484 



SCIENTIFIC NEWS, 



[May 25, iS 



accumulators, and which can also be set to ring a bell in 

 the house in the event of there being anything wrong 

 during the process of charging. The switch board is 

 fitted with a simple crank switch for cutting out ot, or 

 putting in circuit, 11, 12, or 13 cells. There is also an 

 ammeter for measuring the charging and the discharging 

 currents. When the cells are first charged, they 

 usually take a current of 34 amperes by 28 volts, and 

 when their back electromotive force is at its highest, 

 the charging plant is able to put into them a current of 

 30 amperes by 25 volts. It has been found that during 

 the 6 months from October to March the lights were 

 used an average of 6 hours, and it is expected that 

 during the remaining 6 months they will be used an 

 average of 4 hours each da}'. 



The actual cost of the whole of the generating and 

 storing plant delivered and fixed was ^266, and this 

 comprises the following : — 



Engine, piping, belting, exhaust pit, etc. 



Dynamo, with adjustable base and foundation. 



Accumulators and testing apparatus. 



In the winter half-year, the weekly working cost of 

 840 lamp-hours (20 lamps x 42 hours) is as follows : — . 



£ s. d. 

 Gas for engine (20 hours) := 1,400 cubic 



feet, at 2S. gd. per 1,000 cubic feet 0310 

 Attendant — two days at 3s. . , ..060 



Renewals of lamps, allowing for 20 



lamps to be renewed once a year . . o i 10 

 Oil, belting and sundries. . . . ..010 



Depreciation at 10 per cent, per annum 



on ^266 . . . . . . . . o 10 3 



Interest at 5 per cent. per annum on ;^266 051 



£^ 8 o 

 For the summer half-3'ear the w^f^^ working cost of 

 5 60 lamp-hours (20 lamps x 28 hours) is estimated as 

 follows : — 



Gas for engine 



Attendant, two days at 2s. 6d. 

 Renewals of lamps, as above 

 Oil, belting, and sundries 

 Depreciation and Interest as above 



£^ 



15 4 



5 4 



The total working cost per annum will therefore be as 

 follows : — 



Winter half-year. . 

 Summer ditto 



..^36 8 o 

 .. 33 14 4 



Per annum 



..^70 2 4 



The number of lamp-hours in the winter half will 

 be 21,840, and in the summer half 14,560, or a total of 

 36,400, and the average cost will be under ^d. per lamp 

 per hour. 



The total number of watt hours, at 19 watts per lamp, 

 will be 691,600, or at the rate of 2S. 3d. for each Parlia- 

 mentary unit. 



In the above estimate we have not included the cost 

 of wires and fittings, as these depend so much on indi- 

 vidual taste, but it may be assumed that they cost about 

 the same as gas fittings. In General Webber's case they 

 have certainly cost less. 



In London, the Gas Companies are obliged to supply 



gas which gives a light of not less than sixteen standard 

 sperm candles when the gas is consumed at the rate of 

 five cubic feet per hour, in a standard Argand burner, 

 under favourable conditions. With ordinary burners 

 the result is not so good, and approximately it may be 

 assumed that for a five-candle power light the consump- 

 tion will not be less than two cubic feet, and allowing 

 for fluctuations of pressure and for unsuitable burners 

 being used for so small a consumption, say three cubic 

 feet per hour. If we multiply this by 840 lamp-hours 

 for a winter week, we shall therefore have 2,520 cubic 

 feet, and this at 2S. gd. per 1,000 cubic feet will cost a 

 fraction under 7s. 



From this it would seem that the gas-lights cost only 

 about one-fourth what the electric lights cost. It must 

 not, however, be forgotten, that in all rooms where gas 

 is used regularly, the ceilings must in consequence be 

 washed and coloured frequently, but that the electric glow- 

 lamps cause absolutely no dirt or discolouration. We 

 do not attempt to estimate the harm done by gas to 

 curtains and other decorations, but speaking roundly it 

 appears to us probable that the direct and indirect cost of 

 gas is about the same as of the electric lights. Whether 

 this is precisely so or not, it will be seen that for a 

 capital outlay of £266 — exclusive of conductors and 

 fittings — and with an average working cost of ;^i 6s. 8d. 

 per week, it is possible to enjoy the comfort of perfectly 

 steady lights which do not vitiate the air. The cost will 

 be much less when houses are supplied by electricity 

 from central stations, but in the meantime we are 

 indebted to General Webber and others who have brought 

 the subject of small installations within the range of 

 practical economies. 



In conclusion, we may add that an installation of this 

 kind is very instructive from a scientific point of view, 

 especially as a practical illustration of the interchange- 

 ability of different forms of energy. The gas in the 

 cylinder of the engine is exploded, and its heat energy 

 is thereupon converted into mechanical energy ; this in 

 turn is converted into electrical energy at the dynamo. 

 In the accumulator cells the electrical energy is changed 

 into chemical energy, and again into electrical energy, 

 and finally it is reconverted into heat and light 

 energy at the lamps. In each of these transformations 

 there is, after allowing for waste due to friction and 

 other causes, a definite equivalent for the energy ex- 

 pended. We thus have a very simple and interest- 

 ing example of the great principle of conservation of 

 energy. 



Asphalt. — Although the experiments made with Pro- 

 fessor Dietrich's patent asphalt paving in Berlin, in 

 which the raw material obtained from the deposits in 

 Vorwohl and Zimmer (province of Hanover) were em- 

 ployed, have not proved perfectly successful, the use of 

 this asphalt as a filling for granite and wood paving is 

 rapidly extending. This asphalt, mixed with powdered 

 limestone, has also recently been introduced in buildings 

 for preventing the walls from becoming damp. When the 

 foundation walls have reached the ground level a layer of 

 asphalt, in the form of thin rolled sheets, is applied, and 

 the walls of the building are erected upon this layer, which 

 is perfectly impervious to moisture. The demand for 

 asphalt for various purposes is thus on the increase. To 

 obtain a larger supply, the EgestorfF works are now pros- 

 pecting for new deposits in the neighbourhood of Hanover, 

 and several new shafts are being sunk.— 7»dusfries. 



