50 



more friction to overcome than that of the axis. The friction 

 therefore remaining always the same, it is evident that an in- 

 crease of velocity may be obtained, without a violent exertion 

 of the moving power. That is to say, when a horse on a rail 

 road can draw ten tons comfortably at the rate of 3| miles an 

 hour for six hours every day, if his motion is increased to five 

 miles an hour for four hours every day, his consequent wear 

 and tear will be owing entirely to the change of pace ; and 

 will correspond to that natural wear and tear induced by the 

 same change of pace in all situations. It is not so on a canal. 

 The force which the moving power has here to overcome, is 

 not friction, but resistance of the fluid. This resistance in- 

 creases nearly as the square of the velocity. All writers con- 

 cur in this fact. Where the speed on the canal is not greater 

 than three miles an hour, the resistance of the fluid does not 

 exceed the friction of the rail road ; but as the speed on a ca- 

 nal is increased, and particularly on a narrow one, the resis- 

 tance is found to increase, nearly as the square of the increase 

 of the speed. Supposing the horse to be drawing his load on 

 the canal, at the rate of two miles an hour, the Resistance at 

 that rate assumed, would be 150 lbs., it is evident, since by 

 doubling the speed the resistance is quadrupled, that by in- 

 creasing his speed to four miles an hour, the resistance is in- 

 creased four times, and that the horse has, instead of 150 lbs., 

 no less than 600 lbs. to overcome ; and if the speed is further 

 increased to six miles, the resistance is increased beyond the 

 sum total of the horse's powers, which are seldom equal to 

 1350 lbs. Here is one great advantage of rail roads over ca- 

 nals. On the former, if the distance for the day is not increas- 

 ed, the speed may be augmented from two miles an hour up- 

 wards, without inconvenience. On the latter, every trifling 

 increase of speed accelerates the destruction of the "animal; 

 which at any rate of speed in canal labor is at some disad- 

 vantage, the line of friction being oblique to the direction of 

 his motion. It results from the calculations on this subject, 

 that where the rate of motion on a canal does not exceed two 

 miles an hour, for 20 miles every day, a horse will draw three 

 times as great a load as he can on a rail road ; but w here the 

 speed is required to be at the rate of six miles an hour, for 20 

 miles every day, one horse on a rail road will do the work of 

 three upon a canal. 



It may be perceived therefore that the beneficial effects of a 

 horse's labor, result from the systematic observance of the law 

 of motion, and of his natural powers. It appears that where 

 load and speed are properly adjusted, a horse will do his work 

 comfortably every dav for a distance of 20 miles. That this 



