182 



NA TURE 



[December 21, 1905 



The results of an interesting research on the selective 

 reflection, by various crystals, in the infra-red spectrum 

 are published by Mr. J. T. Porter, of Johns Hopkins 

 University, in the November number of the Astrophysical 

 Journal. It has previously bean shown by Prof. E. F. 

 Nichols that in the neighbourhood of 8-5/1 the reflection 

 from quartz is twenty or thirty times greater than in 

 other parts of the spectrum, so that after three reflections 

 from such a surface the spectrum practically contains only 

 radiations of that wave-length. The wave-lengths of the 

 " Reststrahlen," or the rays remaining after reflection, 

 have already been determined for seven other substances 

 by previous workers, and Mr. Porter examined fourteen 

 additional crystalline compounds and found that at least 

 seven of them exhibited unmistakable maxima in various 

 parts of the spectrum. The radiometer and the method 

 employed are fully described and illustrated in his paper, 

 which also shows the energy curves of the spectra of the 

 reflected radiations. The list given for nine of the sub- 

 stances tested shows that the wave-lengths of their 

 "Reststrahlen" vary from 2-30/1 for copper sulphate to 

 10-31/1 for potassium dichromate. 



Messrs. Whittaker and Co. have published a third 

 edition of Mr. Joseph Poole's " Practical Telephone Hand- 

 book." The new edition has been entirely re-written and 

 greatly enlarged. 



We have received from the superintendent of Govern- 

 ment printing in India two volumes of the agricultural 

 statistics of India for the years 1899-1900 to 1903-1904. 

 The statistics have been compiled in the office of the 

 Director-General of Commercial Intelligence. The first 

 volume is concerned with British India, and the second 

 with the native States. The volumes will prove of value 

 to statisticians interested in Indian agriculture. 



"Who's Who" and the "Who's Who Year I k" 



for 1906 have now been issued by Messrs. A. and C. Black. 

 " Who's Who " is a familiar work of reference every- 

 where ; its price remains the same, 7s. 6d. net, but the 

 volume has been enlarged by the addition of eighty-two 

 pages. Interesting additions are made this year to many 

 of the biographies by a record of the number of a person's 

 sons and daughters. Motor and telephone numbers and 

 telegraphic addresses have been added where requisite. 

 The biographical notices of Fellows of the Royal Society 

 and other men of science contained in the volume are of 

 particular interest to us. This indispensable reference book 

 is admirably supplemented by the year-book with its con- 

 veniently arranged tables, among which are to be found 

 lists of the learned societies and university professors. 



OUR ASTRONOMICAL COLUMN. 



Discovery of a Third New Comet, 1905*2. — A telegram 

 from the Kiel Centralstelle announces the discovery of yet 

 another new comet. Apparently the proximity of this 

 object was discovered from the appearance of its image on 

 a photographic plate exposed on November 2.., and ex- 

 amined subsequently. The discoverv was made by Mr 

 Slipher at the Flagstaff (Lowell) Observatory, and the 

 position of the comet on November 2gd. gh. 27m (Flac- 

 staff M.T.) was found to be 



R.A. = 22h. 44m., dec. = n° 18' S. 



Diis is situated in the constellation Aquarius, about 

 half-way between A and t Aquarii. 



The daily movement in R.A. is given as —1° 33', or 

 6m. 12s.. and in declination as +25'. From this it will 



be seen that tin net was at that time travelling in the 



direction of the constellation Aquila. 



NO. l886, VOL. 73] 



Comets 1905b and 1905c. — An observation of comet 1905b, 

 made by Prof. E. Millosevich on December 13, gave correc- 

 tions of — 2s. and — 2 '-3 to the ephemeris published in 

 No. 4057 of. the Astronomische Nachrichten. The observed 

 magnitude was 1 1-5. 



The following set of elements for the orbit of comet 

 1905c have been computed by the discoverer, M. Giacobini, 

 and, together with an ephemeris, from which an extract 

 is given below, is published in the Comptes rendus for 

 December 1 1 : — 



T=i9o6 January 31-620 (Paris). 



co =i 7 °i 237 s ) 

 S3 = 89 42-0 V 1905-0 

 i = 42 44-3 J 

 log q - 1 72728 

 Ephemeris 12I1. (M.T. Paris). 



1905 o 8 log i Bright- 



Dec. 22 ... ii 41 51 ... +12 27-3 ... 0-1251 204 



„ 26 ... 16 3 49 ... + 9 44-0 ... CI153 ... 2-45 



The Recent Aurora and Magnetic Disturbances.- 

 From an account published in the current number of the 

 Observatory, we learn that on November 15, the date of 

 the recent great displav of the aurora, the greatest dis- 

 turbance of the Greenwich magnets which has been re- 

 corded during the present year took place. All three 

 elements were affected, a deflection of about 40' being 

 recorded by the declination-needle at 9 p.m. Of the two 

 considerable streams of sun-spots which appeared near to 

 the place of the great October spot (October 14-27), the one 

 was a little ahead of the central meridian and the other 

 not quite up to it at the time of the disturbance. 



Photographs of Jupiter's Sixth and Seventh 

 Satellites. — At the meeting of the Royal Astronomical 

 Society held on November 10, the Astronomer Royal ex- 

 hibited and explained some photographs of the sixth and 

 seventh satellites of Jupiter, obtained with the 30-inch 

 reflector of the Thompson equatorial at Greenwich. 



The results of the provisional measures of the photo- 

 graphs, and their comparison with the angles and distances 

 given by Dr. Ross's ephemeris, the dates, and the ex- 

 posures are given in No. 1, vol. lxvi., of the Monthly 

 Notices. The exposures for the seventh satellite varied 

 from 17 minutes to 177 minutes. 



The Intrinsic Light of the Corona. — Employing a 

 modified " Mascart " photometer, M. Chas. Fabry deter- 

 mined the relative brightness of the intrinsic light of the 

 corona during the recent total eclipse of the sun. As a 

 result, he found that at a distance of 5' from the edge 

 of the sun, and in the neighbourhood of the solar equator, 

 the light of the corona has an intrinsic value of about 720 

 candle-power. Comparing this with the mean intrinsic 

 value of the light of the full moon (viz. 2600 candles), he 

 obtains the ratio 0-28 : 1, a value which confirms Prof. 

 Turner's ratio of 0-25. To illustrate the great difficulty 

 which attends the photographing of the corona in full sun- 

 light, M. Fabry compares the value he thus obtained with 

 the accepted value for the brightness of the sky near to 

 the sun, and arrives at the conclusion that even the most 

 brilliant parts of the corona are probably some 2000 times 

 less bright than the sky on which they are projected 

 (Comptes rendus, No. 23). 



Suggested Name for Neptune's Satellite. — Writing to 

 the Observatory, M. Fouche suggests that Neptune's 

 satellite should be named after the most renowned of 

 Neptune's sons, i.e. Triton. He states that this name has 

 already been used for designating the satellite by several 

 well known astronomers. 



The "Companion to the Observatory," 1906. — As in 

 former years, the well known " Companion to the Observ- 

 atory, " published by Messrs. Taylor and Francis at is. 6d., 

 contains all the data that an ordinary astronomer is likely 

 to require in the briefest and handiest form. Messrs. 

 Denning, Maw, and Lcewy have again provided the data 

 referring to " Meteor Radiants," " Double Stars," and 

 " Variable-star Ephemerides " respectively, and Dr. F. E. 

 Ross's ephemeris for Jupiter's sixth satellite is given 

 amongst the other tables which deal with the satellites of 

 the major planets. 



