382 THE POPULAR SCIENCE MONTHLY. 



emits no smoke. Probably its greatest advantage is to be found in 

 the influence it exerts on bealtli. At Glasgow, where the light has 

 been applied, all causes of trouble arising from the vitiation which was 

 occasioned by other lights have ceased. Health has been engendered, 

 and more work has been got out of the men ; and experience has 

 shown that the electric light will pay for itself in the superior return 

 it makes in this point alone. 



Mr. Preece has published in a separate paper some facts bearing 

 upon the economy of the electric light. The Loan Court of the South 

 Kensington Museum, a room not favorably arranged for the diffusion 

 of light, has been lighted for nine months with sixteen Brush lamps, 

 at a cost for working of 3s. lOcl. per hour of light. Had gas been used, 

 a consumption of sixteen hundred cubic feet per hour would have been 

 required, at a cost of I65. Considering that the museum is lighted 

 uj) for seven hundred hours every year, the total saving effected by 

 the use of electricity is at the rate of 426 or $2,130 a year. It is fair, 

 however, to add something for the use of the capital, wear and tear, 

 etc., to the annual expense. Reckoning this at five per cent, all around, 

 the annual saving is still 316 IO5,, or |1,580. The reading-room of 

 the British Museum is lighted by the Siemens electric light, at a cost 

 of 5s. 6<:?. per hour, one third of what would be required for gas, were 

 it used. A shed at the sugar-refinery of Messrs. Henry Tate & Sons, 

 Silvertown, is lighted by a Crompton lamp in the ceiling, assisted by 

 a canvas reflector. The whole of the shed is well lighted four or five 

 times more strongly than with gas and the light penetrates an ad- 

 joining shed. The cost for fourteen hours of illumination is Is. 9<f., 

 or l^d. an hour ; the cost of illumination by gas was 3s. Qfd., or ^d. an 

 hour. At the ship-building dock, Barrow-in-Furness, a work-shed is 

 lighted by Brush lights at 4 14s. a week, where oil blast-lamps were 

 formerly used at 8 9s. a week ; and the erecting-shop, formerly dimly 

 lighted by gas at 22 a week, is now efiiciently lighted by electricity 

 at half the cost. 



-^^- 



DEGEJSTEEATIOK 



By Dk. ANDEEW WILSON. 



IN groups of the animal series, both nearly allied to the crustacean 

 class and far removed from it in structure, equally interesting and 

 often curious examples of degradation may be found. The class of 

 insects and the nearly related group, including the mites, spiders, and 

 scorpions as its representatives, number in their ranks instances of 

 degraded and degenerate forms. Among the insects which are par- 

 asitic in habits a notable absence of wings is discernible, and this 



