One of the types of trailers worked out has four wheels, 44 inches in diameter for the front and 46 for the rear with a 10-inch tread all around. The trailer is fastened to the truck by a long pipe coupling. The most satisfactory trailer, according to Fenn, is the two-wheeled rubber-tired with wheels 40 to 44 inches in diameter. Roads which theoretically require steel tires for ironing out ruts would better be planked or otherwise hard surfaced. Proper attention and routing will greatly prolong the life of the truck. A longer smoother road is rather to be preferred to a short rough one. The depreciation of the truck is figured on a basis of 100,000 miles as its minimum life. =Other Uses of the Truck.=--But the use of the truck in the lumbering industries is not limited to logging. About the saw mills it is used for getting the logs to the saw and taking the sawed lumber away. And at yards, all over the country, for taking the lumber from the railroad tracks to the storage piles and for delivering it to customers. Special loading devices save much time. A gantry or other type of crane will pick up and handle an entire load of lumber at one time. =Amos Log Loader.=--The Amos log loader is described as an efficient loading machine in which a friction drive takes power directly from the drive shaft of the motor truck and by means of a worm gear transmits it to a long winding shaft, or small diameter drum, which extends the length of the truck bed, being mounted parallel to it just under the bed. Loading chains are attached to this drum either at the ends or middle as the driver wishes. The movement is regulated by means of a lever just over the truck step. By a small movement of his foot the driver has control of the friction drive while his hands are free to operate the engine. He can raise or lower the log or stop it at any point. Stopping it if desired so he can leave his position to make needed adjustments of the log, chains, or skids. The small diameter of the winding drum insures steady strong pull. It may also be used for skidding logs into position for loading. It is claimed the truck driver soon becomes very expert as he realizes the possibilities of the loading device. After the logs are loaded the loading chains are used to bind them to the truck.