The cost of light equivalent to that of seven mould candles (six to the pound) is in coal-gas three farthings per hour, in an Argand oil-lamp 3d. per hour, in mould candles 3½d. per hour, and in wax candles 1s. 2d. per hour.
Gas has also been manufactured from oil, rosin and other substances. Oil-gas is procured abundantly by the decomposition of oil, trickled into a red-hot retort, half-filled with coke or brick. It contains no sulphuretted hydrogen, requires no purification, and is much richer in carburetted hydrogen than coal-gas. Its expense has however led nearly to the entire disuse of this kind of gas.
In London there are eighteen public gas establishments and twelve companies; the capital invested in works and apparatus is estimated at 3,000,000l.]
FOOTNOTES
[432] Athen. Deipn. vi. 8. p. 236.
[433] Joh. Meursii Opera, ex recensione Joannis Lami. Florent. 1745, fol. v. p. 635.
[434] Pet. cap. lxxix. That the author here speaks of Naples, I conclude from cap. lxxxi., where the city is called Græca urbs. Others, however, with less probability, are of opinion that Capua is meant.
[435] Libanii Opera, Lutet. 1627, fol. ii. p. 387.
[436] Ib. 526.
[437] See vol. ii. p. 170.