23S On Chain Calla or Moorings. 



strength from a given quantity of materials, keeping in mind th(? 

 direction in whicli the strain is to be borne. If the tendency of 

 a strain applied to a link of a bad form be once properly con- 

 ceived, a great step is gained towards tlic adoption of a good 

 form. Let AB, fig. 1, (Plate V.) re})re8ent a circular link of a 

 chain, the substance of the iron one inch. Let the outer circum- 

 ference l)e fifteen inches, and let the* inner circumference be nine 

 inches. If receding forces be appHed to the tv*o links C and 

 D (shown in section), pulling C towards E, and D towards 

 F, the ultimate tendency of the effort of such forces is to change 

 the form of the circular link into one which shall have round 

 ends and parallel sides, as figure 2 : but a very slight examina- 

 tion will sho\V that, before this can be effected, the link must 

 be destroyed : for in such a circular link the corrcsi)onding seg- 

 ments of the outer and inner circumferences are in the propor- 

 tion of 5 to 3 ; and therefore every effort to increase the distance 

 between C and D, or, in other words, to make the parts A and i» 

 approximate, must disturb the relative position of everv particle 

 of the metal, and operate to destroy its corpuscular attraction. 

 Thus (in figure 1), the segment jMN of the outer circumference 

 being taken equal to three inches, the correspiniding segment of 

 the inner circumference will be or.c in<.h and eight-tenths of an 

 inch. If this segment of tlie link is bv the force of a strain to 

 be changed from a curved to a straight ibrm (as in figure 2), 

 the corresponding segments of the outer and inner circumference 

 must be brought to one length ; to effect which, the matter 

 contained in three inches of the outer circumference must be 

 compressed into one inch and eight-tenths of an inch, or the 

 matter which now occupies only one inch and eight-tenths of 

 an inch in the inner circumference, must be made to dilate itself 

 to three inches without losing its cohesion, or the required 

 compression and expansion must I)e divided between the two ; 

 all of which are impossible with»)ut a derangement of the relative 

 position of every particle in the mass. — To be brief: the matter 

 in this part of the outer circumference mav be conceived to pre- 

 sent an infinite munber of fulcrums, over which the said receding 

 forces, by an effort to render the curve straight, must ruptiire 

 and separate the matter of the inner circumference. Nor is this 

 the only mischief that must occur, as will appear by a consider- 

 ation of what must take place .where the link folds round C and 

 D ; for Xi\e larger semi-circles in figure 2, each containing four 

 inches and a half (nearly) of the outer circumference, answering 

 to two inch.es and seven-tenth-, of an inch of the inner circum- 

 ference of figure 1, must now correspond to the semi-circum- 

 ference of the links C aufl D, wliich are each only one inch and 

 a half (nearly); so that in the.ae parts ihe effect, produced by the 



action 



