RECENTLY DISCOVERED GASES. 269 



the other hand, only traces of hydrocarbons and hydrogen. One 

 mineral only, malakon, gave sufficient argon to be recognizable by the 

 spectroscope ; the others which contained helium gave off generally also 

 a trace of argon, as was later shown by our diffusion experiments. 

 Naturally it was impossible to be certain that the few cubic centime- 

 ters of gas which we collected from these minerals contained no new 

 gas, but we failed to detect the presence of any new lines with the 

 spectroscope. 



You will, undoubtedly, recall that soon after the discovery of helium 

 doubts were expressed in many quarters as to whether the gas was 

 really uniform or a mixture. In order to dispel these doubts, and also 

 to search for the missing gas, Doctor Collie and I carried out a long 

 series of diffusion experiments. Through these we reached the con- 

 clusion that it was, in fact, possible to separate helium into two constit- 

 uents, one of which possessed a somewhat higher density than the 

 other. Later experiments, however, in conj unction with Doctor Travers, 

 showed that this conclusion was erroneous. In this second series much 

 larger quantities of helium were at our disposal, and, to our disappoint- 

 ment, we found that the heavier fractions of our gas owed their greater 

 density to the presence of a trace of argon. Here, again, we were 

 unable to find any new line in the spectrum, and thus far our search 

 was fruitless. 



We next directed our attention to meteorites and to mineral waters. 

 Only one out of seven meteorites examined by Dr. Travers and myself 

 showed the presence of helium and with it a trace of argon; the others 

 gave only hydrogen and hydrocarbons, which were also present in the 

 gases from the meteorite which contained helium and argon. Here, 

 again, our search was in vain. The mineral water from Bath has been 

 investigated by Lord Bayleigh; in the waters from Oantarets, in the 

 Pyrenees, Dr. Schlosing has found both argon and helium. Dr. Travers 

 and I examined these gases for new lines, but, as before, none were 

 found. 



Our patience was now well-nigh exhausted. There seemed, however, 

 to be a single ray of hope left, in an observation which had been made 

 by Dr. Collie and myself. You will recall that the atomic weight of 

 argon was apparently too high ; at all events it would be more in har- 

 mony with the periodic law if the density of argon were 19 instead of 

 20, and hence its atomic weight 38 instead of 40. Hence, after some 

 fruitless attempts to separate argon into more than one constituent by 

 means of solution in water, we undertook a systematic diffusion of argon. 

 We did not, however, carry this procedure very far, for, at that time, 

 we believed that helium was a more probable source of the desired gas; 

 nevertheless, we found a slight difference in density between the gas 

 which diffused first and that which remained undiffused. We, there- 

 fore, decided to prepare a large quantity of argon, and, after liquefying 

 it, to investigate carefully the different fractions on distillation. 



