[ 6i ] 



▼enient parts of the deck, to be bunged up or open- 

 ed occafionally, from whence the flatc of the corn- 

 may be known, from the effluvia which afcend 

 when the ventilator is working. 



The power of the ventilator is determined by 

 the fquare of its diameter, multiplied into the length 

 of the ftroke, and that again by the number of 

 flrokes in any given time. 



To find the area of a circle and the folidity of a 

 cylinder raifed on that circle, Archimedes gives 

 the following proportion : 



As I is to .785398 decimal parts, fo is the fquare 

 of the diameter to the area of the circle. 



And as 1 is to .785398, fo is the fquare of the 

 diameter multiplied by the height to the folidity 

 of the cylinder. 



The cubical contents both of cylinders and tubes 

 are found in the fame manner, their difference con- 

 fiding not in Ihape but fohdity, the latter being 

 hollow. 



Then to find the contents of a cylindrical veflel, 

 whofe internal diameter is ten inches, multiply thj^t 

 into itfelf, and the fquare thus obtained by .7854, will 

 give the contents of the circle in cubit inches, which 

 multiplied again by 24 inches or lengths of the 

 ftroke, being the proportion of the barrel filled 

 with air, gives in cubical inches the amount of each ' 

 difchar^je on the dcfcent of the pifton. As thus: 



Internal 



