kilogrammeter of mechanical work performed. In recording these
experiments, Dr. Pacinotti points out that although these results do
not show any special advantage in his machine over those of other
construction, still they are very encouraging, when it is considered
that the apparatus with which the experiments were made were full of
defects of workmanship, the commutator, being eccentric to the axis,
causing the contacts between it and the rollers to be very imperfect
and unequal.

In his communication to the _Nuovo Cimento_, Dr. Pacinotti states that
the reasons which induced him to construct the apparatus on the
principle which we have just described, were: (1) That according to
this system the electric current is continuously traversing the coils
of the armature, and the machine is kept in motion not by a series of
intermittent impulses succeeding one another with greater or less
rapidity, but by a constantly acting force producing a more uniform
effect. (2) The annular form of the revolving armature contributes
(together with the preceding method of continuous magnetization) to
give regularity to its motion and at the same time reduces the loss of
motive power, through mechanical shocks and friction, to a minimum.
(3) In the annular system no attempt is made suddenly to magnetize and
demagnetize the iron core of the rotating armature, as such changes of
magnetization would be retarded by the setting up of extra currents,
and also by the permanent residual magnetism which cannot be entirely
eliminated from the iron; and with this annular construction such
charges are not required, all that is necessary being that each
portion of the iron of the ring should pass, in its rotation, through
the various degrees of magnetization in succession, being subjected
thereby to the influence of the electro-dynamic forces by which its
motion is produced. (4) The polar extension pieces of the fixed