352 
LOGGING 
thrown through the perforated screen plate are carried by the draft 
against the fine netting (E) . In firing up, the natural draft through 
(A) around (B) and under (E) is unobstructed by netting. This 
has two advantages: (1) the possibility of clogging is eliminated; 
(2) there is an easy, free draft when starting the fire. This stack 
acts as a centrifugal separator which prevents the emission of the 
larger and more dangerous sparks and only allows the escape 
of small, light sparks which are dead 
by the time they leave the stack. 
WATER 
Provision is made for watering 
locomotives either at the mill or at 
some convenient point along the 
railroad. Water may be supplied 
from storage tanks, by gravity pipe 
lines from streams, or taken direct 
from the streams by an injector. 
The amount of water required is a 
variable factor, depending on the 
amount of work performed by the 
engine and the efficiency of the fire- 
man. 
Trautwine says that between 6 and 7 pounds of water are 
evaporated for each pound of average-grade coal that is con- 
sumed. On a basis of 6| pounds of water (0.8 gallons) per 
pound of coal, 1600 gallons will be required for each ton of coal, 
or 800 gallons for each cord of wood consumed. Engines which 
"blow-off" at frequent intervals will require more water than 
the amount mentioned. 
B. CARS 
Logging cars are subject to severe usage and are built chiefly 
with wooden frames so that repairs can be made at the loggers' 
machine shop. 
NARROW GAUGE 
When light rails are employed, the same type of car as de- 
scribed for the stringer-road^ is often used. When a 35- or 
40-pound rail is in use a hea\der car is desirable. The main 
1 See page 282. 
Fig. 118. — The Radley-Hunter 
Spark Arrester. 
