PREFENTION OF SLIPPING. 663 



their use on either is but temporary ; projecting beyond 

 the surface of the shoe, and opposing but a limited surface 

 to the ground, their duration is limited, and when they 

 are worn off, the foot, though in a better position, has 

 nothing to prevent it from slipping on pavement. 



For very many years inventors have endeavoured to 

 remedy the defects of calkins in various ways. Indeed, the 

 very earliest specimens of hoof-armature show us that the 

 primitive farriers were no mean adepts in providing their 

 steeds with a ' biting ' foot-hold. The nails that fastened 

 on the shoes had large semicircular heads that projected 

 beyond the lower face of the metal on a level with the 

 calkin, and were supported in the oval cavities of the 

 shoe ; forming, together with the calks, no less than eight 

 catches — all powerful aids in aiding progression under 

 certain circumstances, and guaranteeing a secure support. 



Flaschi and Blundevil give us more modern examples 

 in their way ; the ' catches ' of which they speak, however, 

 being notches in a raised welt on the border of the shoe. 

 In this century, many plans have been adopted ; the iron 

 or steel employed being, in a number of instances, rolled 

 by machinery, and generally channelled into grooves or 

 concavities. The most successful of these attempts to 

 fabricate shoes to prevent slipping appears to be that 

 adopted by Mr Gray, of Sheffield. The bars of iron 

 and steel from which his shoes are made are grooved up 

 the middle by either one or two cavities, or notched in 

 various ways. These ridges and teeth are extremely 

 hard, the shoes being tempered after they are forged; 

 consequently they can be made lighter than Rodway's 

 shoes, which were also made from rolled bars. 



