528 



NATURE 



[August 24, 1916 



tration of the acid in the ware below the glaze." 

 Time would have been better spent in developing this 

 point than in high-temperature experiments, which, 

 for dishes, were superfluous. The ware is made 

 very much thinner than has been customary, and con- 

 sequently is unduly fragile. In spite of careful pack- 

 ing two of the specimens arrived broken. It is very 

 desirable that we should be independent of foreign 

 supplies of porcelain, and it is to be hoped that the 

 enterprise of the Royal Worcester Porcelain Company 

 and other British porcelain manufacturers will be 

 rewarded, but prolonged use in the laboratory is the 

 only certain means of proving the qualities of the 

 new ware. 



^^ Messrs. Williams and Norgate announce 

 " Raphael Meldola : Reminiscences by those who 

 knew- him," with a preface by Lord Moulton and a 

 chronological list of Prof. Meldola 's publications. The 

 work will be divided as follows : — Biographical 

 memoir ; early years ; professor of chemistry ; chemical 

 investigator; naturalist; astronomer; personality. 



OVR ASTRONOMICAL COLUMN. 



The Solar Physics OfiSERVATORY.^The report of 

 the director of the Solar Physics Observatory for the 

 year ending March 31, 1916, has recently been issued, 

 this being the third annual report since the transference 

 of the observatory from South Kensington to Cam- 

 bridge. The work of the observatory' has been car- 

 ried on with difficult}- on account of the war, two 

 members of the staff now being absent on military- 

 service and two on munition work. Observational work 

 with the Newall telescope and the Huggins instru- 

 ments was not attempted, but the spectroheliograph 

 was in regular use, photographs of the sun's disc in 

 K2_3_, light having- been obtained on 112 days, and of 

 prominences at the limb on 93 days. Sun-spot spectra 

 in the region A 5300 to A 5500 were also successfully 

 photographed with the McClean installation. Mr. 

 Baxandall has made considerable progress in the 

 assignment of chemical origins of lines in stellar 

 spectra, and in a revision of the origins given by 

 Rowland for lines in the solar spectrum. The great . 

 majority of Rowland's identifications have been con- 

 firmed, and terrestrial equivalents for many line? not 

 identified by Rowland have been found by reference 

 to data subsequently published. Experimental work 

 has established the identity of the G group of the 

 solar spectrum with the hydrocarbon band A 4314 (see 

 N.ATURE, July 20), and it is thought that a 

 clue has been obtained to the interpretation, in terms 

 of carbon, of the remarkable spectrum of Comet Wells, 

 1882. In the department of meteorological physics, 

 Mr. C. T. R. Wilson has continued the study of 

 lightning discharges. 



With regard to the "Annals of the Solar Physics 

 Observatory," of which vol. iii., part i, has already 

 been distributed, it is now explained that vol. i. is 

 intended to contain historical and descriptive matter, 

 vol. ii. to refer to stellar investigations, and vol. iii. 

 to deal with work on the sun. 



Relative Luminosities of Sun and Stars. — A con- 

 venient formula for comparing the luminosity of a 

 star with that of the sun has been given by Mr. C. T. 

 Whitmell (L'Astronomie, August, 1916). Assuming 

 the stellar magnitude of the sun to be —26-5, and 

 designating the luminosity, parallax, and magnitude 

 of the star by L, p, and m, the luminosity of the star 

 in terms of that of the sun is given by the equation : 



log L = 0-0289 — 2 log/) — 04 m. 



In the case of Sirius, for example, where p — o-2,S" and 



NO. 2443, VOL. 97] 



"'"~':^' 'og'^=i-5"93 and L = 32-3, showing that 

 Sinus Ks about 32 times as bright as our sun. The 

 constant term in the equation depends upon the value 

 assigned to the sun's stellar magnitude, and is equal 

 to 106289 4- o-4(S), where S is the adopted value. 



The Thermopile in Photographic Photometry.— 

 The usual method of arriving at the magnitudes of 

 stars shown on photographs is to measure the dia- 

 meters of the stellar images, or to determine the 

 opacity of images purposely taken out of focus. In 

 either case the result depends in part on the judgment 

 of the observer, and the application of some purely- 

 physical method is evidently desirable. Such a method 

 has been devised by Mr. H. T. Stetson, of the Yerkes 

 Observatory, in which the star image is surrounded 

 by a small circular diaphragm, and the intensity of 

 the transmitted beam from a steady source of light, 

 as compared with that of the unrestricted beam, is 

 measured by means of a thermopile and galvanometer. 

 Theory leads to the expectation of a fourth-root rela- 

 tion between galvanometer deflections and stellar mag. 

 nitudes, and this has been confirmed experimentally. 

 The device appears to have reached a convenient prac- 

 tical form, and measurements of a plate of the 

 Pleiades, for example, indicated a probable error of 

 0-022 mag. for a single star. An extensive applica- 

 tion of the method to the eclipsing variable U Cepht'i 

 has been commenced, and variations not explained by 

 the eclipse theory have been detected. When provided 

 with a stage having a micrometer screw, and the 

 circular aperture being replaced by a slit, the appa- 

 ratus becomes well adapted for certain investigations 

 of spectra. In this form it seems likely to be especially 

 useful in the study of colour index, and may possibly 

 aid in the determination of radial velocities of faint 

 stars from objective prism plates taken through a neo- 

 dymium absorption cell {Astrophysical Journal, vol. 

 .xliii., pp. 253 and 325). 



RECENl INDIAN MUSEUM 

 PUBLICATIONS. 



THE latest serial publications of the Indian Museum 

 reach a very high level of excellence. Vol. v., 

 No. 3, of the Memoirs consists of Mr. Stanley Kemp's 

 report on the Decapod Crustacea of the Chilka Lake, 

 an area where the density of the water ranges ac- 

 cording to season between freshness and a saltness 

 equal to that of the sea. The si>ecies, which number 

 54, include crabs, hermit-crabs, Thalassinids, Caridea 

 and Peneids. Among the permanent inhabitants, 0; 

 species capable of withstanding every seasonal change 

 in the water, from fresh to salt, it is surprising to 

 find such characteristically marine forms as Leucosiid 

 and Xanthid crabs, Alpheidae, and the pelagic Lucifer. 

 The permanent inhabitants constitute 72 per cent. 0: 

 the whole. The seasonal immigrants (about 7'5 

 the whole) all appear, whether normally marine o: 

 fresh- water species, to breed in the lake. The casu.i 

 visitors (about 20 per cent.) are almost all from th- 

 sea. Among the 12 species described as new i- 

 Athanas polymorphus, the males of which are trimor- 

 phic. The report is a model of clear and critical 

 exposition, being rich in inference and illustration, but 

 always concise and explicit. 



No. I of vol. vi. of the Memoirs contains two 

 important papers, one on Indian Tunicata by Dr. 

 Asajiro Oka, the other by Colonel J. Stephenson on 

 Oriental earthworms. The first deals with simple 

 Ascidians and pelagic forms, and does not go much 

 outside the collections made by the Investigator, i 

 Perhaps the most interesting item is a full descrip-j 



