Page:Popular Science Monthly Volume 16.djvu/687

 strong brick cupola-furnace with an iron shell, as gas-generator; this connected by a flue with a secondary chamber as superheater, filled with loose fire-brick nearly to the top. The gases generated from an anthracite fire in the furnace are driven by the air-blast through the connecting flue into the secondary or superheating chamber, at the bottom; here they meet a second air-blast, which urges them to a blaze of intense and complete combustion; and in this superheated condition they are forced up through the labyrinthine interstices of the firebrick with which the interior of the chamber is piled.

So effective are these simple arrangements that, in the few minutes required to kindle the mass of coals in the furnace to a cherry-red, the mass of fire-brick in the superheater becomes white-hot and ready for use. This result is the work of carbonic oxide and other products of imperfect combustion usually passed off in the smoke of our domestic chimneys, and finely illustrates the main point of advantage in gaseous fuel—its more complete utilization. If any of us could see the regular gaseous waste from our kitchen-stoves kindled up in the chimney to a pitch of heat sufficient to melt iron there, it would be a convincing proof of the estimated loss of ninety-five per cent, of our fuel, and would resemble faintly what is done outside the fire-chamber of the Lowe or Strong furnace, and in what answers to the chimneys of our dwellings.

At this point (to return) the air-blast is shut off; the outlet of the chimney is tightly closed; and a cock is turned which lets a jet of steam from a boiler into the bottom of the furnace and up through the mass of glowing coals. Instantly the process of combustion ceases (as between the coal and atmospheric oxygen), and the generation of water-gas begins; in other words, the coal now takes oxygen in combustion from the steam which has been substituted for air, and leaves the water hydrogen free. The hydrogen, lightest and thinnest of gases, which had been pent in the form and consistency of water, is now itself again, expanding to vast volume, like the ethereal génie let out of the casket by the Arabian fisherman, and ready to do the bidding of its liberator. At the same time a valve is opened in the upper part of the furnace, which lets fall a steady shower of crude petroleum on the fire. The pungent and fuliginous vapor in which the oil rebounds from the burning coals is a heavy solution, so to speak, of carbon in hydrogen. Into this thick mixture the free water hydrogen, rushing up from the decomposition of steam below, freely enters, diluting it to proper proportions for burning completely and cleanly, without smoke, in the open air. Another ingredient, rolling up from the fiery laboratory, also mingles in the tempest of hot gases, and still further heightens the calorific and consuming powers of the compound. This is carbonic oxide, the great value of which, either in a fuel or illuminating gas, and its spontaneous development in place of incombustible carbonic acid, are among the advantages which have