C 165 i 



XV. 



THE MEASUKEMENT OF VEEY SHOET TIME INTEEVALS 

 BY THE CONDENSEE-CHAEGING METHOD. 



By JOHN J. COWLING, M.A., F.Inst. P.; ^^=,ontari m 



AND /^ 



DONAL DONNELLY, M.Sc. p MAR [- I 



(In conjunction with the late Pkof. J. A. McCLELLAND^EtS.)i 



[Read December 21, 1920. Published Febkuaky 21, 1921.] ^-~~_- 



SoMEWHAT similar methods have been employed by other workers, and our 

 aim has been to examine what degree of accuracy the method was capable of 

 when applied to measure the shortest time-interval we could reproduce with 

 sufficient accuracy. It was, furthermore, desirable that the apparatus should 

 be kept as simple as possible, in view of the possible application of the method 

 in the workshop or testing room. We had intended to test the application of 

 the method to the measurement of the velocity of explosion in explosives, 

 but this part of the investigation was not carried out. Eeferences to previous 

 work have been fully given by Klopsteg^ in a recent paper, and need not be 

 repeated here; while the results of a similar investigation to ours were 

 published by Webster,^ and came to our notice in the last issue of Science 

 Abstracts. 



The particular method employed is based on the charging of a condenser 

 from a battery of steady e.m.f. through a non-inductive resistance. The 

 charge q acquired during t seconds is given by : — 



q = q„(l-e^<^j (1) 



or, t = 2-3 EC [log q, - log(^o ~ q)] . . . (2) 



or, approximately, t = — - (3) 



' The problem was submitted to us by Messrs. Nobel's Explosives Co., and this paper 

 is published with their permission. We desire to express our thanks to the Company 

 and Mr. Rintoul for their courtesy. 



- Klopsteg : Physical Review, xv, 7, 12. 1920. 



3 Webster and Allen : Am. Phil. Soo. Proc. 58, No. 6, p. 382. 1919. 



SCIENT. PKOC. K.D.S., VOL. XVI, NO. XV. 2 A 



