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
------
£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
----------
£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
-------
Total.......... £109 10