Page:Inland Transit - Cundy - 1834.djvu/42

 30 INLAND TRANSIT, under such peculiar circumstances, that no general conclusion can be safely drawn from it. I can venture to affirm, that a similar result would not be found to attend the propulsion of a boat by a steamengine acting on paddle-wheels.

From what has been stated, it appears that the resistance to the motion of a vessel in a liquid does not increase in proportion with the weight of the vessel and its cargo. Two vessels of equal transverse section, but different lengths, may have very different weights, and yet suffer nearly equal resistance from the liquid in which they are moved. This forms a very important circumstance favourable to transport by canals, as compared with transport on other roads. On roads, the resistance is always in proportion to the weight; and by combining this circumstance with what has been already explained respecting the dependence of the resistance on the velocity, it will be easily perceived, that the most advantageous mode in which canals can be used is in the transport of very great weights at a very low speed. Indeed, independently of the limit of speed imposed by the law of resistance, there are other circumstances connected with canals which render any considerable rate of motion inapplicable to them; and one of the principal of these is, the wear and even destruction of the embankments, which would be produced by the rapid flow of water caused by boats propelled through them at any rapid rate of motion; although I am of opinion that a light steam boat can be propelled with more speed on a canal than on the sea, with equal force. But when a carriage is drawn or impelled along a hard and level road, the motion which it receives from the first impulse would continue undiminished for a short