Robinson thinks that the electric light might be so modified as to be used in public dwellings! There are exhaustless stores of latent electricity, but the difficulty is to know how to develop and utilise it. Street gas lit by electricity, by Mr. St. George Lane, Fox's method: trial partially successful, Pall Mall, etc., 13th April, 1878. British Museum Reading Room illuminated by electric light, October, 1879. Common bituminous coal obtained from the mines of Northumberland, Durham, York, South Wales, and a few other coal districts is the kind from which most of the gas of this country is manufactured. The Cannel or Scotch Parrot coals produce a gas of a much richer quality, which, though expensive, has the advantage of superior illuminating power. Gas companies use to a very great extent coals from the following mines:--Pelaw, Leverson's Wallsend, Pelton, New Pelton, Dean's Primrose, Garesfield, South Peareth, (The London Gas-Light Company use principally Peareth) Urpeth, Washington, Yorkshire, Silkstone, Haswell, West Wear, Wearmouth, Brancepeth, South Brancepeth, and Ravenshaw Pelaw. The resulting products of carbonization of these coals when an exhauster is employed will be found to give about the following average per ton:-- Gas, 9,500 cubic feet; Coke, 13 cwt., or one chaldron; Tar, 10 gallons; Ammoniacal Liquor, 13 gallons. Ammonia, a compound of Nitrogen and Hydrogen, is converted into Sulphate of Ammonia, Sal Ammonia, Carbonate of Ammonia, etc., etc. Tar, which is a Hydro-carbon, after producing Naptha and light oils, becomes useful as Asphalt, or for exterior paint work. Benzole, the base of our newly-discovered dyes, is extracted from the Naptha; which, besides, is either used as a solvent for india-rubber and guttapercha, or yields a brilliant light when burned in a common lamp. Gas, as it issues from the retorts, is chiefly composed of light carburetted and bicarburetted hydrogen or olefiant gas, accompanied by condensable vapours and other gaseous impurities. The condensable vapours are principally hydro-carbon compounds which become deposited in the form of oil, and amongst a variety of deleterious substances may be mentioned as the chief: ammonia, carbonic acid, carbonic oxide, and sulphuretted hydrogen, but the value of coal-gas principally depends on the presence of bicarburetted hydrogen, and the greater proportion of this the higher will be its light-giving properties.