CHAPTEE V 



OF THE TEKDONS COMPARED WITH CORDAGE 



WHERE nature has provided a perfect system 

 of columns, and levers, and pulleys, we may an- 

 ticipate that the cords by which the force of the 

 muscles is concentrated on the movable bones 

 must be constructed with as curious a provision 

 for their offices. In this surmise we shall not be 

 disappointed. 



To understand what is necessary to the strength 

 of a rope or cable, we must learn what has been 

 the object of the improvements and patents in 

 this manufacture. The first process in rope-mak- 

 ing is hatchelling the hemp ; that is, combing out 

 the short fibres, and placing the long ones paral- 

 lel to one another. The second is spinning the 

 hemp into yarns. And here the principle must 

 be attended to which goes through the whole 

 process in forming a cable ; which is, that the 

 fibres of the hemp shall bear an equal strain : and 

 the difficulty may be easily conceived, since the 

 twisting must derange the parallel position of the 

 fibres. Each fibre, as it is twisted, ties the other 

 fibres together, so as to form a continued line, 



