SOURCES OF HEAT AND COLD. 



129 



" Instead of blowing out the flame, it is better to put an extin- 

 guisher over it, for as short a time as will cause the flame to disap- 

 pear. For this purpose, a small phial, or test tube, is preferable to 

 the metallic cap usually employed." 



" The metallic coil appears to serve as a reservoir for the caloric, 

 and gives to the combustion a stability, in which it would otherwise 

 be deficient." 



" There is some analogy between the operation of the wire, in act- 

 ing as a reservoir of heat in this chemical process, and that of a fly 

 wheel, as a reservoir of momentum, in equalizing the motion of ma- 

 chinery." 



Dr. Hare introduced a blowpipe, in which the air was propelled 

 by hydrostatic pressure ; and in this manner he used also the oxygen 

 and hydrogen gases.* I have found such a blowpipe very useful, 

 and it will be mentioned again in this work. 



The blowpipe of the enameler and of the thermometer maker, is 

 fed by a double bellows, worked by the foot, and terminates in a 

 pointed tube, which rises above a table, and thus supplies a lamp. 



3. Alcohol Blowpipe,. 



" A flame resembling that 

 of the enameler's lamp, may 

 be produced by a small boiler, 

 A, containing alcohol, in which 

 alcoholic vapor is generated, 

 as steam is, by the boiler of a 

 steam engine." 



" The vapor thus generated 

 is substituted for air in the blast 

 of the blowpipe, being directed 

 upon the flame of a lamp in 

 the same way, by means of a 

 pipe proceeding from the boil- 

 er, and terminating in a beak, 

 with a capillary orifice, B. 

 the boiler is furnished with a 

 safety valve, V." 

 " It may be objected to flame thus excited, that as the oxygen is 

 not so copiously supplied, as when a stream of air is used, the oxide 

 of lead in flint glass tubes is reduced by it, and the glass consequently 

 blackened." 



' The apparatus here represented, is furnished with an adjusting 

 screw, S, by which the height of the boiler is regulated ; while the 



See his Compendium, p. 73. 

 17 



