If the mean of the two results in Table IV. are taken, the working cost per Board of Trade Unit will be 3·22_d._, which shows that with both systems, after making due allowance for interest on capital, directors’ fees, bad debts, and other sundries omitted by Mr. Crompton, there is a probability of a very fair return on the capital expenditure, and the prospect of a handsome dividend for an electric lighting company who can sell electricity at the average price of 7_d._ per Unit. * * * * * The cost of maintaining and working electric lighting plant at private installations is usually much in excess of a supply from a central-station; but where the installation is over 500 lights, the difference is not very great. The working cost at the Athenæum Club of 387 lamps for the past year is given as follows:— £ _s. d._ Gas for gas-engine 446 7 10 Oil ” ” 71 3 8 Water ” ” 35 0 0 Wages 175 2 1 Sundries 30 3 0 Maintenance of lamps, etc. 98 4 1 Repairs 103 1 1 ————— £959 1 9 ————— Average cost of lighting by gas and oil for previous years, for two-thirds number of lights £840. At the Naval and Military Club, 420 lights cost £821 18_s._ for the same period, a steam-engine being used instead of a gas-engine. The annual report of the cost of the electric light at the South Kensington Museum shows that in a larger installation, consisting both of arc and incandescent lamps, the annual cost of the latter is much less than in either of the clubs mentioned. At the Museum there are 860 16 candle-power lamps, working 655½ hours per annum, or 562,387 lamp hours; the total cost for working last year was £386, which includes £66 for repairs of engines, boilers, dynamos, and maintenance of lamps; but rent, interest on capital, depreciation of plant, and management is not included. The light is used only three evenings a week, so that the wages of the attendants are proportionately in excess of what they would be in a central-station. * * * * * The cost of arc lighting for street purposes may be estimated from the following tenders. At Taunton the local electric light company offered to extend the lighting of streets from 29 to 60 arc lamps of 1,200 candle-power nominal on the Thomson-Houston system, at the following rate:— Per annum. £ _s. d._ Burning on average of 6 hours per night each lamp 17 7 6 7 ” ” 18 12 6 8 ” ” 19 17 6