AFFIXING WEIGHT. 163 



any portion of weight on his back tliat he can so 

 much more easily draw is preposterous. A fact has 

 been often proved on the other side to this : put a load 

 behind a horse which he cannot move, and then put 

 an 18st. man on his back, he will draw it. This only 

 shows the effect of increased weight against weight ; 

 but it would be a rather curious manoeuvre to put an 

 18st. postilion on one of a pair of horses in order to 

 facilitate his going ten miles an hour in harness, even 

 allowing we took the 18st. from the carriage. Still in 

 many ways are the powers of horses wasted in nearly 

 as ridiculous a manner from want of consideration. 

 It is quite clear, that whatever presses against the 

 front part of the axle has a tendency to drive the 

 wheels back, while whatever acts upon its back part 

 has an opposite effect. If the hind-wheels of those 

 enormous machines the omnibusses were placed a 

 yard further backwards, every jolt would act with a 

 retrograde effect, whereas now each jolt that gives 

 the body a swaying motion actually appears to be 

 kicking the axle (and consequently the wheels) for- 

 wards, and to a certain degree does so. Place 

 an elastic perch between two sets of wheels, namely, 

 the fore and the hind ones, and let a weight fall 

 on the centre of the connecting perch, the hind- 

 wheels will be found to move backwards and the fore 

 ones forwards, which shows that pressing behind one 

 axle and before the other produces the effect I have 

 stated : make the perch perfectly stiff, no effect on the 

 wheels as to propelling backwards or forwards would 

 be produced. It may be said the body of an omnibus is 

 not elastic : granted ; and place that body straight on 

 the two axles, the two pair of wheels would each move 



forward in the same degree if the carriage was pulled, 



n 2 



