July 27, 1911] 



NATURE 



in connection with the institute are printed as appendices, 

 ral of these deal with questions of thermometer and 

 rain-gauge exposure. Among the remaining papers we 

 may mention a detailed summary of the observations of 

 motion over Hildesheim, extending over the period 

 M 4 S, by Th. Bbtel, observer at Hildesheim, and a re- 

 port by W. KSnig of the heavy rainfall experienced in 

 Germany during the first few days of August, igio. 

 Appendix xi. reports on the comparison of the standard 

 imeters and magnetic instruments of Potsdam Observa- 

 tory with those of de Bilt, Paris, Val Joyeux, and 

 Pavlovsk, carried out by Dr. W. Kuhl in conformity with 

 resolutions of the International Meteorological Committee. 

 Further papers on magnetic comparisons are contributed 

 by Prof. Ad. Schmidt and Dr. O. Venske. Prof. Schrrvdt 

 also contributes a paper on the detailed magnetic survey 

 of east Prussia, a region of great magnetic disturbance. 

 This is accompanied by a chart of isogonic lines for the 

 epoch 1911-0. 



If the collimator and telescope of a spectrometer are so 

 placed that their axes coincide, and a block of plane parallel 

 glass is placed between the collimator lens and the telescope 

 lens, no deviation of the image of the collimator slit is 

 produced. If the upper part of the glass block is provided 

 with a prism-shaped cavity which contains a liquid having 

 an index of refraction which differs from that of the block, 

 the upper part of the image of the slit will be deviated 

 by an amount proportional to the difference of the two 

 indices of refraction. Now the deviation of a narrow 

 pencil of homogeneous light on passing through a lens is 

 proportional to the distance of the point of the lens on 

 which the pencil falls from the axis of the lens. By 

 making the light which has passed through the liquid 

 pass through a lens at the proper distance from the axis, 

 the deviation due to the liquid may therefore be com- 

 pensated. It is on this principle that the Fery refracto- 

 meter is constructed. The block of glass containing the 

 prism-shaped hollow for the liquid the index of refraction 

 of which is required, is enclosed in a small water tank tin- 

 sides of which are plane convex lenses. The tank and con- 

 tents can be moved horizontally across the field by means 

 of a screw, and the distance through which they have to 

 be moved to make the resultant deviation zero, is found to 

 be proportional to the difference of refractive indices of 

 glass and liquid. In the instrument as constructed by 

 Mi ssrs. Hilger, the range of refractive index is from 

 1-3300 to 1-6700, with a degree of accuracy of nearly o-oooi. 

 Tin- reading is direct, and by heating the water in the 

 tank to different temperatures the effect of temperature on 

 the index of the liquid may be determined. A measurement 

 can be obtained with i c.c. of liquid. 



The second issue of Le Monde, which is described as a 

 monthly illustrated encyclopaedia, being an anthology of 

 the reviews of all countries, has reached us. Copies may 

 be obtained in this country from Messrs. Nilsson and Co., 

 16 and tS Wardour Street, London, W., at the price of 

 three francs. Among other contributions to this issue we 

 notice translations into French of Mr. H. H. Suplee's 

 article in Cassier's Magazine on the determination of alti- 

 tudes reached by aeroplanes, and an article from The 

 Times on the great ocean liners which now connect Europe 

 and America. 



We have received from Prof. C. Ulpiani a reprint of a 

 paper from the Atti delta Societa Italiana per tl Frogresso 

 delle S dense, 1910, discussing the work of the United 

 States Bureau of Soils, especially the applications of 

 pin sical chemistry to the soil. 



NO. 2 1/8, VOL. 87] 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrenxes for August : — 

 Aug. 1. Jh. 11m. [upiter in conjunction -with the Moon 

 (Jupiter 1" 13' N.). 

 7. 22I1. 46m. Uranus in conjunction with the Moon 



(Uranus 4' 28' N.). 

 S. iSh. om. Mars at quadrature to the Sun. 

 10. ih. 0111. Venus at greatest brilliancy. 

 10-12. Maximum of the 1'erseid Meteors. 



12. 2ih. om. Mercury at greatest elongation E. 



13. 6h. om. Saturn at quadiatuie to the Sun. 



16. I5h. 53111. Mars in conjunction with Saturn (Mars 



o° 21' N.). 

 16. 2oh. 2m. Saturn in conjunction with the M 1 



(Saturn 4° 2' S. ). 

 16. 2oh. 12111. Mars in conjunction with the Moon (Mars 



3° 40' S.). 

 19. I9h. om. Venus in Aphelion. 

 zi. ih. 20111. Neptune in conjunction with the Moon 



(Neptune 5" 36' S. ). 

 22. I4h. 0111. Venus stationary. 

 25. nh. 50111. "Venus in conjunction with the Moon 



(Venus I0 : 23' S.). 

 28. 22h. om. Jupiter in conjunction with the Moon 



(Jupiter I u 41' N.). 



Discovery of another Comet (1911c). — A telegram 

 from the Kiel Centralstelle announces the discovery of a 

 comet at the Geneva Observatory (U.S.A.) on July 20. At 

 9h. 52m. (Geneva M.T.) the comet's position was 



R.A. 22I1. 13.6m., dec. 20° 57' N., 

 and it was moving in a north-westerly direction. A second 

 observation was made on July 21 at the Lick Observatory, 

 and at 9h.' 53-im. (Lick M.T.) the position was 

 R.A. 22h. 13m., dec. 21° 34' 40" N. 

 This position precedes the Great Square, and forms, 

 roughly, an equilateral triangle with a and /3 Pegasi ; it 

 transits at about 1 a.m. According to the Lick observers, 

 the comet was of about the tenth magnitude, and was 

 moving in a N.N.W. direction. 



The Kiess Comet, 191 16. — A number of observations of 

 comet 1911b appear in No. 4512 of the Astronomische 

 Nachrichten, where the magnitude is variously recorded 

 with values varying from 4-0 to 8-5. The object is blue 

 or green, and has a faint tail, which on a photograph taken 

 at Simeis on July 9 was 0-5° long, in position angle 285 . 



Later observations have made it possible for Dr. Kobold 

 to improve his elements and obtain an ephemeris which 

 practically agrees with the observations ; these he publishes 

 in a supplement to No. 4313 of the Astronomische 

 Nachrichten. 



Ephemeris (12/1. M.T. Berlin). 



1911 a(irue) S(ttue) log'- log A mag. 



h. m. 

 July 26 ... 4 I5'0 ... +3° 3 - 3 000 



„ 28 ... 4 9-9 ... +28 577 ... 99515 .. 9 ^5° 2 ■•■ 5'8 



,, 30 ... 4 4-2 ... +27 40-2 

 Aug. 1 ... 3 575 •■■ + 26 3'5 ••• 9 9755 •■■ 97742 ... 5-4 



,, 3 ■•■ 3 497 ■■■ +24 5'6 



Perihelion occurred on June 30, so that the comet is now- 

 receding from the sun ; but it is approaching the earth, and 

 later, in August, will come within 0-2 of an astronomical 

 unit. It should then provide a striking spectacle, especially 

 to those situated in the southern hemisphere, in the early 

 morning sky. At present its calculated magnitude is about 

 6-0, but when nearest the earth the comet should ini 

 in brightness to about magnitude 3-3. The present posi- 

 tion lies about half-way between 1 Aurigae and the Pleiad--. 

 and on August 3-4 the comet should be very near to the 

 latter asteris'rn. 



Wolf's Comet, 1911a. — Observations of this faint comet 

 are recorded in No. 4512 of the Astronomische Nachrichten. 

 M. Javelle, observing at Nice on July 5, found it to be a 

 star-like object of less than magnitude 14-0, having a faint 

 nebulosity about it. M. Kamensky finds that the correc- 

 tion to his ephemeris is about — o-ss. and —6-3". and asks 

 observers to communicate their positions to him. 



