The operation of the engine is as follows: The piston, _g_, being at the inner end of its stroke, the crank is turned round in the direction of the arrow, and the piston draws air in through the holes, _w_, and gas through the holes, _x_, the two mixing as they pass under the inlet valve, _z_. When the piston has advanced far enough to uncover the firing valve, P, the flame is drawn in and the inflammable mixture exploded, the expansion of the air and gas closing the inlet valve, _z_, and carrying the piston to the end of the stroke. The momentum of the fly-wheel then carries the piston back through its return stroke, during which the tail-piece, K, presses the spindle, H, and opens the exhaust valve, G, through which expanded air and gas escape to the exhaust pipe, _p_. It is claimed that this arrangement is very effective in securing a complete clearance from the cylinder of the products of combustion, which, when not wholly removed, vitiate the incoming charge and reduce efficiency. When the piston arrives at the inner end of its stroke, the exhaust valve, G, is closed by the spring, I, and a fresh supply of air and gas are drawn in through the inlet valve seat, _v_, as the piston again commences its outer stroke. In order to keep the cylinder, _e_, sufficiently cool, whether the water casing at _r_, be used or not, the whole supply of air is drawn from the front end of the cylinder through the openings, _n n_, and thence between the cylinder, _e_, and the casing, _f_, and round the end of the latter to the inlet valve, _v_. And in order to prevent or lessen the noise of the explosions, the hollow trunk, _h_, is made of such length that its front edge closes the openings in the guide, _l_, through which air is drawn into the air casing _m_, and through the openings, _n n_, just before the explosion takes place, the noise of which therefore cannot escape. For the same purpose fibrous or porous material, such as mineral or slag wool, may be placed loosely in the space between the cylinder and the casing, _f_. The engine may be made to revolve in the opposite direction to the arrow by turning the piston and connecting rod round so that the tail-piece upon the latter is above instead of below, and instead of the water casing, _r_, radial ribs may be formed upon the cylinder, _e_, from which the air passing between them inside the casing, _f_, absorbs the heat. The cylinder is arranged preferably in the inclined position shown, but it may, of course, be fixed in any other convenient position.--_Engineering._ [Illustration: IMPROVED GAS ENGINE.] * * * * * METERS FOR POWER AND ELECTRICITY.[1] By MR. C. VERNON BOYS.