160 On the maximum o*" mechanic powers, and 



time in passing througli 6 feet, hence v/l'', 7=1', 34 

 nearly is the time, Mhich if the piston return in the 

 same time, will give 2'', 68 for the time of one entire 

 stroke, being at the rate of 22, 4 nearly in the minute. 

 Now a cylinder whose height is 6 feet, and diameter 

 7,8 inches contains 12,23 gallons, and this is the 

 greatest possible quantity that can be raised through 

 a space of 6 feet in 1 '34 of time, by a cylindrical 

 column of the atmosphere, Avhose diameter is 30. in- 

 ches. Then 22,4X12.23 gives 274 gallons nearly 

 in the minute, or 261 hogsheads in the hour, which 

 is more by thirty-three hogsheads than what is com- 

 puted by the common method, where the diameter 

 of the pump would be ten inches. But by that 

 method no accelerative force is allowed, except 

 what must arise from some additional weight given 

 to the steam piston : and it may not be improper to 

 observe here, that if ten be put for p in the expres- 



^^^^ ac^^'Zd^^Lf ' ^^ ^'^^^^ vanish, for then the power of 

 the cylinder and the weight of the water are in equi- 

 Jibrio, and the accelerative force is equal to nothing. 



If these two cases be compared with each other, 

 in order to know which would be the most proper for 

 obtaining the dimensions of the cylinder and pump, 

 we must observe that in the first, where the etfect is 

 required to be a maximum in a giveti time, the velo- 

 city is much greater than in the other, and the time 

 in passing over six feet consequently much less ; 

 and therefore, by giving the greater number of 

 strokes in the hour, the effect is so much more in- 

 terrupted by the returning of the pump piston, and 

 of course the whole effect within that hour is dimi- 

 nished, and in fact is less than in the second case, as 

 appears from the foregoing computations. But were 

 the pump in the iirst case allowed to ascend till r',34 

 was elapsed (which is the time in the second) it 

 would pass through tlie space often feet nearly, and 

 in the course of the hour would raise 311 hogsheads, 

 which is more by fifty hogshcacb than in the max- 

 imum 



