THE ROYAL ARTILLERY INSTITUTION. 
337 
Mobility. 
With regard to the third requisite in a wagon, the conditions which 
influence the draught have already been sufficiently dwelt upon when 
speaking of artillery carriages. The height of the hind wheel of trans¬ 
port wagons varies usually from 4 ft. 2 in. to 5 ft. The greater it is, the 
more advantageous for draught; but a high wheel carries with it the 
evil of increasing the height of the bottom of the wagon for loading, 
and diminishing the stability. The height of the fore wheel should be 
also as great as possible, for ease of draught. In most wagons, the 
height of the hind wheel being determined, that of the fore wheel is 
made a maximum consistent with locking under, so that the wagon 
may be able to reverse in a short space; in some wagons, however, the 
latter is sacrificed, and the fore wheel made of equal diameter to the 
hind. 
Durability, &c. 
The remaining essential qualities of a wagon need no comment, 
Carts. 
Carts are used for transport as supplementary to wagons; for they 
furnish convenient means of moving small loads. They could not 
entirely take the place of wagons, for their capacity is not sufficient; and 
even if made capacious enough, so many more carts than wagons would 
be required, that columns of route would be too long. Carts have, 
however, another and more serious defect—viz., that of being much 
more fatiguing to the shaft horse, not only from the amount of weight 
which must necessarily be thrown upon him, but from the jolts or shocks 
which, more or less, are communicated to him as the cart passes over 
rough ground. The position of the centre of gravity of the cart (and 
load) is the only point which needs particular notice in the construction. 
It should always lie to the front of the axis of the axletree, and only so 
far so as to throw a moderate weight upon the shaft horse. It might, 
at first sight, be supposed that it would be better to balance the cart 
exactly on its axletree, and not have any pressure upon the shaft horse 
when the cart is at rest. If, however, this was done, it would be found 
that the inequalities of even a tolerably good road would produce such 
jolts that the horse would be more fatigued than with a constant 
moderate pressure upon his back. 
Springs. 
The advantages obtained by the addition of springs to a wagon or cart, 
are “ lightening of the draught,” and “ saving to the carriage and load 
in passing over rough ground.” In order that a wagon or cart without 
springs may surmount each successive obstacle of a rough road, both it, 
and as a consequence its load, have to be raised to the height of the 
particular obstacle as the wheels pass it. Suppose, now, the same wagon 
