318 Prof. W. Ramsay and Mr. M. W. Travers. 



distance up, and lay parallel to the previously mentioned horizontal 

 tnhe. It, too, had six vertical branches, each of which communi- 

 cated with the other limb of the two-way stopcock of each reservoir. 

 By raising the reservoir of the Topler pump and expelling gas into 

 the collecting tube J, the gas could be transferred to any one of the 

 reservoirs. 'The accompanying diagram makes it clear how the 

 apparatus was set up. 



The actual method of conducting a diffusion was as follows : — 

 Reservoir I was raised until the mercury in the diffusion jar A 

 stood at the level of the dotted line. The clip L was then closed, 

 and the stopcocks G and D opened. The Topler pump was then 

 worked until all gas was removed from A ; the gas, if air (as at 

 the commencement of the whole series of operations), being allowed 

 to escape by moving the collecting jar J, so that it no longer covered 

 the end of the exit tube of the Topler pump. Stopcocks C and D 

 were next closed, and stopcocks E and 6a opened, so that the gas 

 from 6 entered the diffusion vessel A. By raising the reservoir belong- 

 ing to 6, all gas was expelled through E into A, clip L being opened 

 meanwhile. Reservoir 6 was now full of mercury, and all gas was 

 in A. Stopcock C was then opened, and the gas in A diffused 

 through the pipe stem B (closed at one end by means of an oxy- 

 hydrogen blowpipe) into the pump. This diffusion proceeded until 

 half the gas in A had passed into the pump reservoir F. Stopcock C 

 was then closed, and the Topler was worked, the diffused gas being 

 delivered into J. Stopcock 6a was then opened, and the reservoir of 



