Maximum Magnetism of Iron, Steel, ete. 419 
The magnetizing current made its circuit in the following 
manner (see fig. 1). The current from the battery A passed toa 
commutator B, thence to the tangent-galvanometer C, thence to 
another commutator D, thence around the magnet either a 
rng or a very long bar magnet): in returning it passed through 
when the coil G, placed on a horizontal surface, is turned over, 
‘n induced current is produced due to twice cutting the lines 
a by those helices. It is evident then that the number of 
wes of force passing through the magnet in the unit we have 
chosen will be given by 
h 
Q’ = 2n’(627 sin 74° 50')7Ri ano? 
rere n' is the number of coils in the ring G, m the number in 
ehelix F, R, the radius of G, 6-27 the total magnetism of the 
earth at this place (meter, gram, second, system), and 74° 50 
f - The quantity 2n’ (6-27 sin 70° 50’)7R? is a constant 
or the coil and had a‘value of 14-51. 
‘ Asa test of the whole arrangement, I have obtained the 
cer of lines of force in a ver long solenoid: the mean of 
Wo solenoids gave me Q’ = 12°67 M(zR?), while from theory 
