Page:Report from the Select Committee on Steam Carriages.pdf/149

  , and take in and out the cargo. The principles of the leading power being matured, all the applications will soon follow. 



you paid any attention to the general nature and advantages of wheels and springs for Carriages, the draft of cattle, and the form of roads?—I paid considerable attention to it during the sitting of a Committee of this House about Twenty years ago, of which Sir John Sinclair was Chairman, and I then drew up some Observations on the nature of wheels and springs on roads, which, with some alterations, I printed in the Eighteenth volume of the Journal of Sciences, and which I would beg to deliver in to the Committee as the result of my observations on the subject.

"Taking wheels completely in the abstract, they must be considered as answering two different purposes.

"First, they transfer the friction which would take place between a sliding body and the comparatively rough uneven surface over which it slides, to the smooth oiled peripheries of the axis and box, where the absolute quantity of the friction as opposing resistance is also diminished by leverage, in the proportion of the wheel to that of the axis.

"Secondly, they procure mechanical advantage for overcoming obstacles in proportion to the square roots of their diameters, when the obstacles are relatively small, by increasing the time in that ratio, during which the wheel ascends; and they pass over small transverse ruts, hollows or pits, with an absolute advantage of not sinking, proportionate to their diameters, and with a mechanical one as before, proportionate to the square roots of their diameters, consequently, wheels thus considered, can not be too large; in practice, however, they are limited by weight, by expence, and by convenience. 