MEEITS AND DRAWBACKS OF FROST COGS. 167 



Their disadvantages, however, are : — 1. That even with care- 

 ful fitting they are sometimes lost. This seldom occurs when 

 the cogs are inserted by the farrier ; on the other hand, it is 

 favoured by the horse cutting. When the snow ' balls ' in the 

 feet, and when horses are going up-hill over hard roads, the 

 cogs are verv liable to become loose, because thev fail to touch 

 the ground. 



2. Cogs are difficult to renew on account of becoming fixed 

 in position, though this can be prevented by removing them 

 immediately the horse returns home. To facilitate removal 

 different instruments have been invented, most of which, how- 

 ever, can only be used when the heels are very long ; but such 

 heels are a great disadvantage, especially in riding horses. 

 When the horse is worked without cogs the lower margin of the 

 hole ' burrs up,' and the insertion of new cogs becomes difficult. 

 After the drift has been in use for some time its edges become 

 rounded and the cogs no longer fit the holes it produces. 



5. Shoes with Eemovable Toe-grips. 



Koughing by the insertion of one or two ordinary screws in 

 the toe of the shoe has long been practised. Provided animals 

 thus shod are not used on stone pavements this method 

 succeeds ; but in larcje towns screws of anv form soon become 

 loose and fall out. As thev have afterwards to be removed 

 the attendant frequently refrains from screwing them fully 

 home : hence under the action of the severe strains to which 

 they are exposed they are soon lost. It is better to employ 

 blanks, which can be screwed in firmly at first, for although 

 this certainly does not get rid of the strains to which the 

 screw is exposed, it greatly diminishes the number of lost 

 screws. 



Toe-cogs have stood the test of many years' trial and 

 deserve to be more widely employed. The simplest forms are 

 the best, and none of those which require any special contriv- 

 ance, such as a wedge, a split pin or screw, to prevent loosening, 

 can be regarded as practical. The chief point is the shape of 

 the shank. This should increase in thickness about 1 in 7 or 

 8 ; when less tapered, — for example, 1 in 10 or 1 in 12, — cogs 

 at first become too firmly fixed and are difficult of removal, and 



