Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1879-11-17
The Electric Light AT the British
Museum.

Ine AlARlt al tne BFttbsu
Museum.
On Monday evening one Of the most
successful attempts which have hith-
erto been made to illuminate a large
open space by means Of electricity was
conducted at the British museum
in the presence of most of the
officials Of the institution, and of
many gentlemen interested in the inn
provement and utilization of the new
process. The vast area of the reading
room was radient with a food of light,
brilliant as that of a summer noon,
but withal soft and pleasing to the
eye, and steady enough to enable read
ers to pursue their studies without the
least discomfort. At a few desks
furthest from the center of the room
the light was not, perhaps, as good as
might IN future be found needful, and
a shadow was in some cases thrown
upon a portion Of the surface; but this
slight defect could, no doubt, be rem
edied by a arrangement, or possibly
by an addition of yet another lamp.
The reading room is lighted at present
by four large lanterns, each of the
enormous power of 5000 candles, the
light being produced bycontinuousc cur
rents of electricity. The regulators arc.
the invention of Messrs. Siemens &
Halske, of Berlin, and are so simply
constructed that they can be managed
by inexperienced hands. A notable
feature in the system is that they are
made to take carbon points of nine
teen inches in length, and, as these are
consumed at the rate of nearly three
inches per hour, the light can be main
tanned for about six hours without re-
quiring attention. The wires from the
machines to these lights are taken
over the roof Of the building to the
lantern on the top of the dome, so that
there is nothing unsightly or any i'm
pediments of the reading. room. Seven
other lamps, each of 400 candles. are
distributed over the entrance halls
and the outside Of the museum, these
being connected In one Circuit of about
twelve hundred yards in length to aa
alternate-current machine. In this
system the regulators employed are
actuated by two solenOids on a differ
entail principle, one solenoid forming
part Of the main circuit, and tending
to separate the carbons, and the
other forming a shunt around
the carbOns and tending to bring
them together. By this arrangement
the position Of the carbons will depend
not on the strength of the currents,
but on the relative amount of electric
lty passing through each solenoid. and
by choosing suitable resistances for
each coil, an arc of a given resistance
can always be maintained independent
ly OF the strength Of the current. The
necessity Of any regulation after the
lamps have been fitted up is also obyi-
ated, and the regulators are again so
arranged that the failure of one lamD
owing TO, perhaps, want of carbon
does not effect the burning ofthe other
lights upon the circuit. New carbon
can be put in such a lamp in about
half a minute, when it will be ready
to burn for another five hours. The
machines which supply the motive
power, to the entire system are two
lighthouse semi-fxed engines, con-
structed by Messrs. Wallis and Stee.
vens, OF Basingstoke, a firm which has
directed its attention with marked suc.
cess to the one pointof supreme impor-
lance in manufacture Of machines for
electric lightning, viz, regularity of
the speed at which they NAV be- for
the time working. The experiment
having proved highly satisfactory. and
the press generally having expressed
approval Of the advantages to literary
mel that would result from its adon.
ton, the authorities Of the museum
have determined to throw omen the
reading-room to ticket-holders for one
month until z p. m. On Wednesday
night upward Of one hundred readers
availed themselves of the ADVANTAGE NJ
continuing their work until seven
O'Clock, and it is presumed that MANY
more will do so when the extended
privilege is more generally known
The four lights burned very steadily
and the readers were unanimous In
their expressions Of approval of tho
result. The trustees and Mr.. Bono
have thus earned the gratitude of tho
numerous frequenters of the room fol
the extra facilities which have thus
been so literally afforded them.