82 Prof. W. Ramsay. Helium, a Gaseous [May 2, 



that they should have escaped my observation. They did not. Both 

 Dr. Hallock and I observed numerous bright lines on one or two 

 occasions, some of which, apparently, could be accounted for by 

 known elements as mercury, or sulphur from sulphuric acid ; but 

 there were others which T could not identify with any mapped lines. 

 The well-known variability in the spectra of some substances under 

 vaiying conditions of current and degree of evacuation of the tube, 

 led me to ascribe similar causes for these anomalous appearances, and 

 to reject the suggestion made by one of us in a doubtfully serious 

 spirit, that a new element might be in question." 



It appeared to me unlikely that any substance should give free 

 nitrogen on treatment with an acid ; and on examining a sample of 

 gas evolved from cleveite, which I procured from Mr. Gregory, the 

 conclusiou was confirmed. 



The mineral is imbedded in felspathic rock, and forms black nodules 

 and veins in the light reddish felspar. A considerable quantity of the 

 pure mineral could be picked out ; but ifc was found more advan- 

 tageous to powder the whole rock and to boil it with dilute sulphuric 

 acid (1 to 8). Under this treatment the mineral rapidly disinte- 

 grates, and an abundant evolution of gas takes place, even in the 

 cold. 



The gas is most conveniently collected by the device shown in the 

 accompanying woodcut. The mineral is placed in the flask A, which 

 is exhausted of air by means of a Topler pump ; to expel the last 

 traces of air, some water is admitted so as to moisten it. Acid which 

 has been boiled is run in hot through the funnel B, and the con- 

 nexion with the gas-holder, C, is opened. After half an hour's boiling 

 with the mineral all gas had been evolved. The stop-cock communi- 

 cating with the gas-holder was closed, the remaining gas taken out 

 by means of the air-pump, and restored to the gas-holder through the 

 arrangement depicted at D. 



The gas-holder is, of course, filled with water, thoroughly boiled vn 

 vacuo, so as to avoid contaminating the gas with nitrogen, oxygen, or 

 argon. 



The method of extracting the gas on a small scale is practically 

 identical, the difference consisting solely in the size of the vessels 

 employed.* 



2. Preliminary Experiments. 



These experiments are described in the Preliminary Note com- 

 municated to the Society on March 26, 1895. I shall only add that 

 it appears pretty certain, in the light of subsequent experiments, that 



* For preliminary experiments on the extraction of gas, my thanks are due to 

 Mr. Donald Matthews. Mr. Morris Travers, my assistant, has kindly carried out 

 all subsequent experiments on the extraction of gases. 



