removable in a moment for cleaning or replacement. They are mounted
upon a metal support, and are surrounded on all sides by a free air
space, and cannot, therefore, lose their insulated condition. This
feature of air insulation is peculiar to this system, and is very
important as a factor in the durability of the commutator. Besides
this, the commutator is sustained by supports carried in flanges upon
the shaft, which flanges, as an additional safeguard, are coated all
over with hard rubber, one of the finest known insulators. It may be
stated, without fear of contradiction, that no other commutator made
is so thoroughly insulated and protected. The three commutator
segments virtually constitute a single copper ring, mounted in free
air, and cut into three equal pieces by slots across its face. Four
slit copper springs, called commutator brushes or collectors, are
allowed to bear lightly upon the commutator when it revolves, and
serve to take up the current and convey it to the circuit. These
commutator brushes are carried by movable supports, and their position
is automatically regulated so as to control the strength of the
developed current--a feature not found in other systems. This feature,
as well as the fact that the commutator can be oiled to prevent wear,
saves attendance and greatly increases the durability of the wearing
surfaces, while the commutator brushes are maintained in the position
of best adjustment. The commutator and brushes, in consequence, after
weeks of running, show scarcely any wear.


THE AUTOMATIC CURRENT REGULATOR.

This consists of a peculiar magnet attached to the frame of the
generator, and the movable armature of which has connections to the
supports of the commutator brushes for controlling their position. The