74 BULLETIN 711, U. S. DEPARTMENT OF AGBICULTUBE. 
assists the rigging slingers with their work. The swamper works 
just ahead of the rigging men. knots the logs, fells small timber that 
may be a source of danger to the crew, chops out the brush, and im- 
proves the roads, so that the logs can be brought out without being 
hung up. "When necessary, the sniper rounds off the under side of 
the front end of the logs, so that they will slide over obstructions. 
In rough country, where the logs are apt to roll and to be dragged 
first on one side and then on the other, they are usually sniped all the 
way around. The depth of the snipe depends partly on the size of 
the log and partly on the ground conditions, ranging from little or 
nothing to 9 inches. The head rigging slinger is the hook tender's 
assistant. Working alone or assisted by another rigging slinger. 
sometimes two others, he unhooks the chokers from the butt chain 
when the main line is returned, hooks up the new load of logs, and 
starts it toward the landing. The principal duty of the choker men 
is to put the chokers around the logs. The chaser, standing near the 
butt chain block, signals to the engineer in case there is need for 
stopping the engine. His principal work is to pass the load of logs 
by the butt-chain block. The signal man. by means of signals, usually 
given by pulling on a wire attached to the whistle of the yarder or 
by an electrical device, transmits the order of the hook tender, rigging 
slinger. or chaser to the engineer. 
EQUIPMENT. 
Ground logging engines. — Engines used in swinging and roading 
on the ground, as well as ground yarding engines, are dealt with in 
this section. While their inclusion here is not exactly logical, clear- 
ness and convenience of discussion make it advisable. 
Figures 29 and 30 show the compound-geared and tandem-drum 
logging engines, the two standard types used for ground logging. 
As a rule, the narrow-drum, compound-geared engine is used, the 
compounding of the gears having proved the best method of securing 
the proper relation between the two drums in regard to speed and 
pulling power. 
The wide-drum, simple-geared engine is also used, but principally 
swinging and roading. where high speed in the lines and large 
drum capacity are of major importance. Wide-drum engines bear 
special trade names, depending on whether they are adapted for yard- 
ing and swinging or roading. the chief differences lying in the drum 
proportions and friction devices. The engines and boilers of a long- 
haul road engine are. of course, larger than those of an engine adapted 
to haul at relatively shorter distances. 
Probably no other class of machinery is called upon for such ex- 
tremely severe service as logging engines. The demands made upon 
