284 



NA rURE 



[January 20, 1898 



OUR ASTRONOMICAL COLUMN. 



A New Spectroscopic Binary. — In the Harvard College 

 Observatory Circular {'^o. 21) Prof. E. C. Pickering announces 

 that, from an examination of the Draper Memorial photographs, 

 Mrs. Fleming has found that the star A. G. C. 20263, ^ Lupi, 

 is a spectroscopic binary. The period has not yet been deter- 

 mined, but photographs are being taken for this purpose. 



Measures of the spectroscopic binaries /u' Scorpii and A. G. C. 

 10534 show that the relative velocities of the components are 

 approximately 290 and 380 miles respectively. The velocities 

 are therefore much greater than in the case of C Ursse Majoris 

 and ,'3 Aurigde. The separation of some of the lines amounts to 

 as much as nine tenth-metres. 



Winnecke's Periodic Comet. — Ashorttime ago (Nature, 

 December 23, 1897) we gave Hillebrand's search ephemeris for 

 this comet, and subsequently (January 6, 1898) announced its 

 discovery by Perrine at the Lick Observatory, with a slightly 

 different position from that calculated. 



A supplementary note in the Astronomical Journal {'if^o. 423^ 

 gives the corrections to be made to Hillebrand's ephemeris as 



Aa = + 2m. 8s., AS 



9 3- 



Berlin M.T. 

 1898, Jan. 18-5 



Applying these values, we have the following approximately 

 corrected ephemeris. 



a S 



h. m. s. o / 



16 22 8 ... - 7 5r4 



225 ... 16 39 7 ... - 8 46-3 



„ 26-5 ... 16 54 44 ... - 9 39'6 



30-5 ... 17 14 57 ... -10 30-6 



Level of Su.\-spots. — Much has been said on both sides 

 of the question as to whether sun-spots are concave or convex ; 

 and although the Wilsonian doctrine is generally accepted, there 

 are at the same time many difificulties which tell against it. 



At first sight it would seem that notches, seen and photo- 

 graphed when a spot is on the limb, go to support the theory ; but 

 on the contrary, as Father Sidgreaves pointed out {Monthly 

 Notices, vol. Iv. p. 285, 1895), t^hey are difficult to account for by 

 it. Again, a more serious objection than this is that both 

 Langley and Frost have found that the ratio of umbral radiation 

 to that of the neighbouring photosphere undoubtedly increases 

 with the distance from the centre of the sun's disc ; from this 

 result it would seem that the umbral region whose radiation was 

 measured was above the level of the photosphere, and conse- 

 quently subjected to less absorption. 



In the Astrophysical Journal (vol. vi. p. 366), Prof. George 

 E. Hale considers the conclusions which seem to be at variance 

 \vith the idea that spots are depressions, and suggests that spots 

 •may be hollows in comparatively small areas of the photosphere 

 which are raised above the ordinary level ; for most ad|^iit that 

 the penumbra is at a higher level than the umbra, and it cannot 

 be doubted that penumbral filaments overlie the umbra, and 

 frequently unite to form bridges extending completely across it. 



This theory, so far as he has examined it, seems to reconcile the 

 conflicting testimony offered by the supporters of the two views. 

 Notches at the sun's limb are accounted fur by assuming that the 

 side of the spot nearest us is somewhat lower than the opposite 

 penumbra, and the darkening of the limb might thus be produced 

 by the smaller radiations of the penumbra. Also, to account 

 for the results obtained by Langley and Frost, it is only necessary 

 to assume that the region of the umbra is slightly raised above 

 the general level of the photosphere. 



A Variable Bright Hydrogen Line. — From a compari- 

 son of the Draper Memorial photographs of the star A. G. C. 

 9181, taken on different dates, Miss A. J. Cannon has found 

 that the bright hydrogen line H;3 is variable (Harvard College 

 Observatory Circular, No. 21). On October 5, 1892, it was in- 

 visible. On November 28, 1894, it was about half as bright as 

 the corresponding line in A. G. C. 9198, a> Canis Majoris. On 

 April 27 and30, 1895, the line in A. G. C. 9181 was dislinctly the 

 brighter of the two, while in January 1897 it vyas again invisible. 

 From a large number of photographs of this object taken 

 recently it appears that this line, which was bright in October 

 1897, is now, December 27, invisible. 



Astronomical Constants. — It will be remembered that 

 Dr. Fr. Porro, in a long letter to Nature (December 9, 1897) 

 on " Astronomical Constants and the Paris Conference," some- 



NO. 1473. '*''^^L. 37] 



what depreciated the adoption of some of the constants 

 (especially that of precessional motion), believing " that a 

 general renovation of fundamental astronomy must precede a 

 new and authoritative definition of the numbers that the twentieth 

 century must accept as the more probable values." In the 

 Astronomical Journal (No. 423) Prof. Lewis Boss gives his re- 

 joinder to Prof. Newcomb's remarks on his first paper, which 

 critici.sed the adoption of the constant of precessional motion, 

 and regrets that others have not replied before him. The 

 additional note to Dr. Porro's letter referred to above, although 

 very concise, formed to some extent a reply to Prof. Newcomb ; 

 but Prof. Boss's second paper goes into the matter in minuter 

 detail. In conclusion, he thinks ftiat the present time seems 

 singularly inopportune for the adoption of a new evaluation of 

 the precessional motion, and suggests that a new and ingoing 

 investigation of the motion of the equinox should be made ; 

 for although the investigation made by Newcomb a quarter of 

 a century ago was exhaustive for its time, new evidence has 

 since accumulated which has not been brought to bear upon 

 the problem ; and we may confidently look for still more 

 valuable observations from several observatories within the next 

 ten years. 



Longitude of Madras. — We have recently received the 

 *' Report on the Determination of the Longitude of Madras," 

 by the officers of the Indian Survey. The difference of longi- 

 tude actually determined on this survey was that between 

 Greenwich and Karachi, the latter place being at the end of 

 the submarine cable of the " Persian Gulf Telegraphs." It was 

 only necessary to commence at Karachi, for the whole area of 

 India has been covered with a network of longitude, arcs, and 

 by their means the difference of longitude between Madras and 

 Karachi had been accurately determined beforehand. 



The distance from Karachi to Greenwich, extending over 

 5197 miles of wire, was divided up into four main arcs, viz. : — 

 Karachi — Bushire, Teheran — Bushire, Teheran — Potsdam, Pots- 

 dam — Greenwich, the clock comparisons being made by signalling 

 over the telegraph wire connecting these places. The final 

 result of these observations gives the longitude of Madras as 

 5h 20m. 59s. '113, with a probable error of ±os. 0227. 



It now rests with the Government of India to decide whether 

 this value should be adopted or not, for a change in the longi- 

 tude of Madras affects noi only British India, but the Malay 

 Peninsula, Tonquin, China, the Dutch Indies, and Australia. 



THE ELECTRO-CHEMICAL INDUSTRIES} 



"T^WO months hence there should be celebrated in Como the 

 -*■ centenary of Volta's famous discovery, to which we owe 

 the rise of electro-chemistry. Electrical phenomena had been 

 studied long before Volta's time ; but if we except the action of 

 the electric spark employed by Cavendish to induce the com- 

 bination of affinitive gases, no electro-chemical effects had been 

 observed. The analytical power of the voltaic pile was first 

 actually demonstrated by Davy, who made memorable the year 

 1806 by the electrolytic extraction of potassium from potash. 

 To Faraday, who succeeded Davy, we owe the discovery of the 

 law of electrolytic conduction and the enunciation of the 

 principles of the dynamo. As early as 1842 magneto-electric 

 current generators were employed in the Elkington factories at 

 Birmingham, for electro-plating purposes ; and comparatively 

 within recent years the principle of electrotyping has been 

 applied also to copper refining. It is estimated that one- third 

 of all the refined copper required is now produced electro- 

 lytically. Metal produced in this way is purer and has a higher 

 conductivity than that produced by the older method, which 

 leaves an admixture of arsenic. The power required is relatively 

 small, and the current density may vary within very considerable 

 limits without detriment to the product and with the gain of 

 great rapidity of deposition. The conditions required are to 

 adapt the strength of the solution to the strength ot the current, 

 and when the current density is high to effect a rapid circulation 

 of the electrolyte. Mr. Swan referred to a method devised by 

 himself for producing pure copper wire directly by electrolytic 

 action, so avoiding the slight loss of conductivity due to fusion 

 and drawing. The process, however, was found to be too 

 costly for commercial use. 



1 Abstract of the pre.sidential address delivered by Mr. J. \V. Swan 

 F.R S., before the Institution of Klfctrical Engineers, January 13. 



