entury, the new development can be characterized as the turn from
inorganic to organic phosphates, from the substance of minerals and
strong chemical interactions to the components in which phosphate groups
remained combined with carbon-containing substances.

[Illustration: Figure 10.--ELECTRIC FURNACE FOR PRODUCING ELEMENTAL
PHOSPHORUS, invented by Thomas Parker of Newbridge, England, and
assigned to The Electric Construction Corporation of the same place. The
drawing is part of United States patent 482,586 (September 13, 1892).
The furnace was patented in England on October 29, 1889 (no. 17,060); in
France on June 23, 1890 (no. 206,566); in Germany on June 17, 1890 (no.
55,700); and in Italy on October 23, 1890 (no. 431). The following
explanation is cited from the U.S. patent:

Figure 1 [shown here] is a vertical section of the furnace, and Fig. 2
is a diagram to illustrate the means for regulating the electro-motive
force or quantity of current across the furnace.

F is the furnace containing the charge to be treated. It has an
inlet-hopper at _a_, with slides AA, by which the charge can be admitted
without opening communication between the interior of the furnace and
the outer air.

B is a screw conveyer by which the charge is pushed forward into the
furnace.

_c'c'_ are the electrodes, consisting of blocks or cylinders or the like
of carbon fixed in metal socket-pieces _c c_, to which the
electric-circuit wires _d_ from the dynamo D are affixed. The current,
as aforesaid, may be either continuous or alternating. _c^{2}c^{2}_ are
rods of metal or carbon, which are used to establish the electric
circuit through the furnace, the said rods being inserted into holes in
conductors _c^{3}_ (in contact with the socket-pieces _c_) and in the
furnace, as shown.

_g_ is the outlet for the gas or vapor, _h_ the slag-tap hole, and _x_
the opening for manipulating the charge, the said openings being closed
by clay or otherwise when the furnace is at work.

I use coke or other form of carbon in the charge between the electrodes
_c'_, the said coke being in contact with the said electrodes, so that
complete incandescence is insured.

A means for varying the electro-motive force or quantity of current
across the furnace with the varying resistance of the charge is
illustrated by the diagram, Fig. 2. _c' c^{2}_ indicate the electrodes
in the furnace, as in Fig. 1, and D is the dynamo and T its terminals. E
represents the