C 4^ 3 

 thickness, and to remove part of the iron.* It 

 seems in theory, an easy matter to remove such 

 parts as are become useless, and to leave such as 

 are useful, untouched; but in point of fact, this is 

 very difficult. This difficulty arises from there 

 not existing any strong marks or lines, by which 

 what is useless can be distinguished from what 

 is useful ; and therefore some dependence must 

 necessarily be placed upon the judgment of the 

 workman. 



Since, therefore, there is not any line to point 

 out the division between what ought to be taken 

 away, and what ought to be left, it becomes ne- 

 cessary to look out for some other circumstance, 

 which may serve as a guide in distinguishing 

 them ; and some important knowledge, in this 

 respect, may be gained, by attending to the man- 

 ner in whicli a foot, which has been long shod, 

 is gradually disencumbiered of its useless por- 

 • tions, when left to itself. 



When the shoe is taken off, the crust will be 

 found to have grown beyond the level of the 

 sole, the surface of which will appear irreo-ular, 



• As this is a matter of great importance, the Author 

 trusts he shall stand excused for having recurred to it more 

 than once. 



