OF TRANSPLANTING. 
13 
the exact time and in the exact quantity that is 
required, and ceases of itself as the necessity for 
it ceases. 
The principle of locking two-wheeled car¬ 
riages by creating friction on the wheels induces 
a slight downward pressure on the horse’s back. 
But the long shafts act as a lever in the horse’s 
favour, and the extra pressure on his back is 
not to be spoken of in comparison with the 
labour of bearing back a loaded cart. 
That this is a fact any one may convince 
himself practically, by taking the water-cart 
which I have described down a hill which is so 
steep that he could not hold the cart back 
without this mode of blocking the wheels. 
Might not this mode of blocking be applied to 
two-wheeled carts ? 
