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insulated from the framing by suitably formed pieces of 
ebonite, and also from the shaft, by a cylinder of the same 
substance. Through the side of the disk, and parallel with 
its axis, sixteen holes are bored, at equal angular distances 
from each other, for the reception of the same number of 
cores or armatures. The cores project about two inches 
through each side of the disk, and are held firmly in their 
places by screws tapped through its periphery. Around 
each inside face of the circular framing; and concentric with 
the driving shaft, sixteen cylindrical electro-magnets are 
fixed, at the same angular distance from each other and 
from the centre of the shaft as the iron cores round the 
disk ; the two circles of magnets, consequently, have their 
poles opposite each other, with the disk and its circle of 
iron cores revolving between them. The ends of the 
cores are terminated with iron plates of a circular form, 
which answer the double purpose of retaining the helices 
surrounding the cores in their places, and overlapping for a 
short distance the spaces between the poles of the electro- 
magnets. 
The cylindrical bar magnets are each coiled with 659 feet 
of copper wire, 0075 of an inch in diameter, insulated with 
cotton. The helices are grouped together to form a fourfold 
circuit, 2,636 feet in length, and are joined up in such a 
manner that adjacent magnets in each circle, as well as those 
directly opposite in both circles, have north and south 
polarity in relation to each other. A charge of permanent 
magnetism w T as imparted to the system of electro-magnets 
by the current from a separate electro-magnetic machine. 
The armatures, although formed of sixteen pieces of iron, 
are, by projecting through both sides of the disk, thirty-two 
in number. The length of insulated wire on each armature 
is 116 feet, and the thickness is the same as that on the 
electro-magnets. These helices are divided into eight groups 
of four each, and coupled up for an intensity of 4x116 feet. 
