ON HOOKS. 21 



and much more than sufficient room for the 

 passage in would indeed be an absurdity, and if 

 there be no mechanical arrangement, such as a 

 point guard, or other similar abomination, there 

 will clearly be plenty of room for passage out. Mr. 

 Pennell is surely inconsistent in considering this 

 alleged influence of the hook's shape in a contin- 

 gency that might arise (viz., the hook's slipping 

 backwards after penetration), and ignoring the 

 fact that precisely the same influence has, a 

 fortiori, a right to be included, when he is 

 examining the circumstances affecting penetration 

 itself. 



STRENGTH. 



It is an old axiom that the strength of a chain 

 is that of its weakest link, and it is equally clear 

 that the strength of a hook is that of the part 

 where it is most likely to break. There are two 

 points which require examination behind the 

 barb, where too much wire is often cut away ; 

 and the point at the greatest distance from the 

 line of pull, which is subject to the greatest 

 strain. The thickness of the wire behind the 

 barb, measured parallel to the line of pull, is of 

 far greater importance than its thickness at right 

 angles to this line. Messrs. Hardy take advan- 

 tage of this principal in their " harpoon " hook, 

 and cut the barb (in this case the barbs), not 

 from the upper or under surface, but from the 

 near and off sides of the wire. The same effect 

 might be got by flattening the wire at these 

 sides before cutting the barbs in the ordinary 

 way. 



Fig. 7 illustrates geometrically how the 

 tendency of the hook to break at the upper angle 

 of the bend, is affected by its distance from the 

 line of pull. It will be observed that I have con- 

 sidered the final line of pull, since the tension of 



