Soldier's revenge, a 409 Utility of letters of recommendation 424 South-American seaman, letters of 79, Spain Spectre of Pont Vathew, the Sporting St Mark's eve Steam coach Strawberry, cultivation of 17 471 336 88 288 287 Voltaire, anecdote of 407 301 Stature, elasticity of Superstitions in the west of England Subaitern, the, notice of Sweden, &c. Tales by the O'Hara family, notice of 67 Woman's hate 322 Watch-glass microscope 447 -248 50 Weaving in Scotland 126 Wife and the witch, the 129, 175 156, 171 115, 160, 186, 213, 272, 306, 332 Varieties 45, 86, 124, 164, 208, 247, 287, 324, 367, 405, 446, 485 THE HE strong feeling of interest and curiosity which this subject is now exciting in the public mind; the variety of companies which are daily forming, to connect, by means of rail-ways, the most important mercantile and manufacturing stations in the kingdom; the secret opposition which is now vigorously exerting itself on the part of interested bodies, with any object in view but the public good; seem to point out the propriety of setting before the public a general view of the advantages which rail-ways are likely to furnish, and to direct their attention to the quarters whence opposition may be expected. On a well made road a horse will draw one ton, in a cart weighing about 7cwt., or about 3000lb., at rate of two miles an hour. On a a rail-way of the best construction he will draw, at the same rate of travelling, about 15 tons; let us call this 30,000lb. for the convenience of having round numbers; and on a canal he will draw about 30 tons in a boat weighing 15 tons, or about 90,000lb. Hence, on a rail-way, the draught of a horse is ten times, and on a canal thirty times, as great as on a well made road. Now a rail-way costs about three times, and a canal about nine times, as much as a good road; and it is probable that the expense of keeping them in repair, is in proportion to the original outlay. It is obvious, therefore, if railways should 1 ATHENEUM, VOL. 3. 2d series, come into general use, that the expense of transporting commodities will be about two-thirds less than on the best roads. a rail-way over a canal, which is the With respect to the advantages of question here principally at issue, we may observe, in the first place, that if a horse power effect three times as much on a canal as on a rail-way, the original cost and subsequent repairs of a canal are about three times as great; consequently, a canal will require about the same rates or dues way. It must next be observed, that to repay the proprietors as a railthis comparison relates entirely to the transporting of goods at two miles an hour. Now it is easy to show, that so long as horse power is emsufficiently deep and broad to admit ployed on canals, and they are not the application of steam, this rate of transporting goods cannot be increased without an increase of freight, which would entirely destroy their seen that a horse will draw about We have superiority over roads. 90,000lb. at the rate of two miles an hour. If we increase the velocity of the boat, the resistance will also be increased, and with amazing rapidity. The resistance of a fluid increases as the square of the velocity. 90,000lb., therefore, is drawn at the rate of two miles an hour by one horse ; Since increasing the velocity on a rail-way, the resistance is not at all increased; it is, if any thing, rather diminished. Abstracting from consideration the resistance of the air, the very force which impels a body at two miles an hour, may, by very simple contrivances, be made to impel it at ten or twelve miles an hour. If we apply to the body to be moved on a rail-way, a force just equal to the resistance due to the friction, it will not move; it will be exactly in a state of equilibrium. But the smallest increase of force will put it in motion. If this small increase of force be a constantly acting force, like that due to steam, its motion will be continually accelerated, and would, ultimately, become greater than any assignable limit. Here we see the advantage of steam power; animal power could never be so applied as to produce this effect; because, as the velocity of the vehicle increases, the draught of animal power is diminished, becoming small indeed when it reaches the velocity of ten or twelve miles an hour. When the vehicle has attained any proposed velocity, whether that velocity be generated in the first instance by the continued action of the impelling force, or by any other means, it is merely necessary, in order that it should retain that velocity, that there should be an impelling force just sufficient to overcome the friction and the resistance to the air. Hence, on a rail-way, the expenditure of force due to a velocity of ten or twelve miles an hour, is very little more than that due to a velocity of two miles an hour. This is the grand mechanical advantage which a rail-road possesses over a canal. But it is on the application of steam, and on a consequent capacity of maintaining a constant action, however great the velocity of the vehicle, that this advantage depends. Without steam a railway would be of no use; it would possess no superiority over a canal. In this computation it is assumed that the draught of a horse is the same at two, four, six, and eight miles an hour. In fact, however, its draught diminishes very rapidly as its velocity increases, a great portion of its strength being exhausted in supporting its velocity. If 100lb. measure the force of traction of a horse, when travelling at the rate of two miles an hour, then will this power be reduced to 641b, when he travels at the rate of four miles an hour; and for higher rates of travelling it diminishes still more rapidly. Here the draught of a horse on a canal, at the rate of four miles an hour, is little more than 12,000lb. It is needless to push this inquiry any farther; it is quite clear that goods can never be transported on a canal at a rate exceeding two or two and a half miles an hour.Let us sce now what will be the effect of an increased rate of travelling on a rail-way. And here we shall arrive at a series of conclusions diametrically opposite to those we have deduced for canals. The resistance to communication of motion on a rail-way arises from the friction and the resistance of the air. For any rate of travelling which is likely to be adopted, 8, 10, or 12 miles an hour, the resistance arising from the atmosphere is very trifling compared with that due to the friction. We shall, therefore, altogether neglect its consideration. The resistance due to the friction is proportional only to the pressure. It is entirely independent of the velocity. This is the grand circumstance which distinguishes a rail-way from a canal, and which gives the former such an immense advantage over the latter. On a canal, by increasing the velocity of the boat, we increase the resistance to its motion at a very rapid rate; by Animal power could not have been applied with any advantageous effect, because its draught diminishes so rapidly with an increase of velocity. |