250 Major P. Garde w. Instrument for Indicating [June 21, 



PiO. 14. 



The phenomena of a plain tube are shown when the disk is down, 

 and when up the regular bright bands are produced. This experi- 

 ment is very striking. 



IV. " On an Instrument for Indicating and Measuring Difference 

 of Phase between E.M.F. and Current in any Alternating 

 Current System." By Major P. CARDEW, R.E. Communi- 

 cated by Lord KELVIN, P.E.S. Received June 21, 1894. 



If the periodic time of an alternating E.M.F be T, and if, owing to 

 the presence of capacity or self-induction, or both in the circuit, the 

 current passes through the value at times differing from the times 

 of passage of the E.M.F. through the same value by t, the electrical 

 power will be VxCx cos (27r/T), where V indicates the effective 

 volts and C the effective current. 



If a momentary contact be made at intervals exactly synchronising 

 with the period of the alternating E.M.F. to complete the circuit of 

 a suitable and suitably connected galvanometer, aud if the time of 



