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ANNALS NEW YORE ACADEMY OF SCIENCES 



the principle of the parallelogram of forces, we may resolve BD into two 

 forces, the first AB acting in the direction of the rod AC and tending 

 to press AC against its fulcrum A, the second component BR acting at 

 right angles to the first and tangent to the arc of rotation BB'. The 

 first component AB may be called the "centripetal component," the sec- 

 ond BR may be called the "rotation component." In Fig. 2 (II), the 

 contractile spring bd is of the same length as before, but the angle of 



Pig. 2. — Diagram illustrating the direct relation of the angle of insertion (a, a' ) to the 

 "rotation component" (BR, or) and the inverse relation of the angle of inser- 

 tion (a, a') to the "centripetal component" (AB, ao) and to the speed of the 

 insertion point (proportional to BB', of). 



insertion abd (a) is increased; then the centripetal component ab will 

 be less than AB, but the "rotation component" br will be greater than 

 BR. Accordingly as the angle of insertion increases, the pull across the 

 shaft becomes more direct, while the pull along the shaft decreases; in 

 other words, the rotation component varies directly, the centripetal com- 

 ponent inversely, with the angle of insertion. 



