23,173. Humphrey, H. A., and Rusdell, W. J. Oct. 10. Direct explosion apparatus.-Internal-combustion engines are cooled by providing within the cylinder a body of liquid between which and the cylinder walls there is relative movement, the water being stationary or having less movement than the relative movement between the piston and cylinder. In Fig. 1, showing a two-stroke cycle engine, the reciprocating cylinder 1 slides over a fixed piston 9 having a renewable liquid column 15 above it, the explosion occurripg between the cylinder top and the liquid ; 6 and 7 are gas and air inlets, 2 the inlet valve into cylinder, and 3 the exhaust ports. A shield may be provided over the liquid, and in this case the shield is attached by a rod to the fixed piston top. In another form of engine, the inlet valve 2 is omitted and a ring of ports substituted. In a modification, Fig. 4, both the inlet valve and a ring of ports are provided in the cylinder, the former opening into a space 20 containing gas, and the latter into a space 19 containing only compressed air which scavenges the cylinder before gas is admitted. In a further modification, the valve 21, Fig. 5<a>, is positively actuated after the scavenging to allow the gas to enter the cylinder. In Fig. 6 the gas valve 6 is situated above the air valve 7, and the spring on the valve 6 is of such a strength that the valve closes as soon as the air valve opens. Fig. 7 is a modification showing a four-stroke-cycle engine. The inlet and exhaust valves are actuated by cams 23, 24 on a telescopic cam shaft, the inlet and exhaust conduits being also telescopically arranged. The liquid above the piston is renewed by means of two pipes. In Fig. 8, the moving cylinder 1 is attached to a pump piston 28 of greater diameter. Inlet valves 30 and outlet valves 31 are supplied for the liquid being pumped, and the space in the cylinder 29 below the pump piston may be used as an air cushion to assist the upward stroke, or may be provided with extra valves so that the pump is double-acting. The compression space is divided into two parts, a large part 8<b> and a small part 8<a>, the latter acting as a cushion to prevent undue upward motion of the cylinder, and air compressed in the space 32 may by expansion assist on the downward stroke. Instead of ports in the stationary cylinder, valves may be used and are closed by the action of the cooling-liquid when they descend below the surface thereof, or by gearing. In Fig. 10, which shows a single-acting two-strokecycle pump, the pump piston has a number of valves 30, and the proportions of the various parts and of their masses are such that the liquid pumped is still moving upwards after the pump piston has started its downward stroke by the help of the cushion 8<a>. Preferably the arrangement is such that the liquid in 29 comes to rest at the point of maximum compression. Fig. 11 shows a fourstroke-cycle pump in which a column of liquid in the pipe 40 being pumped moves in the opposite direction to the reciprocating cylinder 1, the parts being so arranged with regard to weight and size that the flow of the liquid in the delivery pipe is always in the same direction, but varies in velocity. The inlet and exhaust valves are actuated as described in Specification 18,595/07, and an air cushion 44 helps the descent of the cylinder. A similar arrangement to Fig. 8 is described, but as a four-stroke engine, and in this case pumping occurs only on the power stroke, the suction stroke being very short, and the air in the cushion 32 is not compressed to the pressure to cause the valves in the delivery pipe to open. By fitting an air valve in the cushion 32, by which air can be drawn in and expelled until covered by the liquid, the height to which liquid is pumped can be increased as described in Specification 19,617/10. The engine may be of the double-acting type, Fig. 13, in which one series of ports are made in the reciprocating cylinder adapted to coact with two sets of ports 44 in the stationary cylinder, two receivers 47, 48 being provided for the gas, and mixture and air valves 6 being provided in the stationary cylinder. In a modification the piston side rods are dispensed with and the top of the stationary cylinder is formed as a crank case, the air valves in this case being arranged on the receivers. A two-strokecycle pump is also shown, the air and gas or mixture being in this case compressed separately ; an air cushion is provided below the fixed piston, liquid being pumped on both up and down strokes. The supply on each stroke can be arranged by varying the areas of the pump and power pistons. A double-acting two-stroke-cycle pump is shown in Fig. 16 in which two differential pump pistons 58, 58<a> and 28, 28<a> are arranged symmetrically. In another form, the liquid is taken in at one side and expelled through the other, an air cushion being provided to assist the down stroke. In Fig. 21 a ball valve 64 is shown controlling the cooling-water supply. The amount of cooling-water above the fixed piston may be varied to vary the compression space, and the excess of cooling liquid may flow through the exhaust, where it is vaporized and may be used with the exhaust gases to drive an engine of the piston type or a turbine. Specifications 3228/72 and 749/95, [both in,Class 122, Steam engines], are also referred to.