THE BOOK OF THE LANTERN. 75 



easy matter, but in large halls, which are now commonly 

 lighted by one or two sunlights high overhead, the 

 operator finds himself in a serious difficulty. In this jet 

 the two gases do not mix until they reach the point of 

 combustion, and for this reason the apparatus is dis- 

 tinguished by the word " safety." For hydrogen and 

 oxyen, when mixed together, form an explosive vapour of 

 most terrible power, and one which is most difficult to 

 control. If any one should wish to prove this, let him fill 

 a soda-water bottle with the gases over a pneumatic trough 

 in the proportions of two volumes of hydrogen to one of 

 oxygen. Then close the bottle with a well-greased cork, 

 and, after wrapping it in a towel in case of fracture, take 

 out the cork, and put the mouth of the bottle in front of a 

 candle flame. The report caused by the explosion of the 

 gases will be quite equal to a heavily-charged fowling- 

 piece. But when the two gases are used in conjunction 

 with the safety-jet there is no risk of explosion, for no 

 mixture takes place until the gases meet on the lime 

 cylinder. I know that accidents have happened when 

 this jet has been in use, but they are traceable to im- 

 proper use of the apparatus. A case of this kind came 

 under my notice quite lately. An optician had employed 

 a new hand to see after the making of the oxygen gas and 

 filling the bag with the same. This individual was, after 

 a time, left to his own devices, and finding, upon one 

 occasion, that the bag was not full, he attached it to the 

 nearest gas-bracket until it was properly distended. This 

 bag was used in public the same evening, and a few 

 minutes after bhe proceedings commenced it blew up, and, 



