442 



Dr. Beattie on Leakage of Electricity from 

 Table IV. 



II- 



H calculated. 



H observed. 



•38 



2-25 



95 



•64 



2-15 



6-09 



•79 



2-08 



4-67 



•92 



1-92 



431 



301 



•83 



1-33 



7-48 



•21 



•44 



1-54 



1-56 



1-44 



In this case the discrepancy is very marked. The observed 

 and calculated forces are quantities of the same order ; and 

 that is all that can be said. Possibly this may be due to the 

 very close proximity of the river which runs parallel to the 

 line. The horizontal disturbance is due to the vertical com- 

 ponent of the leakage-current, We may possibly look upon 

 the river as an extended sink. Currents which start in a 

 horizontal direction from the side of the rail opposite to the 

 river may be diverted by it, gradually becoming vertical, and 

 finally, after having the direction turned through 180°, 

 passing horizontally, or nearly so, back under the rail and 

 into the river : or it may be that the water-surface under 

 the ground is not very far below the level of the rails — the 

 observing-stations were in most cases only 3*5 metres above 

 the water-level, — and that in consequence of this the lines of 

 flow are inclined at a less angle to the vertical than they would 

 otherwise be. 



The presence of the river ought clearly to affect the hori- 

 zontal disturbance more than the vertical. 



XL. Leakage of Electricity from Charged Bodies at Moderate 

 Temperatures. — II. By J. C. Beattie, D.Sc, F.B.S.E., 

 Professor of Applied Mathematics and Physics, South African 

 College, Cape Town *. 



•J 7. TN a previous paper f the rate of leakage of electricity 

 JL from insulated plates covered with different sub- 

 stances was observed when the plates were charged with 

 positive electricity to a potential of between 200 and 100 



* Communicated by the Author. Read before the Royal Society of 

 Edinburgh, July 1900. 



f Phil. Mag. ser. 5, vol. xlviii. pp. 97-106 (July 1899). 



