Description of the Percussion Gun-Lock. 1S3 



In tlic case of hydrogen gas ascending in the atmosphere, if it 

 were not combined or mixed in its progress, it would continue 

 to ascend till it surmoinited all the other ingredients which com- 

 pose the latter, l)ecause it would expand as the pressure dimi- 

 nished: consequeiitly its specific gravity would at anv height bear 

 the same proportion to that of the atmosphere as it does at the 

 surface of the earth : therefore its progress upwards would con- 

 tinue till it was beyond the means of either ignition or combus- 

 tion. 



XXVIII. Description of the Percussicyii Gun-Lock invented by 

 Mr. CoLLlNSoN Hall, of High-street, Mary-le-hone'^. 



L HE cock, or hammer, and the t^ouch-hole are the only parts 

 in which Mr. Hail's gun differs from those in ordinary use ; and 

 these parts are so simple that a common lock may be converted 

 into a percussion lock on Mr. Hall's plan, at a very small ex- 

 pense. 



The detonating powder which is used for the priming is made 

 iiito the form of a pellet, and is fixed in the centre of a small 

 round piece of paj^er covered with wax. In this state it is ap- 

 plied to a cavity countersunk in the head of the hammer, to which 

 it adheres by means of the wax, and is thus preserved from the 

 effect of wet. The touch-hole consists of a cylindrical ping 

 screwed into the side of the barrel, and having a pin or nipple 

 projecting from it at right angles: this pin is perforated in the 

 direction of its axis, and thus forms a communication with the 

 powder in the cavity of the plug. When, by the release of the 

 tumbler, the hammer is let go, the countersunk cavity, contain- 

 ing the patch of deton^ting paste, strikes on the top of the pin 

 of the touch-hole, the paste explodes, and, communicating^its 

 percussion through the perforation of the pin, fires tift povvder 

 in the cavity of the j)Iug, and thus discharges the gun. The 

 corrosive and deliquescent salt resulting from the decomposition 

 of the detonating paste can act only on the hollow of tlie ham- 

 mer, where it does no material injury, instead of soiling and oc- 

 casioning damp in the touch-hole itself. Hence a lock on this 

 construction hardly ever misses fire, and the (lischarsce is remark- 

 ably rajjid; both of them circumstances which very materially 

 influence the success, and consequently the satisfaction, of the 

 sportsman. 



• From the Transaction qf the Suclety for the Eiicowaffement of Arts, 

 Jtfnitiifacluret, and Commerce, vol. xxxvi. The Scciety's silver njcdal was 

 yoUii to Mr. Hull for this cominumcation 



The 



