CURVES—CONSTRUCTION. 
119 
By formula (3) the maximum load on a level is.„. 770 tons. 
By formula (2) the maximum grade for load of 76 tons is. 250 feet. 
By formula (4) the maximum grade for 76 tons is.. 173 “ 
By formula (1) the maximum load up a grade of 150 feet is. 119-1- tons. 
By formula (3) the maximum load for same grade is. 85 “ 
By formula (1) the maximum load on a 200-feet grade is. 93J “ 
By formula (3) the maximum load on a 200-feet grade is. 67 “ 
For a 30-ton engine on six drivers: 
The total adhesive weight is... 67,200 lbs. 
By formula (1) the maximum load on a level is. 1,6S0 tons. 
By formula (2) the maximum grade up which this engine can draw a load of 
76 tons is. 401 feet. 
By formula (4) the maximum grade for the same load is. 281 “ 
By formula (1) the maximum load this engine can draw up a grade of 150 feet is. 186 tons. 
By formula (3) the maximum load for same grade is. 133£ “ 
By formula (1) the maximum load for grade of 200 feet is. 146 “ 
By formula (3) the maximum load for the same grade is.. 104J “ 
CURVES. 
On the Virginia Central road there are curves of 300 feet radius on a grade of 32S feet per 
mile. 
On a level, trains run on curves of 300 feet radius at a velocity of 20 miles per hour. 
A radius of 150 feet, and even less, is practicable; but in such cases the velocity of the train 
must be greatly diminished. 
There are various formulas for the calculation of the resistance on curves, but the simple inspec¬ 
tion of a wheel that has been some little time in use will show the inaccuracy of the results. 
The formulas are based upon the supposition that the surface of the tire is conical; this shape is 
soon destroyed by what is called the channeling of the wheel. 
The resistances in question can probably be determined only by the result of many experi¬ 
ments with a dynanometer. 
On the Pennsylvania Central road the grade is reduced on curves at the rate of 0.025 per 100 
feet per degree of curvature. 
CONSTRUCTION. 
To lay the rails. —The road-bed being prepared, cross-ties placed, and iron distributed, a party 
of six men will lay half a mile of track per day. 
The cross-ties should be prepared with corrosive sublimate; the sulphurets do not answer a 
good purpose. 20,000 spruce cross-ties were prepared in this way, and laid in 1840; they are 
now perfectly sound, although the natural duration of the wood is but five years. Cross-ties 
average about twenty-five cents each. 
Shallow excavations may be covered with workmen. In the case of deep excavations , where the 
earth cannot be removed laterally, sections of one-half mile, worked from both ends, are usually 
most advantageous; this distance, however, will depend chiefly upon the relation between the 
established gradients and the natural surface of the ground. The end of a cut composed of 
loose gravel or sand will accommodate a force capable of moving 15 to 20,000 yards in a month. 
In one case, 26,000 cubic yards of sand were moved in that time, the average haul being three- 
quarters of a mile. 
Long, deep cuts of gravel, sand, or similar deposite, can be opened, (working two levels at 
each end,) with an average haul of one mile, at the rate of 15,000 to 25,000 cubic yards in 26 days. 
Ordinary gravel can be dug, thrown into a car, and moved an average haul of 1,000 feet for 
