MEANS OF COMMUNICATION. 13 
would have to yield if unfavorable grades occurred, or the direct line could 
only be obtained by a disproportionate expenditure. 
An important point to be kept in view in the location of a road is the 
distribution of excavations and embankments, which should, if possible, be 
so arranged that the amount of earth to be moved in either case is nearly 
equal. Opportunities of using the earth from neighboring hills for embank- 
ments must also be regarded; the surplus of excavated earth must either 
be disposed of by augmenting the side slopes of the embankments or else a 
suitable place of deposit must be provided near the road. Of still greater 
importance are the grades of the road, and great changes of direction or 
even the abandonment of a particular route may be occasioned by the 
unfavorable nature of the country. It is generally received that from 8 to 
9 lbs. per ton is the resistance of friction on a level road, so that 1 in 280 is 
about the inclination at which the action of gravity equals the resistance of 
friction. 
Descending grades should be carefully avoided when the point to be 
reached is higher than the point of departure. When favorable gradients 
cannot be obtained, we must at least endeavor to cross valleys on their 
highest ridges and hills on their lowest depressions, or else, if a satisfactory 
line cannot thus be obtained, the obstacles must be overcome by stationary 
steam-engines or by tunnels. The admissible grades on a railroad will be 
determined by the probable amount of transportation and the power which 
may be available in each case. The gradients may either conform in 
general to the face of the country and undulate with the same, or else the 
elevation to be overcome may be concentrated in some few places, where 
in consequence the grades will be short and steep, requiring the employ- 
ment of additional locomotives or of stationary engines, while for the 
remainder of the road much more favorable grades and partial levels will 
be obtained. A road laid out on the first system requires in general less 
capital, and less labor on the part of the engineer, while the second system 
calls for the exertion of the highest powers on the part of the latter, and 
frequently involves a much larger capital ; but on the other hand the speed 
will be much more uniform and the wear and tear of locomotives will be 
less than on the undulating grades, the varying power on which is very 
injurious to the engines. To which of these systems the preference is due 
in any particular case must be determined by existing circumstances, the 
value of a railroad depending mainly on the amount of transportation of 
freight and passengers. Whether the road is mainly to be used for travel 
or for transportation of freight will materially influence the choice of 
location, as in the former case speed, in the latter power, are the chief con- 
siderations. In cases where the bulk of transportation is in one direction, 
as on roads carrying coal from the mines to market, ascending grades in 
that direction will, if possible, be avoided altogether. 
Another essential point to be kept in view in the location of a railroad 
line are the curves arising from changes of direction. Independently of the 
increase in length of the road the curves exert a very injurious influence on 
the locomotives and cars. In turning a curve the flanges of the wheels will 
ICONOGRAPHIC ENCYCLOPADIA.—VOL, IV. 38 593 
