80 PRACTICAL HORSESHOEING. 



tion contributes to the preservation of the wood by pre- 

 serving it from the action of humiditv. 



Horn is a very slow conductor of heat, and it requires 

 a very prolonged application of the hot shoe to affect the 

 hoof to any considerable depth. Three minutes' burning 

 of the lower face of the sole has been found necessary to 

 produce any indication of increase of temperature by the 

 thermometer on its upper surface. It is never required 

 that the shoe should be applied longer than a few seconds. 



The hot shoe, in fusing the horn with which it comes 

 in contact, imprints itself like a seal in melted sealing- 

 wax, and in this way the two surfaces of foot and shoe 

 exactly coincide ; while no matter how expert the work- 

 man may be in using his tools to level the horn in a cold 

 state, he can never do it so quickly or so completely as 

 may be done by making an impression with the heated 

 shoe, and consequently establishing between the lower 

 margin of the hoof and the shoe an exact coaptation. 



It may be added that, when the surface of the horn 

 has been softened by the action of caloric, the nails enter 

 it more readily, the clips and inequalities are more easily 

 embedded, and when it recovers its habitual consistency 

 after cooling, the union between it and the metallic parts 

 which are in contact becomes all the more intimate be- 

 cause of the slight contraction that follows the expansion 

 produced by the heat. Under these conditions, the horn 

 contracts on the shanks of the nails, and retains them 

 most securely. 



All the highest veterinary authorities who have studied 

 the subject are unanimous in recommending hot fitting in 

 preference to cpld ; the latter is only justifiable when it is 

 impossible to adopt the former. The red-hot shoe at once 

 disposes of those inequalities which cannot be discovered, 

 or removed by tools; and it shows the workman at a 

 glance the bearing of the shoe on the hoof, as well as the 



