372 



ON LIGHT. 



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



(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 1 8 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 



KXXXXlX 



Fig. 15- 



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

 vibration similarly it will be found at the same time at 



