Improved Crane and Flexible Chains. 255 



The flexibility is inversely as these momenta, and proves 

 the superiority of chains ; for (on the average of the trials) 

 with the chain in the grooves, 



One pound raised - 3 r 25 lbs. 



With a half-worn strand-laid tarred rope, 



three inches and a half in circumference - £611 do. 

 And with the chain in the usual way, only - 24-47 do. 

 It also appears (contrary to the general opinion), that 

 chains are safer than ropes; for it is an established axiom, 

 that those bodies whose fibres are most in the direction of the 

 strain, are the least liable to be pulled asunder ; and in ourex- 

 amination of the properties of a rape, we find that the 

 strands cross the direction of the strain in undulated lines, 

 and consequently prevent its uniform action thereon. A 

 rope is subject to this inconvenience even When stretched in 

 a direct line, but more particularly so when bent over a pul- 

 ley, as in that position the upper section, moving through a 

 gr'eater space than the under one, is acted upon by the 

 whole strain ; and hence the frequent breaking of ropes 

 in bending over pulleys, from the double strain overloading 

 the strands of which the upper section is formed. 



The links of a chain are subject to the transverse strain, 

 where they move in contact* but as such strain is in propor- 

 tion to the length of the bearing, it must be very trifling. All 

 the links having axles of their own, the chain moves simul- 

 taneously with the strain, and both are in consequence re- 

 tained in continual equilibrio. A chain in grooves will 

 therefone sustain as great a weight when bent over a pulley, 

 as it will in a direct line, and consequently is safer than 



a rope. 



A safe, uniform, and flexible method of applying chains 

 in the working of machinery has long been a desideratum 

 in the arts ; for they are but little affected by exposure to 

 the weather, or the heat of manufactories, whilst either pro- 

 duces the specdv destruction of ropes. 



The discovery is of additional importance, as it substitutes 

 a durable article for a very perishable one, and gives employ- 

 ment to our own manufactories at the expenw of foreign im- 

 portations. 



