372 



ON LIGHT. 



or radius; and the same is true of c i, c 2, <r 3, c 4, 

 '5- 



(150.) This premised, we are now in a condition to 

 trace the movement of a molecule affected at once by 

 both these causes of displacement. Let it be O. Then 

 at the expiration of the first interval of 18 units of time 

 it will in virture of the vibration parallel to C A, be 

 carried to a distance equal to C i in a direction O P 

 parallel to that line, and will be found so far from the 



c 



Ffe. 15. 



line O / parallel to c a. And in virtue of the other 

 vibration similarly it will be found at the same time at 



