£>68

GAS-LIGHT.

leading points may be stated. The coals required for heating the retorts used to constit" 1one half of the quantity required for charging the retorts themselves. When five retortare heated by one fire, the expenditure for fuel is only one third of that when each retorhas a fire. The coke which remains in the retorts constitutes about 60 per cent, ofweight of the original coal; but the volume is increased by the coking in the proporU f 'of 100 to 75. When the coke is used for heating the retorts, about one half of the wh®,is required. If we estimate the coke by its comparative heating power, it represents oper cent, of the coals consumed. One hundred pounds of good coal yield in distiH atl ° e10 pounds of ammoniacal liquor, from which sulphate or muriate of ammonia may “made, by saturation with sulphuric or muriatic acid, and evaporation. The liquor cOtains likewise some cyanide of ammonia, which may be converted into Prussian blue 1the addition of sulphate of iron, after saturation with muriatic acid.

Two hundred pounds of coal afford about 17 pounds of tar. This contains in *pounds 26 pounds of coal oil, and 48 pounds of pitch. The tar is sometimes employe"a paint to preserve wood and walls from the influence of moisture, but its disagree®smell limits its use. The coal oil, when rectified by distillation, is extensively empl°?for dissolving caoutchouc in making the varnish of waterproof cloth, and also for burn 1 »in a peculiar kind of lamps under the name of naptha. Oil of turpentine, howeveroften sold and used for this purpose, by the same name. If the coal oil be mixed vlits volume of water, and the mixture be made to boil in a kettle, the mingled vaporspassed through a perforated nozzle may be kindled, and employed as a powerful m eof artificial heat. The water is not decomposed, but it serves by its vapor to expan"bulk of the volatile oil, and to make it thereby come into contact with a larger vol ,of atmospherical air, so as to burn without smoke, under a boiler or any other vesThe pitch may be decomposed into a light-gas. . a t

The relative cost of light from coal gas and oil gas may be estimated as one to si*Jeast. Rosin gas is cheaper than oil gas. See Rosin. e „t

I shall conclude this article with a summary of the comparative expense of din emodes of illumination, and some statistical tables.

One pound of tallow will last 40 hours in six mould candles burned in succession*

a n“

„ e 'm'’hour s >

costs 8 d .; a gallon of oil,'capable of affording the light of 15 candles, for 4U . jjps.costs 5s.; being therefore j of the price of, mould candles, and -JL of the price o ^ g jThe cost of wax is about 3J times that of tallow; and coal gas, as sold at the jjeS9s. for 1000 cubic feet, will be one sixth the price of mould candles; for 500 cU H C goO 51of coal gas give a light equal to the above candle for an hour; therefore 40 X20,000 cubic inches = 11 57 cubic feet, worth 1| d., which multiplied by 6 g ivethe average price of mould candles per pound. . re fef'

The author of the article Gas-light in the Encyclopaedia Britannica, observes, 1 egn ge-ence to the economy of this mode of illumination, that while the price of coal,quence of the abundant and regular supply of that article, is liable to little f uC g0 urc eSthe cost of wax, tallow, and oil, on account of the more precarious nature of the. _ th® 1from which they are obtained, varies exceedingly in different seasons. «Assn® ^jne-a pound of tallow candles, which last when burned in succession forty hours, ?°,jj n g th®pence” (seven-pence halfpenny is the average price), “ that a gallon of oil, Y ie ; ce oflight of 600 candles for an hour, costs two shillings” (five shillings is the i°Tthe exP e " >a gallon of such oil as a gentleman would choose to burn in his lamp), ‘ that tn cl ibi cof the light from wax is three times as great as from tallow, and that a thou® sa® efeet of coal gas cost nine shillingshe concludes the relative cost to be or nce jve tf*.®quantity of light,—from wax, 100; tallow, 25; oil, 5; and coal-gas, 3. I C °Ued llestimate given above to be much nearer the truth; when referred to wax cabecomes, for tallow, 28'6; oil, 14-3; coal-gas, 4-76. . r nO

Gas-lighting has received a marvellous development in London . In the ye® ^ goO,® unumber of gas lamps in this city was 168,000, which consumed daily abou ^’gldrt>n s ,cubic feet of gas. For the purpose of generating this gas, more than 200,Otioor 10,800,000 cubic feet of coals were required. readers ® a

For the following valuable statistical details upon gas-light, my p u blin > n( jindebted to Joseph Hedley, Esq., engineer, of the Alliance Gas Works, ta )ent ® „gentleman who to a sound knowledge of chemistry, joins such meC 1 a reat a r>" de r rlindefatigable diligence, as qualify him to conduct with success any g re ® t j, e bp® j ncommitted to his care. He has long endeavored to induce the directors whi cl1 . sgas-works to employ a better coal, and generate a more richly carbureted n apartiB e smuch smaller quantity would give as brilliant a light, without heating . ll \. j oU s vie r( .unpleasantly, as their highly hydrogenated gas now does. Were his J" j D atln? Padopted, coal gas would soon supersede oil, and even wax candles, for lJUvate mansions.