OF HYDRAULIC ENGINES. 139 



Each stroke raises a column of water 18 inches long, LECT. 

 and four inches thick, in the pump barrels ; which co- ,^-vx 

 lumn, upon the descent of the piston, is forced into the 

 main pipe, whose perpendicular altitude above the sur- 

 face of the well is 64 feet. 



Now, since a column of water 18 inches long, and 4 

 inches thick, contains 226.18 cubic inches, this number 

 multiplied by 1683 (the strokes in an hour) gives 380661 

 for the number of cubic inches of water raised in an hour. 



A gallon, in wine measure, contains 231 cubic inches, 

 by which divide 380661, and it quotes 1468 in round 

 numbers, for the number of gallons raised in an hour ; 

 which, divided by 63, gives 264 hogsheads. If the 

 horses go faster, the quantity raised will be so much the 

 greater. 



In this calculation it is supposed that no water is 

 wasted by the engine. But as no forcing engine can be 

 supposed to lose less than a fifth part of the calculated 

 quantity of water, between the pistons and barrels, and by 

 the opening and shutting of the valves, the horses ought 

 to walk almost 24 miles per hour, to fetch up this loss. 



A column of water 4 inches thick, and 64 feet high, 

 weighs 340re pounds avoirdupoise, or 424^ pounds troy ; 

 and this weight, together with the friction of the enginCj 

 is the resistance that must be overcome by the strength 

 of the horses. 



The horse-tackle should be so contrived, that the horses 

 may rather push on than drag the levers after them. 

 For if they draw, in going round the walk, the outside 

 leather straps will rub against their sides and hams ; 

 which will hinder them from drawing at right angles to 

 the levers, and so make them pull at a disadvantage. 

 But if they push the levers before their breasts, instead 

 of dragging them, they can always walk at right angles 

 to these levers. 



It is no ways material what the diameter of the main 

 or conduct pipe be : for the whole resistance of the wa- 



