PHYSICS: BARUS AND BARUS 
69 
such a way that the sum is a geometrical progression. Thus for N turns 
Q =Sg = (4/5)k N q coulombs, nearly, where k is a large empiric constant 
depending on the method of initial charging and on the effective capacity of 
the armature-quadrant condenser. 
Finally if there are N turns per second and n = 4 segments, the average 
current is in the first second: 
/ = k N DLHv/1.8 X 10 21 amperes. 
W-<§ 
FIGS. 2 AND 3 
Thus even if N = 10 turns for 1 second, 20 turns for 2 seconds, etc., the 
current would soon be appreciable. 
Observations with the Intensifier. — The telephone and galvanometer may be 
inserted together and their indications as to intensity are identical; but the 
galvanometer additionally shows the sign of the current. The average cur- 
rent of 10 -7 amperes could still be easily heard in the telephone. The elec- 
