Page:Report from the Select Committee on Steam Carriages.pdf/152



Davies Gilbert Esq. M.P. 17 August, 1831.

and to all rates of travelling, yet they are eminently so in cases of swift conveyance, since obstacles when springs are not interposed, require an additional force to surmount them beyond the regular draft, equal to the weight of the load multiplied by the sine of the angle intercepted on the periphery of the wheel between the points in contact with the ground and with the obstacle, and therefore proportionate to the square of its height; and a still further force, many times greater than the former when the velocity is considerable, to overcome the inertia, and this increases with the height of the obstacle, and with the rapidity of the motion both squared. But, when springs are used, this latter part, by far the most important, almost entirely disappears, and their beneficial effects, in obviating the injuries of percussion, are proportionate also to the velocities squared.

"The advantages consequent to the draft, from suspending heavy baggage on the springs, were first generally perceived about forty years since on the introduction of mail coaches; then baskets and boots were removed, and their contents were beaped on the top of the Carriage. The accidental circumstance, however, of the weight being thus placed at a considerable elevation, gave occasion to a prejudice, the cause of innumerable accidents, and which has not, up to the present time, entirely lost its influence; yet a moment's consideration must be sufficient to convince any one, that when the body of a Carriage is attached to certain given points, no other effect can possibly be produced by raising or by depressing the weight within it, than to create a greater or less tendency to overturn."

The extensive use of waggons suspended on springs, for conveying heavy articles, introduced within these two or three last years, will form an epoch in the history of internal land communication not much inferior perhaps in importance to that when mail coaches were first adopted; and the extension of vans, in so short