The first motor using ordinary petroleum was brought out twenty-six years ago by Brayton in 1872, and may be said to be the father of the large family of motors which consume oils varying from naphtha to others which have boiling-points as high as 150° C. _Ready motor (Brayton)._—This motor belongs to the third group of the table on page 21 (combustion and compression). There are two cylinders, one motive the other auxiliary, and used for compressing air. The compressed air passes through a space filled with some absorbent material such as felt, and kept saturated with petroleum injected into it by a special pump. The carburation of the air proceeds as follows: the high-pressure jet of air causes the petroleum to froth up, and in passing through it draws along a quantity of oil in the shape of finely-divided particles. This petroleum mist passes on to the cylinder. The advantage of this method of obtaining an explosive mixture is that it matters not what oil is used, in fact, the heavier oils are even to be preferred, as their partial condensation in the cylinder helps to lubricate it. One volume of petroleum will by this process produce 24,000 of explosive mixture. The motor is constructed in both the horizontal and vertical form, the auxiliary being superposed upon the motor cylinder. The admission of the pulverized petroleum lasts for one-third of the forward stroke, and the return stroke expels the burnt gases. The engine is double-acting, using both sides of the piston. A reservoir of compressed air is used for starting the engine, and saves the trouble of turning the heavy fly-wheel round by hand to give it the necessary impetus. The Brayton motors are constructed by an American firm from 1 to 10 horse-power. The cost of maintenance and fuel is moderate, rendering them exceedingly practicable where coal gas or the lighter petroleum are unobtainable. A later type than the one we have just described appeared in 1890 which is slightly more economic, single-acting, and uses the Otto cycle. The process for obtaining a spray of oil is also much improved. Both the auxiliary and the motor cylinders are connected by a beam and connecting rods to the shaft. A red-hot platinum tube ignites the explosive mixture.