192 



SCIENTIFIC AMUSEMENTS. 



reservoir the gas is forced out at the side tap, and so led by an 

 india-rubber pipe to the jet. Instead of this a jar of oxygen with 



a cork and tap in the top may 

 be used, the jar being pressed 

 down in a bucket of water so 

 as to force the gas out in a 

 current; or a bladder provided 

 with a tap may be filled with 

 oxygen by first collecting in such 

 a jar and then transferring to 

 the bladder, or by directly con- 

 necting the bladder with the 

 oxygen gas generator, or from 

 a gasholder, as in fig. 74. If 

 the oxyhydrogen flame is made 

 to impinge on a lump of chalk 

 or marble, the heat will burn the outer surface of this to quick- 

 lime (Chapter XIII.), and will make it glow most brilliantly, 

 so as to give out an intense light. 



Without a suitable holder it is difficult to obtain a steady light 

 in this way ; fig. 83 represents one form of compound burner 

 arranged for the purpose, oxygen being supplied by one tap and 

 hydrogen (or coal gas) by the other from a pair of gas bags (fig. 

 76), or compressed gas cylinders (fig. 77); and a cylinder of quick- 

 lime being supported by an iron rod so that the flame shall 

 impinge nearly horizontally upon its surface. Fig. 84 represents 

 another arrangement of the kind, such as is used in theatres to 



Fig. 83. Lime Light. 



Fig. 84. Lime Light. 



produce the "lime light"; by means of a pair of bevel wheels 

 turned by a long rod, the lime cylinder can be turned round from 

 time to time, so that the flame may heat up a fresh smooth part of 

 the surface when the former one becomes roughened and injured 

 by use. 



Expt. 212. To make Oxygen burn in Hydrogen. Arrange a 



