When the signal is "line clear" the passage of the
brush over the fixed contact produces no result; but when the signal
marks "danger," the commutator brings the negative pole of the battery
in direct communication with the ground, and when the brush passes over
the contact the completion of the electric current causes the whistle to
be sounded, so as to alarm the driver.--_L'Ingen. Univ._
* * * * *
FURNACE FOR THE MANUFACTURE OF SULPHIDE OF CARBON.
Sulphide of carbon (CS_2) is prepared by passing the vapors of sulphur
over charcoal heated to redness. In laboratories, charcoal and roll
brimstone are employed so as to obtain as pure a product as possible;
but sulphide of carbon having now become so important a commercial
product, and being employed for so large a number of industrial
purposes, it has been found more economical to substitute coke for
charcoal and pyrites for brimstone.
The Messrs. Labois, in their system of furnace represented herewith,
have had in view the manufacture of this product under as economical
conditions as possible, by coupling over two connected fireplaces the
retort in which the pyrites is distilled, and that in which the reaction
of the sulphur and carbon takes place.
The pyrites is fed from the hopper, A, into a distributing box, B,
furnished with a valve which is maneuvered by a lever.
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