370 Proceedings erf the British Association. 



pounds in each ton, would gravity give this back in the descent? 

 It was true that no power was required in descending, but while 

 only nine pounds were gained in the descent, twenty-seven pounds 

 were lost in the ascent. Beside the loss of power, there was 

 also the danger resulting from the too great velocity occasioned 

 by sudden descents. In one of the lines of railway, for which a 

 bill had been applied to the House of Lords, there was a slope 

 of 1 foot in 106, in a descent of two miles and a half long, and 

 the velocity given to an engine on arriving at the foot of the 

 slope could not amount to less than seventy miles an hour. To 

 mitigate defects arising from these abrupt descents, breaks were 

 applied, but not always with success. The break is a piece of 

 wood, pressed against the tire of the wheel by a lever, and if it 

 acts with full effect, it ought to prevent acceleration. He had 

 seen several cases in which it had totally failed, and one instance 

 which occurred, he would detail. At one of the slopes be- 

 tween Manchester and Liverpool, he was descending with a 

 loaded train of 150 tons. The operative engineer, whether 

 through a desire of displaying the engine's movements, or through 

 neglect, forgot to apply the break at the commencement of the 

 slope; when half-way down, the velocity became so great, that 

 he requested the breaks to be applied, but on doing so, they 

 were instantly burned. The train went down at a tremendous 

 speed, although the supply of steam had been cut off. When 

 the train had been stopped, it was found that the wheels of one 

 of the waggons which revolved with the axis, had been broken, 

 and yet, notwithstanding this accidental drag, the speed amount- 

 ed to at least fifty miles. It was objectionable to have any slope 

 exceeding 1 in 250, for when the excessive natural powers of 

 gravitation were resorted to, control over its movements was im- 

 possible. The conclusion to be arrived at, although it appears 

 paradoxical, is, that you may construct two rail-roads, say of 

 100 miles in length, one level, the other going over mountains, 

 and yet the two rail-roads may be worked by the same mecha- 

 nical power. Suppose in the one you ascend 1 in 250, and de- 

 scend in the same ratio, a pull of eighteen pounds to the 

 ton is required only fifty miles, and on the other half you de- 

 scend by inertion. On the level road, a pull of nine pounds to 

 the ton is required, from the entire distance of miles, and thus 

 the extent of exertion is equalized. It was not, however, to be 



