602 



IMPROVEMENT GF 



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and thofe in the wooden cylinder, which are to oorrefpond with 

 them, muft be nicely attended to. 



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Firft, when the tin-cylinder Is foldered longitudinally, and one end 

 of it loldered on, as at A, fix holes through it nauft be made longi- 

 tudinally on four oppofite fides of it, each hole mufl be exadlly half 

 an inch wide, and five eighths of an inch long, the length to be parallel 



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to the length of the cylinder. 



The centre of the firfl of thefe holes mufl be five inches diftant 



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from the clofed end A, the centre of the fecond hole mufl be eight 

 inches diftant from the centre of the firft, and fo on till fix holes are 

 made longitudinally along the cylinder. Then another fuch line of 

 fix fimilar holes is to be made on the oppofite fide of the cylinder, and 

 then two other fuch lines between the former, in all twenty-four;, 

 and the fize of all thefe holes mufl be nicely obfarved, as well as their 

 diflances. 



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Secondly, The wooden cylinder fixed on the axis is now to be in- 

 troduced into the tin cylinder, but not quite to the end of it, but fo 



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as to leave exa<£lly one inch of void fpace at the clofed end A, and 

 then the fize of all thefe apertures through the tin cylinder, each of 

 which is exadly half an inch wide, and five eighths of an inch long, 

 are to be nicely marked with a fine point on the wooden cylinder 



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which mufl not previoufly have any excavations made in it. 



T^hirdly. The twenty-four hoi 



marked 



he wooden cy 



linder are now to be excavated exadly three eighths of an inch deep, 

 but with an addition alfo of three eighths of an inch at that end of 

 every one c ' ' 



one of them which is next to A ; fo that, when the wooden 



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cylinder is again replaced in the. tin cylinder as before, wit'^h one inch 

 of void fpace at the clofed extremity of it, the excavations in the 



wooden cylinder will be three eights of an inch longer, than the per 

 forations in the tin cylinder over them. Thefe excavations in th 



wooden cylinder mufl alfo be rather narrower at the bottom than a 



the 



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