_Carburetted air motors for horseless carriages._—Although not to such a great extent in England, self-propelled vehicles have within the last two years come rapidly into favour on the Continent, and the success which has attended them has caused inventors and makers to concentrate their efforts on building the motors as light and as practicable as possible, as much for purposes of locomotion as for a host of other uses. We have already spoken of the Daimler motor, which is used to drive several different types of motor cars; we will now speak of more recent developments in the same direction. Among many of the same character, the most noticeable is the high-speed motor of MM. de Dion and Bouton, who have applied them with great success to the propulsion of tricycles (Fig. 28). [Illustration: FIG. 28.—De Dion Motor Tricycle.] The cooling is effected by radiating cast-iron ribs offering a considerable surface to the air. The ignition is obtained by an induction coil and accumulator with a contact mechanism, invented by Captain de Place. The rotation of the crank-shaft is transmitted to the wheel-shaft of the tricycle by a reduction gear. Among other motors we must mention the benzoline engines for self-propelled vehicles of Lepape, Gautier, the Gladiateur tricycles and quadricycles constructed by the Société des Voitures sans Chevaux; also the exceedingly light motors of the Kane-Pennington type; and lastly, the voiturette-tandem of M. Leon Bollée, some of whose vehicles have shown a remarkable speed with a very small consumption of fuel. A few monstrosities have also appeared in the shape of a five-cylinder motor driving a bicycle called the “bicyclette Soleil Millet,” and a heavy and complicated mechanism by Wolfmüller, also driving a bicycle and using petroleum. These motors have not, however, obtained any success, nor will they at a future date, by reason of their complication and weight. It is almost unnecessary to state, that any of the above types may be equally well used for driving a dynamo and producing electric energy or light. CHAPTER V PETROLEUM ENGINES There is a great deal of difference, from an economic point of view, between spirit or carburetted air engines which we have just described and motors using ordinary commercial petroleum oil. As a rule such oil is much less dangerous, having a lower flashing-point, while at the same time it is cheaper than the more artificial products such as benzoline, naphtha, etc. We shall presently give a table comparing the cost of power produced by various systems of motors, and which will explain why the petroleum engine is gradually ousting the carburetted air motor from its place.