422 OPTICAL PROJECTION 



is left for any explosive mixture ; and (2) by dispensing as much as 

 possible with long rubber connections. 



Saturators are now either placed within the lantern itself, as in 

 the * Gridiron ' or ' Lawson ' forms, or hung as near to the taps of 

 the jet as possible. In the former case the generator itself gets 

 hot with the warmth of the lantern, and the evaporation of the 

 ether is thereby so much accelerated that the supply of oxygen 

 passing through the ether must gradually be turned off. After 

 half an hour's use in a small lantern, such a generator usually pro- 

 duces enough ether-gas by its own evaporation, and only free 



FIG. 237. 'Gridiron' Saturator 



oxygen at the mixing chamber is required. In the * Gridiron ' 

 form (fig. 237), which is one ofthe best of its type, there are three 

 taps: one to control the supply of oxygen passing through the 

 generator, one to control the supply of free oxygen to the mixing 

 chamber, and one to control the supply of ether-gas (or ether and 

 oxygen, as the case may be) to the chamber. 



I have found in practice that, after stopping the supply of oxygen 

 to the ether, the evaporation still sometimes goes on so fast that 

 the third tap, connecting the ether chamber with the nipple, has 

 to be partially turned off as well. There is a disagreeable feeling 

 of ' sitting on the safety-valve ' in doing this, but in reality the 



