488 



PROFESSOR W. E AYRTON, MR. T. MATHER AND MR. F. E. SMITH: 



difference made ; the value of this difference varies from 2/t to 3/x for the different 

 pairs of coils. A confirmation of this difference appears on p. 516. 



In Tables III. to VI. there are given the diametral measurements of the coils in 

 various planes, the mean diameter of the wire with which the coils are wound, and 

 the mean diameter of the coils to the central filament of the wire. In the 



TABLE III. Results of Measurements of the Diameters of the Coils, to Centres of 

 Wires, on Suspended Cylinder No. 1. Temperature, 15 '5 C. 



conversion of inches to centimetres the ratio 2'539998 has been taken. For the data 

 relating to the steel gauges employed we are indebted to Mr. ATTWELL, of the 

 Metrological Department. A good conception of the ellipticity and conicality of 

 the coils is afforded by the calibration curves which follow (figs. 13, 14, 15, 16). The 

 suspended coils are very slightly elliptical, and the conicality is also very small and 

 uniform. The difference in the extreme mean diameters of suspended cylinder No. 1 

 is 17/1, equivalent to an average slope of 1 in 8000; the corresponding value for 



