THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF -SCIENCE. 



[SIXTH SERIES.] 



\ 



MA Y 1903. 



v 



%. 



LI. On the Measurement of Small Capacities and Inducta flees. 

 By J. A. Fleming, D.Sc, F.R.S., Professor of ' JElectrieal 

 Engineering in University College, London, and W. C. 

 Clinton, B.Sc., Demonstrator in the Pender Elecffif&!it ,r 

 Laboratory, University College, London*. 



[Plate XII.] 



THE measurement o£ small capacities and inductances has 

 become important in connexion with Hertzian Wave 

 Wireless Telegraphy. The experimental determination of 

 the electrical capacity of telegraph wires and of the overhead 

 wires used for the conveyance of high tension alternating 

 currents, is also called for in connexion with the calculation 

 of sending speeds and of voltage drop in a power line. The 

 advantage of possessing an appliance which will conduct this 

 work quickly and well has led us to design the instrument 

 which is here described. 



It is generally admitted that for the measurement of small 

 capacities, when the dielectric is air or some other substance 

 not possessing the quality commonly called absorption, no 

 method is so easy to apply as that depending upon the rapid 

 charge and discharge of a condenser through a galvanometer. 

 This method is almost the only one applicable to the measure- 

 ment of the small electrical capacities of wires insulated in 

 the air, such as the aerial wires employed in Hertzian Wave 

 Telegraphy, or ordinary telegraph-wires, or small air-con- 

 densers, or in fact any form of condenser in which the. 



* Communicated by the Physical Society : read February '27, 1003. 

 Phil. Mag. S. 6. Vol. 5. No. 29. May 1908. 2 L 



