_Sécurité petroleum motor._—This engine was patented in 1887 by MM. Belmont Chabout and Diedrichs, and appeared at the Paris Exhibition of 1889. An Otto cycle is used, and ignition is obtained by a platinum capsule heated to incandescence by a jet of carburetted air which passes through a spiral coil warmed by the waste heat of the cylinder. This ignition tube is situated at the back of the cylinder, and is placed in communication with it by a port and valve, which determines the exact instant at which the explosion takes place. The petroleum is vaporized by passing through pipes coiled up in a vessel traversed by the heated products of combustion. The vapour thus formed has a high enough pressure to draw air along with it as it passes across an air space between two nozzles; an explosive mixture is therefore formed. The motor is started by carburating a small quantity of air by means of a reservoir containing a light oil, and this supplies sufficient energy to work the motor until the spiral coils are hot enough to vaporize the petroleum. The whole apparatus is rather complicated, especially as there are two separate vaporizers using different oils. This disadvantage, combined with only a moderate efficiency and a high prime cost, has severely handicapped the engine. _Priestman oil engine._—The first patent of this interesting engine was taken out in 1886 by Messrs. Dent and Priestman. The engine as a whole represents probably the highest point of perfection which it is possible to attain to in this class of motor, and the general arrangement is somewhat similar to that of Dr. Otto’s engines, but in addition there is a very ingenious apparatus for working with heavy petroleum oils. A single-stroke pump, driven by an eccentric keyed to an auxiliary shaft turning half as fast as the main shaft, compresses the air to a standard pressure (depending in value, on the size of the engine) in a reservoir supplied with a governing valve and placed near the front of the engine. This reservoir contains petroleum, and the pressure of the air forces it up into a spray-maker, where it is pulverized. From thence the petroleum spray passes to a vaporizer heated by the waste gases, and becomes mixed with a certain volume of air forming an explosive mixture, which is admitted to the cylinder by an automatic valve. Compression and ignition take place in the cylinder, and the waste gases escape through a valve worked by the same eccentric which drives the air-pump. The number of parts of the mechanism is by this means reduced to a minimum, and it is found that this peculiar vaporizing process completely prevents the cylinder from being fouled, as is usual when petroleum is heated to such a high temperature, often decomposing it. The Priestman engine gave a fresh lease to the life of oil motors, which had at one time been almost abandoned by engineers. It is well adapted for all kinds of industrial