along Wires and their Reflexion at the Oscillator. 153 



on the other hand, as was seen in the last paper on the 

 absorbing bridge, the long-wave theory seems to hold within 

 a close approximation. 



Reflexion from Condenser only. — However, in order to 

 test the matter experimentally a little further, a second set 

 of plates like PP' SS' (fig. 1) was made and put up at the 

 end of the circuit at TT', but this set had simply one wire in 

 the form of a semicircle to connect the far plates instead a 

 spark-gap as at G. The induction-coil was also omitted 

 entirely at this end of the line. 



Hence the long-wave theory for reflexion for this arrange- 

 ment gives Z = l/S/? and 



p -l/Sp + Lv (10) 



And this equation, applied to an incident wave of the type 

 </>! sin nt, gives for the reflected wave <f>' sin (nt-\-a), where 



-2Li.S» > (11) 



and tana=- — /T Q . \ 



Here then is an opportunity of comparing simply the 

 behaviour of the short waves with what may rightly be 

 expected of the longer ones. For in this arrangement there 

 is no spark-gap whose heated state in the former case leaves 

 one in some doubt as to how far, when the waves return to 

 it, it acts as a short circuit and so possibly cuts out the 

 induction-coil entirely. 



The experiment was now conducted by alternating electro- 

 meter readings (1) with the condenser at T T', fig. 1, and 

 (2) with a no-resistance bridge placed across the wires just 

 before the end of the line. 



If then the condenser reflected all, as by equations (10) 

 and (11) must be the case with long waves of the simple 

 harmonic type whatever the capacity of the condenser, we 

 should find the ratio of the electrometer-throws taken under 

 the two conditions to be unity. Whereas the experiment 

 gave the ratio of throws with no-resistance bridge to those 

 with condenser only to be 1'26 + 0*07, the lengths of the line 

 before and after the electrometer being H7"5 m. and 48 m. 

 respectively. Applying now to this case the theory of the 

 phenomena analogous to that developed in the early portion 

 of this paper, and substituting for p 2 and s in the equation so 

 derived the values 04776 and 0-000564 as shown in Table II., 

 we obtain for the reflexion coefficient of the condensers alone 



p' = 0-82 (12) 



Phil. Mag. S. 5. Vol. 44. No. 267. August 1897. M 



