238 BULLETIN 711, U. S. DEPARTMENT OE AGRICULTURE. 
PORTABLE 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 machinery, 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 In other regions it has to a great extent been superseded 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 Eiver, 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 
