ery), the quality of the work being better than would be obtained by horse power.

The tractor referred to has also been used by the town chiefly for hauling gravel and crushed stone and doing other work of this nature, but in this particular instance has, during the late fall and winter, been a source of revenue to them as it has been rented to private parties for operating machines by belt power and also for ditching.

A tractor can be used successfully for hauling, and under average conditions on dirt or gravel roads, 20,000

FIG. 189.-Harvesting With Avery Gas Tractor in North Dakota.

pounds, exclusive of the weight of the machine, can be hauled with a tractor of but 15 horse-power. On macadam roads, or good gravel roads, the hauling capacity is, of course, increased. As a rule, the character of the road surface greatly affects the hauling capacity. On a plank road but 100 pounds draft per ton hauled is necessary. Upon macadam road it will require from 150 to 225 pounds draft to haul one ton. The amount of power necessary increases to about 300 pounds per

FIG. 190.-I. H. C. Gas Tractor Pulling Three McCormick Harvesters,

ton on a gravel road and an average of about 400 pounds pull per ton on a common dirt road. Wagons intended to be pulled by tractors are of special form and are made so they can be coupled up in a train. As the width of wheels has material bearing upon the hauling capacity, most wagons adapted for use on soft roads have wide wheels. Such a vehicle with a platform body is shown at Fig. 187.

The construction of a combined gas tractor and road roller is clearly shown at Fig. 188. The view at A shows the roll in place under the front end of the machine and the auxiliary smooth steel tires attached over the grouters of the driving wheels. A tractor designed for use either as a road roller or tractor usually has a different method of front suspension than is commonly employed on tractors in order to use a roller of larger diameter than usually allowed for the front wheels. At B a one-piece axle carrying two wheels has been substituted for the roll assembly and the smooth steel tires have been removed from the traction members so that the grouters on the wheels again become effective. This makes possible the use of the machine as a tractor. The change from one to the other can be readily effected on the road, so the general contractor finds the combination machine a very good investment.

With the development of the successful binder hitch, it has been found practical to use the gas tractor for power in harvesting. Six-foot binders require from three hundred to five hundred pounds draft to pull them at a speed high enough to do good work. Mowing machines without binder attachment and capable of taking a five or six-foot cut are usually operated with two horses and therefore require a draft of about 250 to 300 pounds when hauled by a tractor. This value may be increased

largely by dull knives, binding or tight boxes, or when cutting highly resistant grains or grass. Timothy is the hardest crop to cut and takes the most power. As almost all mowers run at speeds that are variable, it is difficult to give exact figures regarding the power consumption of mowing machines or binders. As a high speed must be maintained on a binder, it is common practice to use three horses, whereas two are sufficient for the mower. As the machines work to best advantage at a speed of about two and one-half miles per hour,

FIG. 192.-Gas Tractor Not Only Cuts but Stores the Fodder.

it will be apparent that the gas tractor is particularly well adapted for use in harvesting, as even the lower powered forms are capable of pulling three mowing machines at this speed. The views at Fig. 189 and Fig. 190 show the application of the gas tractor in harvesting work.

The gas tractor is particularly suitable for threshing after the grain is harvested, owing to the ease with which it can be utilized as a stationary power plant for