538 SCIENCE PROGRESS. 



large volume of inert gas ". This is, of course, far from 

 a condition tending to give results of great accuracy. The 

 apparatus used by the author of this paper possessed the 

 following advantages: (i) The gases were admitted to the 

 measuring vessel direct from the generating; vessel without 

 having to be transferred by manipulation at a pneumatic 

 trough ; (2) the measuring vessel was the same for both 

 gases, the volume being kept constant by varying the pres- 

 sure at which the gases were measured ; (3) the residue in 

 each experiment was measured and analysed and the unab- 

 sorbable residue (considered as impurity) was at any rate 

 a maximum as it would contain any gas evolved by the 

 liquid re-agents used (as carbonic oxide from the alkaline 

 pyrogallol) ; (4) the water formed by the combination of the 

 gases was not admitted into the measuring vessel, and so 

 accurate measurement of the residual gas was rendered pos- 

 sible, and this was done in a narrow tube forming part of 

 the measuring vessel ; (5) the gases were obtained by a 

 method of fractional preparation, so that any variation in 

 the ratio of the combining volumes would have been de- 

 tected and any change of composition or purity in the gases 

 made apparent. Thus it was discovered that oxygen from 

 potassium chlorate always gave a low ratio, and that this 

 was due to traces of chlorine escaping careful washing by 

 caustic potash solution was proved by direct experiment 

 afterwards. It is very probably to this impurity that 

 Morley's lower ratio is due, as he used potassium chlorate 

 as the source of his oxygen. In three of the last series of 

 twelve experiments the volume of hydrogen taken ex- 

 ceeded twice that of the oxygen, yet giving a residue of 

 oxygen, thus proving most conclusively that the ratio 

 notably exceeds 2:1. The volumes in these experiments 

 were — 



