184 W. E. Ayrton — Qualitative Method [No. 2, 



Eliminating y, z, (a + /?), and M from the preceding five 

 equations we obtain — 



G + F 



(a a a a \ 



"c " f d ~~ b ~"e~ )' 



As an illustration of the method described in this paper I made 

 the following experiments with three earth plates, each 2 feet by 4, 

 and using a Wheatstone's Bridge as my testing arrangement. 



Experiment 1. The plates were buried vertically and parallel 

 to one another with the longer edges horizontal and so that the 

 line joining the centres of the plates was perpendicular to each 

 plate. The centres were 4 feet apart, and 2 feet 6 inches below 

 the surface of the ground. 



The resistances of the circuit from plate A through the ground 

 to plate C was very little more than that of the circuit from plate 

 A through the ground to plate B although C was twice as far form 

 A as B was, thus showing than in earth circuits the resistance is 

 not so much in the earth itself, but exists between the surface of 

 the metal plate and the earth. Using in the way previously ex- 

 plained in this paper the values I obtained I found that — 



[Resistance of plate A = 2-49 Siemens Units. 

 ,, „ „ B = 5-86 „ „ 



„ C = 10-23 „ 

 Experiment 2. The plates A and C remained as before, but B 

 was placed horizontally, its centre being still 2 feet 6 inches below 



