54 



ANIMAL MECHANICS. 



of gravity, which is made to ascend and descend, as before, 

 like an inverted pendulum, by the thrust and subsequent fall 

 of the other leg. The forward movement of the body, or its 

 horizontal transport, is effected by the pendulous movement 

 of the legs, caused by the successive raising of the centre of 

 gravity ; and, consequently, the work done in walking one 

 step, is simply the work of lifting the man's weight through 

 the height, to which his body is lifted at the commencement 

 of each step. 



It has been ascertained, by means of an apparatus in- 

 vented by Messrs. William and Edward Weber,* that in ordi- 

 nary walking, when the length of the step is 28.740 inches, 

 the mean elevation and depression of the centre of gravity of 

 the whole body is 1.248 inch; and it was also found that 

 this proportion remained the same for different lengths of 

 steps. 



From this observation we find, 



Vertical elevation 1248 1 

 Horizontal transport ~ 28740 ~ 23.03 



Hence it follows that a man walking 23.03 miles along a 

 horizontal road has done as much work as if he had lifted his 

 body up a vertical ladder through a height of one mile. 



Under such unfavourable circumstances, it is not to be 

 wondered at, that poor Crambe's courage failed him, when he 

 commenced the ascent of the staircase, with the corpse upon 

 his back ; and that, finding himself unable to ascend with the 

 alacrity required by the occasion, he quietly let go his hold, 

 and rushed breathless into the presence of his master, being 

 completely overcome by his unwonted exertions. 



The work done in the horizontal transport of burdens may 



* Mechanik der mensehliclien Gewerkze\ige 7 p. 238. Gbttingen, 1836. 



