4 
^.IR. E. RUTHERFORD OR A MAGRETIC DETEOTOR OF 
The ordinates of the curve represent the deflection of the magnetometer and the 
abscissse the dep)th to which the iron has been dissolved by the acid, measuring 
from the surface inwards. Each division of the ordinates corresponds to a depth 
— *00057 centim. 
! 
(f). 
f 
\ 
1 
V 
'\ 
\ 
\ 
\ 
\ 
Depth 
of Pt 
'netr& 
V 
tion. ^ 
•>» 
Each 
di\/f 
1 
= •coo'cvcma 
^ 
1 
Ihe deflection of the magnetometer at first was 85 divisions. As the needle 
commenced to dissolve, the deflection increased rapidly to 156, remained nearly 
steady for a short time, and then rapidiy diminished to zero ; when this was the 
case the diameter of the needle was *032 centim., so that the magnetization had 
penetrated to a distance of *024 centim. 
If the variation of the value of I, the intensity of magnetization from the surface 
inwards, be deduced from this curve, it will be seen that the surface layer is 
magnetized in one direction and an interior layer in the opposite direction. This 
apparently gives evidence of onlj’ two half oscillations, in opposite directions, in the 
discharge. A large number of needles were dissolved after magnetization under 
various conditions, and the same peculiarity was observed, although, from other 
evidence, it was known that there were a large number of vigorous oscillations 
before the discharge was much damped down. 
When a needle magnetized to sataration was subjected to the discharge, the 
magnetization of the needle was always diminished, and on solution of the iron 
the same effect was observed, viz., a surface layer magnetized in the opposite 
direction to the internal maD'netism. 
O 
Since a Leyden jar discharge in general gives several complete oscillations before 
it is greatly damped down, it would be expected that the surface layer of a 
uniformly magnetized needle would either be completely demagnetized or show 
evidence of several oscillations in opposite directions. The effect observed may 
be explained when the demagnetizing force of the ends of a short needle on itself 
is taken into account. The first half oscillation that tends to demagnetize the 
O 
