IN MAGNETISM AND ELECTEICITY. 
105 
as well as those of the brass blocks in contact with them, are truly planed, and the 
several parts of the cylinder are bolted together at the top and bottom by means of 
twelve copper bolts 1 inch in diameter. The bore of the magnet-cylinder is 10 inches, 
and its weight, when fitted up with iron pillars and brass cross-heads, is IT ton. 
70. The machine is furnished with two armatures, one for the production of “inten- 
sity,” and the other for the production of “ quantity ” effects. These armatures are made 
of cast iron, and are precisely alike in dimensions, as they were cast from the same 
pattern. The thickness of the rib G, fig. 5, uniting the segmental sides of the armatures 
is 1-75 inch, and the latter are turned one-eighth of an inch less in diameter than the 
bore of the magnet-cylinder. A pulley, 10 inches in diameter, is keyed upon one end 
of each armature, and upon the other end is fixed a commutator, by means of which 
the waves of electricity from the armature can be taken, either in the same or in alter- 
nate directions as required (15, 16). 
71. The intensity armature is coiled with an insulated conductor consisting of a bundle 
of thirteen No. 11 copper wires, each 0T25 of an inch in diameter, the same as that 
coiled round the sides of the electro-magnet (68). The conductor is 376 feet in length 
and weighs 232 lbs., and is covered with a casing of wood extending the entire length of 
the armature, for the purpose of protecting it from external injury. Strong bands of 
sheet brass, 1 inch in width, encircle the armature at intervals of 6 inches, for the purpose 
of keeping the casing and the convolutions of the conductor in position during their rapid 
revolution (11). The total weight of this armature with all its fittings is 0 - 3 of a ton. 
72. The quantity armature is enveloped with the folds of an insulated conductor, con- 
sisting of four plates of copper, each 67 feet in length, 6 inches in width, and one-six- 
teenth of an inch in thickness. These plates are superposed in metallic contact with 
each other, so as to form a single copper plate one-quarter of an inch in thickness, 
67 feet in length, and nearly wide enough to occupy the entire width between the 
segmental sides of the armature. This division of the conductor into four plates was 
made for the greater convenience of bending it round the armature. The inner extremity 
of the conductor is held in intimate contact with the body of the armature by means of 
flat-headed screws ; and the convolutions are insulated from one another by placing 
between them a band of thick cotton and india-rubber fabric, of the same length and 
width as the laminated conductor ; and the edges of the latter are insulated from the 
sides of the armature by means of thin pieces of wood. The outer extremity of the con- 
ductor is terminated by a thick copper stud which connects it with the insulated half of 
the commutator fixed on the armature axis ; and the convolutions are retained in position, 
by means of bands, in the same manner as those of the intensity armature (11, 71). 
The weight of the laminated copper conductor is 344 lbs., and the total weight of the 
armature is 035 of a ton. 
73. The armatures were accurately balanced before being placed in the magnet-cylinder, 
for the purpose of avoiding the excessive vibrations which were produced when they 
revolved at high velocities without being balanced. By means of a small carriage, the 
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