THE EFFECTS OF MACHINES \VHEN IN MOttON. 161 



imum for space, when that space is six feet. But 

 the orieat velocity with which the machine must 

 liiave, is a sufficient objection against the maximum 

 in time ; because however well proportioned the parts 

 might be, the perpetual reciprocation, where the 

 motion is very great, tnust tend to injure the whole 

 apparatus ; and on this account, the latter case is 

 much to be preferred. 



I HAVE said nothing of friction, because in the cases 

 I have considered, it must be but tritling, except 

 in the pistons; and I have not mentioned the chain 

 and pump rods as separate quantities from a'f and 

 2/)*/, though, to be minutely correct, this ought to 

 have been done; but as this part of the apparatus 

 will act at both ends of the lever, and whose weight 

 compared to those of the water, and the atmosphere, 

 will be but small, no o-reat error will arise from this 

 neglect. And as my object has been to establish a 

 general theory, upon principles that admit of fur- 

 ther prosecution to any degree of accuracy, I feel 

 less anxious as to these particulars. 



VOL. vf. L VIII, 



