uld present serious inconveniences. In
the first place, it seems to us quite difficult to transmit the motion
of the solenoid to the axle, supposing the former to revolve within
the armature. In the second place, considerable friction would surely
occur between the spirals and core, and the axle, being submitted to a
lateral stress, would be placed in a poor condition for work. It is
even allowable to doubt whether such a type could be practically got
up. At all events, no trial has as yet been made of it.

Compared with the Gramme machine, from an absolutely theoretical point
of view, the Pfaundler apparatus presents undoubted advantages. A
theoretically perfect dynamo electric machine would be one in which
there was a complete reciprocity between the magnetizing action of the
current and the inductive action of the magnetic field. Now, such is
not the case in the Gramme machine. In this apparatus the soft iron
core is at the same time a magnet through favorable induction and a
disadvantageous electro-magnet. This double polarization is only
remedied to a certain extent by the adjustment of the brushes. In the
Pfaundler machine, on the contrary, the electro-magnetism and
magnetism through induction act in the same direction, and concur in
effecting a polarization that favors the production of the current.
Looked at it in this light, the latter machine more nearly approaches
the type of perfection than does that of Gramme.

But we must not forget that such qualities are purely theoretical. In
practice the best machine is that in which the copper is best
utilized, that is to say, that which with a given weight of this metal
furnishes the most work. Now, this is certainly not the case in the
Pfaundler machine, for here half or more than half of the ring is
inert--a defect which is apparent at first sight. It results from this
that as soon as we propose to obtain an electromotive force, however
slight it be, we must get it with machines of large dimensions. Now,
it is permissible to believe that under such circumstances (taking
into consideration the complication of mechanical means that the
construction of such apparatus necessitates, and the great friction
that occurs) it would be impossible to obtain practical rotary
velocities. Comparing his machine with Gramme's, Prof. Pfaundler
expresses the idea that between them there is the same analogy as
there is between a constant pressure and an expansion engine. With
cylind