442 Mr. T. T. P. Bruce Warren on a New Method 



or 



5465 + * 11-93 _ 



— i.Koo — '83 shunt-power of oc. 



Resistance of x— = tttt^ =800 B.A. units. 



n — \ 6*83 



As this method does not involve direct completion of the bat- 

 tery-circuit, it is adapted to the determination, more especially, of 

 the resistances of liquids which are subject to electrolysis. 



If the galvanometer-needle be deflected when the terminals 

 are immersed in a liquid, it may be brought to zero in the ordi- 

 nary way. Such a current will not interfere with the results,, so 

 long as it acts without interruption. 



In these cases, and also for the measurement of the internal 

 resistance of batteries, a-\-x together with the liquid should be 

 inserted as a shunt, and x afterwards varied by a known quantity. 



When measuring the internal resistance of a battery-cell, it 

 may be necessary to insert a small but known resistance between 

 its poles, so as to diminish the action of its current on the needles. 

 The following illustration will explain this operation : — 



Resistance of galvanometer .... =5384 B.A. units. 



„ battery-cell (shunted) = x „ 



„ a added to battery-cell = 40 „ 



„ interposed between poles of battery 1 B.A. unit. 



Discharge from condenser, galvanometer'! 1Qn ,. • • 

 i ,i •.! / >. ?■ — 1 o\J divisions, 



shunted with (a + x) f 



(a+44 + #)=360 

 writing x for a + x, 



5884 + ^ (5384+ (44+^\ 



X \ 44 + 3? / ' 



a = 40; .*. a—x=5'2 ; 

 and by the formula for the derived circuit, 

 40 x x x 1 



40 + ^+1 



= 5-2, 



from which we obtain 6*1 B.A. units for the resistance of the cell. 

 This method also supplies a simple means of arriving at the 

 position and resistances of faults in insulated wires or cables. 

 The most accurate results are obtained when the two ends of 

 the cable or core are available for simultaneous operation. With 

 submerged cables it will be more satisfactory to perform the tests 

 from each end; but if this be impossible, the distant end should 



