TRACTION.--Steam engines were in a fairly perfected condition two hundred years ago, and it has been considered remarkable that for over one hundred and fifty years no practical road device was brought out. The reason for this was not due to engine faults, but attributable to other things which were not understood at the time. One of these was the question of traction. PUSH LEGS.--It was believed in the early history of the art, that some other means should be adopted for applying the power, rather than to exert it on the wheels; but as late as 1824 Gordon secured a patent for an improved form of “push legs,” which stepped along and thus propelled the vehicle. This form of propulsion has been revived, in a measure, by the so-called “caterpillar tractors,” in which the wheels are provided with feet, which step along, and are thus specially adapted for heavy trucks on soft roads or on cross country travel. POWER.--One other difficulty was in the construction of the boiler. What is now understood as the water tube boiler was then unknown, hence they were made in such a manner that a large body of water had to be carried in the boiler, and this meant great weight to be transported. SPRINGS.--Prior to the attempted introduction of steam, vehicles had springs, and the great problem then appeared to find a type of vehicle which would permit the transfer of the power from the engine to the wheels, since the springs change the relative positions of the engine and axle. WATER TUBE BOILER.--From 1820 to 1840 was the great period of boiler development. The water tube type provided a means whereby considerably less than one-half of the water was required in the boiler itself; and in 1832 a motor drawn vehicle, having springs arranged for carrying the entire load, was devised by Dr. Church, of Birmingham, England. THE FIRST DIFFERENTIAL.--Hills, in 1840, made the first differential. Before that time the power was applied to a single wheel, but in that year Dietz invented a form of rubber tire. This, and the differential, made wheels the tractors for all time. But now a new era was ushered in. It was not a period of active work in the development of motor-driven wagons, but the possibilities of using other than steam-driven vehicles was felt. THE FIRST GAS MOTOR CAR.--In France, Lenoir was the first to devise a gas motor car. Compressed gas was used; and Ravel, in 1870, also produced a gas-driven machine. As early as 1862 Gardner used a gas motor fed with carbureted air instead of gas, but the weight of the engine was against all attempts in that direction. GASOLINE CAR.--Markus, of Vienna, built a gasoline car in 1877, and this was followed by Levassor, the engineer of Panhard and Levassor, in France, who used Daimler’s invention in the development of their car. Gottlieb Daimler, the father of the automobile industry, produced the first practical gasoline motor, his invention being based on the four-cycle type of engine.