254  Ellectro-Magnetic Apparatus and Experiments. 
solid bar for reaction upon the coil wires. Mr. Bachoffner proba- 
used this compound arrangement before myself, as I made 
the discovery February 14th, 1838. Mr. Bachoffner remarks, © 
“that it is necessary to iicealete the wires of the bundle, and that 
it is difficult to understand their action, as the magnetic power is 
not so great as that of a solid bar.” In every experiment hith- 
-erto tried, I have invariably found the magnetic power to be 
greater than that of a solid bar of the same weight. I have 
never found it necessary to insulate the wires to insure their ope- 
ration, although I would not say that a very careful insulation 
might not improve their operation. For I apprehend that in the 
development and return of magnetic forces; electrical currents are 
excited in the body of the magnet at ri right angles to its axis, aS 
well as in the wires surrounding the magnet. In this case the 
exterior portion of the — would act asa closed circuit upon 
the interior. . - 
By a closed circuit is meant a FLOWING socuchlan’ current, 
which has the effect to re-magnetize the bar after the primitive 
battery current has ceased to act. That the operation of these 
secondary closed. circuits has never yet been considered in the 
construction’of machines, will appear from the agg facts 
and practical observations. . 
First.—Enclosing a compound* slonevacegent in .a tube of 
metal, almost entirely prevents the formation of secondary cur- 
rents in the exterior wires, although by this arrangement the 
tic power is not perceptibly affected, with the exception, 
that its development requires more time.t .'The short and com- 
plete right angle currents in the metallic casing have a greater 
magnetizing power than the secondary of an extended and © 
lique coil of wire. Hence, after the battery current ceases, the 
chief portion of the secondary will flow in this short’circuit, and 
the magnetism of the bar be prolonged to a perceptible degree, 
and if it were possible to break this. closed circuit immediately 
after the battery circuit, a secondary and tertiary current would 
be observed from the coil of wire. This ¢ertiary circuit I have 
perceived 3 in another way. 
* Or a common single ~— 
t The increase of ti e- nocewazy to effect the full development of magnetism, 
is due to the femclian of the initial secondary flo owing against the battery current. 
