no sensible (aste, for want of a sufficient gravity m the 

 air to press their particles into the pores of the tongue. 



Another property of air is elasticity. It yields to an 

 impression, by contracting its dimensions, and returns to 

 them on removing the impressive cause. This endeavours 

 to expand itself, every particle of air continually exerts 

 against an equal endeavour of the ambient particles. 

 Hence it is; that a bladder full of air will burst in aiv 

 exhausted receiver ; while one that befo?e seemed 

 empty, swells and appears to be full of air. 



This power does not seem to have any bounds ; nor 

 ig it easy to be destroyed. Let air be expanded ever so 

 much, it still retains its spring; nor is* this sensibly di- 

 minished by any experiment which has yet been made* 



There is no fixing any bounds to its condensation any 

 more than to its dilatation. It will dilate into a thousand 

 times its former space, \ea into 13,679 times; and all 

 this by its own expansive force, without any force of 

 fire. The air we breathe near the surface of the earth, 

 is comprest by its- own weight into at least the 13,()'7i)tli- 

 part of the space it would possess in vacuo. And if the- 

 same air be farther condensed by art, the space it will 

 take up when most dilated will be (according to Mr.- 

 Boyle) to that it possessed when most condensed, a& 

 550,000 to owe. 



Jf while we increase the elasticity of air on one side 

 by compression, we iucrcase it on the other side by heat, 

 the force of both soon becomes irresistible; and a 

 French philosopher supposed that air thus confined and 

 expanding was sufficient for the explosion of a world. 

 In order to determine the elasticity of air, the wind-gun 

 has been invented, \\hicli is an instrument that com- 

 presses a large quantity of air into a tube in which there 

 is an ivory ball, and then gives the compressed elastic 

 air free power to act and drive the ball as directed. 

 The bail thus driven will pierce a thick board, and will 

 be iKs fatal at small distances as if driven with gun- 

 jpewder, I do not know whether ever the- force of this 



