As previously mentioned, the automobile is carried almost entirely by the steel frame of the tractor attachment on which the rear axle rests and which is fastened rigidly to the front axle so that the power exerted at the traction wheels is distributed evenly on the entire automobile chassis. It is claimed that the device has been examined carefully by automobile manufacturers and engineering experts and that no criticism was offered after a close study of the principles of operation had been made. It is believed that this attachment will serve to still further promote the sales of automobiles to farmers.

Future Possibilities.-The field of usefulness to which the tractor can be applied is enormous. Over ten million horses are in use in the big farming States or agricultural purposes. If the farmers of these States would replace but one out of five horses or 20 per cent, it is claimed that there is a market for over sixty thousand tractors of the medium power class, not to mention the large sale and great market for the smaller machines designed to do the work of three or four horses on the small farm.

The tractor has demonstrated its worth and is practical in construction. It has demonstrated that it will cut the cost of production of all farm products and will reduce the cost of marketing as well because the road to market is shortened by mechanical power.

FIG. 200.-Rear View of Automobile With Auto-tractor Attachment, Showing Practical Application in Ploughing.

One authority says, "The tractor is at the dawn rather than at the twilight of its development." It has developed from a monstrous, inefficient toy into a powerful and efficient servant.

It is not only on the farm that the tractor can be

used to advantage. In contracting and construction work its uses are unlimited. Many deposits of stone have been converted into surfacing material for highways by its aid. It has been used in building and maintaining roads, in digging irrigation canals, and filling drainage ditches. It has hauled machinery to the mines, brought the ore to the surface and carried it to the railroad or smelting plant. Enormous logs have been taken from forests where big teams of horses could not be handled. It has been used even in the field of modern amusement enterprises, and a number of the big tent shows are shifting their heavy trucks with a traction engine which also runs a dynamo and furnishes power for electrically lighting the tents during the evening exhibition.

The performance of the tractor in the past is but a promise of what it may accomplish in the future. Much depends on the education of the farmer. It is not natural to assume that one who has been familiar with horses since childhood will be ready to replace these with mechanical power about which he knows comparatively nothing. As the tendency of modern farming is to make it more scientific and an engineering proposition, the farmer of the future will be trained in solving mechanical problems. While it is to the younger element that we must look for substantial progress and ready adoption of new methods, much will be accomplished by even the conservative old-time farmer who will realize the advantages of mechanical traction, study the applications and forms of gas tractors best suited to his work and link the invaluable experience of the past with the progressive ideas of the future.

CHAPTER XI.

TRACTOR DESIGNS FOR 1917.

Trend of Design-Requirements of All-purpose Tractor-Threewheel Tractors-Tractor that Acts as Horse-Two-cycle Oil Engine Used-Motor Cultivator-A Garden Tractor-Dust Separator-Anti-friction Bearings for Tractors-Specifications of Late Tractor Designs.

Trend of Design.-The most prominent feature noted in late tractor designs is the endeavor of builders to have light and strong tractors better adapted to general work on small and medium-sized farms than the earlier heavy designs. The trend is unmistakably toward the small and medium-weight machine, just as the trend in automobile designing is toward the medium-weight cars of moderate price. Tractor prices have been reduced and their use is increasing in all sections of the country. Before describing the improvements in light-tractor design it may be well to recapitulate briefly the requirements of the ideal, all-purpose tractor:

First, it should be universally adaptable, so that it can do all kinds of belt or drawbar work. It should be just as well adapted for running farm machines requiring power as it is for hauling ploughs, harrows or loaded wagons.

Second, the ratio between power and weight and the arrangement of components are important things to consider. If the tractor is too light it will not have the required traction effort between the drive wheels and the ground, and considerable useful power will be

dissipated in slippage. On the other hand, if the machine weighs too much it will pack the soil and will not be practical for use on soft ground.

Third, as much contact area as possible between the traction members and the ground should be provided in order to avoid loss of power through slipping and packing of the soil due to concentration of much weight on a limited bearing area.

Fourth, it is desirable that the engine be capable of operating on the cheaper liquid fuels such as kerosene, distillate and others of the more plentiful products of petroleum. The rapidly increasing cost of gasoline makes it imperative to use other fuels and as the tractor engines, for the most part, are heavy-duty constantspeed types, no difficulty should be experienced in using kerosene.

Fifth, the tractor should be designed with special reference to the work it is to do and should be constructed of sufficiently good materials so that the weight may be kept within reasonable limits and combine strength with lightness. The tractor should be easy to start and the various controlling functions such as gear shifting, clutch operation and steering should be simplified and control levers so proportioned as to be handled without requiring great muscular exertion. It is evident that the simple tractor will be easier to understand, maintain, and repair. In fact, the simpler designs will be more easily operated by the average farm hand. The construction should be so arranged that automatic steering can be secured when doing certain classes of work, such as ploughing, so that the engineer or operator may utilize part of the time in handling the ploughshares.

Quite a number of the tractors of modern design