THE ANGLE OF TEACTIOX, ETC. 233 



nation to the horizon is equally so with regard to a line 

 representing the axis of a carriage. In fact, the well- 

 known advantage of applying force as near as possible 

 to the centre of gravity of the object to be moved 

 depends to so great an extent on the possibility there- 

 by acquired of avoiding waste of power by the force 

 being exerted at a wrong angle or in a wrong direction, 

 that this consideration (the angle or the direction) be- 

 comes the principal one. 



It is indeed well known to artillery officers that a 

 considerably greater weight per horse may be calculated 

 on for teams of four than for those composed of six, 

 eight, or twelve horses ; but this does not depend on 

 the greater distance of the leaders from the carriage, 

 but on the difficulty of getting the increased number of 

 horses to act simultaneously and in the proper direc- 

 tion — in proof of which may be mentioned the fact that 

 it is well understood that no real advantage can be 

 attained by harnessing more than ten horses to one 

 carriage, however these may be disposed, and at what 

 distances. It is, then, the angle under which the effi^rt 

 is exercised, much more than the distance of the motor 

 from the load, that requires study and consideration. 

 For instance, no one ever thinks of using in the trac- 

 tion of canal-boats a towing-rope only just long enough 

 to reach the bank. On the contrary, it may be advan- 

 tageously lengthened till it forms a very small angle 

 with the keel-line of the boat, otherwise there will be 

 great waste of power through the action of the rudder. 

 No doubt the weight of the longer rope must be also 

 taken into consideration ; but what an enormous diflfer- 

 ence there is between the length of a towing-rope and 

 that of an ordinary carriage-trace, and still people wiU 



