33 



tip. These are intended ; to direct the line through the- 

 ring at the summit, so as to make it keep close to the rod : - 

 ail the way (wliereby it is not allowed to hang about in a- ! 

 loose manner), and to give to every part a due bend. 



The rings should be rather numerous than scanty, espe~ 

 cially on tho thinner parts) for; the closer the line is kept;, 

 the greater are the angles it makes between any two con- 

 tiguous rings* and consequently, the more equable is the 

 bend throughout every part: of the arch described by a- 

 rod when in a state of -exertion. . 



When the rings are too distant, they frequently tear 

 out, or the rod snaps in the too long interval between 

 them, which is thus obliged to bear- more than, its due- 

 proportion of the stress. 



The. following scale willj perhaps, be found as good as 

 any mat can be devised. Place your first ring at two. 

 inches and a half fiom that on the tip of the rod. Now 

 the inches on most rulers being divided into eight equal' 

 parts, in the above distance there will be twenty equal; 

 spaces, each equal to the eighth of an inch* 



Let every succeeding space be increased by the gddition 

 of one-fifth of the measure of its preceding interval.. 



Thus, the uppermost* interval- being twenty-eighths* 

 one- fifth of that added to itself, will give twenty- four, 

 eighths (i. e. three inches) for the second interval. 



Then, for. the third interval, take twenty-four eighths, . 

 and its fifth, which is nearly five- eighths, and its measure^ 

 ment will be about twenty- nine eighths, or some tiling 

 more than three inches and a half* 



The fourth interval will be twenty-nine, added- to its 

 fifth, say six-eighths, which give, a tytui'of three iacfo'.j 

 and three-eighths, - - 



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