880. Lent by J. J. Griffin & Sons. 
 
 72. Jones's Hygrometer with bulb at an acute angle. 
 1893. Lent by the Royal Society. 
 
 This is a mercurial thermometer which can be used to obtain 
 both the temperature of the air and the dew point. For the 
 latter purpose the bulb has a black, enlarged, and somewhat 
 convex top on which the deposition of moisture is observed. The 
 other part of the bulb is covered with silk, and over this ether is 
 poured to lower the temperature of the mercury as in Daniell's 
 and other, condensation instruments. The thermometer, which 
 is about 4J inches long, is supported by a brass wire attached to 
 the case, and can be set at any desired angle. 
 
 A hygrometer of a somewhat similar pattern, but with the bulb 
 on an arm bent twice at right angles, to bring the bottom of the 
 bulb uppermost, is described in the Philosophical Transactions 
 of the Royal Society, 1826, p. 53. 
 
 73. Regnault's Hygrometer. 
 
 E. 40. 1893. Made by Elliott Bros. 
 
 Both the thermometer for air temperature and that for dew 
 point are contained in glass tubes partly enclosed in silver 
 thimbles, and are thus exposed under somewhat similar 
 conditions. 
 
 The tube for dew point observations is about half filled with 
 ether, through which air is drawn by an aspirator connected to a 
 pipe in the stand of the apparatus. 
 
 The lowering of temperature by the evaporation of the ether, 
 as the air passes through it, causes a deposition of dew on the 
 silver thimble, and iroin observations of the temperature at 
 which this deposit takes place the hygrometric state of the 
 atmosphere is determined in the usual way. 
 
 It^is claimed for this instrument that it is more accurate than 
 Daniell's, for the whole of the ether being kept at one 
 temperature by the agitation of the air, the indications of the 
 dew point thermometer are more reliable. The error in the 
 readings arising from the proximity of the observer can also be 
 avoided by the use of a telescope. 
 
21 
 
 74. Appold's Automatic Hygrometer. 
 
 1893. Lent by the Royal Society. 
 
 This apparatus was designed by the late J. G. Appold, F.R.S., 
 for the registration and regulation of the moisture in the 
 atmosphere of the rooms of his house, and was presented by 
 Mrs. Appold to the Royal Society. 
 
 The essential part consists of a glass tube with bulbs at its 
 extremities, which is connected to a brass rod, the whole turning 
 on a knife edge after the manner of a balance. Mercury fills 
 the tube and, in part, the bulbs, while in the latter also is a 
 small quantity of ether. Half the tube and one bulb are covered 
 with a paper which is kept constantly moist by water supplied 
 through a pipe at the top of the case. The knife edge is placed 
 immediately above the covered bulb, and beyond the latter is an 
 arm carrying a counterpoise, with which and a helical spring 
 the tube is balanced and adjusted. 
 
 With dryness of atmosphere evaporation takes place from the 
 paper, and the consequent lowering of the temperature causes a 
 contraction of the ether in the covered bulb. This is followed 
 by a transference of mercury from the uncovered to the covered 
 bulb under the influence of the pressure of the ether vapour in 
 the former. Equilibrium is thus destroyed, and the uncovered 
 bulb and tube rise, and, acting through a lever, open a valve 
 which allows water to pass through a tube to some heated pipes 
 covered with paper. 
 
 By evaporation from these pipes moisture is added to the air 
 till the required hygrometric condition is attained. 
 
 A pencil can be made to record on paper the movements of 
 the mercury tube, and this record can be checked by readings of 
 the Mason's hygrometer attached to the case of the instrument. 
 
 See Proceedings of the Royal Society, Vol. XV. Science 
 Library, Victoria and Albert Museum. 
 
 75. Geissler's Hygrometer. 
 
 E. 123. 1877. Made by Dr. H. Geissler, Bonn. 
 
 This is a modification of Daniell's instrument. The dew point 
 and the temperature of the surrounding air are obtained from 
 two separate thermometers mounted on one stand. 
 
 The bulb of the dew point thermometer is enlarged and 
 answers the purpose of the blackened or silvered bulb of Daniell's 
 instrument in making apparent the deposition of dew. On an 
 arm at right angles to the stem is a muslin-covered bulb by 
 means of which temperature can be lowered by evaporation. 
 
 Both thermometers are graduated to read to the fifth of a 
 degree. 
 
22 
 
 76. Hygrometer, horizontal form. Designed by the 
 late G. Dines. 
 1893. Made by L. Casella. 
 
 This is a condensation hygrometer, and used in a somewhat 
 similar way to that employed in taking observations with a 
 Daniell's instrument. 
 
 Ice and water, or cold water only, are put into the small 
 upright cistern, whence the water flows under the thermometer 
 to a small chamber in which rests the bulb of a thermometer. 
 The bulb and chamber are covered with a thin, smooth, black 
 glass plate. 
 
 As the water flows out of the pipe at the further extremity of 
 the hygrometer, the temperature of the black glass plate is 
 lowered to the dew point, and a film of moisture is deposited on 
 the plate. The temperature at which this deposition takes place 
 can be noted from the thermometer, and the dew point tempe- 
 rature thus ascertained. This known, and the temperature of 
 the surrounding air obtained, the hygrometric state of the 
 atmosphere can be calculated by the usual methods. 
 
 77. Hygrometer, vertical form. Designed by the 
 late G. Dines. 
 
 1893. Made by L. Casella. 
 
 In this form of instrument ether may be used, a receptacle for 
 its storage being supplied. Cold is produced by forcing 
 air through the ether. The deposition of moisture on the 
 black glass plate takes place as in the horizontal instrument. 
 
 78. Psychrometer, or dry and wet bulb hygrometer, 
 with thermometers graduated in tenths from - 28 to 
 
 46 C. 
 
 E. 122. 1877. Designed by Dr. H. Geissler, Bonn. 
 
 79. Psychrometer, with thermometers divided into 
 tenths from 20 to 50 C. 
 
 E. 172. 1877. 
 
 Made by Warmbrunn, Quilitz, & Co., Berlin. 
 
 80, Psychrometers (2), one in oak frame ; the other 
 with brass support and silvered scale, on circular 
 wood stand. 
 
 1860 & 1875. Lent by Pastor elli & Co. 
 
23 
 
 81. Reduction Disc for Psychrometers. 
 
 E. 222. 1877. Prof. Klinkerfues, Gottingen. 
 
 This is an arrangement for finding mechanically the dew point 
 temperature from the readings of the dry and wet bulb 
 thermometers. 
 
 It consists of a circular scale above which turns a cardboard 
 disc. From the scale is found the dew point temperature ; the 
 revolving disc is marked for dry bulb indications. 
 
 If the numbers on scale and disc which correspond to the wet 
 bulb reading be brought into coincidence, the dew point tem- 
 perature will be shown on the scale in line with that number on 
 the disc which represents the dry bulb reading. 
 
 The coloured part of the scale must be used when the air 
 temperature is below freezing point. 
 
 82. Psychrometer Scale, for determining the relative 
 and absolute moisture of the air, as well as the dew- 
 point, without calculation. 
 
 E. 223. 1877. Designed by Prof. Prestel, Emden. 
 
 83. Casartelli's Mill Hygrophant. Designed specially 
 for use in weaving and spinning mills. 
 
 E. 27. 1897. 
 
 Given by J. Casartelli & Son, Manchester. 
 
 By means of this instrument the hygrometric state of the 
 atmosphere can be ascertained directly by inspection. It consists 
 of a dry and a wet bulb thermometer, between which is placed a 
 case containing a scale to represent dry bulb readings and a 
 revolving cylinder marked with percentages of moisture for each 
 degree of difference of the two thermometers from 1 to 21. 
 
 This difference ascertained, the corresponding column of per- 
 centages as indicated by the number at the top, is turned to 
 the front, when, in line with the number representing the dry- 
 bulb reading, will be found the percentage of moisture in the 
 atmosphere at the time of observation. Saturation is represented 
 by 100. 
 
 84. Photomicrographs of Cotton Yarns (magnified 50 
 diameters) shewing the advantages of having in the 
 atmosphere of the spinning mill a due percentage 
 of humidity. 
 
 1897. Photographed and presented by W. W.Midgeley, 
 F.R.Met.Soc. 
 
24 
 
 85. Six's Thermometer with mercurial wet bulb 
 thermometer attached to the same stand, thereby 
 combining four instruments, namely maximum, minimum, 
 and present temperature thermometers, and hygro- 
 meter. 
 
 1876. Lent by S. G. Denton. 
 
 E. RAIN GAUGES AND EVAPORIMETEES. 
 
 86. Rain Gauge. In use at meteorological stations 
 belonging to the Norway Meteorological Institute. 
 
 1876. Lent by Prof. H. Mo Jin, Christiania. 
 
 Square surface, 15 x 15 centimetres, and height 60 centimetres ; 
 for catching snow ; the lower part protected against evaporation. 
 The rain (or melted snow) water is to be poured out of the 
 gauge through one of its upper corners, into a measuring cylin- 
 drical glass, divided to show the height of fallen rain in milli- 
 metres. The gauge is made of sheet iron, after the design of 
 Professor H. Mohn. The measuring glass was calibrated at the 
 Meteorological Institute in Christiania. 
 
 87. Rain Gauge. (The " Bradford Water Works.") 
 1893. Lent by L. Casella. 
 
 This is a five-inch gauge of 24 inches length, with a cylinder 
 above the funnel. 
 
 The cylinder is found of advantage in obtaining more accurate 
 measurements, especially in the case of snow fall. 
 
 The collecting pail will hold about 15 c. inches, and the 
 measuring jar is graduated to TOO c. in. 
 
 88. Rain Gauge. (The " Symons' Snowdon.") 
 1893. Lent by L. Casella. 
 
 A five-inch gauge in form somewhat similar to No. 87, but 
 17 in. long. 
 
 It is supplied with both collecting bottle and pail. The 
 measuring jar is graduated to '50 c. inch. 
 
 89. Rain and Snow Gauge. Designed by the late 
 Jas. Sidebottom ; made by J. H. Steward. 
 
 1893. Lent by the late Jas. Sidebottom, F.KMet.Soc. 
 
 This is an eight-inch gauge with its lower part surrounded by 
 a hot water jacket for melting snow. A funnel and tap are 
 
25 
 
 supplied, the one for filling the jacket, the other for withdrawing 
 the water from it. 
 
 The collecting can is protected by a box with glass front, which 
 encloses also the lower part of the gauge. The measuring jar is 
 graduated to -50 c. in. 
 
 90. Hellmann's German Rain Gauge. 
 
 1893. Lent by the late G. J. Symons, F.R.S. 
 
 Diameter of gauge 6J in. ; length, 1 ft. 4J in. Constructed to 
 be supported above the ground by means of a stake. 
 
 91. Eight-inch Rain Gauge, tin, japanned. Con- 
 structed upon the principle recommended by Glaisher. 
 With graduated measuring glass. 
 
 1860. Lent by Pastor elli & Co. 
 
 92. Rain Gauges (2) with funnels, pan, bottles and 
 measuring glasses. 
 
 1875 & 1876. Lent by F. Barton d Co. 
 
 93. Rain Gauge, consisting of bottle, measuring glass 
 and funnel. 
 
 1888. Lent by P. Harris & Co. 
 
 94. Rain Gauge, in copper and glass, with evaporating 
 pan, and measuring glass. 
 
 1865. Lent by F. Newton & Co. 
 
 95. Ronalds' Rain and Vapour Gauge, erected at the 
 Kew Observatory in 1843. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
 An instrument constructed at the Kew Observatory in 1843 
 by Mr. Francis Ronalds, for indicating a mean result from the 
 quantity of water which may have fallen between any two given 
 periods, minus the quantity of vapour which has evaporated in 
 the same time, on and from a circular" plane of one foot diameter. 
 It is described in the British Association Report for 1844. 
 
 It consists of two cylindrical vessels, connected by a tube, the 
 one being one foot in diameter, and open at the top, whilst the 
 other is 3 inches, and (with the exception of a small hole) 
 entirely closed by a cover, which carries a frame, holding a cir- 
 cular divided arc, with an index moving over it. The index is 
 
26 
 
 attached to a small pulley, over which a cord passes, having its 
 end fixed to the float in the cylinder. This, rising and falling 
 with the changes of water level, indicates the amount of rain or 
 evaporation on the metal scale. 
 
 
 
 96. Crossley's Self-registering Rain Gauge. 
 
 1893. Lent by L. Casella. 
 
 This is a ten inch square gauge, with oscillating bucket and set 
 of counters contained within the case. Each movement of the 
 bucket caused by the weight of water conveyed alternately to its 
 right and left halves by the gauge, is transmitted to the wheel 
 work of the counters by a lever acting between two projecting 
 plates on the bucket. 
 
 There are three counters for cubic inches, tenths and hun- 
 dredths respectively. 
 
 A pipette -shaped measure is supplied for testing the accuracy 
 of the registration. This measure will contain 5 cubic inches of 
 water, and its contents should, as the gauge has an area of 100 
 s(j. inches, advance the hand of the hundredths counter five 
 divisions. 
 
 97. Crossley Rain Gauge. (East India Co.'s pattern.) 
 1893. Lent by the late G. J. Symons, F.R.S. 
 
 In this the oscillating bucket and the wheels for recording its 
 movements are separated by a partition. The bucket, which is 
 constructed to tilt with every tenth of a cubic inch of rainfall, 
 actuates a pin wheel of somewhat large diameter. 
 
 The wheel is marked on its periphery by tenths from '1 to 5 
 cubic inches, and as the vibrations of the bucket turn the 
 wheel, the amount of rainfall within these limits can be read 
 from an opening in the side of the case. For higher readings, a 
 dial marked for 5 to 100 cubic inches, which is in connection 
 with the graduated wheel, is used. 
 
 98. Electrical Self-recording Rain Gauge. 
 
 1893. Lent by Yeates d Son, Dublin. 
 
 This gauge is similar in principle to Crossley's, but consists of 
 two distinct parts, the gauge and the recorder. 
 
 The former, which is fitted with a funnel, is of square section 
 and of 10 in. side. 
 
 The rain collected by the gauge passes by the funnel to an 
 oscillating bucket, so made and supported that the weight of a 
 cubic inch will cause it to tilt to discharge its contents. 
 
 This act of tilting is made use of to record the amount of 
 rain received. 
 
 The recorder has two dials, graduated to read to cubic inches 
 and hundredths, and is supplied with a train of wheels, the 
 
rnovement of which is controlled by the armature of a pair of 
 electro-magnets. 
 
 The gauge, the recorder and a battery being connected by 
 wires, the oscillation of the bucket completes the circuit, and the 
 electro-magnets, acting by their armature, move forward the 
 hand on the dial. 
 
 A record of each one hundredth of a cubic inch of rain is thus 
 obtained. 
 
 The advantage of this system is, that the recording dials may 
 be kept in the house, and thus preserved from damage by 
 exposure, while at the same time they may be readily consulted. 
 
 99. Watson's Evaporation and Rain Gauges. 
 
 1893. Lent by the late G. J. Symons, F.R.S. 
 
 These are circular copper vessels of 10 in. diameter which by 
 means of funnels deliver the rain into receivers set under the 
 stand on which they are placed. 
 
 The Evaporation Gauge differs from that for rain in having 
 within it an upright J in. tube, of 4-|- in. length, connected 
 with the funnel tube. In use, this gauge is filled to the level of 
 the top of this tube and placed at about 1 foot from the Rain 
 Gauge, both being set 3 ft. 6 in. above ground. 
 
 With dry weather evaporation causes the water to sink below 
 the level of the top of the tube, and this loss has to be replaced 
 before any water can pass into the receiver. If after a fall of 
 rain a measure be taken of the contents of the receivers of both 
 gauges, the difference will give the amount of water evaporated 
 from the surface ot the Evaporation Gauge during the dry days. 
 For a full description of 'these instruments, see Symonss British 
 Rainfall, 1869 and 1870. 
 
 100. Evaporation Gauge, designed by the late G. 
 Dines. 
 
 1893. Lent by W. H. Dines, B.A. 
 
 In making observation with this gauge, the cylindrical vessel 
 is placed in a large tank of water, so that its temperature may be 
 kept the same as that of a large body of water, and it is set with 
 its edge about half an inch above the surface. 
 
 With the cylinder is connected, by a pipe passing through the 
 tank, the rectangular graduated vessel which registers the level 
 of the water in the cylinder, and from the readings taken the 
 evaporation for any period of time can be found. The graduations 
 represent a depth ol O'l in. of water, but a depth of O'Ol in. can 
 be measured. 
 
 An overflow pipe is provided in case of rain. This should lead 
 into the measuring glass of a rain gauge. 
 
 As the evaporation diminishes when the water sinks below the 
 
28 
 
 level of the top edge of the cylinder, it is advisable for accurate 
 observations that the high level of the water should be main- 
 tained as far as possible. 
 
 101. Atmometer or Evaporimeter, for determining the 
 quantity of water evaporating from the surfaces of 
 waters as well as from different sorts of soil. 
 
 E. 224. 1877. Designed by Prof. Prestel, Emden. 
 
 102. Photograph of Registering Evaporimeter, ac- 
 cording to the last plan adopted by the inventor, Prof. 
 Ragona. 
 
 1877. Given by the Observatory of the Royal 
 
 University of Modena. 
 
 103. Apparatus for determining the evaporation from 
 different soils. 
 
 1876. Lent by Sydney B. J. SkertMy, F.G.S. 
 
 The apparatus consists essentially of an evaporimeter com- 
 posed of two vessels, the innermost of which receives the material 
 to be experimented upon, and the external one supplies water to 
 compensate for evaporation. Over this is a glass vessel which 
 receives the vapour given off by the material. The tempera- 
 ture, &c., are registered by a hygrometer and barometer in the 
 glass receiver, and the temperature of the soil by a ground 
 thermometer. Any given temperature can be obtained by means 
 of a platinum spiral heated by a galvanic battery. The evapori- 
 meter maintains the material in a natural condition so far as 
 regards temperature and moisture. Dry air is admitted into the 
 glass receiver, and the air with the evaporated water passes from 
 the top of the receiver into a train of drying tubes ; the current 
 of air is produced by an aspirator containing oil. By means 
 of this apparatus various soils, &c., can be brought under similar 
 conditions of temperature, &c., and the evaporations compared 
 for any temperature. The apparatus was especially designed to 
 determine the proper amount of water which should be dis- 
 charged by the artificial drainage system of the Fen Land. 
 
 104. Pickering's Evaporimeter. 
 
 1896. Lent by L. Casella. 
 
 The surface from which evaporation takes place is a piece of 
 blotting paper 100 mm. long by 50 mm. wide, which is set in a 
 frame above a small copper cylinder containing water. To keep 
 
29 
 
 this paper moist there is connected \vith it a narrow strip of the 
 same material, which dips into the water. 
 
 The amount of evaporation is read from a glass gauge at the 
 side of the cylinder, Avhich is graduated to directly express by a 
 number of cubic centimetres or cubic inches the evaporation 
 from each square centimetre or square inch of surface. 
 
 Full particulars and instructions for use are issued with each 
 instrument. 
 
 F. ANEMOMETERS. 
 
 105. Drawing and description of D'Ons en Bray's 
 Registering Anemometer, invented in the year 1734. 
 
 1892. Lent by R. B. Prosser. 
 
 This instrument is described in the Memoires de 1' Academic 
 des Sciences, Paris, for 1734. The plate exhibited is a 
 reproduction of one contained in the Memoires. 
 
 106. Photograph of an Anemometer, made by Niccolo 
 Cacciatore in 1832. 
 
 1877. Given l)y Prof. G. Cacciatore, Director of the 
 Royal University, Palermo. 
 
 107. Whewell's Self-registering Anemometer. 
 
 1893. Lent by the Astronomer Royal. 
 
 At the top of a case containing an upright cylinder marked 
 for the points of the compass is placed a horizontal circular 
 plate to which is attached a wind- vane and a fly of eight fans. 
 Connected to this plate, but contained in the case, is a vertical 
 screw of some 15 inches length, which is s,et parallel to the 
 cylinder and carries a nut to which is fastened a pencil. As the 
 horizontal circular plate, by the action of the vane, turns with 
 the wind, the pencil is carried round the cylinder, and the direc- 
 tion of the wind shown from the position of the pencil trace with 
 regard to the compass points. 
 
 In addition to being carried round, the pencil descends. For 
 the fly revolved by the wind, turns the vertical screw through the 
 action of the intervening wheelwork, and the pencil carrier is 
 lowered. The time being known during which the wind had 
 been blowing in any particular direction, the velocity of the wind 
 could be ascertained from the length of the trace made by the 
 pencil in its descent. 
 
 This instrument was used at Greenwich Observatory from 1843 
 till superseded by Robinson's Cup Anemometer in 1862. 
 
 For further information see Knight's English Cydopcedia, 
 e Library, Victoria and Albert Museum. 
 
30 
 
 108. Robinson's Cup Anemometer for registering the 
 velocity of the wind. Graduated in miles and tenths 
 to 505 miles. 
 
 1893. ' Lent by L. Casella. 
 
 The rotation imparted to the cups by the wind is transmitted 
 by a vertical rod to a horizontal spindle furnished with an end- 
 less screw which gears with two worm wheels set together behind 
 the dial. With the front wheel, which has 100 teeth, the dial 
 revolves ; with the hind wheel, which has 101 teeth, the long index 
 hand turns. 
 
 The dial is graduated on its inner circle for 1 to 5 miles, and a 
 reading is taken by the short stationary pointer above it. The 
 outer circle has 101 divisions to represent each 5 miles to 505, the 
 long hand serving as index. 
 
 This latter indication results from the different rates of 
 revolution of the two wheels. The dial wheel with its 100 teeth 
 and the index wheel of 101 teeth move in a direction the reverse 
 of the graduations. On each complete revolution of the former, 
 the latter falls one tooth behind, consequently the hand which 
 moves with it falls one space behind on the dial and thus is 
 apparently advanced one graduation. In this way the 5 miles 
 shown by a complete revolution of the dial are recorded. 
 
 109. Anemometer, with Robinson's Cups. Grad- 
 uated in miles and tenths to 500 miles. 
 
 1876. Lent by F. Barton & Co. 
 
 This is similar in principle to No. 108, but differs in the number 
 of teeth of the recording wheels. 
 
 110. Windmill Vane with electrical arrangement 
 whereby the direction of the wind at any instant may 
 be known by sound, constructed for stations of the 2nd 
 and 3rd order in connexion with the Meteorological 
 Office of the Dominion of Canada. 
 
 1876. Lent by G. T. Kingston, M.A., Toronto, Canada. 
 
 This instrument is designed to meet the case when a vane, if 
 suitably exposed, is too distant to admit of being connected by a 
 shaft with a dial in an accessible position. 
 
 Surrounding the step of the vane and attached to the bottom 
 of the box is a flat brass ring divided by radial lines into four 
 equal parts corresponding to, but not necessarily in the direc- 
 tion of, the four cardinal points, and separated by small equal 
 intervals. 
 
 The direction arcs (as they may be termed) are insulated 
 except as regards connexion with their screw cups. 
 
 Clamped to the spindle, and capable of adjustment in azimuth, 
 
31 
 
 is a circuit maker, which consists of an arm bearing a brass arc, 
 which is made to press on the flat brass ring. The length of 
 this arc is 45 + interval between the fixed arcs. The step of 
 the vane is connected by wire with one pole of a battery, and 
 the direction arcs with four screw cups in near proximity to a 
 brass plate fastened to the wall of the office, and so contrived 
 that, by aid of a plug, metallic connexion may be made at will 
 between the brass plate and any one of the four wires. 
 
 Finally, two wires from the poles of a small telegraph sounder 
 are attached to the brass plate and to the other pole of the 
 battery, and the apparatus is complete. 
 
 To ascertain the direction of the wind, notice by the sounder 
 which direction arcs or pair of arcs is placed in circuit as the 
 brass plate is connected by the plug with the four wires in 
 succession. 
 
 If, ior instance, N. only sounds, the direction is nearer to 
 N. than either to N.W. or N.E., unless it be N.N.W. or 
 N.N.E. exactly, but if N. and E. both sound the direction is 
 nearer to N.E. than either to N. or E., unless it be N.N.E. or 
 E.N.E. exactly. 
 
 The azimuth of the vane box need be governed only by 
 appearance and the position of the door. 
 
 To adjust the vane, unclamp the circuit maker, and insert a 
 pin (provided for the purpose) through holes at the middle 
 point of the circuit maker and the arc at the left of the box, 
 which arc may represent any one of the four cardinal points. 
 Turn the vane to that point, clamp the circuit maker, and 
 remove the pin, when the adjustment will be complete. 
 
 The apparatus works well with a single gravity cell, when 
 the vane is 60 ft. or more from the battery and sounder. 
 With a stronger battery it works well at the distance of a mile 
 or more. 
 
 111. Anemometer, with shaft whose length can be 
 adjusted to suit different stations, and with dial reading 
 to 10,000 miles, constructed for stations of the 2nd and 
 3rd order connected with the Canadian Meteorological 
 service. 
 
 1876. Lent by G. T. Kingston, M.A., Toronto, Canada. 
 
 This instrument is designed to reconcile adequate exposure of 
 the hemispheres with accessibility of the dial. 
 
 A short spindle bearing a small set of Robinson's cups is 
 connected with a horizontal cogged wheel resting on friction 
 rollers, and with a long shaft suspended from its centre, as in 
 the anemographs of the British observatories. It is contrived so 
 that the shaft may make 101 complete turns for 200 miles of wind. 
 
 The mode of recording the miles is as follows : 
 
 At the lower end of the shaft is an endless screw which acts 
 on the circumferences of two toothed wheels of equal diameter, 
 
32 
 
 turning in vertical planes about a common axis, and having 100 
 and 101 teeth respectively. 
 
 From the centre of the back wheel (that of 100 teeth) pro- 
 jects forwards a short hollow pin which incloses arid works on a 
 solid pin fixed to a support behind the back wheel. 
 
 The front wheel (that of 101 teeth) which turns on the above- 
 named hollow pin, and slides closely on the face of the back 
 wheel, has a graduated ring on its face, containing 100 divisions. 
 The outer ends of the lines of graduation indicate miles, while 
 the inner ends of the same lines, reckoned in the reverse order, 
 indicate hundreds. 
 
 The endless screw, at every turn, causes both wheels to 
 advance two teeth, so that for 100 miles the front wheel makes 
 one complete turn, or 100 divisions, while the back wheel makes 
 one complete turn and one tooth, and thus advances one divi- 
 sion with respect to the front wheel. The miles up to 100 are 
 shown by a fixed pointer, and the hundreds by a pointer attached 
 to the end of the hollow pin. 
 
 For fractions of a mile there is a contrivance which needs 
 adjustment at each observation. 
 
 A correction of 1 per cent, nearly should be subtracted from 
 the fractional parts. 
 
 112. Galton's Hand Anemometer. 
 
 1894. Lent by the Meteorological Council. 
 
 This is a small portable arrangement of Robinson's cups with 
 a dial which reads to 45 miles an hour. Attached to the frame 
 of the instrument is a sand glass which empties in two minutes. 
 The sand glass is connected at the back of this frame with the 
 dial, so that, on its being turned to allow the sand to run out, 
 the dial is put in gear with the screw of the spindle of the cups, 
 but on reversal of the glass is thrown out of gear. 
 
 In this way the velocity of the wind as indicated by a short 
 period of exposure is registered 
 
 This instrument was designed for the use of seamen in order 
 that the records kept in log books of the force of the wind 
 might be obtained by a uniform method of observation. 
 
 113. LiiicTs Water Anemometer, for indicating the 
 pressure of the wind. 
 
 1876. Lent by F. Darton & Co. 
 
 For observations the tube is filled with water until its level 
 reaches the zero mark on the scale. If it then be brought into 
 position with the mouth of the longer branch facing the wind 
 the water will rise in the shorter branch to an extent which will 
 vary with the wind's force. 
 
 From the difference of levels, with the aid of scales prepared 
 
33 
 
 for each instrument, the pressure and also the velocity of the 
 wind can be ascertained. 
 
 The wind vane serves to turn the mouth of the tube to the 
 wind, and also indicates direction. 
 
 Oscillations owing to rapid changes of pressure are lessened by 
 narrowing the tube connecting the two branches. 
 
 !. Lind's Anemometer, as modified by Sir W. Snow 
 Harris. 
 
 1 894. Lent, Inj the Meteorological Council. 
 
 In this modification a longer range is obtained by setting 
 part of the registering branch of the tube in a horizontal 
 position and nan-owing its bore. 
 
 Sir W. Snow Harris also furnished his instruments with a 
 plummet or other means of setting them in a vertical position. 
 
 115. Portable Anemometer, designed by W. H. Dines. 
 Adapted for use at sea, 
 
 1896. Lent In) L. Casella. 
 
 In observations the tube is drawn from its case, and, using the 
 latter as a handle, held in a vertical position with the nozzle as 
 nearly as possible facing the wind.- The height to which the 
 liquid rises in the tube then indicates by the scales the velocity 
 of the wind in miles per hour and its pressure in Ibs. on a square 
 foot, 
 
 Instructions for observers are issued with each instrument. 
 
 116. Balance Anemometer constructed by Mr. 
 Francis Eonalds at the Kew Observatory, in 1843, 
 for the purpose of measuring the force of the wind. 
 
 1876. Lent />// the Kew Committee of the Royal Society. 
 
 It consists of a light board, 1 foot square, fixed transversely 
 to a cross of wood, ^suspended by a brass axis passing through 
 its centre, and turning in glass " tubes in such a way that the 
 system can partially rotate in a vertical plane. The lower end 
 of the bar carrying the board is counterpoised, so as to keep the 
 surface of the board vertical, and a scale pan, hung to one end 
 of the horizontal bar of the cross, serves to receive the weights, 
 which are necessary to counterbalance the force of the wind 
 pressing on the board opposed to it, at any time. A small box, 
 covering the scale pan, serves to shield it from the action of the 
 wind. The instrument was, at the time of observation, placed 
 so that the surface of the pressure plate should stand at right 
 angles with the direction or the wind, as indicated by a vane. 
 
 3179, C 
 
34 
 
 117. Dynamic Anemometer for obtaining the hori- 
 zontal and vertical pressure of air in motion upon 
 inclined surfaces of different forms and angles. Manu- 
 factured by John Browning. 
 
 1876. Lent by the Council of the Aeronautical 
 
 Society of Great Britain. 
 
 This instrument is intended simultaneously to determine the 
 component parts i.e., how much pressure is due to the hori- 
 zontal, and how much to the vertical of a current of air when 
 directed against planes of different areas, and of different forms, 
 at angles varying from 15 to 90. The experiments are tabu- 
 lated in the Aeronautical Society's Report for the year 1871 
 (Hamilton & Co.). 
 
 118. Apparatus, designed by W. H. Dines, for deter- 
 mining the pressure of the wind on inclined surfaces. 
 
 1898. Lent by W. H. Dines, B.A. 
 
 This arrangement was constructed with a view to its being 
 revolved by some form of whirling machine ; and the results 
 obtained by a number of experiments with it, when connected to 
 the 56 feet diameter apparatus at Hersham, have been published 
 in the Proceedings of the Royal Society for 1891. 
 
 When carried round by the machine the pressure of the air 
 is balanced by the centrifugal force upon the two horizontal bars. 
 Of these the larger is adjusted by hand and clamped, but the 
 final adjustment is effected by the automatic action of the 
 smaller bar. 
 
 The pressure board is inclinable, and the lever which carries it 
 can be set at any angle with the help of the graduated arc, to 
 which, when used for observations, it is clamped. This arc is 
 connected by an arm and stud with the pivoted frame carrying 
 the two horizontal bars in such a way that the movement in a 
 vertical plane of the lever produces a movement in a horizontal 
 plane of the bars. This allows a pulley to act through a 
 crown wheel, pinion and rack on the smaller bar, which is 
 carried along until equilibrium is established between the wind 
 pressure and the centrifugal force. The pressure is then deter- 
 mined from the positions ot the bars, as shown by their 
 graduations. 
 
 119. Shot Wind-pressure Gauge. 
 
 1893. Lent by W. H. Dines, B.A. 
 
 This instrument measures the maximum wind pressure. The 
 upper receptacle is filled with shot, which fall through the hole 
 at the bottom, until the weight of the shot in the lower vessel is 
 equal to the pressure of the wind on the plate. 
 
 As soon as this occurs, the plate moves forward, and at the 
 
35 
 
 same time closes the opening. On the occurrence of a stronger 
 gust of wind, the plate is forced back, the hole is opened, and shot 
 fall through until equilibrium is again obtained. 
 
 To read the instrument, the plate is fastened in its forward 
 position by the catch on the upper receptacle, and the shot are 
 then withdrawn from the lower receptacle and weighed, or, 
 preferably, measured in a glass which has been tabulated once for 
 all. The weight of shot gives the maximum pressure which has 
 occurred since the instrument was last set. 
 
 120. Apparatus used for determining the distribution 
 of wind-pressure upon flat surfaces exposed perpen- 
 dicularly to the wind. 
 
 1893. Designed and lent by R. H. Garth, F.R.M.S. 
 
 The object of these experiments was to investigate the distri- 
 bution of wind-pressure over flat surfaces of different areas 
 exposed perpendicularly to the wind. 
 
 The plates used for the purpose were pierced with holes half an 
 inch in diameter, and situate at known distances from the centre, 
 where there was a similar hole called the " standard." 
 
 In making an observation all the holes except the " standard " 
 and one other which was the hole to be compared with the 
 standard were closed by means of plugs, inserted from the back, 
 and fitting flush with "the front surface of the board, so as to 
 make it continuous. Into the two open holes brass nozzles were 
 then inserted from the back ; and these were connected by india- 
 rubber tubes with two graduated glass tubes standing vertically 
 in a glass jar containing water. 
 
 The face of the board being presented to a current of air a 
 depression of the water was caused in the glass tubes ; and the 
 observation was made by noting the amount of this depression 
 in the two tubes at the same moment. 
 
 Experiments were made with square surfaces of 1, T2, 6'25 
 and 16-0 sq. ft. area respectively, and with a circular surface of 
 2 sq. ft. area. 
 
 From the mean results obtained, the distribution of pressure 
 over the surface was determined ; and it is shown graphically by 
 means of lines drawn upon diagrams representing the surface 
 experimented upon. 
 
 [For further particulars see the Quarterly Jov.rnal of the 
 Royal Meteorological Society, Vols. VIII. and IX.] 
 
 121. Howlett's Anemograph for registering the direc- 
 tion and force of the wind. 
 
 1893. Lent by Elliott Bros. 
 
 The sphere to receive the wind pressure and the pencil to 
 record it are connected by a brass rod, which acts as a lever 
 
 3179, 2 c 
 
36 
 
 having as fulcrum the gimbal support at the top of the case of 
 the recording slate. 
 
 According as light or heavy pressures have to be measured, 
 the sphere is raised or lowered on the rod, and its position and 
 that of the weight on the recording end of the rod serve with 
 the trace in determining the force of the wind in Ibs. per square 
 foot. 
 
 These instruments are constructed so that when the sphere is 
 in its lowest position to 20 Ibs. pressures can be shewn, Avhen 
 at its highest to 5 Ibs. and with the small weight at the top 
 to 21 Ibs. 
 
 The circle of the recording slate is divided from to 360 by 
 5 intervals, and the direction of the wind and the value of the 
 pressure are ascertained from the position and length of the 
 pencil trace. Specially constructed scales are issued for use with 
 each instrument. 
 
 122. "Self-recording Wind Components Integrator." 
 Constructed by P. Schultze, designed by Dr. Arthur 
 Von Oettingen, Professor at the Imperial University, 
 Dorpat (Russia). ^ 
 
 1880. Lent by the late W. Spottinvoode, F.R.S., ami 
 the late Warren de la Rue, F.R.S. 
 
 The wind moves a system of hemispherical cups, like Robin- 
 son's (which motion is replaced by clockwork for exhibition), 
 acting on a circular plate, whose velocity is ordinarily propor- 
 tional to the velocity of the wind. Four systems of sliding- 
 rollers rest on this plate, whose bearings can be moved round a 
 vertical axis, the principal planes of which imitate all variations 
 of a wind vane. Each sliding-roller can rotate about a hori- 
 zontal axis, but only in one direction, and after a half rotation 
 an electrical contact is made. A mechanism limits the contact 
 to a fraction of a second. When the contact is made, one of 
 four wheels, with number -types, is moved. Every half hour the 
 position of these four wheels is shown by printed numbers on a 
 strip of paper. The differences of those readings represent the 
 mean velocity of the wind from N., E., S., and \V. They are 
 converted into absolute values by means of a table. Different 
 mechanism adjusts the position of each sliding-roller. 
 
 123. Integrating Anemometer. Designed by Walter 
 Bailey, M.A , F.R.'S. 
 
 1889. Lent Inj the (Sort. Grant Committee, Roy. Soc. 
 
 This is somewhat similar to the Integrating Anemometer 
 of Dr. A. von Oettingen, the records being obtained from wheels 
 revolved by the friction of a plate turned by the wind. 
 
 There are two spindles, one to support the Robinson cups, 
 and transmit their movement to the circular plate on which 
 
37 
 
 the recording wheels rest, the other for the vane to change 
 the position on the plate of the two recording wheels in 
 accordance with the direction of the wind. That this change 
 may be readily effected, the wheels are connected to small 
 carriages which run between tram lines . on a plate placed 
 parallel to, and above that which revolves. 
 
 By the method of connection with the direction spindle, 
 one wheel turns when the wind is at either of the four chief 
 points of the compass; in intermediate directions, as N.E., 
 S.S.W., both are turned. 
 
 As the speed of the revolving plate is ordinarily proportional 
 to that of the wind, a measure can be obtained of the velocity 
 of the latter from the number of revolutions of the wheels. 
 The recording is effected by an electrical contact made at 
 each turn of the wheels, which allows a current to actuate 
 a set of counters. 
 
 These counters are contained in a box, and are connected 
 with the instrument by wires to the binding screws which 
 represent the N., S., E., and W. points. 
 
 The value of the records can be determined either by 
 measurement of the instrument or by direct experiment. 
 
 For a full description of this anemometer see Philosophical 
 Magazine, June, 1884. 
 
 124. Photograph of an Anemograph with Rain Gauge 
 annexed. A description of the instrument is shown 
 with the photograph. 
 
 1877. Given by Prof. Palmier I, Vesuvius 'Meteoro- 
 logical Observatory, Naples. 
 
 125. Anemometer consisting of inclined vanes, con- 
 tained in circular brass band, with registering apparatus. 
 Used in regulating the ventilation of mines. Diameter 
 21 in. 
 
 1875. Lent l>!) Pastoreili <& Co. 
 
 126. Anemometer. Consists of a series of inclined 
 vanes with a registering apparatus in a brass circular 
 band. Used in mine ventilation. Diameter 6 in. 
 
 1876. Lent by F. Darton d Co. 
 
 127. Self-timing Anemometer. 
 
 1893. Lent by Messrs. Dams ck Sou, Derby. 
 
 By this instrument the use of a watch in ascertaining the 
 velocity of the air is dispensed with. 
 
 In taking observations, the anemometer is exposed for a 
 few seconds with its back to the current, and the spring plunger 
 
38 
 
 pushed in ; the position taken up by the index then shows 
 the velocity in feet per second or the air. When more than 
 one revolution of the index has been made the inner circle 
 of figures must be read. 
 
 The screw with milled head is used to release the plunger 
 and bring back the index to zero. 
 
 G. OZONOMETERS. 
 
 128. Smyth's Ozonometer, made of brass, lined with 
 sealing wax, and provided with brass stop-cocks. 
 Invented by contributor previous to ozonometer No. 132. 
 
 1876. Lent by John Smyth, jun. 
 
 In this and succeeding instruments the amount of ozone 
 present is judged by its action on a test paper contained in the 
 box. These papers are prepared in various ways, the substance 
 used by Schonbein being iodide of starch. 
 
 The papers after exposure for a definite time are taken out and 
 compared with some standard tints forming a scale. 
 
 129. Smyth's Ozonometer, made of brass, lined with 
 glass, and provided with glass stopper to admit air. 
 Invented by contributor previous to ozonometers Nos 
 128 and 132. 
 
 1876. Lent by John Smyth, jun. 
 
 130. Diagram showing the rough form of ozonometer 
 and aspirator used by contributor in his first experi- 
 ments, August 1865. 
 
 1876. Len t by Joh n Smyth , jun . 
 
 131. Diagram showing the contributor's ozonometer 
 connected to Dr. Andrew's form of aspirator by means 
 of which his later experiments have been made. 
 
 1876. Lent by John Smyth, jun. 
 
 132. Smyth's Ozonometer, for the determination of 
 the amount of ozone in a measured volume of air by 
 means of an aspirator. Invented by the contributor and 
 
3D 
 
 described by him in a paper read at the meeting of the 
 British Association in Birmingham in 1865. 
 
 1876. Lent by John Smyth, jun. 
 
 It consists of a boxwood tube or cylindrical box, abouf 2 inches 
 long and 2 inches in diameter, one end of which is closed, except 
 in the centre, where it is pierced by a quarter-inch tube com- 
 municating with the aspirator ; the open end is covered by a lid 
 or second box of the same material, which is so large as to slide 
 over the first, and is also pierced by a quarter-inch tube, which, 
 vvhen the ozonometer is arranged for an experiment, directs the 
 air against the centre of the test paper stretched across the open 
 end of the inner or first box, and secured there by an india- 
 rubber band lying in a groove. 
 
 H. MISCELLANEOUS METEOROLOGICAL APPARATUS. 
 
 133. Instruments issued by the Meteorological Coun- 
 cil on loan for the use of observers. 
 
 1893. Lent by the Meteorological Council. 
 
 Barometer, Negretti arid Zambra. Similar to barometers lent 
 to small ports and fishing stations. 
 
 Specimens of Instruments, lent to observers for use at 
 sea: 
 
 Barometer, " Adie." 
 
 Thermometers. Dry and wet bulb. In a screen. 
 
 Water Thermometer. 
 
 Hydrometer. Casella. 
 
 Additional Instruments for use at Telegraphic Reporting 
 Stations : 
 
 Thermometer, Maximum. 
 
 Minimum. 
 
 Rain Gauge, with collecting can and measuring glass. 
 
 134. Photographs of Padre Secchi's Meteorograph 
 and the curves traced by the instrument. A printed 
 description is shown with the photograph. 
 
 1877. Given by the Observatory of the Collegio 
 Romano. Director, Padre Secchi. 
 
40 
 
 135. Photographs of Meterological Instruments ex- 
 hibited in the Loan Collection of Scientific Apparatus, 
 1876. 
 
 Kreil's Barograph. 
 
 Milne's Barograph. 
 
 Ronald's Photo-Baron letrograph. 
 
 Diagonal Barometer. Date about 1750. 
 
 Mercurial Barometer by Reballio. 
 
 Two Barometers formerly belonging, the one to Lavoisier, the 
 other to H. B. de Saussure. 
 
 Barometers by Dr. Wild, W. Gloukhoft* and Dr. A. Krueger. 
 
 Observatory Standard Barometer by Casella, 
 
 Negretti and Zambra's Self-registering Mercurial Barometer. 
 
 Bourdon's Balance Barometer and a Goldschmid's Aneroid. 
 
 Window Stand and Screen used at German Naval Obser- 
 vatories. 
 
 Thermometers and Screens used at Norwegian Meteorological 
 Stations. 
 
 Hygrometer of early form. (This apparatus is at King's 
 College Museum.) 
 
 Hair Hygrometers by H. B. de Saussure. 
 
 Richer's 8-hair Hygrometer and two single-hair Hygrometers. 
 
 Anemometer with electrical registration. Made by Yeates and 
 Son. 
 
 Anemometer with electrical registration. Made by Pastorelli. 
 
 Lind's Anemometer as modified by Sir W. Snow Harris. 
 
 136. Meteorological Table, arranged by the late 
 Bennet Woodcroft from data kept by Mr. Glaisher. 
 
 The observations of the thermometer and barometer extend 
 over a period of 80 years, those of the rain gauge over 39 years. 
 
 137. Hypsometer. An instrument for determining 
 altitudes by observations of the boiling point of water. 
 
 1893. Lent by L. Casella. 
 
 It consists of a cylindrical chamber for water, connected to 
 a tube along which the steam that has been generated makes 
 its way to the outer air. In this tube, which is protected 
 from cold by an outer casing, is placed a thermometer with 
 its bulb supported a short distance above the level of the water. 
 
 The heating is by a spirit lamp screened from the wind by a tin 
 box. 
 
 Altitudes are ascertained by means of specially prepared 
 tables in which the heights corresponding to a particular 
 temperature of the boiling point are given, also the corrections 
 to be made for variation in mean temperature and for other 
 sources of error. 
 
 The outer casing is made to telescope, and the whole 
 apparatus constructed with a view to portability. 
 
41 
 
 138. Cloud Mirror. Designed to ascertain the direc- 
 tion from which the clouds are moving. 
 
 E. 2. 1863. Given by J. T. Goddard, from 
 
 Exhibition 0/1862. 
 
 For observations, the mirror is laid on a horizontal support 
 near a window and set so that the point marked north is 
 directed to the south point of the horizon; the several points 
 will then be reversed. The edge of a conspicuous cloud is 
 brought to the centre of the mirror and the point of the 
 compass noted where it passes off the margin. This gives the 
 point from which the clouds are coming. 
 
 139. Apparatus to illustrate the formation of 
 Tornado Clouds. 
 
 1897. Designed b y W. H. Dines, B.A. 
 
 The apparatus for this experiment, as made by Mr. Dines, is 
 of a simple and inexpensive form ; that shown is of a somewhat 
 more substantial character, to adapt it for exhibition. 
 
 Three glass plates, 18 inches by 24 inches, are set in each of 
 two frames, so as to form when put together a hollow hexagonal 
 prism. These frames are placed upon a table with their edges 
 apart and slightly overlapping, to allow of the entry of ail- 
 obliquely. A board, with a hole in its centre, in which is set a 
 fan that can be rotated by a pair of pulle}^s, forms a cover to the 
 prism, and a shallow copper evaporating pan and a burner 
 complete the essential parts of the apparatus. 
 
 If, when sufficient steam is generated from the water in the 
 pan, the fan is rotated, a column will be produced in many 
 respects similar to that of a Tornado Cloud. 
 
 The points of resemblance to the actual tornado cloud for- 
 mation are stated by Mr. Dines to be : 
 
 1. A distinct rotary motion round the centre, increasing in 
 violence towards the centre. 
 
 2. A strong up-draft. 
 
 3. A decrease of pressure in the centre of the column. 
 
 4. The hollo wness of the column. 
 
 See Journal of tJie Royal Meteorological Society, January, 
 1896. Science Library, Victoria and Albert Museum. 
 
 140. Portion of a Conductor fused by lightning at 
 Caterham. 
 
 1893. Lent by the Lightning Rod Conference, per 
 
 the late G. J. Symow, F.R.S. 
 
 The bright spots near the rivet and the end of the screw 
 shew fusion. 
 
42 
 
 141. Inefficient Lightning Conductor. Removed from 
 the Royal Hospital for Incurables, Putney. 
 
 1893. Lent by the Lightning Rod Conference, per 
 the late G. J. Synwns, F.KS. 
 
 142. Spratt's Patent Lightning Conductor, 12 wires 
 (No. 15, B.W.G.), 2 wires (No. 18, B.W.G.). Weight, 
 3 *3 ozs. per foot. 
 
 1893. Lent by the Lightning Rod Conference, per 
 
 the late G. J. Symons, F.R.S. 
 
 143. Portions of a Rafter shattered by lightning at 
 Kentish Town. 
 
 1893. Lent by the late G. J. Symons, F.R.S. 
 
 144. Rhe Electrometer of Marianini, for observing 
 electric discharges between the atmosphere and the earth. 
 
 1876. Lent by the late Robert James Mann, M.D. 
 
 This instrument was planned by Professor Melsens. It con- 
 tains a coil of copper wire which is to be made continuous 
 with the system of a lightning rod, or with the earth wire 
 of a telegraph line. When an electric current passes through 
 the coil a soft iron bar in its interior is magnetised, and 
 a traversing magnetic needle pivoted above the coil is deflected 
 out of the north and south line of the earth's magnetism 
 towards either the east or west. When the interior iron has 
 been magnetised it must be replaced by a neutral bar before 
 another observation can be made. 
 
 145. Photograph of a Bifilar Electrometer and appar- 
 atus with movable conductor. With printed descriptions. 
 
 1877. Given by Prof. Lidgi Palniieri, Vesnvian and 
 Meteorological Observatory, Naples. 
 
 146. Sky Sketches, a series of 533 in 72 frames, taken 
 between September, 1883, and September, 1886. 
 
 1888. Drawn and lent by W. Ascroft. 
 
 These sketches illustrate optical phenomena attributed to the 
 eruption at Krakatoa in the Java Straits, August 27, 1883. 
 
43 
 
 147. The Chromatics of the Sky. A selection of 18 
 coloured drawings taken in latitude 51 31' 15" N. and 
 longitude 9' 45" W., at 135 feet above sea level. 
 
 1889. Lent by J. S. Dyason, F.R.G.S., F.R.Met.Soc. 
 
 These are taken from a series of about 300 drawn by the 
 exhibitor. 
 
 I. TERRESTRIAL MAGNETISM. 
 
 148. Photograph of an Inclinatorium (Dipping Needle), 
 by Daniel Bernoulli, made by Johann Dietrich, of 
 Basle, in 1751. 
 
 1877. Given by Professor Hageribach-Bischoff, 
 
 Director, The Physical Institute in the 
 Bernoullianum, Basle. 
 
 This instrument gained the prize of the Academy of Paris in 
 1743. 
 
 149. Dip Circle for observations at sea, fitted with 
 special arrangements for finding the magnetic meridian. 
 By Nairne and Blunt ; date, 1772-1834. 
 
 1876. Lent by the Hydrographic Department of the 
 Admiralty. 
 
 This instrument may be considered as intermediate in con- 
 struction between that made by Nairne for Captain Phipps, in 
 his voyage towards the North Pole in 1773, and the Fox circle 
 introduced by Mr. R. W. Fox in 1834. 
 
 It is suspended by an universal joint from a wooden stand 
 carrying one adjusting screw. The needle, 9 in. long, with 
 steel axles, vibrates within a circle graduated to 20', and the 
 ends of the axis are fitted to work in the agate holes of two 
 adjustable screws in the vertical bars supporting the circle, and 
 otherwise strengthening the instrument. The sliding pointers 
 on the graduated circle are intended to be adjusted to the mean 
 position of the needle when the motion of the vessel causes it to 
 vibrate on either side of the dip. The screw on the under side 
 of the circle works the metal supports on which the needle 
 is placed until adjusted in the agate holes. A thermometer 
 graduated to -38 is placed inside the instrument. 
 
 The peculiar arrangement for ascertaining the magnetic 
 meridian consists of a small compass gimballed at the end 
 of a wooden arm. The other end of this arm has a brass 
 fitting to fix on pins in the graduated circle on the top of 
 the frame. The motion of the arm in azimuth causes the 
 whole apparatus to move in the wooden stand until the 
 dip circle is in the magnetic meridian, as indicated by the 
 compass. 
 
44 
 
 150. Dip Circle and Intensity Apparatus. Fitted 
 with arrangements for ascertaining the magnetic 
 meridian by three methods. By Dollond ; probable 
 date, 1776-1834. 
 
 1876. Lent by the Hydrogmphw Department of the 
 Admiralty. 
 
 The dip circle is made after the pattern described by the 
 Hon. Henry Cavendish in the Phil. Trans., vol. xlvi., in which 
 the dipping needle rolls upon horizontal agate planes, and a 
 contrivance is applied for lifting it off and on to the agates 
 at pleasure. A milled-headed screw works this lift, and an 
 adjacent butterfly screw, an arrangement for causing the 
 needle to vibrate. The vertical circle is graduated to 20' : 
 the outer circle of the base plate is also graduated to 
 every 45. 
 
 The direction of the magnetic meridian may be ascertained 
 by two methods other than that usually adopted : 1. An edge 
 bar horizontal needle fitted with an agate cup may be placed 
 on the steel point fixed to a balanced axis provided for placing 
 on the agates like the dipping needles. The coincidence of 
 this needle with the plane of the vertical circle shows the 
 latter to be in the magnetic meridian. 2. The same edge 
 bar needle can be placed on a pivot screwed in the centre 
 of the graduated circle at the bottom of the travelling box. 
 
 Of the three dipping needles, two are flat and one cylindrical 
 and sharply pointed. The axes are made of gun metal, and 
 one of the flat needles is fitted with a brass cone on Mayer's 
 principle. 
 
 Intensity Observations. For this purpose the box which 
 carries the dip circle is fitted with two apertures filled with 
 glass, and a torsion circle on the top. The two flat needles, 
 one of gun metal for eliminating torsion, and the other for 
 horizontal vibrations, have metal pins screwed into the centres 
 by means of which they are attached, to the stirrup suspended 
 by silk fibres from the torsion circle. The vibrations are 
 observed through the glass sides, and the magnetic meridian 
 by the edge bar horizontal needle before described. 
 
 This apparatus closely resembles that used by David Douglas 
 on the north-west coast of America and the Sandwich Islands 
 in 1829-34. 
 
 151. Dip Circle. By Robinson. 
 
 E. 13. 1900. Bequeathed bif W. Tucker Radford.M.B. 
 
 This is a similar instrument to those described under Nos. 152 
 and 153. Four 6-inch needles are supplied, and also a horizontal 
 edge bar needle with pointed support for finding the magnetic 
 meridian after a manner described in No. 150. 
 
45 
 
 152. Dip Circle. By Robinson ; date, 1830-75. 
 
 1876. Lent hy the Hydrograpkic Department of the 
 Admiralty. 
 
 In this circle the needles are in. long, flat, and pointed. 
 They move on agate planes in the centre of a graduated circle, 
 and observations are read off by means of lenses fixed in the 
 ends of a movable arm centred on one of the glass sides of the 
 instrument. 
 
 The advantages of this form of dip circle are: 1. That 
 the needles can be read off for nearly every angle of dip. 2. 
 Portability, from compactness of stowage in the box, as the 
 vertical circle is fitted so as to be readily detached from the 
 horizontal. 
 
 An instrument of this kind was used by Major Estcourt during 
 the survey of the River Euphrates in 1836. 
 
 153. Dip Circle used by Sir James C. Ross. 
 
 1876. Lent In) the Kew Committee of the Royal Society. 
 
 A Robinson dip circle with 6-inch needles, supported on agate 
 planes, and read off direct on the circle of the instrument. 
 Similar to Nos. 151 and 152. 
 
 154. Dip Circle. 
 
 E. 18. 1889. Made by A. Dover. 
 
 This instrument is of the type usually found in magnetic 
 observatories, and was employed during the recent magnetic 
 survey of the United Kingdom. 
 
 155. Dip Circle, similar to that used by M. Moureaux 
 in the magnetic survey of France, 1884-5. 
 
 E. 26. 1889. Made ly Bnoiner Freres, Paris. 
 
 The dimensions of this instrument are considerably less than 
 those of the English form, but the principle is the same in both. 
 The circle reads to T. 
 
 156. Drawing of a Dip Circle. 
 
 1876. Lent Inj the late J. P. Joule, F.R.S. 
 
 The needle, constructed of a thin ribbon, of annealed steel, 
 weighing 20 grains, is furnished with an axis made of a wire of 
 standard gold. This axis is supported by threads of the Diadema 
 Spider attached to the arms of a balance suspended by a fine 
 stretched wire. The whole is hung by a wire which can be 
 twisted at the head through 180. At the bottom is attached 
 a paddle immersed in castor oil, which brings the instrument 
 speedily to rest in a fresh position, The deflections are read off 
 
46 
 
 by a short-focus telescope, placed on an arm revolving on an 
 axis in the centre of the circle. With this instrument the dip 
 can be determined within the fraction of a minute of arc in less 
 than a quarter of an hour. 
 
 With this drawing is exhibited a specimen of the thread of the 
 Diadema Spider, also thread of the Diadema Spider Cocoon. 
 
 157. Dipping Needle Instrument, designed by W. T. 
 Goolden, M.A. 
 
 1893. Lent by L. Casella. 
 
 A 3 J -inch needle, provided with adjustable counterpoises 
 contrived so as to bring the centre of gravity very accurately 
 into the axis of support, is carried in jewelled centres on a 
 horizontal axis. The inclination of the needle to the horizon 
 is read upon a metal circle, graduated in degrees on both 
 sides, and the whole is enclosed in an air-tight box with glass 
 faces, revolving about a vertical axis. In order to facilitate 
 the adjustment of the needle to the magnetic meridian, the 
 vertical axis of the instrument is furnished with a spring arm, 
 which can be clamped to it, and there are four metal studs on 
 the stand at right angles to each other, into which the head 
 of the spring arm fits when pressed down with the finger. 
 
 The instrument is similar to those occasionally lent by the 
 Department to Science Classes. 
 
 158. Hansteen's Intensity Apparatus, used by Capt. 
 Barnett, in H.M.S. " Thunder," in 1841. 
 
 1876. Lent by the Kew Committee of the Royal 
 Society, Kew Observatory. 
 
 Consists of a glazed box 4 in. square, standing on a levelling 
 stand and carrying a brass suspension tube 6 in. in length. It 
 also has an ivory circle fixed to its bottom. 
 
 There are two magnets 2'7 in. long, each of which when 
 not in use is kept in a separate little copper box, where, fitted to 
 an armature, it is embedded in iron filings. 
 
 159. Hansteen's Intensity Apparatus ; date, 1819-50. 
 
 1876. Lent by the Hydrographic Department of the 
 Admiralty. 
 
 This form of intensity apparatus is that first adopted by 
 M. Hansteen in his magnetic survey of Norway and the Baltic 
 shores in 1819-24, and since largely used by various observers. 
 The vibrating needle is cylindrical, pointed at the ends, 2 - 6 
 in. long and O15 in. in thickness. It is suspended from the 
 movable pulley at the end of the brass tube by a fibre of 
 
47 
 
 silk secured to a brass strap and loop in its centre. By means 
 of the pulley the needle can be adjusted to the required height 
 in the vibrating box. 
 
 The value of the observations depends on the permanency of 
 the magnetic condition of the needle. 
 
 160. Magnetometer, Kew pattern. 
 
 E. 40. 1889. Made by Elliott Bros 
 
 This magnetometer is intended for use either in the observa- 
 tory, the laboratory, or the field, for the determination (a) of the 
 magnetic declination, (b) of the horizontal component, of the 
 earth's magnetic force, commonly denoted by H. 
 
 In finding the magnetic declination two distinct determina- 
 tions have to be made : First, that of the direction of true or 
 geographical north by means of sun observations ; secondly, that 
 of the direction of magnetic north by means of a properly 
 suspended magnet. 
 
 The Kew magnetometer consists essentially of a divided circle, 
 supported on three levelling-screws, by which it can be made 
 horizontal, and a second circle, concentric with the first, which 
 can turn about a vertical axis through their common centre. 
 The second circle carries two verniers and reading microscopes 
 at opposite ends of a diameter, by means of which its position with 
 regard to the first, or lower circle, can be read to 20" of arc. 
 It carries also, at opposite ends of a diameter, a horizontal tele- 
 scope with cross wires in the eye-piece, and a small square mirror 
 which is capable of turning round a horizontal axis, and of which 
 the supports are carried by a circular table which may be rotated 
 and clamped in any position, so that the plane of the mirror is 
 adjustable in any required way. There are also various other 
 small adjustments by means of which the axis of the mirror may 
 be made horizontal and perpendicular to the line of collimation 
 of the telescope, and the plane of the mirror made parallel to its 
 own axis of rotation. 
 
 As the proper adjustment of the mirror is a matter of impor- 
 tance, the telescope is specially constructed to give a convenient 
 method of adjusting it in the field. For this purpose the brass 
 tube of the telescope is cut away near the eye-piece, and replaced 
 by a short length of glass, within which a piece of polished 
 platinum, forming the end of the tube which carries the eye-piece, 
 is placed at an angle of 45 to the optic axis. 
 
 This platinum reflector is pierced by a hole so that it does not 
 form an opaque stop across the telescope, but sufficient reflecting 
 surface is left for a good light to be thrown on the cross wires 
 when it is turned to a bright part of the sky ; then the mirror at 
 the opposite side of the instrument is rotated, until the image of 
 the illuminated cross wires formed by reflection from it is seen 
 to coincide with the cross wires themselves. When this is the 
 case the mirror is correctly adjusted. To cut off external light 
 
48 
 
 from the object glass during this adjustment, a small blackened 
 screen is fixed to the stand behind the mirror, and a blackened 
 tube placed between the mirror and the telescope, of such length 
 that the object glass just enters within it. 
 
 In making sun observations, the whole of the upper part of the 
 instrument is rotated, and the mirror tilted at a proper angle, 
 until an image of the sun is seen by reflection from it in the field 
 of view of the telescope. 
 
 Dark glasses of two shades are carried either in the eye-piece or 
 just in front of the object glass to reduce the brightness of the 
 image, if necessary. 
 
 The observer, by means of a chronometer ticking half seconds, 
 notes the exact times at which the two edges of the sun's disc 
 touch the vertical cross wire as the image moves across the field 
 of view, reading also by means of the verniers the position of 
 the upper circle with regard to the lower graduated one. These 
 observations properly worked out will give the reading on the 
 circle corresponding to the direction of true north. 
 
 The second part of the observation consists in suspending a 
 specially constructed magnet, and determining by its means the 
 magnetic meridian, 
 
 The magnet used for this purpose is a hollow cylindrical bar 
 of steel, closed at one end by a lens, and at the other by a piece 
 of plane glass on which a tiny scale is photographed. This is 
 suspended by a silk thread about a foot long and hangs, within 
 a wooden box (to exclude draughts) with glass windows, on a 
 level with the telescope. 
 
 The thread is fastened at its upper end to a torsion head at the 
 top of a stout glass tube ; the lower end of the tube screws into 
 the wooden box, and the wooden box is screwed on at the centre 
 of the instrument, between the telescope and the mirror, after the 
 sun observations have been made. Diffused light may be re- 
 flected either from the mirror or a piece of white paper, right 
 through the hollow magnet, so that the scale on its plane glass 
 end is clearly visible through the telescope. The magnet is 
 allowed to swing freely, and the upper part of the instrument 
 again rotated until the central division of the scale is seen to 
 coincide with the vertical cross wire in the eye-piece. The posi- 
 tion of the upper circle with regard to the lower is again read by 
 means of the verniers, this reading corresponding to the direction 
 of magnetic north. The difference between the two readings 
 thus obtained, viz., that corresponding to the geographical, and 
 that to the magnetic meridian, will evidently be the required 
 magnetic declination, which may thus be obtained to within a 
 third of a minute of arc. 
 
 To find H, or the horizontal component of the earth's magnetic 
 force, two distinct experiments have as a rule to be made. If a 
 freely suspended magnet is set swinging, its time of vibration 
 depends both on its own strength (or more correctly magnetic 
 moment), and on the strength of the magnetic force in its 
 neighbourhood, 
 
If the moment of the magnet were a constant quantity, it 
 could be determined once for all, and then one experiment would 
 be sufficient to find H at any point. But as a magnet cannot be 
 constructed which does not become weaker with time, two ex- 
 periments have to be performed, one of which gives the product 
 and the other the ratio of the two changeable quantities, from 
 which either or both may be found. 
 
 In the vibration experiment, which gives the product of H 
 and the moment of the magnet, the disposition of the instrument 
 remains exactly the same as in finding the declination ; the 
 magnet is set swinging steadily through a small arc, and the 
 time which it takes to make one vibration found by means of 
 the ordinary eye and ear method with the chronometer ticking 
 half-seconds, the experiment lasting until 100 complete swings 
 have been made. A thermometer is placed within the box in 
 which the magnet swings, to give its mean temperature during 
 the observation, this being important from the alteration pro- 
 duced by a change of temperature in the magnetic moment of 
 a magnet. 
 
 The second part of the experiment consists in determining the 
 angles which the magnet used in the first part is able to deflect 
 a second magnet from its position of rest in the magnetic 
 meridian, when held at two definite distances, in certain positions, 
 from it. It is obvious that the stronger the first magnet is, the 
 greater will be the deflection of the second produced by it ; while 
 the greater the horizontal component of the earth's magnetic 
 force, the less will be the deflection of the second magnet 
 under the influence of any neighbouring magnet. To perform 
 this part of the experiment the wooden box and glass tube 
 used before are removed, and another shorter tube screwed 
 on at the centre of the instrument, protecting the silk fibre by 
 which the second magnet is suspended at a lower level than that 
 at which the declination magnet was hung. 
 
 A second telescope, carrying a scale engraved on ivory above 
 the eye-piece, is fastened by screws to the instrument below the 
 telescope already mentioned, which is not used in this part of 
 the experiment, and, as it would be inconvenient to send light 
 through, the suspended magnet in this case, the scale is seen by 
 reflection from a small mirror which is rigidly attached to it, 
 the arrangement answering just the same purpose as the lens 
 and photographed scale in the first case. 
 
 A carefully graduated brass bar, about one metre in length, is 
 now attached horizontally to the circle, so that it passes beneath 
 the centre of the suspended magnet, and is at right angles to the 
 telescope, and on this bar, at certain distances, the first magnet 
 (that is, the one that was suspended during the decimation and 
 vibration experiments) is successively placed, supported on a little 
 stand so as to be on a level with the second and perpendicular to 
 it. The instrument is rotated as before until in each case the 
 central division of the scale coincides with the vertical cross wire 
 in the eye-piece of the telescope, and from the angles of rotation 
 
 3179. D 
 
50 
 
 when the deflecting magnet is at different distances, and with its 
 N. and S. poles alternately directed towards the suspended 
 magnet, the required ratio is deduced. A thermometer is hung 
 on the brass bar during the observation, as near as possible to the 
 deflecting magnet, for the same reason as in the case of the vibra- 
 tion experiment. 
 
 161. Portable Magnetometer similar to that used by 
 M. Moureaux in the magnetic survey of France, 1884-5. 
 
 E. 27. 1889. Made by Brunner Freres, Paris. 
 
 This instrument differs from the Kew magnetometer No. 160 
 chiefly in point of dimensions, and in the method by which the 
 sun observations are made. The latter instrument, in its box, 
 weighs about 50 Ibs., while the French pattern weighs only about 
 9 Ibs. In an observatory the extra size and weight of the English 
 instrument are of no consequence, and even in the field its extra 
 solidity may sometimes be an advantage, but there is no doubt as 
 a general rule that in outdoor work the much greater portability 
 of the French form is a strong point in its favour. 
 
 The main difference in principle between the two instruments 
 is that in the French form the mirror ( for reflecting the sun ) is 
 done away with, and the telescope can rotate in a vertical plane 
 about a horizontal axis, so that it forms an altazimuth instrument, 
 and the sun is looked at directly instead of being seen by reflec- 
 tion. By this arrangement an exact knowledge of true Lime 
 becomes less important than in the other case. 
 
 The magnet is a solid cylinder, 6*5 cm. in length, 4 mm. in 
 diameter /and weighing 74 grammes : its ends are slightly concave 
 and polished, and serve to form an image of a cross wire in the 
 reading microscopes, which are moved when the declination is 
 being determined until the wire and its image are coincident, 
 thus answering the same purpose as the holloAv magnet, scale, 
 and lens of the Kew pattern. 
 
 The accuracy attainable in the determination of declination is 
 about the same with the French as with the English instrument, 
 notwithstanding the much smaller dimensions of the former. 
 But in the vibration and deflection experiments less care is taken 
 with regard to the temperature of the magnet, and there is little 
 doubt that " H " is found with a greater degree of accuracy with 
 the English form of instrument than with the French. 
 
 162. St. Helena Magnetometers. 
 
 (1.) Declinometer and Telescope, used at St. Helena, 
 1840-1849. 
 
 (2.) Bifilar Magnetometer and Telescope, used at 
 St. Helena, 1840-1849. 
 
51 
 
 (3.) Vertical Force Magnetometer, used at St. Helena, 
 1840-1849. 
 
 1876. Lent' by the Kew Committee of the Royal Society. 
 
 The three magnetometers, the declination, horizontal force and 
 vertical force instruments, respectively, were made by Grubb, of 
 Dublin, and formed one set of those used in the Colonial Magnetic 
 Observatories, founded by the Government in 1840. The instru- 
 ments were described in the Report of the Royal Society 
 Committee of Physics, &c. 
 
 These instruments were erected at St. Helena in 1840, and 
 constantly observed from that date until 1849. 
 
 The declinometer consists of a magnet bar, suspended by fibres 
 of untwisted silk, and carrying a collimator arrangement of lens 
 and scale, the whole being enclosed in a cylindrical casing, per- 
 forated with windows, through which the scale is viewed by means 
 of a telescope. 
 
 The bifilar is a somewhat similar arrangement, but the support 
 of the magnet is formed of two parallel wires, which are twisted 
 so as to bring the magnet into a position at right angles to the 
 meridian. 
 
 The vertical force magnetometer is a light magnet, 12 in. long, 
 carrying a brass frame with cross wires at each end ; it is supported 
 by a steel knife edge, bearing on agate planes, and its movements 
 are observed by microscopes, fitted with micrometers, by which 
 the position of the cross wires on the magnet is read. 
 
 163. Declination Compass, used by Sir J. Richardson 
 and Capt. Pullen. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
 It consists of a square glazed box, containing a compass card, 
 formed of a light metal divided circle, and two needles, 
 connected to an agate cup in the centre. This card is mounted 
 so that it can either be suspended by a silk thread, or rest upon 
 a point in the ordinary manner. 
 
 Two microscopes are fixed vertically above it, so that the 
 divisions on the circle may be read by them, concave metallic 
 reflectors being fitted to them for the purpose of illuminating 
 the scale at the time of reading off. 
 
 164. Photographs of a " Compass Theodolite/ 1 an in- 
 strument invented by the exhibitor, for observing, with 
 a microscope, the exact position of the magnetic needle. 
 In two frames. 
 
 1877. Given, by Prof. Joseph Schlesinger, Vienna. 
 
52 
 
 165. Self-recording Magnetometer. 
 
 1876. Lent by the late Chas. Brooke, F.R.8. 
 
 Hough home made apparatus, by which the first automatic 
 records of magnetic variation by reflected light were obtained. 
 The cylindrical lenses are water-lenses. 
 
 166. Self-registering Balanced Magnetometer, with 
 compensation for changes of temperature, and warm 
 water envelope for testing the same. The compensation 
 is effected by the weight of the column of mercury in a 
 thermometer tube. 
 
 1876. Lent by the kite Chas. Brooke, F.R.S. 
 
 This instrument can be used with the recording apparatus 
 No. 168, or observations can be made with a telescope. 
 
 The magnet is supported by a bar at right angles to it, which 
 rests by knife edges on agate planes. At the other end of this 
 bar are a concave metal reflector and a plane mirror. The 
 former is used for reflecting to the photographic recording 
 apparatus rays of light received from the lamp ; the latter, for 
 reading the deviations of the magnet with a telescope in the 
 ordinary way. As any movement of the magnet is necessarily 
 conveyed to the concave mirror, the curve traced by the reflected 
 pencil of light on the revolving recording drum will serve as a 
 record by which the change of inclination of the magnet can be 
 ascertained. 
 
 167. Self- registering Syphon Barometer, used in con- 
 nection with the magnetic recording apparatus. 
 
 1876. Lent by the late Chas. Brooke, F.R.S. 
 
 The registration is effected by a lever bearing at one end a 
 card with a slit and at the other a float which rests on the 
 mercury in the cistern. 
 
 The rise or fall of the mercury causes a rise or fall of the slit 
 in front of the photographic recording apparatus, and a curve is 
 traced on its revolving cylinder by the light from a lamp. A 
 base line is obtained by the light from the same lamp being 
 reflected on to the cylinder by means of two prisms contained 
 in a tube. From the two lines traced, the extent of the rise or 
 fall of the barometer can be ascertained. 
 
 168. Photographic apparatus, for registering simul- 
 taneously the variations of both the above instruments, 
 Nos. 166 and 167. 
 
 1876. Lent by the late Chas. Brooke, F.R.S. 
 
53 
 
 169. Self-registering Bifilar Magnetometer, with 
 compensation for changes of temperature, and warm 
 water envelope for testing the same. 
 
 1876. Lent by the late Chas. Brooke, F.R.S. 
 
 The compensation is effected by diminishing the lower interval 
 of the double suspension, by means of the differential expansion 
 of glass and zinc, in proportion to the diminished magnetic 
 energy of the bar, due to elevation of temperature. 
 
 Records are obtained with this instrument by a method similar 
 to that adopted in the magnetometer, No. 166. 
 
 170. Photographic Apparatus for registering the 
 variation of No. 169 by means of a reflected pencil 
 of light, 
 
 1876. Lent by the late Chas. Brooke, F.R.S, 
 
 171. Illustrations of curves, drawn by Brooke's 
 magnetometers. In frame, 2 ft. 1 in. by 1 ft. 8 in. 
 
 1876. Lent by the late Chas. Brooke, F.R.S. 
 
 172. Photographic Self-registering Horizontal Force, 
 or Bifilar Magnetometer, constructed in 1847, at the 
 Kew Observatory, by Mr. Francis Ronalds. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
 Described in the British Association Report for 1849. 
 
 The magnet, 15 in. long, is suspended in a loop of fine 
 wire, by means of a pulley, forming a bifilar arrangement. It 
 carries, attached to its lower side, a light brass bar, which moves 
 a little shutter in front of an oil lamp, allowing a pencil of rays 
 to pass through a hole in it. The light is then thrown, by 
 means of a lens, upon a daguerreotype plate, which is steadily 
 drawn upwards by means of a clock. 
 
 The curves upon the daguerreotype plates were sometimes 
 etched in, and engravings subsequently worked off, or tracings 
 were made upon sheets of gelatine, which, being preserved, 
 allowed the silvered plates to be repeatedly used. 
 
 This instrument was superseded by the improved magneto- 
 graphs erected at Kew by Mr. Welsh in 1857, which have since 
 remained in almost continuous action. 
 
 The suspension frame originally fitted has been replaced by 
 one not belonging to the instrument when in use. 
 
 3179. E 
 
54 
 
 173. Photographic Self - registering Declination 
 Magnet, constructed in 1846, at the Kew Observatory, by 
 Mr. Francis Ronalds. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
 Described in the Philosophical Transactions for 1847, vol. i. 
 
 The magnet 2 ft. long, when in use, was suspended by a 
 silken skein 9 ft. long; on its under side it carries a brass 
 bar, from one end of which hangs a perforated metal plate, 
 which, moving in front of a lamp, permits a pencil of light to 
 fall upon a daguerreotype plate, carried slowly upwards by a 
 clock suitably arranged. 
 
 The magnet is surrounded by a damper, made by electro- 
 
 lating a frame of mahogany with copper. Both are enclosed in 
 ouble wooden cases, having both surfaces covered with gold 
 paper. 
 
 This instrument Avas superseded by the improved Kew 
 inagnetographs, which have been in almost continuous action 
 since 1858. 
 
 174. Mascart's Magnetic Apparatus. 
 
 E. 5 to 9. 1884. Made by J. Car pentier, Paris. 
 
 This apparatus is used for photographic recording. It 
 includes : 
 
 Declinometer. This consists of a cylindrical copper cage with 
 a graduated circle at its base, supported on a stand with levelling 
 screws, and capable of motion round a vertical axis. On one of 
 the sides of this cage is a circular opening, furnished with a convex 
 lens, ordinarily of 1 metre focal length. A tube 17 centimetres in 
 height, fixed by its base to a second graduated circle, has at its 
 upper extremity a small windlass, to which is attached the silk 
 thread by means of which the magnetic needle is suspended. 
 This magnetic needle is of square section and 5 centimetres 
 long, and the stirrup which carries it is furnished with a 
 vertical mirror to indicate the displacements of the magnet. 
 The stirrups are of two kinds ; in one the mirror can be placed 
 parallel, and in the other at right angles to the bar. Another 
 vertical mirror just below forms part of the cage, and can be 
 adjusted horizontally or vertically by two screws. By this 
 mirror a base line is obtained. 
 
 Bifilar. The Bifilar is constructed to measure variations of 
 the horizontal component of the earth's magnetic force, and ds 
 very similar to the declinometer. The chief difference is in the 
 mode of suspension and the direction of the needle. The stirrup 
 which carries it has a bifilar suspension, the two threads of silk 
 being kept at a distance of about 5 millimetres from each other. 
 The two screws at the top are for regulating the length of the 
 threads and for modifying the distance between them, so as to 
 alter the sensibility of the instrument. The upper part of the 
 
55 
 
 cage has a second graduated circle, furnished with a vernier and 
 adjusting screw. 
 
 Balance. The magnetic balance indicates the variations of 
 the vertical component. This apparatus consists of a magnetic 
 needle supported by means of knife edges on a surface of agate. 
 The adjustment is made Avith the aid of an index, so fitted that 
 it can be directed towards either pole of the needle to produce 
 equilibrium. A. screw nut, mounted on a vertical rod, allows 
 the centre of gravity to be raised or lowered, and consequently 
 regulates the sensibility of the needle. The balance is furnished 
 with two mirrors, laid horizontally, one movable, the other fixed 
 but capable of adjustment by screws. The whole is enclosed in 
 a small cage. On the upper part above the mirrors are two 
 apertures, on one of which is mounted a rectangular isosceles 
 prism, one of whose sides is a little convex, so that it is equivalent 
 to a converging lens of about 1 metre focal length : the other 
 aperture contains a thermometer placed in a vertical position. 
 
 The Comparison Rule is used in graduating the photographic 
 records, that is, in determining the values of the components of 
 the earth's magnetic force from the curves traced on the record- 
 ing plate. It is divided into millimetres, and is mounted on a 
 copper stand; on this rule is a sliding piece, which carries a 
 vertical circle with face perpendicular to the direction of the 
 rule. This circle is made to carry a magnet, and is movable in a 
 vertical plane. At one end of the rule there is a projection that 
 can be raised or lowered, as required, by means of a screw. 
 
 The Clock is supplied with a lamp having slits in the metal 
 caps of its three faces, by which light passes to the mirrors of the 
 declinometer and magnetometers. It has also two right-angled 
 prisms and a slit for receiving the reflected rays and passing 
 them to the sensitized recording plate. This plate, which is 
 marked for the 24 hours, moves by means of a rack and wheel- 
 work in connexion with the clock train inside the case; 
 and is protected from all light rays, except those coming 
 from the instruments, by means of a wooden partition. 
 
 (See " Notice sur les appareils magnetiques de M. Mascart." 
 Tolmer & Cie., Paris, 1883.) 
 
 175. Drawings of Kew Magnetometers. 
 In frame, 1 ft. 2 in. by 1 ft. 9^ in. 
 
 1876. Lent by the Kew Committee of the Royal Society. 
 
 176. Magnetarium for reproducing the phenomena of 
 terrestrial magnetism and the secular changes in its 
 horizontal and vertical components. 
 
 E. 21. 1894. Designed and presented by H. Wilde, 
 
 F.R.S. 
 
 The instrument consists of two geographical globes, one 
 rotating within the other, on separate axles. The outside of the 
 
56 
 
 internal globe is wound with insulated copper wire, and mounted 
 with its axis at an angle of 23*5 to the axis of the external 
 globe, so as to revolve in the plane of the ecliptic. The under 
 surface of the mapped globe is also wound with insulated wire* 
 and the ocean areas are covered with thin sheet-iron to produce a 
 difference between the magnetism of the land and ocean areas; 
 Electric currents are transmitted round the wired surfaces of the 
 globes by contacts with insulated metal rings fixed on the axles, 
 and turning with them. By means of an epicyclical train of 
 wheels, a slow differential motion is given to the internal globe, 
 by which the principal phenomena of terrestrial magnetism and 
 the secular variations of" the declination and dip at London, Cape 
 of Good Hope, St. Helena, and Ascension Island for the last 
 three centuries are closely reproduced. The period of backward 
 rotation of the internal electro-dynamic sphere required for the 
 secular variations of the magnetic elements on different parts of 
 the earth's surface is 960 years, or 22*5' of a degree annually. 
 
 The instrument also shows (1) the inequality of the declination 
 periods about the same meridians in the northern and southern 
 hemispheres, as instanced in the short period of outward westerly 
 declination at London (160 years), and the long period of out- 
 ward westerly declination at the Cape of Good Hope (272 years), 
 and St. Helena (256 years). (2) The single downward or 
 upward motion of the dipping needle, for the double outward 
 and return march of the declination needle, as instanced in the 
 continued diminution of the dip in the British Isles during the 
 westerly outward and return march of the declination since the 
 year 1723. (3) The secular changes of the dip in opposite 
 directions about the same meridian in the northern and southern 
 hemispheres, as instanced in the dip diminishing in the British 
 Isles and increasing at the Cape of Good Hope, St. Helena, and 
 Ascension Island for the present epoch. (4) The rapid increase 
 of the dip about the Atlantic node of the magnetic equator 
 (17' annually), as first indicated by Sabine in the Gulf of 
 Guinea and St. Helena, together with the westerly progression of 
 the node itself. 
 
 With the apparatus are tables showing results obtained 
 with the Magnetarium, and diagrams of curves of equal magnetic 
 variation and inclination, 1880. 
 
 177. Apparatus to illustrate the phenomena of terres- 
 trial magnetism. 
 
 E. 47. 1886. Made bii Elliott Bros. 
 
 It consists of a hollow iron globe, round the central portion of 
 which is wound some insulated copper wire. 
 
 The globe is supported on a horizontal axis, attached to the 
 two uprights of the frame. These uprights are furnished with 
 small magnetic needles, which are free to turn in a horizontal 
 plane above the globe. 
 
 If an electric current be sent through the wire, the directions 
 of the needles vary as the globe is turned on the axis. 
 
178. Globe, illustrative of the Earth's Magnetism, 
 1872. Designed by Staff-Captain F. J. Evans, RN., 
 F.RS. 
 
 1876. Lent by the Hydrographie Department of the 
 Admiralty. 
 
 On this globe four magnetic elements are exhibited : 
 
 (i.) The absolute intensity, or " total force " of magnetism, 
 (ii.) The " magnetic foci," or points of maximum intensity, 
 
 of which there are two points in each hemisphere, 
 (iii.) The magnetic equator, or line on earth's surface where 
 
 the dip is zero, 
 (iv.) The " magnetic poles," or points where the dip is 90, 
 
 of which there is one in each hemisphere. 
 
 (i.) and (ii.) are expressed by lines of equal force in absolute 
 measure (British units), (iii.) is shown by the gold band, arid 
 (iv.) by two studs. 
 
 The magnetic equator forms the boundary of the earth's 
 " red " or " blue " magnetism, terms adopted to avoid confusion 
 and to express the two kinds of magnetism, blue magnetism 
 being that of the north pole of the earth and of the south end of 
 a magnetic needle, red magnetism being that of the south pole 
 of the earth and of the north end of a magnetic needle. 
 
 179. Terrestrial globe, showing magnetic meridians for 
 epoch 1880, and general distribution of the secular 
 change of the declination. 
 
 R. 126. 1886. Prepared by Captain E. W. Creak, 
 R.N., F.R.S. 
 
 The meridians coloured red are drawn according to the results 
 of observations of the declination, made principally during the 
 years 1865-85, reduced to the epoch 1880. The blue lines 
 round the terrestrial poles enclose areas in which no observations 
 have been made. 
 
 SECULAR CHANGE. 
 
 Declination. The red arrows denote the direction in which 
 the north or marked end of the needle is moving. 
 
 The white discs show the approximate positions of the 
 foci of greatest change of the declination. The black lines 
 are drawn through positions where there is no secular 
 change of this element. 
 
 Vertical force. The red discs denote foci of greatest secular 
 change in the vertical force, an upward force being marked 
 with the sign - , and a downward force -f . At the African 
 focus, the north end of the dipping needle is moving upward 
 about 14' annually, at the South American focus downward 
 about IT. 
 
Judging from analogy, another focus of upward vertical force 
 exists near the north magnetic pole, or a focus of downward 
 force near the position of the Siberian focus of total intensity. 
 
 A consideration of the foci of greatest secular change in the 
 declination and vertical force shows the general angular motion 
 of the north or marked end of a freely suspended needle as 
 regards secular change. Thus at the declination foci the needle 
 moves only in the horizontal plane, at the foci of vertical force 
 only in the vertical plane, and at intermediate stations in the 
 resultant of the two directions. 
 
 The north or marked end of the needles mentioned is identical 
 with the " red " end of the needle, as proposed by Sir George 
 Airy, late Astronomer Royal. 
 
 180. Diagram showing curves of Equal Magnetic 
 Variation, 1871. Compiled by Staff-Captain F. J. 
 Evans and Navigating-Lieutenant E. W. Creak, R.N. 
 
 1876. Lent by the Hydrographic Department of the 
 Admiralty. 
 
 181. Maps, illustrating the distribution of the Earth's 
 Magnetism. Prepared for the Polar Expedition, 1875. 
 
 1876. Lent by the Hydrographic Department of the 
 Admiralty. 
 
 These maps are marked similarly to the globes above (Nos. 
 178 and 179). The earth's magnetism is shown by lines 
 of equal total force in absolute measures (British units), and 
 the position of the magnetic poles, equator, and regions of 
 blue and red magnetism are marked. 
 
 In the same frame there are also three other maps showing 
 the lines of equal magnetic dip, equal horizontal force, and 
 equal variation. [The western variation is denoted by con- 
 tinuous lines, eastern by dotted lines.] 
 
 182. Diagram showing curves of Equal Magnetic 
 Variation, 1880. By Staff-Commander E. W. Creak, 
 RN. Published under the superintendence of 
 Capt. F. J. Evans, K.N., C.B., F.R.S. In frame 
 2 ft. 6 in. by 3 ft. 6 in. 
 
 1884. 
 
LIST OF CONTRIBUTORS AND MAKERS. 
 
 Admiralty, Hydrographic Department, 3, 43 to 46, 57, 58. 
 
 Aeronautical Society of Great Britain, 34. 
 
 Ascroft, W., 42. 
 
 Astronomer Royal, 29. 
 
 Bayard, F. C., 17. 
 
 Bourdon, E., Paris, 8. 
 
 Brooke, 0., F.R.S. (the late), 52, 53. 
 
 Brunner Freres, 159, Rue de Vaugirard, Paris, 45, 50. 
 
 Cacciatore, Prof. G., Royal Observatory, Palermo, 29. 
 
 Carpentier, J., 20, Rue Delambre, Paris, 54. 
 
 Casartelli, J., & Son, 43, Market Street, Manchester, 23. 
 
 Casella, L., 147, Holborn Bars, E.G., 2, 7, 8, 10, 11, 16, 17, 22, 24, 26, 28, 30, 
 
 33, 40, 46. 
 
 Creak, Capt. E. W., R.N., F.R.S., 57. 
 Curtis, R. H., F.R.Met.Soc., 35. 
 Barton, F., & Co., 7, 25, 30, 32, 37. 
 Davis & Son, Derby, 37. 
 De la Rue, Warren, F.R.S. (the late), 36. 
 Denton, S. G., 10, 24. 
 Deutschbein, R,, Hamburg, 6. 
 Dines, W. H., B.A., 27, 34, 41. 
 Dover, A., 45. 
 
 Dring & Fage, 145, Strand, W.C., 10, 11. 
 Dyason, J. Sanford, F.R.G.S., F.R.Met.Soc., 43, 
 Elliott Bros., 101, St. Martin's Lane, W.C., 2, 20, 35, 47, 56. 
 Geissler, Dr. H., Bonn, 21, 22. 
 Goddard, J. T., 41. 
 
 Griffin, J. J., & Sons, 20, Sardinia Street, Lincoln's Inn Fields, W.C., 18, 20, 
 Guthrie, Prof. F., F.R.S. (the late), 4. 
 Hagenbach-Bischoff, Prof., The Physical Institute of the Bernoullianum, 
 
 Basle, 9, 43. 
 
 Harris, P., & Co., 144 and 146, Edmund Street, Birmingham, 2, 25. 
 Hooker, Sir Jos., F.R.S., 15. 
 
 Jordan, Jas. B., The Elms, Cherry Orchard, Staines, 3. 
 Joule, J. P., D.C.L., F.R.S. (the late), 45. 
 
 Kingston, G. T., M.A., Meteorological Office, Toronto, Canada, 30, 31. 
 Klinkerfues, Prof. Dr., Gottingen, 19, 23. 
 Ladd, W. (Harvey & Peak), 56, Charing Cross Road, W.C., 19. 
 Lightning Rod Conference (per the late G. J. Symons), 41, 42, 
 McLeod, Prof. H., F.R.S., 13. 
 Mann, R. J., M.D. (the late), 42, 
 
Meteorological Council, 2, 4, 9, 15, 32, 33, 39. 
 
 Midgeley, W. W., F.R.Met.Soc., 23. 
 
 Modeua, Royal University, 28. 
 
 Mohn, Prof. H., Christiania, 12, 13, 24. 
 
 Negretti & Zainbra, 38, Holborn Viaduct, E.G., 13, 14. 
 
 Newton, F., & Co., 3, Fleet Street, B.C., 25. 
 
 Palmieri, Prof. L., Vesuvian & Meteorological Observatory, Naples, 37, 42. 
 
 Pastorelli & Co., 8, 22, 25, 37. 
 
 Prestel, Prof., Emden, 23, 28. 
 
 Prosser, R. B., 29. 
 
 Pulkowa Observatory, 3. 
 
 Radford, W. Tucker, M.B., 44. 
 
 Redier, M., Paris, 6, 7. 
 
 Royal Meteorological Society, 9. 
 
 Royal Society, 1, 9, 18, 20, 21. 
 
 Royal Society, Government Grant Committee, 36. 
 
 Royal Society, Kew Committee, 5, 18, 25, 33, 45, 46, 50, 51, 53 to 55. 
 
 Sehlesinger, Prof. J., Vienna, 51. 
 
 Secchi, Padre, Observatory of Cpllegio Romano, Rome, 39. 
 
 Sidebottom, Jas., F.R.Met.Soc. (the late), 24. 
 
 Skertchly, Sydney B.J., F.G.S., 28. 
 
 Smyth, J., 38. 
 
 Spottiswoode, W., F.R.S. (the late), 36. 
 
 Stanley, W. Ford, 4 and 5, Great Turnstile, Holborn, W.C., 3, 6, 7, 12, 16 
 
 Stewart, Prof. Balfour, F.R.S. (the late), 11. 
 
 Stow, Rev. Fenwick W., M.A., 16. 
 
 Studii Superiori, Royal Institute, Florence, 4. 
 
 Symons, G. J., F.R.S. (the late), 2, 9, 10, 19, 25 to 27, 42. 
 
 Usteri-Reinacher, Th., Zurich, 14. 
 
 Wainwright, R. C., 18. 
 
 Warmbrunn, Quilitz & Co., Berlin, 22. 
 
 Wild, Dr. H., Central Physical Observatory, St. Petersburg, 3, 6 
 
 Wilde, H., F.R.S., 55. 
 
 Yeates & Son, Dublin, 26. 
 

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