IMPROVEMENTS IN OR APPER- TAINING TO APPARATUS FOR PRODUCING OR CONCENTRATING ELECTRICITY, AND IN THE PRODUCTION OF ELECTRIC LIGHT OR COMPOUND ELECTRIC AND COMBUSTION LIGHT
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Silvanus Phillips Thompson and
William Phillips Thompson at the Office of the Commissioners of Patents on
the 5th December 1878.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, in the County of
Gloucester, Doctor of Science, and WILLIAM PHILLIPS THOMPSON, of 6, Lord Street,
Liverpool, in the County of Lancaster, and 323, Holborn, London, in the County of
Middlesex, Consulting Engineer and Patent Agent "IMPROVEMENTS IN OR APPER-
TAINING TO APPARATUS FOR PRODUCING OR CONCENTRATING ELECTRICITY, AND IN
THE PRODUCTION OF ELECTRIC LIGHT OR COMPOUND ELECTRIC AND COMBUSTION
LIGHT."
In dynamo electric machines as ordinarily constructed it is of advantage to have
the rotating armatures as small as possible. We find that by substituting silver
wire for the copper at present used we can reduce the size considerably, as a smaller
cross section of wire is required on the coils with silver, the proportion being about
7 silver to 10 copper; this enables us to decrease the size of the rotating armatures
without increasing the internal resistance, and also to place the poles of the fixed
magnets nearer together.
2nd. In Ruhmkorff's coils and all induction apparatus where the polarity of an
iron core has to be rapidly reversed or made and broken, and in the rotating ring of
the Gramme machine, bundles of thin soft iron wire have to be used. Now it is
found that this core must be of a special size (only found by experiment) to have a
maximum effect, but it is always considered necessary. We, however, propose to do
away with or to at least minimise the core while retaining the iron. This is effected
by using a spiral coil of iron wire (in place of the spiral coil of copper wire and an
iron core inside it usually used), but iron is a poor conductor, the conductivity of
iron to copper being as 1 to 6. It will not therefore do to use iron alone as it would
have to be of such large size as to be unworkable. We consequently use a composite
wire of iron and silver, or iron and copper. Preferably we employ a wire of seven
strands of previously plated or silvered iron wire twisted together, and drawn
together so as to squeeze silver into the interstices. This wire is then externally
electro plated with silver to increase' conductivity, after that it is overspun with

page_text: silk or other insulating material. Of course in the Gramme ring it will be necessary
or may be found desirable still to have an iron core to wind the wires round, but
this should be made as thin as possible consistent with the required strength and
rigidity.
3rd. We take the electricity produced by using a machine with our aforesaid
improvements (or from some other source) and pass it between two platinum points
or other poles in a flame containing a current of material conducting particles. This
flame can be lit by the current itself in some cases, and is preferably formed by the
combustion of graphitic material between the two poles. Thus, for instance, make
a pencil of black lead and pipe clay, plaster of Paris, or other similar material; the
ordinary household black lead made into a paste with the cementing material and
heated gently at first and then baked at a red heat will do; then feed this pencil
gradually in by clockwork or other mechanism between the poles.
If, however, the two metallic poles are made so that the space between them be
slightly wedge shaped and the composition rod be rather larger in section than the
furthest (and narrowest) portion of the wedge shaped interval, its own weight or that
of a weighted lever or weight pressing against it, or a spring or similar mechanical
equivalent pressing it into the orifice between the poles, will continuously feed it.
If in such case it be found that the composition rod slips down too fast a refractory
stop of nonconducting material or an insulated iridium point or edge can support it,
and even admit of the wedge shape being dispensed with in the orifice. For many
purposes, however, clockwork will answer best. The current being let on the
material will heat at the point, catch fire, and burn with a brilliant flame, producing
at the same time the well known electric light. The advantages of this Invention
are that the poles can be made of a permanent non corrodable material such as the
difficultey oxydizable metals.
They can be both perfectly stationary or adjustable to various sizes of pencil or
various flames according as we want a strong light or a small one. If the flame be
entirely gaseous it must be insulated by using a nonconducting burner or wick tube,
but we prefer a solid incandescent fuel between the two poles to a simple flame
heavily charged with incandescent metallic or graphitic matter.