under consideration

      Discovery of Argon.—It is a curious fact that during the 30 or 40 years immediately preceding the discovery of argon, little work was done by chemists on the atmosphere. They seemed to feel that here at least an end had been reached, and the wise man should bend his energies in other directions. No suspicion was entertained that the air was a veritable gold mine for chemical research, and even after the evidence seemed to indicate that we had not yet found out all there was to know about our atmosphere, there was a feeling of doubt and uncertainty that made the work move slowly. The first cue to the undiscovered elements was partly accidental. In 1882 and several succeeding years, Lord Rayleigh worked on the relative densities of hydrogen and oxygen. In 1893 he published his results on the densities of some other gases, notably those of oxygen, nitrogen and air. 2 He prepared oxygen and nitrogen by different methods ; and while the density of oxygen proved in all cases to be the same, that of nitrogen prepared by chemical methods differed from that of nitrogen obtained from the air. The latter was about 0.5 per cent heavier than the former. A difference of this magnitude could not be accounted for on the basis of experimental error, and the riddle remained unanswered for some time. Finally, Prof. (afterwards Sir) William Ramsay asked permission of Lord Rayleigh to take up the matter from the chemical standpoint.     (Etc.) 1 Chief chemist, bureau of Mines, Washington, D. C. 2 Proc. Roy. Soc., 1892, Vol. 53, p. 146; 1894, Vol. 55, p. 340. ( Liddell vol II p. 911 sect 28