Mr. W. H. Preece writes to the _Journal of Arts_ as follows:
At the South Kensington Museum, very careful observations have been made
on the relative cost of the two systems, _i. e._, gas and electricity.
The court lighted is that known as the "Lord President's" (or the Loan)
Court. It is 138 feet long by 114 feet wide, and has an average height
of about 42 feet. It is divided down the middle lengthwise by a central
gallery. There are cloisters all around it on the ground floor, and the
walls above are decorated in such a way that they do not assist in the
reflection or diffusion of the light. The absence of a ceiling--the
court being sky-lighted--is to some extent compensated for by drawing
the blinds under the sky-lights.
The experiments commenced about twelve months ago, with eight lamps
only on one side of the court. The system was that of Brush. The dynamo
machine was driven by an eight horse-power Otto gas engine, supplied by
Messrs. Crossley. The comparison with the gas was so much in favor of
electricity, and the success of the experiment so encouraging, that it
was determined to light up the whole court.
The gas engine, which was not powerful enough, was replaced by a
14-horse power "semi-portable" steam engine, by Ransomes & Co., of
Ipswich--an engine of sufficient power to drive double the required
number of lights. The dynamo machine is a No. 7 Brush. There are sixteen
lamps in all--eight on each side of the court. The machine has given no
trouble whatever, and it has, as yet, shown no signs of wear. The
lamps were not all good, and it was found that they required careful
adjustment, but when once they were got to go right they continued to
do so, and have, up to the present, shown no signs of deterioration,
although the time during which they have been in operation is nine
months.
The first outlay has been as follows:
Engine and fixing, including shafting and
belting................................ £420
Dynamo machine......................... 400
Lamps, apparatus, and conducting wire . 384
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£1,204
The cost of working has been, from June 22, to December 31, during which
period the lights were going on 87 nights for a total time of 359 hours:
£ s. d.
Carbons............................... 18 9 0
Oil, etc.............................. 4 11 6
Coal.................................. 11 14 0
Wages................................. 34 7 6
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£69 2 0
being at the rate of 3s. 10d. per hour of light.
Now, the consumption of gas in the court would have been 4,800 cubic
feet per hour, which, at 3s. 4d. per 1,000 cubic feet, would amount to
16s. per hour, thus showing a saving of working expenses of 12s. 2d. per
hour, or, since the museum is lit up for 700 hours every year, a total
saving at the rate of £426 per annum.
In estimating the cost as applied to this court, only half the cost of
the engine should be taken, for a second dynamo machine has lately been
added to light up some of the picture galleries, and the "Life" room of
the Art School. The capital outlay should, therefore, be £994. In making
a fair estimate of the annual cost, we should also allow something for
percentage on capital, and something for wear and tear. Take--
£ s.
5 per cent, on the capital............................. 49 10
5 per cent, for wear and tear of electrical apparatus.. 39 0
5 per cent, for depreciation of engines, etc........... 21 0
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Total.......... £109 10
leaving a handsome balance to the good of £316 10s. as against gas. The
results of the working, both practically and financially, have proved to
be, at South Kensington, a decided success.
I am indebted to Colonel Festing, R.E., who has charge of the lighting,
for these details.
The same comparison cannot be made at the British Museum, for no gas was
used in the reading-room before the introduction of the electric light,
but the cost of lighting has proved to be 5s. 6d. per hour--at least
one-third of that which would be required for gas. The system in use
at the Museum is Siemens', the engine being by Wallis and Steevens, of
Basingstoke.
"An excellent example of economic electric lighting, is that of Messrs.
Henry Tate & Sons, sugar refinery, Silvertown. A small Tangye engine,
placed under the supervision of the driver of a large engine of the
works, drives an 'A' size 'Gramme' machine, which feeds a 'Crompton' 'E'
lamp. This is hung at a height of about 12 feet from the ground in a
single story shed, about 80 feet long, and 50 feet wide, and having an
open trussed roof. The light, placed about midway, lengthways, has a
flat canvas frame, forming a sort of ceiling directly over it, to help
to diffuse the illumination. The whole of the shed is well lit; and a
large quantity of light also penetrates into an adjoining one of similar
dimensions, and separated by a row of columns. The light is used
regularly all through the night, and has been so all through the winter.
Messrs. Tate speak highly of its efficiency. To ascertain the exact cost
of the light, as well as of the gas illumination which it replaced, a
gas-meter was placed to measure the consumption of the gas through
the jets affected; and also the carbons consumed by the electric
illumination were noted. A series of careful experiments showed that
during a winter's night of 14 hours' duration the illumination by
electricity cost 1s. 9d., while that by gas was 3s. 6d., or 1½d. per
hour against 3d. per hour. To this must be added the greatly increased
illumination, four to five times, given by the electric light, to the
benefit of the work; while this last illuminant also allowed, during the
process of manufacture of the sugar, the delicate gradations of tint
to be detected; and so to avoid those mistakes, sometimes costly ones,
liable to arise through the yellow tinge of gas illumination. This alone
would add much to the above-named economy, arising from the use of
electric illumination in sugar works."
I am indebted for these facts to Mr. J. N. Shoolbred, under whose
supervision the arrangements were made.
Some excellent experience has been gained at the shipbuilding docks in
Barrow-in-Furness, where the Brush system has been applied to illuminate
several large sheds covering the punching and shearing machinery,
bending blocks, furnaces, and other branches of this gigantic business.
In one shed, which was formerly lighted by large blast-lamps, in which
torch oil was burnt, costing about 5d. per gallon, and involving an
expenditure of £8 9s. per week, the electric light has been adopted at
an expenditure of £4 14s. per week.
The erecting shop, 450 feet by 150 feet, formerly dimly lit by gas at a
cost of £22 per week, is now efficiently lit by electricity at half the
cost.
I am indebted for these facts to Mr. Humphreys, the manager of the
works.
The Post office authorities have contracted with Mr. M. E. Crompton,
to light up the Post-office at Glasgow for the same price as they have
hitherto paid for gas, and there is no doubt that in many instances this
arrangement will leave a handsome profit to the Electric Light Company.
They are about to try the Brockie system in the telegraph galleries,
and the Brush system in the newspaper sorting rooms of the General
Post-office in St. Martin's-le-Grand.
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