324 



NATURE 



[Feb. 22, 1872 



Taken, then, on the whole, this aurora of February 4th was 

 one of the most brilliant, most interesting, and most widely- 

 visible which has been witnessed for many years past, and is 

 probably one that will cause renewed attention to be paid to the 

 still unsolved problem of their causes. 



J. r. Earwaicer 



[We have also received the following from J. W. Spengel 

 of Berlin: — "At Berlin, the sky being covered by clouds, 

 no one could see anything. But a young astronomer of our 

 observatory told me that he had recognised the existence 

 of a mighty aurora by means of the spectroscope. The 

 magnets were also vehemently disturbed, and all the tele- 

 graphs failed for several hours. The following appears in tlie 

 LcipTAgcr Allc^anciiic Zdliing for Feb. 8 : — 'Freiberg, Feb. 6. 

 The aurora observed by many on the evening of Sunday caused 

 here a complete interruption of communication through the tele- 

 graph wires for some time. The intensity between 5-40 and 

 6 '45 overcame the strength of the battery at this station, so that it 

 was not possible to change the oscillations of the magnetic needle 

 caused by the earth-stream. After the northern light had be- 

 come fully developed the oscillations became stronger, and fol- 

 lowed one another at short intervals until the phenomena 

 entirely disappeared about 7 P.M.' At Warmbrunn in the 

 Riesengebirge, the aurora Mas seen magnificently from 6 to S'30. 

 Towards 10 it had almost disappeared. The thermometer indi- 

 cated 0° C, with a violent storm from the south-west. About 

 1 1 the storm suddenly subsided ; the thermometer fell to - I '5°, 

 and the aurora appeared for the second time in the same manner 

 and with the same uninterrupted play of colours as at 6. After 

 1 1 '30 the storm recommenced, and the aurora disappeared soon 

 after 12. The play of the aurora on the snow-covered mountains 

 is described as one of the most magnificent sights that can be 

 conceived." — Ed.] 



REFERENCE SPECTRUM FOR THE CHIEF 

 AURORA LINE 



Xl/HILE Nature herself seems to delight in surround- 

 » ' ing some questions with triple difficulties and mys- 

 teries almost inscrutable, there are other questions which 

 she has made the easiest of the easy if men will only use 

 the means which she has prepai'ed. And amongst such 

 easy questions, no more signal example can be quoted 

 than the exact spectrum place, within very narrow limits 

 indeed, of Angstrom's yellow-green aurora line, whenever 

 any aurora at all appears. 



This chief aurora line coinciding precisely (as I believe 

 I may say from my own observations, though by means 

 of the roughest of home-made apparatus) with the second 

 line, at W.L. 5579, of the citron band of the blue base of 

 flame, from any and every material used for artificial 

 illumination by man, and having immediately on one 

 side the ist line, of the same strength with itself, at W.L. 

 5630, and on the other side the fainter 3rd line, at W.L. 

 5535, of the same citron band ; the smallest variation of 

 spectrum place in the aurora line can be instantly per- 

 ceived by the eye on this chemical scale, without the aid 

 of any mensuration apparatus. 



And yet in your last impression a respectable spectro- 

 scopist, after much labour, informs the Academy of 

 Sciences in Paris, on Feb. 5, that Angstrom's yclIow-green 

 aurora line is somewhere close to Fraunhofer's solar line 

 E, ?>. W.L. 5269; and in your previous impression a 

 returning Indian observer considers the same Angstrom 

 line to be somewhere near F, or W.L. 4860. Now, not 

 only are these statements in error to the extent of from 30 

 to 70 times what they need be, but they cruelly drag us 

 backwards in what should be the always onward course 

 of science, and cause men to flounder once again in that 

 slough of confusion they were immersed in a couple of 

 years ago, when the chief solar corona line, at W.L. 5316, 



and Angstrom's grand aurora line, at W.L. 5579, were 

 stated to be one and the same line, in the same place. 



Excuse may, indeed, be proffered for these two obser- 

 vers, that they did not know of such a convenient night 

 reference-spectrum as that which I have now alluded to ; 

 and then comes the question as to whose fault was that. 



A full description of the method (after extensive trial 

 for several months) was sent by me to the Royal Astro- 

 nomical Society on May 30, 1871, with the particular 

 request that the paper might be read at their June meet- 

 ing and printed in the June Monthly Notice. This was 

 mainly with the hope of supplying some possibly useful 

 hints to the intending eclipse-corona-observers of Decem- 

 ber. The paper, however, though taken in, was neither 

 read at the June meeting (if I am rightly informed) nor 

 did it appear in the June Monthly Notice ; but was handed 

 over to secret referees, who simply sat upon it during six 

 long months — or until the eclipse was safely past, and 

 then they began to hint about possible objections being 

 likely to be taken against some parts of the paper. 



Of course 1 could not allow so admirable a society to 

 run any risks of which they were afraid on my account ; 

 so I withdrew the paper thereupon, and am now engaged 

 in publishing it myself, sustained in so doing by the hope 

 that, although the eclipse for which it was mainly intended 

 is irretrievably gone, its pages may yet be useful to some 

 spectroscopists of aurora ; and, in fact, that through their 

 influence certain of both French and English observers 

 will cease to attempt comparing the faint aurora's chief 

 line with a bright solar spectrum, which they can never 

 see in combination therewith (and if they could it has no 

 coincident lines), but with a cheaply-procured chemical 

 spectrum, which only comes well into view under the 

 darkness of night, and is gifted by Nature in the spectro- 

 scope with an easily recognisable line in apparently 

 absolute coincidence with the cosmical line of Angstrom. 

 C. PiAzzi Smyth 



15, Royal Terrace, Edinburgh, Feb. 16 



AMERICAN DEEP-SEA SOUNDINGS* 



UNDER the title at foot a pamphlet of thirty-three 

 pages, accompanied by a large chart, and illustrated 

 by several diagrams and tables, has been issued. The 

 school-ship Mercury is a vessel belonging to the com- 

 missioners having in charge the hospitals and prisons of 

 New York city, and is employed for the purpose of 

 training boys, committed by the magistrates for vagrancy 

 and slight misdemeanours, to become thorough seamen. 

 Instead of growing up to be a curse to the community, 

 such boys are made into valuable men. The adventurous 

 life has a special charm for them. 



An essential feature of the discipline on this ship is to 

 make long cruises, by which the boys are fitted quickly to 

 enter into the service of the navy or mercantile marine. 

 Of 25S boys carried out on this voyage, 100 were on the 

 return of the ship, in the opinion of the captain, capable 

 of discharging the duties of ordinary seamen. 



The commissioners, in addition to the above object, 

 desiring to advance the interests of science as far as lay 

 in their power, instructed the captain, P. Giraud, to obtain 

 a series of soundings on the line of or near the equator, 

 from the coast of Africa to the mouth of the Amazon, to 

 observe the set of the surface currents and the temperature 

 of the water at various depths. He was also directed to 

 bring home specimens of water and of the sea bottom. 



The ship sailed on December 20, 1S70, and arrived at 

 Sierra Leone on February 14. On February 21 she left 



* Cruise of the school-ship Mercury in the Tropical Atlantic, with a 

 Report to the Commissioners of Pubhc Charities anu Correction of the City 

 of New York on the chemical and physical facts collected from the deep-sea 

 researches made during the voyage of the nautical school-ship Mercury^ 

 undertaken by their order in the Tropical Atlantic and Caribbean Sea, 

 1870-71. By Henry Draper, M.D., Professor of Analytical Chemistry and 

 Physiology in the University of New York. 



