128 



SOURCES OF HEAT AND COLD. 



treme mildness to extreme intensity. Common fires, in fire places 

 and stoves ; ' Argarid's lamp ; oil lamps ; spirit lamps ; gaslights; a 

 smith's forge ; the furnaces of the arts and of the laboratory ; can- 

 dles ; the mouth blowpipe, and that fed by oxygen and hydrogen 

 gases, are all familiar instances, in which combustion is seen. 



Combustion is mentioned with propriety, both as a source and as 

 an effect of heat ; for generally, it does not commence and proceed 

 without an augmented temperature, and it raises the temperature in 

 turn. 



I shall omit the description of common furnaces, and subjoin that 



of the following instruments. 

 1. The Mouth I 



L . Dr. Hare, Itol. 



J. J. ? 



" As fire is quickened, by a blast from a bellows, so a flame may 

 be excited by a stream of air propelled through it from the blow- 

 pipe." 



" The instrument, known by the abovementioned appellation, is 

 here represented in one of its best forms,. It is susceptible of vari- 

 ous other constructions ; all that is essential being a pipe of a size at 

 one end suitable to be received into the mouth, and towards the 

 other end, having a bend, nearly rectangular, beyond which the bore 

 converges to a perforation, rather too small for the admission of a 

 common pin. There is usually, however, an enlargement, to catch 

 .the condensed moisture of the breath, as in this figure." 



Berzelius has in an octavo volume, illustrating, the extreme utility of 

 the mouth blowpipe, with which Gahn discovered tin in a mineral 

 containing only one per cent., which had escaped detection by an- 

 alysis ; and he extracted also copper from the ashes of a quarter of 

 a sheet of paper. 



-t 



2. Lamp without a flame.* 

 r j 



" About the wick of a spirit lamp, a fine wire oi 

 platina is coiled, so as to leave a spiral interstice be- 

 tween the parts of the spiral formed by the wire ; a 

 few turns of which should rise above the wick." 



" If the lamp be lighted ; on blowing out the flame, 

 the wire will be found to remain red hot, as it re- 

 tains sufficient heat to support the combustion of the 

 alcoholic vapor, although the temperature be inade- 

 quate to constitute, or produce inflammation." 



See Am. Jour. Vol. IV. p. 328. 



