ever, succeeded; a nd, except in the great ship canals in Scotland, steam-boats have not been generally adopted.
One of the principal causes of the advantage which steam posseses over horse power, arises from the circumstance that speed does not diminish efficiency. A given quantity of steam, whether produced and expended slowly or quickly, will cost the same sum, and will perform the same work; but his is quite otherwise with horses, as has been already explained. The same quantity of actual labour executed in a short space of time, requires a far greater expenditure of horse power than if it were performed at a slower rate; and hence it follows, in the comparison of the effects of steam power with that of horses, that the advantage of the former is slight, when slow rates of motion only are considered. To give the steam-engine its full advantage, if worked upon canals, it would, therefore, be necessary to propel the boat at a greater speed than 2½ miles an hour,—the rate at which horses can work with the greatest effect. But here again an obstacle is interposed, depending upon the nature and structure of canals. A boat moving in a canal at a higher rate than 3 miles an hour, is found to produce such a surge and motion of the water, as to injure or even destroy the embankments, unless in canals of considerable width, such as the great Caledonian Canal. Were the steam-engine, therefore, applied to propel boats upon any of the ordinary canals, it would be necessary to limit the speed to that rate at which the steam-engine competes with horses with the least advantage. It is probable that, even under these circumstances, in most situations, steam power would be found more economical than that of horses. As the other circumstances, however,
