238 BULLETIN 711, U. S. DEPARTMEISTT OF AGRICULTURE. 



rOKTABLE ENGINE. 



"Where it is not practicable to dump all the logs at one spot, or 

 "where it is desirable to dump them at different points, it may be 

 necessary to use a self-propelling unloader, which runs on an inde- 

 pendent track along the main track. Moving from car to car, the 

 machine unloads each car in rapid succession. To unload, the line is 

 passed under the load and made fast to the brow skid. The friction 

 drum is thrown in, tightening the line. This action raises the load 

 free from the bunks, and at the same time pushes it off. This ma- 

 chine can also be used as a general utility car for building bridges, 

 picking up stray logs along the track, building track, etc. 



There are two types of portable unloaders. One has a stationary 

 boom, a single drum, and reversible engines. The other has a live 

 boom, which makes two drums necessary. A live boom increases the 

 use of the machiner}^, since it makes it possible to reach out over the 

 pond to break jams or pick up loads from barges. The engines of 

 this type of unloader are not reversible, they are made to back by 

 a change of gears. The machines have a capacity of about 20 tons 

 and will run up an 8 per cent grade. .The stationary boom machine 

 is shown in figure 81. 



The selling prices of these unloaders f . o. b. the factory are : Sta- 

 tionary-boom type, $2,500; live-boom type, $3,500. Since the use of 

 this machine necessitates a second track, the cost of constructing a 

 dump is greater when it is to be used with a portable log unloader 

 than when some other method is to be used. 



The work of unloading is generally done by the train crew, 

 with the assistance of an unloading engineer. In some cases when 

 the logs are delivered at the dump by a common carrier railway com- 

 pany the unloading is done by the booming and sorting crew. The 

 work proceeds about as rapidly with this method as any other. 



WATER TRANSPORTATION. 



Water has been used to transport logs in every important lumber- 

 ing region of the United States. It is still used extensively in the 

 eastern part. In other regions it has to a great extent been superseded 

 by railroads, because of the exhaustion of the timber supply near 

 drivable streams, the extensive logging of nonfloatable species, and 

 the increased value of stumpage. 



Water transport never gained the foothold on the Pacific coast 

 that it did in other lumbering regions, and it is now of minor 

 importance, except where the logs are brought to the shores of the 

 Columbia River, Puget Sound, Grays Harbor, Willapa Harbor, and 

 other points on the Pacific Ocean, and then rafted and towed to the 

 mills. The superiority of railroads over river driving was realized 



