美国社会，第2卷（共2卷）

streams. Sixty-eight culverts of masonry pass under the road, and eighty-five drains. There are four viaducts of hammer-dressed sandstone, to carry the line over streams. The most splendid of these is over the Conemaugh, eight miles from Johnstown. It has a semi-circular arch of eighty feet span; the top of whose masonry is seventy feet above the water. There is a tunnel through a spur of the Alleghany, nine hundred and one feet long, by twenty feet wide, and nineteen high. The foundations of this road are partly stone and partly wood. Each station has two steam-engines; one being used at a time, and the other provided to prevent delay, in case of accident. Four cars, each loaded with 7000 lbs. can be drawn up, and four such let down at a time; and from six to ten such trips can be accomplished in an hour. A safety-car is attached to the train, both in ascending and descending; and though not an absolute safeguard, it much increases the security. This little machine, when pressed upon from behind, grounds its point, and materially checks the velocity of the otherwise flying train. The iron rails, and some other of the metal portions of the work, were imported from Great Britain. The cost of constructing this rail-road at the contract prices was 1,634,357 dollars; but this does not include office expenses, or engineering, or accidental extra allowances to contractors. During the first year of the two tracks being opened, fifty thousand tons of