264 SCIENCE PROGRESS. 



recorded in the first observations of the solar disturbances, 

 and chronicled in that table of Professor Young's to which 

 I have already called attention ; but the important thing is 

 the marvellously close connection between eclipse- and star- 

 spectrum photographs so far as the "unknown lines" are 

 concerned. 



Nearly all the lines given in the table on p. 259 as 

 visible in the Nebula of Orion and afterwards found in 

 Bellatrix, are also among the lines photographed during the 

 eclipse. 



DISCOVERY OF A TERRESTRIAL SOURCE OF HELIUM, 1895. 



The year 1894 was made memorable by the announce- 

 ment of the discovery by Lord Rayleigh and Professor 

 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 Rayleigh, who 

 found that when he was determining the weight of air in 

 the 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 pro- 

 cesses 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 1895 discovery of argon. 



Early in 1895 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 more in the mind of Mr. Miers than in the 

 minds of the pure chemists. He therefore communicated 

 with Professor 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. 



Professor Ramsay treated uraninite in exactly the same 



