56 



American Fisheries Society. 



grams. A scale is laid off on an arc below the pendulum thus 

 formed, so that the circular distance from d to the point of rest 

 of the pendulum is one-half a radian, (i.e., one-half the length of 



m- 



Fig. 9. — Apparatus used for testing stiffness of lines. 



the pendulum). If the pendulum is displaced to d, and re- 

 leased, it swings through one radian, dg, and will continue to 

 swing, but each oscillation is of lesser amplitude than the pre- 

 ceding, because of the friction in bending the line and, to a 

 negligible extent, because of the friction of the air. When the 

 amplitude has been reduced from one radian to one-half radian, 



NUMBtR OF MONTHS EXPOSED 



Fig. 10. — Stiffness of cotton lines exposed in sea water at Beaufort, N. C. 



