Attempts in this direction have been made by Mr. T.R.  Crampton, by Messrs. Whelpley and Storer, and by Mr. G.K.  Stephenson; but a difficulty has presented itself which seems at present to be insuperable, that the slag fluxes the walls of the furnace, and at that high temperature destroys them.  If it be feasible to keep the flame out of contact with solid surfaces, however, perhaps even this difficulty can be overcome.

Some success in blast burning of dust fuel has been attained in the more commonplace method of the blacksmith’s forge, and a boiler furnace is arranged at Messrs. Donkin’s works at Bermondsey on this principle.  A pressure of about half an inch of water is produced by a fan and used to drive air through the bars into a chimney draw of another half-inch.  The fire bars are protected from the high temperatures by having blades which dip into water, and so keep fairly cool.  A totally different method of burning dust fuel by smouldering is attained in M. Ferret’s low temperature furnace by exposing the fuel in a series of broad, shallow trays to a gentle draught of air.  The fuel is fed into the top of such a furnace, and either by raking or by shaking it descends occasionally, stage by stage, till it arrives at the bottom, where it is utterly inorganic and mere refuse.  A beautiful earthworm economy of the last dregs of combustible matter in any kind of refuse can thus be attained.  Such methods of combustion as this, though valuable, are plainly of limited application; but for the great bulk of fuel consumption some gas-making process must be looked to.  No crude combustion of solid fuel can give ultimate perfection.

Coal tar products, though not so expensive as they were some time back, are still too valuable entirely to waste, and the importance of exceedingly cheap and fertilizing manure in the reclamation of waste lands and the improvement of soil is a question likely to become of most supreme importance in this overcrowded island.  Indeed, if we are to believe the social philosophers, the naturally fertile lands of the earth may before long become insufficient for the needs of the human race; and posterity may then be largely dependent for their daily bread upon the fertilizing essences of the stored-up plants of the carboniferous epoch, just as we are largely dependent on the stored-up sunlight of that period for our light, our warmth, and our power.  They will not then burn crude coal, therefore.  They will carefully distill it—­extract its valuable juices—­and will supply for combustion only its carbureted hydrogen and its carbon in some gaseous or finely divided form.