SLEDS AND SLED-IIAULING 169 
mentioned practice gives the best results, since the ruts will stand 
up under heavier loads. Ruts are cut from 3 to 6 inches deep and 
are made somewhat wider than the thickness of the runner. 
The bottom of the rut may be square or concave depending on the 
shape of the runner shoe. The trough road has a smooth ice 
bottom with sloping ice wings. It is built up to a depth of several 
inches by frequent applications of water and it is then sheared 
off with a steel snow plow which gives a level ice bottom without 
ruts. The advantages claimed for this type of road are that 
it provides easier draft on short hauls, and that the solid ice bed 
makes a more permanent road during the warm winter weather 
which may occur near the close of the hauling season. These 
merits are not conceded by all loggers, however. Trough roads 
usually are made for a gauge of 6 feet or less. This necessitates 
the use of a narrow-gauge sled, with overhanging bunks which are 
more troublesome at landings than those on broader gauge sleds. 
Further disadvantages of the trough road are that the horses 
travel on ice and in the runner track, which necessitates the 
constant removal of manure; the road, unless plowed frequently, 
is built up and then tends to break down on the sides under heavy 
loads; much more water is required than for rut roads; more 
labor is required for maintenance; and on long hauls the capacity 
is no greater than for a rut road. 
Streams and dry watercourses are bridged with structures 
made from round timbers. Bridges are the first part of a sled 
road to weaken. They should be built on a slight downgrade, 
if possible, in order to facilitate the passage of loaded sleds. The 
usual type is one the floor of which is supported on parallel 
stringers, from 12 to 15 inches in diameter resting on abutments and 
piers which are made of logs from 12 to 18 inches in diameter, 
built in crib-fashion. The piers are 10 or 12 feet square and are 
commonly placed from 12 to 16 feet apart, and filled with stone 
to give them stability. The floor is made of skids from 6 to 10 
inches in diameter, placed across the stringers close enough to 
form a solid roadbed, and on these a thick covering of bark is 
spread to hold the snow, and prevent the sled track from break- 
ing up when the load passes over it. The skids are held in place 
by stringers which are laid on top of them, one on each side of 
the bridge. 
Piers are not adapted to use in a stream bed, because freshets 
