16 



Mr. J. H. Poynting on a method of [Nov. 21, 



Inserting these values in equation A we obtain 

 154220-6 



A— 



453290 

 6654 



I V2 J J J r202 



202716 



\A = Cx 



where C = 



15220-6 x 453290x202716 



3 V 2 



and log = 1-8951337, 

 .-. log A = l-8951337, 

 + log r, 

 —log n, 

 -2 loff d. 



■e^cos 2 A. XfX 



6654 



The following table is an account of an experiment made on May 30th, 

 1878, and will serve as a specimen of the method of making the observa- 

 tions. It is the best which I have yet made in the closeness with which 

 all the values of n agree with each other. 



VII.— May 30, 1878.— Determination of r. 



Eider on 

 beam. 



Extremities of 

 oscillations. 



Eesting 

 point. 



Mean of pre- 

 ceding and 

 succeeding 



resting points. 



Of r differences 

 —r. 



E 



260-9 



250-9 

 260-6 



255 -82 







L 



214-6 



205-0 

 212 3 



2u9 -22 



256 -74 



47 '52 



E 



271-9 



246-7 

 269 -4 



257 -07 



210-31 



47-36 



L 



214 3 



209-2 

 212-9 



211 -40 



257-62 



46-22 



E 



249-7 



263-8 

 253-0 



257-57 



212 -23 



45 -34 



L 



204 -9 



220 -7 

 206-0 



213 -07 







Mean r=46'61. 



