of experiments on the pendulum . 95 
a must be l ”1" 2 c, that is, the distance of the centres of the 
cylinders must exceed the length l by twice the radius, and l 
must be precisely equal to the distance of their surfaces. 
Believe me, dear Sir, 
very sincerely your’s, 
THOMAS YOUNG. 
Welbeck Street, 29 Dec. 1818. 
