EXTERNAL FORMATION. 87 
this principle, the legs of the long-backed horse are actually sustaining less 
load than those of the short-backed horse, even though their riders or 
burthens may be of equivalent weights, from the circumstance of their 
operating at a greater distance from the load.” The fallacy of this argu- 
ment is apparent to every person who has the slightest knowledge of 
mechanical powers ; but as my readers may not at all be in a position to 
estimate its value, I shall just make a few observations upon it, as I have 
heard it adduced on several occasions, to support the advantage of a long 
back. Now we will suppose a weight of 500 pounds on a plank, sup- 
ported upon four props, two being five feet from the other two, and the 
pairs one foot apart, resembling, in fact, the relative position of the feet of 
a horse. Let the whole be arranged on a weighing-machine, so that only 
the four legs touch its table and take the weight. Then remove the twc 
pairs of legs to a distance of six fect, and again take the weight. Accord- 
ing to Mr. Percivall it ought to be less than before, but, tested by actual 
experiment, there will not be the hundreth part of a grain variation, even 
if the instrument is sufficiently delicate to register that weight. A. and B. 
carry a weight between them, suspended to a pole, and they find it more 
convenient to have that pole tolerably long, because they can shift the 
weight from one to the other more easily than with a shorter one, but 
they carry the same weight in either case. A. can raise it by means of 
his long lever more easily than with a short one, but he only can effect 
this by making use of B’s hand as a fulcrum, and for the moment throw- 
ing the weight off himself upon it, while B. returns the compliment in 
his turn, and both are relieved.- For the mere purpose of carrying weight, 
therefore, a short back is to be preferred ; but there is a limitation put to 
this by the necessity for length of limb to give pace, and if the legs are 
too long for the back, the action of the fore-quarter is impeded by the 
hind, and vice versd. Hence, in all horses, a reasonable length is preferred, 
and this will vary according to the occasion for weight-carrying power. 
In the thoroughbred horse, pace is essential, and his back must conse- 
quently be of sufficient length to allow the free use of such limbs as will 
give stride enough to develope it. We shall hereafter find, that the cart- 
horse may have a much shorter back, even though he has no weight to 
carry, but he requires strong couplings of the hind and fore-quarter for the 
former to act upon, in dragging heavy weights, and as in him pace, beyond 
the walk, is never required, a short back may be allowed to be a great 
advantage without any attendant evil. The most important elements of 
strength in the back and loins are the depth and breadth of its muscles, 
for they, and not the bones, as I have shown, are the real mechanicai 
means by which not only weight is carried but propelled. Now to lodge 
these muscles, there must be high spinous processes, wide hips, and such 
a formation of the ribs as to give width at their upper parts. Generally 
speaking the two last coincide, hut sometimes the hips stand out in a very 
“ragoed” or prominent position, while the ribs are flat. This formation, 
however, comes next to the most approved combination, and is far better 
than the narrow hips and flat sides which we now see in too many of our 
thoroughbred horses. In connexion with this division of the body may 
be taken the croup, the upper outline of which is formed by the pro- 
longation of the spine towards the root of the tail ; but the essential parts 
are made up by the pelvis. It is very generally assumed that in order to 
develop high speed, the pelvis must be long, and this I believe to be 
perfectly true; but the length need not be in a perfectly horizontal 
direction, and is I think much better if developed at an inelination of 
