102 Atmosphere. , 



by its elastic quality, expands and con- 

 tracts ; and it being found, by repeated 

 experiments in most nations of Europe, 

 that the spaces it occupies, when compres- 

 sed by different weights, are reciprocally 

 .proportional to the weights themselves ; 

 or, that the more the air is pressed, so 

 much the less space it takes up ; it follows 

 that the air in the upper regions of the at- 

 mosphere must grow continually more 

 and more rare, as it ascends higher ; and 

 indeed that, according to that law, it 

 must necessarily be extended to an indef- 

 inite height. At the height of 3-| miles 

 the density of the atmosphere is nearly 2 

 times rarer than it is at the surface of the 

 earth ; at the height of seven miles, 4 

 times rarer ; and so on, according to thr 

 following table. 



Height in miles. Number of times rarer 



3* 2 



7 4 



14 16 



21 64 N 



28 256 



35 1024 



42 4096 



' 16384 



