INSEXSIBLF. CALORIC. 129 



Government. — We shall have something similar when our present grand 

 collection of the Exploring Expedition and that of the National Insti- 

 tute, are ail united under the care of the Smithsonian, which has begun 

 its operations with so much promise of brilliant success. 



ON THE DOCTRI^TE OF LATENT OR INSENSIBLE CALORIC. 



1. It is well known, that when a body is condensed or its particles 

 are brought into closer proximity to each other, heat is produced. Thus, 

 when air is suddenly condensed in a syringe, sufficient heat is evolved 

 to light tinder-, and vvhen a piece of metal is hammered on a smith's 

 anvil, for some time, il is said, that it can be rendered red-hot. Thus 

 too, friction and all other means, by which the condensation of particles 

 can be produced, are attended with the same result. It is in this way, 

 that the Indian and hunter arc said to have occasionally lighted their 

 fires. It is in this way that many explosive compounds are kindled, and 

 the spark is evolved " from the smitten steel." 



Now in all these cases caloric, which did not appear to exist there be- 

 fore, is set free or given out from the bodies acted upon. Mechanical ac- 

 tion did not form it, but only, as it were, drove it from its hiding places. 

 It was in the bodies, but in their ordinary state, there was no evidence 

 whatever of its existence there. Hence it has been called latent or con- 

 cealed caloric ; and, because it did not affect the thermometer or the 

 sense of touch, it has also been denominated insensible caloric. 



2. By a reverse process : that is, by causing the volumes of bodies 

 to expand, heat seems to be lost, and cold produced. Thus when air, 

 and other bodies are rarified, their temperatures become-reduced. A 

 portion of the caloric, which constituted their temperature or the de- 

 gree of their senslhle heat, becomes lost in the expanded bodies. This 

 is obviously the reverse of the preceding. Whatever of sensible calo- 

 ric is lost is added to the insensible, and, vice versa^ whatever is taken 

 away from the insensible or latent caloric by condensation is added to 

 the sensible temperature. It follows, therefore, from this, that the sum 

 of the sensible and insensible caloric of any body is always the same. 

 Further, that, as expansion produces cold by rendering caloric insensi- 

 ble, which had previously been sensible, the more we rarify a body the 

 njore do we increase its power of holding heat in a concealed state, and 

 consequently a vacuum must have the greatest capacity for caloric. 

 This, to a very great extent, will explain the intense cold which is known 

 to prevail in the more elevated portions of tlie atmosj)here ; for if a 

 portion of air, from near the surface of the earth, were carried upwards 



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