39^ Defcrlptlon and Ufe of Regn'ie/ s neiv Powder. Proof, 



the body to be projefted. It clofes the moftth of the fniall 

 cannon, upon which it prcfles with a force equal to four 

 i'ilogramme&. This cap is (Iroiigly failened to one of the 

 fpring radii by a nut at the oppofite end of its tail. G is a 

 piece of ftrong brafs wire, fixed to a projefticn, which, by 

 jneans of a fniall fcrew, is riveted into one of the radii. 

 JH^an index of woollen cloth or leather, which Aides with i. 

 gentle friftion on the wire, when the branches of the fpring 

 are preffed together by the explofion of the powder. This 

 index remains at the place to which it has been puflied, and 

 fliews exaftly how far the fprings have been made to ap» 

 proach. When the inftrument is to be ufed, the two ex- 

 tremities of the fpring are to be prefTed together, to feparate 

 the cap from the mouth of the cannon, into which powder 

 IS poured, till it is exaftly full, by means of a card or a piece 

 of papcr» The ftopper is then fuffered to approach the 

 muzzle gently, fo as to clofe it exaftly, without leaving a 

 lingle grain of powder between them. The circular piece 

 of eloth or leather, which fupplies the place of an index, is 

 to be brought into contadl with that branch of the fpring 

 to which the tail of the ilopper is fixed ; and priming being 

 put into the fmall pan of the cannon, it is difchargcd, the 

 jnftrqment being held fufpended by a firing or ribbon. The 

 effects of the explofion are, that, as the powder occupies a 

 greater fpace by its inilaramation, it drives back the ftopper, 

 and the latter carries with it that branch of the fpring in 

 which its tail is faftened. This branch cannot move, in 

 regard to the other, which is made to move alfo by the recoil 

 of the gun, without driving before it the fmall index piece ; 

 and the fpace over which the index piece is carried will fhcw 

 the force of the powder. 



The arches moved over by the explofion of the different 

 kinds of powder will fliew, by the number of degrees, the 

 comparative ftrength of each. A ftar is marked on that 

 arch uhieh fiiews the llrength of powder of a mean quality; 

 io that the relative value of any fample, in regard to that 



medium. 



