OXY-ETHER AND HYDRO-CARBON LIGHTS 97 



oxygen at the jet than vapour from the other generator, and 

 this test being conclusive. A tank can also be made to con- 

 tain ether enough for any reasonable time, while it is 

 difficult with woollen to saturate the vapour sufficiently for 

 more than an hour and three quarters. 



53. Management of the Ether Light. I consider either 

 generator, as now made, to be practically safe with experienced 

 operators, and especially with such as understand the inherent 

 risks of using volatile fluids. But it is clear that these risks 

 are a serious addition to the ordinary risks of the mixed jet ; 

 and for this reason it is not to be desired that the oxy-ether 

 light should be widely used by the ordinary class of operators. 

 I cannot condemn it wholesale, as Sir Henry Koscoe has done, 

 especially in the porous form ; for I should use it without hesi- 

 tation if I wanted high power where I could not get gas. But 

 since the oxy-spirit jet supplies light for most purposes in 

 country rooms, and compressed gas can be procured for others, 

 the ordinary exhibitor would do well not to run the extra risks 

 of a process, which he will not probably thoroughly under- 

 stand all the dangers of. As the oxy-ether light will, how- 

 ever, probably continue to be used to some extent by skilled 

 operators, in certain circumstances, a few words are necessary 

 regarding its practical manipulation. 



In the first place, the oxygen pressure must be good. The 

 oxygen has to supply two branches of tubing, and in addition, 

 each current has to be driven through the resistance of the 

 pumice chamber, which should always be employed. Where 

 this light is habitually used, the pumice chamber must be 

 examined, and if necessary replenished from a store of sifted 

 material kept always at hand, at short intervals. If a bag is 

 used, at least 1^ cwt., and 2 cwt. to finish, will be needed for 

 a good light ; if a cylinder and regulator, from 9 to 12 inches 

 pressure. 



In the second place, the ether used must be of a certain 

 purity, known by its specific gravity, which should not exceed 



