212 PRINCIPLES AND PRACTICES OF SHOEING HORSES. 
space between it and the heels at the time of application, so as 
to admit of the action of the hoof; yet, after a few days, by the 
closer approximation of the shoe to the hoof, that space became 
less and less, and, before it was necessary to remove it, the hoof 
bore on it as in the ordinary shoe. 
But the bar-shoe, or used without the bar, or the frog bar- 
shoe, clearly and distinctly upsets the inferred principle, that 
crust should bear on the shoe, and sole should not. Let us 
therefore hear no more of such nonsense from any one professing 
to have the least practical knowledge of shoeing horses. There 
is no principle that can be uniformly practised without injury. 
The predisposing and exciting causes of injury of the foot are not 
acting upon all horses. 
I have got rid of all technicalities, to enable us to come to 
some conclusion as to what really are the principles of shoeing 
horses. I have shewn clearly enough, from general practice, 
that the crust only is allowed, or part of the sole also, at the 
toe, to bear on the shoe, till it can bear no longer at the heels : 
the weight is then thrown on the frog, if in a sound state to 
bear on the shoe, until you can get the heels in condition to bear 
on the shoe again. If we are to infer principles from all this, 
what is the result ? — That that depression of the sole, bars, crust 
at the heels, and frog should be allowed in the sound state of 
hoof that is used for its relief when diseased. I am aware that the 
subject is full of difficulty ; it all hinges upon practical utility, 
i. e. whether the ordinary shoes can be superseded by those upon 
principle at the same price. Independently of this, it is easily 
accomplished, as I shall hereafter shew, but not upon the theory 
of expansion, which is not the principle of action in the hoof, 
but that of the spring. 
“ It would be a very easy matter to give instances of the ad- 
vantage derived from springs, by calculating assumed cases ; 
but they seem to be quite unnecessary, since the general prin- 
ciple of changing percussion into increase of pressure, must, by 
its very annunciation, give evidence of its immense importance.” — 
D. Gilbert, Esq. M.F. on the Construction of Mail Coaches . 
“So great is the advantage of springs, that they almost annihi- 
late the resistance which that part of the load which rests on 
them would encounter without them, upon stony roads or rough 
pavement. From the whole of these experiments, it appears that 
the advantage of springs increases with the increased velocity of 
carriages.” — R. L. Edgeworth, Esq. F.R.S. M.R.I.A. Essay on 
the Construction of Roads and Carriages. 2d edit. p. 118. 
Springs. — “They convert all percussion into mere increase of 
pressure ; that is, the collision of two hard bodies is changed, by 
the interposition of one that is elastic, into a mere accession of 
