CHAPTER II. 



THE ANGLE OF TRACTION THE COLLAR THE HAMES THE 



TRACE THE POLE AND POLE-CHAINS THE HEIGHT 



OF THE WHEEL. 



The Angle of Traction* The mathematical or me- 

 chanical law which informs us that a given force, when 

 applied precisely in the direction in which motion is 

 desired to be effected, confers greater power than when 

 applied under an angle, is so perfectly consonant with 

 our everyday experience that it requires no further 

 demonstration. We may, however, just as well say 

 that as a given force applied directly upwards to a 

 wheel would only tend to lift it up, or directly down- 



* The idea of any importance being fairly attributable to an 

 adjustment of the angle of traction has been recently sneered at 

 by some of our " rule of thumb " philosophers, on the ground that 

 the celebrated old coachmen on the Bath, Brighton, and other 

 roads, knew nothing of it. It may be taken for granted that they 

 probably never heard of the existence of such a thing ; but that 

 does not prove that they were indifferent to the position of their 

 traces, or unaware of the fact that their teams or single horses 

 required certain adjustments to be made of the harness, the traces 

 and other parts of the harness, and these they did make, not 

 indeed on theoretical grounds, but from personal observation and 

 experience. The sneerers should prove, if they can, that the 

 results of these observations and experiences were at variance 

 with the theory set forth above, which is grounded, as all theories 

 should be, on still more extended experiences ; by doing so they 

 would extend our knowledge. 



