APPENDIX 419 



for use in small halls where the latter is not available (fig. 234). 

 The burner is cheap (about 12s. 6d.) and simple and easy to use, 

 but the light is not as good as even the gas-burner, and hence is 

 useless for discs above 7 to 8 feet in diameter. 



There is a class of incandescent spirit lamps similar to this, but 

 in which the spirit is put under pressure, either by raising the 

 reservoir a few inches, or by pumping air into it, with the result 

 that the light is considerably increased ; but these can hardly be 



FIG. 234. Incandescent Spirit Burner 



recommended for amateur lanternists, as, if the temperature of the 

 volatilising chamber should fall too low, the spirit is apt to overflow 

 into the lantern and catch fire, and though this may seldom happen 

 the risk is a high price to pay for the extra light, particularly as a 

 brilliant light can now be obtained from acetylene without any 

 danger. 



Acetylene Gas. This illuminant has made immense strides 

 during the last few years, and has now to a very large extent 

 superseded oil lamps, and has even made great inroads upon the 

 popularity of lime-light. A 1 Ib. tin of carbide of calcium can be 

 obtained for about Gd., and on being mixed with water will give off 



