292 APPENDIX 



If liquid air, in such a vacuum receiver, be evaporated 

 very qidcldy, by means of the exhaust pump, the upper 

 layers of the liquid seize Ether so fast from the lower 

 layers, that the la.tter become solid, i.e. " a stiff trans- 

 parent jelly" 1 (temp., 216 C.), or even "a clear 

 transparent, solid ice." 2 



Prof. Dewar illustrates the reaction of liquid air 

 on gases by some very remarkable and instructive 

 fundamental experiments. He fills glass receivers, 

 illustrated in section figs. 5 and 6, of a capacity of 



Fig. 5. Fi S- 6. 



about a litre (say If imperial pints) with gases, and 

 then hermetically seals the flasks. Thus we have the 

 gases imprisoned in the glass receivers the molecules 

 cannot get out. 



The upper part of the glass flask is dished or saucer 

 shaped. He pours into the saucer some liquid air. It 

 immediately, as Prof. Dewar calls it, " boils " away into 

 the gaseous form, fig. 5. The air molecules when 



1 Royal Institution Proceedings, vol. xv. No. 90, 1890, p. 136. 

 " On New Researches on Liquid Air," Prof. Dewar, F.R.S. 



2 Idem, vol. xiv. No. 87, 1893, p. 11. " Liquid Atmospheric Air," 

 Prof. Dewar. 



