Of Hydraulk Engines . 93

Water may be raised by means of a ftxz&mAB turning a wheel piate xm.CDE, according to the order of the letters, with buckets a, a, a, a, ^ e e el p e rsian&c. hung upon the wheel by strong pins b,b, b, b, &c. fixed in the side of w ethe rim: but the wheel must be made as high as the water is intended tobe raised above the level of that part of the stream in whieh the wheel isplaced. As the wheel turns, the buckets on the right hand go down into.the water, and are thereby filled, and go up füll on the lest hand, untilthey come to the top at K-, where they strike against the end n ofthe fixed trough M y , and are thereby o verset, and empty the waterinto the trough; from which it may be conveyed in pipes to the placewhich it is designed for: and as each bücket gets over the trough, itfalls into ä perpendicular position again, and goes down empty, untilit comes to the water at A, where it is filled as before. On each bücketis a spring r, which going over the top or crown of the bar m (fixed' to the trough M) raises the bottom of the bücket above the level ofits mouth, and so causes it to empty all its water into the trough.

Lometimes this wheel is made to raise water no higher than its axis ;and then, instead. of buckets hung upon it, its spokes C, d, e, f, g, bare made of a bent form, and hollow within.; these hollows opening-into the holes C,.D, E, F, in the outside of the wheel, and also intothofe at O in the box N upon the atxis. So that, as the holes C, D y&c. dip into the water, it runs into them ; and as the wheel turns,the water rises in the hollow spokes, c,d , &c. and runs out in a streamP from the holes at 0, and-falls into the trough from whence it isconveyed by pipes. And this is a very easy way of raising water, be-cause the engine requires neither men nor horses to turn it.

The art of weighing different bodies in water, and thereby finding of th e spedfictheir specific gravi ties, or weights, bulk for bulk, was invented by gravnies ofArchimedes j of which, we have the following account. 0 ies ‘

Hiero , king of Syracuse , having employed a goldfmith to make acrown, and given him a mafs of pure gold for that purpofe, fufpectedthat the workman had kept back part of the «gold for his own ufe, andmade up the weight by allaying the crown with copper. But the kingnot knowing how to find out the truth of that matter, referred it to-Archimedes.-, who having studied a long time in vain, found it out atlast by chance. For, going into a bathing tub of water, and obfervingthat he thereby raised the water higher in the tub than it was before,he concluded instantly that he had raised it just as high as any thingeise could have done, that was exactly of his bulk : and consideringthat any other body of equal weight, and of less bulk than himself,.could not have raised the water so high as he .did; he immediately told.