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IMPLEMENTS OF HUSBANDRY

from the ground is lessened; because, when a horse is pullingup hill, his height is inclined to the declivity of the road,though it must be perpendicular to the horizon. For whichreason, the centres of cart-wheels should be somewhat lessfrom the ground than the point of draught, but the exact dif-ference depends on a variety of circumstances; it ought, how-ever, to be such, as to make the line of draught nearly to aright angle with the slope of the horse’s shoulders, whichgives the animal the greatest advantage in pulling. It is atthe same time the opinion of those who have paid great at-tention to this subject, that from four feet to four feet ten in-ches, is a very convenient diameter for cart-wheels; and, ingeneral, the different heights between these two diametershave been, and still are, preferred.

The great disadvantage in very high wheels is in goingdown hill; because the cart and load being raised high, thepressure must be more severe on the cattle, as the supportthey can then give the cart is too low placed ; therefore thelow wheels, in this case, have the advantage over the highefones. If the declivity of the road be such, that the weightof the cart and load is sufficient to overcome the friction, thegreater this is, the less force will be necessary to resist theweight when going down hill. In going up hill, the weightand friction act both on the same side of the centre of theaxle •, therefore, the less the friction is, the less power will berequired to overcome it. But in going down hill, the weightand friction act on different sides of the centre; therefore,the less the friction is, the greater force must be necessaryto resist the weight. From which it appears, that in goingdown hill, the lower wheels have greatly the advantage; be-cause the weight being lower placed, the cattle have morepower to resist the pressure, by that power being applied in aproper direction.

In the choice of carts or carriages, much depends on situa-tion ; there is, however, one certain rule that will always holdgood in every place, which is, that they ought to be of a sim -