Chap; 9.] ?he Air Gun. 433 



might have proceeded from the Client effects of the 

 air-gun *.' 



The air gun defcribed by the author from whom 

 the above is quoted has been in a great meafure 

 fuperfeded by one of a more fimple conftruction, ori- 

 ginally invented by the late ingenious Benjamin Mar- 

 tin. It is formed like a common gun, with a fingle 

 barrel, and the condenfed air is contained in a brafs 

 ball, which fcrews on below the lock. The ball is 

 charged with a ftrong fyringe, and is furniflied with a 

 ftop cock, and fcrews on the end of the fyringe to be 

 charged, and then, when the cock is turned, it may 

 be fcrewed on to the gun. The bullet is made to fit 

 the barrel very exactly, and is rammed in as the ball 

 of a mufket. Each gun is generally furnifhed with 

 two brafs balls, which will contain fufficient air for 

 about twenty discharges ; and that which is not in pre- 

 fent ufe may be carried in the pocket. The gun is 

 charged by turning the cock, which fills a fmall cham- 

 ber at the butt end of the barrel with condenfed air, 

 when the cock may be turned again to fave the reflc 

 for further difcharges. The pulling of the trigger 

 opens a valve, and the fpring of the air forces out the 

 bullet, as in the inftrument already defcribed. 



The elafticity of the air produces alfo confiderable 

 effects in the natural world j for by mfmuating itfelf 

 into the pores of bodies, and pofleffing this power 

 of expanding, which is fo eafily excited, it muft necef- 

 farily put the particles of bodies into which it infinuates 

 itfelf into a ftate of almoft perpetual ofcillation. The 

 truth of this obfervation is evinced particularly in the 

 air veffels of plants, which perform the office of lungs ; 

 for the contained air, expanding and .contracting al- 



* Goldfinith's Plulofophy, Vol. II. p. 96. * ' 



VOL. I. F f ternately, 



