Ixxiv Transactions of the South African Philosophical Society. 



drop to the ocean. I believe we must look to the new astronomy 

 for aid in the solution of many great chemical problems. 



The astronomer of the new school has to thank the physicist and 

 the chemist for the foundation of his science, but the time is coming 

 — we almost see it now — w^hen the astronomer will repay the debt 

 by wide-reaching contributions to the very fundamenta of chemical 

 science. Thirty years ago there was first observed, in the spectrum 

 of the sun's chromosphere, a very remarkable bright yellow line, near 

 the position of the well-known D lines of Sodium. So distinctive 

 was this line, and so certainly not due to any known terrestrial 

 substance, that it was called the Helium line. In 1894 Lord 

 Eayleigh, who was engaged in determining the densities of the 

 principal gases, found what was then to him an inexplicable diffe- 

 rence between the weight of a volume of nitrogen prepared from 

 atmospheric air and the weight of the same volume of nitrogen 

 prepared from ammonia or by other chemical means. Repeated ex- 

 periment showed that the weight of the constant volume of atmo- 

 spheric nitrogen was about -^-^ greater than that of the chemically 

 prepared gas. After exhausting all means of testing the purity of 

 the chemically prepared nitrogen, Lord Eayleigh and Professor- 

 Ramsay, in January, 1895, finally traced the cause of their perplexity 

 to a hitherto unknown gas present in our atmosphere which they 

 named Argon. Here was a great chemical discovery due to the co- 

 operation of the physicist and the chemist. On the publication of 

 this paper Mr. Meirs of the British Museum directed Ramsay's, 

 attention to a paper by Hildebrand, in which the author had found 

 that the mineral ui;anite contained nitrogen ; and Ramsay naturally 

 was desirous of examining every source of nitrogen. Accordingly he 

 boiled clevite — a uranite of lead containing rare earths — with weak 

 sulphuric acid, and after collecting the evolved gas he found that its 

 spectrum gave not only the now known Argon lines but also new lines, 

 one of which, to Ramsay's- intense surprise and delight, absolutely 

 coincided with the Helium line, which had been known for twenty-six: 

 years in the spectrum of the solar chromosphere. Of course, as 

 soon as Helium was prepared, its spectrum was thoroughly studied, 

 and then Lockyer and McClean were quick to show that many of 

 the lines, which occurred in the spectra of a large class of stars, were 

 due to this same Helium. Here was another chemical discovery 

 in which the astronomer and the chemist were mutually helpful — a 

 discovery also that is yet destined to throw much light on the 

 evolution of stars. 



One more illustration, and I am done. The study of the 

 phcnoinena of light has compelled the conviction that light is 



