We lately published a short description of a very interesting
apparatus which may be considered in some sense as a prototype of the
Gramme machine, although it has very considerable, indeed radical
differences, and which, moreover, was constructed for a different
purpose, the Elias machine being, in fact, an electromotor, while the
Gramme machine is, it is almost unnecessary to say, an electric
generator. This apparent resemblance makes it, however, necessary to
describe the Elias machine, and to explain the difference between it
and the Gramme. Its very early date (1842), moreover, gives it an
exceptional interest. The figures on the previous page convey an exact
idea of the model that was exhibited at the Paris Electrical
Exhibition, and which was contributed by the Ecole Polytechnique of
Delft in the Dutch Section. This model is almost identical with that
illustrated and described in a pamphlet accompanying the exhibit. The
perspective illustrations show the machine very clearly, and the
section explains the construction still further. The apparatus
consists of an exterior ring made of iron, about 14 in. in diameter
and 1.5 in wide. It is divided into six equal sections by six small
blocks which project from the inner face of the ring, and which act as
so many magnetic poles. On each of the sections between the blocks is
rolled a coil, of one thickness only, of copper wire about 0.04 in. in
diameter, inclosed in an insulating casing of gutta percha, giving to
the conductor thus protected a total thickness of 0.20 in.; this wire
is coiled, as shown in the illustration. It forms twenty-nine turns in
each section, and the direction of winding changes at each passage in
front of a pole piece. The ends of the wire coinciding with the
horizontal diameter of the ring are stripped of the gutta percha, and
are connected to copper wires which are twisted together and around
two copper rods, which are placed vertically, their lower ends
entering two small cavities made in the base of the apparatus. The
circuit is thus continuous with two ends at opposite points of the
same diameter. The ring is about 1.1 in. thick, and is fixed, as
shown, to two wooden columns, B B, by two blocks of copper, a.
[Illustration: THE ELIAS ELECTROMOTOR.--MADE IN 1842.]
It will be seen from the mode of coiling the wire on this ring, that
if a battery be connected by means of the copper rods, the current
will create six consecutive poles on the various projecting blocks.
The inner ring, E, is about 11 in. in outside diameter, and is also
provided with a series of six projecting pieces which pass before
those on the exterior ring with very little clearance. Between these
projections the space between the inner face of the outer, and the
outer face of the inner ring, is 0.40 in. The latter is movable, and
is supported by three wooden arms, F, fixed to a boss, G, which is
traversed by a spindle supported in bearings by the columns, A and C.
A coil is rolled around the ring in exactly the same way as that on
the outer ring, the wire being of the same size, and the insulation of
the same thickness. The ends of the wire are also bared at points of
the diameter opposite each other, and the coil connected in pairs so
as to form a continuous circuit. At the two points of junction they
are connected with a hexagonal commutator placed on the central
spindle, one end corresponding to the sides 1, 3, and 5, and the other
to the sides 2, 4, and 6. Two copper rods, J, fixed on the base to two
plates of copper furnished with binding screws, are widened and
flattened at their upper ends to rest against opposite parallel sides
of the hexagon. It will be seen that if the battery is put in circuit
by means of the binding screws, the current in the interior ring will
determine six consecutive poles, the names of which will change as the
commutator plates come into contact successively with the sides of the
hexagon. Consequently, if at first the pole-pieces opposite each other
are magnetized with the same polarity, a repulsion between them will
be set up which will set the inner ring in motion, and the effect will
be increased on account of the attraction of the next pole of the
outer ring. At the moment when the pole piece thus attracted comes
into the field of the pole of opposite polarity, the action of the
commutator will change its magnetization, while that of the pole-piece
on the fixed ring always remains the same; the same phenomenon of
repulsion will be produced, and the inner ring will continue its
movement in the same direction, and so on. To the attractive and
repulsive action of the magnetic poles has to be added the reciprocal
action of the coils around the two rings, the action of which is
similar. From this brief explanation the differences between the Elias
machine and the Gramme will be understood. The Dutch physicist did not
contemplate the production of a current; he utilized two distinct
sources of electricity to set the inner ring in motion, and did not
imagine that it was possible, by suppressing one of the inducing
currents and putting the ring in rapid rotation, to obtain a
continuous current. Moreover, if ever this apparent resemblance had
been real, the merit of the Gramme invention would not have been
affected by it. It has happened very many times that inventors living
in different countries, and strangers to one another, have been
inspired with the same idea, and have followed it by similar methods,
either simultaneously or at different periods, without the application
having led to the same results. It does not suffice even for the seed
to be the same; it must have fallen in good ground, and be cultivated
with care; here it scarcely germinates, there it produces a vigorous
plant and abundant fruit.--_Engineering._
* * * * *