538 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
It is certain that anyone may be deceived; but it is not anyone 
indeed who would have been capable of discovering crypton and 
xenon in the air, which contains in volume 1 in 20,000,000 of the first 
and 1 in 170,000,000 of the second. 
This research on the rare gases of the atmosphere will remain a 
perfect model of original research. And if there was anything to be 
admired more than the ability in experimentation and the scientific 
penetration displayed, it was the energy and persevering ardor, 
qualities doubtless less brilliant, but which in this kind of work were 
absolutely indispensable. 
Another question, in this connection, could not fail to present itself 
to Ramsay’s mind. Are there not in the same group of inert gases, 
noble gases, as he liked to call them, other elements, heavier than 
xenon as predicted by the periodic system, or lighter than helium, 
such as nebulium, whose presence is probable in the nebule, and 
coronium, which appears to exist in the solar corona ? 
We will recall in passing that beside the inert gases, Armand 
Gautier recognized in the atmospheric air an appreciable proportion 
of a gas lighter than helium and which was not other than hydrogen, 
whose production proposed a most suggestive geochemical problem. 
Ramsay busied himself then in the search for new rare gases. With 
Watson he examined the lightest gases in the atmosphere in the 
hope of obtaining a gas less dense than helium, but without success. 
He was not more fortunate in the systematic study, undertaken with 
Richard Moore, of the distillation products of an enormous mass of 
liquid air (120 tons), put at his disposal by George Claude. Ramsay 
arrived at the conclusion that if the air contains gases heavier than 
xenon, the proportion of them is extremely small and does not exceed 
one twenty-fifth of one-billionth. 
The discovery of the rare gases had excited universal enthusiasm. 
Physicists and chemists far and near wished to study these new ele- 
ments; and it is interesting, for the glory of Ramsay, to indicate 
briefly the principal results that have issued from this study. 
Some, interested especially in the problem of affinity, sought, but 
in vain, to arouse chemical activity which they supposed to be dor- 
mant in the rare gases. Others, on the other hand, sought for them 
in natural media. Following a systematic study of a great number 
of subterranean gases (gas from thermo-mineral sources, volcanic 
gas; fire-damp), some simple conclusions have been formulated :* 
(1) All the natural gaseous compounds contain the five rare gases, 
and certain of them contain appreciable quantities of helium, some as 
much as 6 per cent (thermal gas of Maiziéres, Cote-d’Or), and even 10 
5 Troost and Ouvrard; C. R., t. 121, p. 394; 1895. Berthelot, C. R., t. 120, pp. 581-660 
and 316, 1895; t. 124, p. 113, 1897. 
6 Charles Moureu and Adolphe Lepape, loc. cit. 
