166 SCIOPTICON MANUAL. 



use a characteristic stop-cock on each, so that there can 

 be no mistaking them, even in the dark. 



By very unequal pressure, gas from one bag may be 

 forced through the cavity, at the foot of a clogged jet, 

 into the other bag, from which it meets no counter 

 current. To get up an explosion in this way would re- 

 quire patience, and either a surprising degree. of care- 

 lessness, or else considerable skill directed to this end. 



It should become habitual to turn oif the oxygen at 

 least, when the light goes out, and to turn it on only 

 after the hydrogen is lighted. 



Stuffing the cavity of a mixed jet with wire gauze is 

 now discarded as not only useless but as often interfer- 

 ing with its successful working. 



Passing the gas through a small wash bottle is de- 

 signed to prevent the back flow of gas or flame. The 

 same advantage is claimed for a valve in the tubing, open 

 towards the jet but closing against any back current. 



The best expedient, however, is to use good appa- 

 ratus, and to exercise common care. 



ANXOTAXCES PECULIAR TO THE MIXED JET. 



The hydrogen flame is somewhat liable to be blown 

 out by too abruptly turning on the oxygen. In this 

 case we have but to turn off the gas and proceed again 

 with more care. 



The mixed gas in the cavity c sometimes explodes and 

 the ignition may continue within the cavity. Whether 

 the flame is extinguished by the explosion or not, the 

 oxygen should be at once shut off; the jet, if hot, should 

 be cooled, by waiting or by wetting it, and the adjust- 

 ments should be revised and regulated. This accident 

 may result from irregular pressure, from turning on the 

 oxygen before lighting, or from neglecting to turn it off 

 before re-adjusting the pressure boards. 



