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The barrel A A, (fig. i.) is almofl: fifteen inches long, and 

 internally in diameter juft two inches ; it is mofl perfe(flly 

 cylindrical, and poliflied like a looking-glafs within. The pifton 

 (fig. 3.) is folid, without any perforation; it confifts of circular 

 plates of leather preffed together between the round plate a, 

 (in the focket of which b, the pifton rod was inferted and 

 faftened by a crofs fcrew, before the leathers were put on) 

 and the two upper plates c and d ; of which the outer one 

 dy being fcrewed upon a fcrew formed on the outfide of the 

 focket, prefTes down the tinder plate, and this the leathers, 

 which latter are not reprefented in the figure. The vipper plate, 

 when fcrewed on, lies even with the upper part of the focket, 

 that, when the pifton is raifed to the top, it may touch the 

 plate covering the upper part of the barrel, leaving no air 

 above the pifton. Thefe two plates of the pifton, efpecially 

 the lower one, are made fo large as juft to move in the barrel 

 without touching it, and care was taken that when the pifton 

 is put down, it fliould be every where in contad: with the 

 plate at the bottom of the barrel, this plate being turned in 

 the lathe upon the pifton rod which fitted its focket exacflly, 

 fo that not the leaft fpace might be left for lodgment of air 

 under the pifton. The leathers are of the beft buck-fkin, 

 drefled in the xifual manner, firm in its texture, but not harfh; 

 and being well dried, were foaked in a mixture of three parts 

 fuet melted with one part oil, before they were put together : 



they 



