A steam-engine from the first stroke of its piston-rod begins to wear out, and before long needs repair.

After acting on the piston head, it is exhausted directly into the chamber or hollow bed-plate through which the pipes pass.

Steam-driven air compressors are usually run at a piston speed of about 350 feet per minute, or from 60-80 revolutions per minute of compressors of average sizes, say 18" diameter of cylinder.

" About this time Finley Morse and his brother Edwards had jointly devised and patented a new "flexible piston-pump," from which they hoped great things.

Being found to be in perfect condition except for the valves, which required some trifling adjustment to take up the wear on the valve stems, and for the piston rings, which needed setting out, it was reassembled and started on another test.

A.The piston is packed with hemp, but the junk ring is made of malleable iron, as cast iron junk rings have been found liable to break: there are four plugs screwed into the cylinder cover, which, when removed, permit a box key to be introduced, to screw down the piston packing.

In one engine you would have an opening one-sixteenth of an inch wide and six inches long and in the other you would have one-sixteenth of an inch wide and four inches long; so you can readily see that it is impossible to give the amount of lead for an engine without knowing the piston area, length of port, speed, etc.

The vapour of water is introduced upon one side of that piston at the moment that a similar vapour is converted into water on the other side, and the piston moves by the unresisted action of the steam.

From the length of the stroke of the piston subtract that part of the stroke which is intended to be accomplished before the steam is cut off; divide the remainder by the length of the stroke of the piston, and extract the square root of the quotient, which multiply by half the stroke of the valve, and from the product take half the lead; the remainder will be the lap required.

Then there comes a loud hiss, with a heavy escape of steam, as the huge pistons tug and pull at the heavy wheels, which slip round and round and fail to grip the rail.

The high pressure valves are of the piston type, all being worked by the ordinary link motion and eccentrics.

Hydraulic piston compressors are subject to the laws that govern piston pumps, and are, therefore, limited to a piston speed of about 100 feet per minute.

The beam attachment of the main connecting rod is made to a pin located above and midway between the pins for piston connections.

When the air pump piston descends, its pressure on the liquid under it will force open the valve in it, through which the hot water will ascend; and when the bucket descends to the bottom of the pump barrel, the warm water which was below it will all have passed above it, and cannot return.

Small grooves are sometimes turned out of the piston rod above and below the cutter hole, and hemp is introduced in order to make the piston eye tight.

Q.Does not the speed of the piston increase with the length of the stroke? A.It does: the speed of the piston varies nearly as the cube root of the length of the stroke.

The hydraulic piston machine not only costs a great deal more in proportion to the power it produces, but it costs more to maintain it, and it costs more to run it.