February 13, 1896J 



NA TURE 



345 



turbances, and chronicled in that table of Prof. Young's, 

 to which I have already called attention ; but the im- 

 portant thing, the unexpected thing, is the marvellously 

 close connection between eclipse- and star-spectrum 

 photographs. 



Chapter V. 



the 



Again I recall you from the heavens to the earth 

 time is the beginning of the present year. 



You remember that last year was made memorable by 

 the announcement of the discovery by Lord Rayleigh and 

 Prof. Ramsay of a new gas called argon, and you know 

 that the discovery was brought about chiefly in the first 

 instance by the very accurate observations of Lord Ray- 

 leigh, who found that when he was determining the 

 weight of air in a globe of a certain capacity, the weight 

 depended upon the source from which he got the nitrogen. 



From the nitrogen from atmospheric air he obtained 

 one weight, and from that obtained by certain chemical 

 processes he obtained another, and ultimately it was found 

 that there was an unknown element which produced these 

 results, these various changes in the weight ; and as a 

 consequence we had the discovery of argon. 



It struck Mr. Miers, of the British Museum, that it 

 might be desirable to draw attention to the nitrogen which 

 we have seen Dr. Hillebrand in 1888 obtaining from his 

 crystal of uraninite ; his observations, of course, were 



to send specimens of the tubes containing this gas round 

 to other people, and he sent one of them to me. 



I received Prof Ramsay's tube on March 28, but as it 

 was not suitable for the experiments I wished to make, in 

 his absence, I obtained some gas for myself by a different 

 method with which I need not trouble you. From March 

 30 onwards my assistants and myself had a very exciting 

 time. One by one the unknown lines I had observed in. 

 the sun in 1868 were found to belong to the gas I was 

 distilling from broggerite, not only D^ but 4923, 5017, 

 4471 [(Lorenzoni's /) 6677 (the BC of Fig. 7), referred 

 to previously, and many other solar lines, were all caught 

 in a few weeks. 



But this was by no means all. The solar observations- 

 had been made by eye, and referred therefore to the less 

 refrangible part of the spectrum, but I had obtained and 

 studied hundreds of stellar photographs, so 1 at once 

 proceeded to photograph the gas and compare its more 

 refrangible lines with stellar lines. 



Here, if possible, the result was still more marvellous. 

 In the few-lined stars, by May 6, I had caught nearly 

 all the most important lines at the first casts of the spec- 

 troscopic net. Fig. 13, which includes some later results,, 

 will give an idea of the tremendous revelation which had 

 been made as to the chemistry of some of the stages of 

 star-life. 



These results enabled us at once to understand how it 



^^ 



% 



Fig. 13. — The spectrum of Kellatrix showing the lines of hydrogen and those which have been traced to the gas obtained from minerals. 



more in the mind of Mr. Miers than in the minds of the 

 pure chemists. He therefore communicated with Prof. 

 Ramsay, who lost no time, because it was very interesting 

 to study every possible source of nitrogen and see what 

 its behaviour was in regard to the quantity of argon that 

 it produced, and in the relation generally of the gas to 

 the argon which was produced from it. 



Prof Ramsay treated uraninite in exactly the same 



way that Dr. Hillebrand had done in 1888. The gas 



obtained as Dr. Hillebrand had obtained it was eventually 



Libmitted to a spectroscopic test, following Dr. Hille- 



nand's example. But here a noteworthy thing comes in. 



// so happened that the pressure and electrical con- 

 ditions employed by Prof Ramsay were so different from 

 those used by Dr. Hillebrand that, although nitrogen was 

 undoubtedly present, the fluted spectrum which, as I 

 have previously stated, floods the yellow part of the 

 spectrum with luminous details, was absent. But still 

 there was something there. 



Judge of Prof. Ramsay's surprise when he found that 

 he got a bright yellow line ; that was the chief thing, 

 and ;w/the strong suggestion of the spectrum of nitrogen. 

 Careful measurements indicated that the twenty-six-year- 

 old helium had at last been run to earth, D-' was at last 

 visible in a laboratory. Prof. Ramsay was good enough 



NO. 1372, VOL. 53] 



was that the " unknown lines " had been seen both in the 

 sun's chromosphere and some nebula,' and stars. The 

 gas obtained from the minerals made its appearance in 

 the various heavenly bodies in which the conditions of the 

 highest temperatures were present, and the more the 

 work goes on we find that this gas is really the origin of 

 most, but certainly not of a//, of the unknown lines which 

 have been teasing astronomical workers for the last 

 quarter of a century. 



A great deal of work has been done upon these gases 

 from other points of view than those which affect my 

 story, and perhaps I may be allowed just to refer for a 

 minute or two to one of the results which have been 

 obtained by myself. 



It is perfectly obvious that the gas as obtained from 

 uraninite is a mixture of several gases ; that the gas which 

 gives the yellow line has not yet been isolated, but is 

 always mixed up with other gases which give other lines. 



In May I communicated to the Royal Society some 

 experiments which indicated in a most conclusive manner 

 the fact that the lines D^ and 667, to deal with two only 

 for the sake of simplicity, were not produced by the same 

 gas, and that 667 seemed to be a compound gas of which 

 D^ represents one of the constituents. 



Some little time after, Profs. Runge and Paschen, from 



