154 On the Meteors of \3th November, 1833. 



by which can be determined the amount of heat extricated from air 

 of any given degree of rarefaction, in reducing it to the state of air at 

 the common density. The formula is as follows. Let 6 denote the 

 degree of rarefaction; then 45 (d — fy will express, in degrees of 



Fahrenheit, the heat evolved by condensation. 



Now at such a height as forty nine miles above the earth, the air is 

 supposed to be more than sixteen thousand times rarer than at the 

 surface ; and if the formula were applied to air in this state, the evo- 

 lution of heat would be immense. But it is not to be supposed that, 

 in the case before us, the air becomes reduced to the density of 

 common air, until the meteor has descended through some dis- 

 tance. Considering, however, the great velocity of the falling body, 

 we may suppose such a density to be attained at an average height 

 of thirty five miles above the earth where the rarity of the air is 1024 

 times that at the surface. Hence, 45 (1024 — TTr % ? ) =46080°. 

 This is the amount of heat which would be extricated by the con- 

 densation of air as it exists at the height of 35 miles; but the com- 

 pression supposed is not that which results from air of this density, 

 but of such as is less dense, commencing with that which is of an ex- 

 treme degree of rarefaction. The amount of heat therefore would 

 be greater than the estimate here made. 



But to form some idea of the intensity of even this degree of heat, 

 we may call to mind, that the temperature required to melt gold is 

 only 5237° ; the highest heat of a glass house furnace, 1 6000° ; and the 

 extreme heat required for the fusion of platina, 23177°.* The tem- 

 perature, therefore, elicited by the falling meteors of Nov. 13th, can 

 be compared only to those immeasurable degrees of heat which noth- 

 ing can withstand, as that of Hare's blow-pipe and deflagrator. 



It has been common to resort to electricity as the agent which 

 produces the heat and light exhibited by meteoric bodies ;f but Biot 

 has satisfactorily shown, that lightning itself is no part of electricity, 

 but is produced by the condensation of air before the electric fluid.f 



A combustible body falling into the atmosphere under such circum- 

 stances, would become speedily ignited, but could not burn freely, 

 until it became enveloped in air of greater density ; but on reaching 

 the lower portions of the atmosphere, it would burn with great ra- 

 pidity. 



* Henry's Chemistry. 



t President Clap's Theory of Meteors. 



t Traite de Physique, Tome II. 439. (Ed. 1816.) 



