ME MO 11 AN DA ON RAILWAYS, 
Washington, D. C., November 21, 1854. 
Sir : I have the honor to submit the accompanying memoranda upon various practical points 
connected with the construction, &c., of railways. 
For the information therein contained I am chiefly indebted to Col. C. Crozet, Messrs. W. 
Raymond Lee, William P. Parrot, J. Edgar Thompson, and William Parker, civil engineers, 
who most kindly afforded me all the assistance I asked. 
The article on tunnels is taken principally from a paper by Mr. W. L. Dearborn, civil engi¬ 
neer. 
I am, sir, very respectfully, your obedient servant, 
geo. b. McClellan, 
Lieutenant Engineers and Brevet Captain. 
Hon. Jefferson Davis, 
Secretary oj War. 
GRADIENTS. 
The following gradients are now, or have been, in use on American railways : 
During the construction of the Baltimore and Ohio railroad a gradient of 528 was used on a tem¬ 
porary track, en boyau, merely to transport small loads of iron, &c. On the Virginia Central 
road the trains pass every day over a gradient of 275 feet—length two miles. On a part of this 
are curves of 300 feet radius (19° 6') on a grade of 238 feet; 40 tons have been carried up this 
by a 30-ton engine on six drivers, with the utmost ease. Brakes of a peculiar construction are 
used, and found to answer well. On the “ Virginia Central” the trains ascend at a velocity of 
about seven miles per hour, and descend at an average velocity of about four miles. In descending 
the steam is cut off and the wheels of the engine allowed to revolve, the brakes on the cars being 
“ hard down.” Reversed curves are frequent and sharp. On the Baltimore and Ohio road are 
grades of 116 feet for 17 miles. Auxiliary power is here employed, the trains being divided, 
and running up at the rate of 15 miles per hour. The trains descend these grades with a velocity 
of 25 miles under perfect control. 
On the Pennsylvania Central road there are gradients of 95 feet for 9f miles; where curves 
occur the grade is reduced at the rate of 0.025 per 100 feet per degree of curvature. Passenger 
trains ascend this grade with a velocity of 24 miles per hour, and descend at 20 miles per hour. 
The ascent, when there are more than three cars, is effected by the aid of an additional engine. 
The working load of the heavy freight engines (weighing 65,000 pounds, and on eight drivers) 
on the 95-feet gradient is 125 tons net, or about 208 tons, including tender and cars. Over the 
53-feet grades on this road (Pennsylvania Central) the general load of the engines (55,000 
pounds, on six drivers) is 150 tons net, or about 250 tons, including tender and cars. On the 
Massachusetts Western road are grades of 83 feet for l£ mile. Engines of 20 tons draw 100 tons 
over this grade. Passenger trains run up at about IS miles per hour without auxiliary power. 
The average amount of wood consumed and cost of haulage, on the whole road, are no greater 
than upon other Massachusetts roads of lighter grades. 
It is the opinion of many able railway engineers that, on a permanent track, grades of 200 feet, 
