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POPULAR SCIENCE REVIEW. 
house-circuit must be overcome. A meter records the time 
each lamp is on. The cost of lamps and switches will not, it is 
said, exceed that of gas-fixtures. The meter is a clock with an 
attachment to throw its hands into connection when the light is 
on. It does not measure the quantity of electricity passing, 
but only the time the lamp is on. 
It is claimed that one horse-power will give by the Sawyer- 
Man system a light of thirty 5 ft. gas-burners per hour. 
Where large power is employed the cost of steam, with every 
item included, is about one cent per horse-power per hour. The 
cost of 150 feet of gas at New York prices is 41 cents, or 
fortyfold dearer. Mr. Sawyer, however, does not rest his cal- 
culations on price only, on account of the purity and superiority 
of the illumination. 
It would be difficult to furnish, in conclusion, a fair state- 
ment of the varied success which has attended the use of this 
illumination in London. Perhaps the best instance of steady 
and pleasant dispersion has been in the burners long ago es- 
tablished in front of the Graiety Theatre, in the Strand, which 
have of late been supplemented by an additional lamp in the 
island for foot-passengers in the middle of the roadway. The 
effect, which, from the straight and level nature of the thorough- 
fare, is well seen at a considerable distance on either side, is very 
powerful and agreeable, resembling strong moonlight. On the 
other hand, the two lamps placed on the Holborn Viaduct have 
been a failure from the first, and are now to be discontinued, on 
account of the cost — seven times greater than that of gas. Some 
technical mistake has evidently been committed here, as the 
loud puffing of the portable engine in a neighbouring waste 
space is to any person acquainted with steam-power entirely 
incommensurable and excessive when compared with the feeble, 
coloured and flickering beam of the two opal globes. Probably 
the fault is insufficient and long conductors, with defective in- 
sulation. 
An excellent trial in a large confined space is that which has 
been established for the past month at the Albert Hall. Five 
large lamps are placed in a ring round the centre of the dome, 
about fifteen or twenty feet below the velarium. At first they 
were uncovered, and produced the usual unpleasant effect of 
solid, heavy shadow ; but latterly they have been enclosed in a 
canoe-shaped case of muslin, which seems to diffuse without 
materially diminishing the radiation. It must, however, be 
noted that at the concert in honour of the Duke of Connaught’s 
marriage one out of the five went out about half-way through 
the concert, which lasted two hours and a half, but was subse- 
quently rekindled ; and another failed just after this event, and 
never reappeared through the evening. The effect on entering 
