44 Messrs. Barton and Bryan on the Absorption of 



incident one. Such an experimental result may, therefore, 

 be accepted as proof that the bridge in use diminishes the 

 wave in the act of reflexion. 

 Further, 



for B < Lv, p has a negative value, . . . (6) 



and consequently the maxima and minima of the curves occur 

 for the same values of the abscissae as when R=0. This is 

 seen to be the case with the dotted curve, F, on the diagram, 

 obtained with the bridge whose resistance was 261 ohms. 

 Again, 



for R > Lv, p has a positive value ; . . . (7) 



hence this curve is, broadly speaking, an inversion of that 

 just considered, the maxima occurring for those values of the 

 abscissae at which the minima of the curve for R=0 occurred, 

 and vice versa. This is exemplified in the dotted curve, H, on 

 the diagram, resulting from the experiment with the bridge 

 whose resistance was of the order 1350 ohms. 

 Finally, we have 



forR=Lr, p = (8) 



In this case, sin'ce no waves are reflected, no stationary waves 

 can obtain, and consequently no waxing and waning of the 

 electrometer-throws can occur. Thus theory predicts a 

 straight line as the outcome of an experiment with a bridge 

 of this critical resistance. This is approximately the case 

 with the full-line curve, G, on the diagram, obtained with the 

 bridge whose resistance was of the order 560 ohms, the theo- 

 retical value of the critical resistance for the line used. 



Of course an absolutely straight line cannot be expected, 

 since the sparks in the oscillator vary slightly. For this 

 reason, throughout the experiments hitherto considered the 

 throws with the bridge under examination at any desired 

 distance beyond the electrometer were alternated with those 

 obtained with a no-resistance bridge at the standard distance 

 of a quarter-wave-length beyond. And the ordinates of the 

 curves on the diagram represent, not the actual electrometer- 

 throws with the bridge and distance in question, but the ratio 

 of these to those obtained under the standard conditions just 

 described. Thus the maximum ordinate in the diagram is 

 unity, all the curves are reduced to the same scale, and the 

 errors due to variations of the sparking at the oscillator are 

 in great measure eliminated. In the above experiments the 

 electrometer was used as a single-needle instrument, and the 

 throws obtained varied up to 100 scale-divisions. 



