a flame of that gas in an atmosphere of, or a bell glass filled with, oxygen: of course, the gas burns brilliantly, and we call the gas the combustible, and the oxygen the supporter of combustion. If I now invert this common order of things, and fill the bladder with oxygen, and the bell glass with coal-gas, I find that the jet of oxygen may be inflamed in the atmosphere of coal-gas with exactly the same general phenomena as when the jet of coal-gas is inflamed in the atmosphere of oxygen. This is precisely your process. You admit a number of jets of air into a heated, inflammable atmosphere, and so attain its combustion in such a way as to produce a great increase of heat, and, as a necessary consequence, destroy the smoke. You, in fact, convert what is commonly called smoke into fuel, at the time when, and the place where, this combustion can be most effectively brought about.

I have now given you my candid opinion respecting your views of the phenomena of combustion and their application to the object proposed in your Essay. There are some of the minor points of which I cannot speak without further consideration; but these do not, in any way, affect the main object of the inquiry in its practical bearings.

I am always, my dear Sir, sincerely yours,

To Charles W. Williams, Esq.,

WILLIAM THOMAS BRANDE.

Dublin Steam Company, Liverpool.

REMARKS BY DR. URE.

London, 13, Charlotte-street, 28th Nov., 1840.

MY DEAR SIR,-I have been perusing your treatise "On the Combustion of Coal and the Prevention of Smoke, Chemically and Practically considered," with extreme pleasure, and shall be able, in the course of a few days hence, to write you more particularly my opinion as to the great merits of your invention for obtaining the maximum calorific effect of fuel, and that without the nuisance of smoke. Meanwhile, I shall only state, that I consider your theoretical views to be chemically correct, and their application to steam-boilers to be fraught with the most signal advantages.

I remain, my dear Sir, your very faithful Servant,

To Charles W. Williams, Esq.

ANDREW URE.

REMARKS BY DR. BRETT.

Laboratory, Royal Institution, Liverpool, Dec. 3, 1840.

MY DEAR SIR,-I have read your work on the Combustion of Coal, and have great pleasure in expressing my unqualified approval of the chemical views contained therein. I, moreover, entertain a strong belief that the most important practical results will flow out of their adoption, and that they will produce a new era in economical combustion. I shall take an early opportunity of sending you a more lengthened opinion as to the value of your discovery. In the meantime, allow me to subscribe myself yours very respectfully,

To C. W. Williams, Esq.

R. H. BRETT, Ph. D., F.L.S.

FURTHER REMARKS BY ANDREW URE, M.D., F.R.S. Having now carefully perused your treatise "On the Combustion of Coals and the Prevention of Smoke, Chemically and Practically considered," I cannot help congratulating you on the profound manner in which you have studied the phenomena of a furnace-phenomena which, like those of the freezing and boiling of water, had been for ages exhibited to the eyes of the philosopher and the engineer, without receiving from the one a scientific analysis, or leading the other to any radical improvement. You have fully demonstrated the defectiveness and fallacy of the ideas generally entertained concerning the operation of fuel in furnaces, and the errors consequently committed in their construction. Nothing places in a clearer light the heedlessness of mankind to the most instructive lessons than their neglecting to perceive the difficulty of duly intermingling air with inflammable vapours, for the purpose of their combustion, as exhibited in the everyday occurrence of the flame of a tallow candle, or common oil lamp; for, though this flame be in contact, externally, with a current of air created by itself, yet a large portion of the tallow and oil passes off unconsumed, with a great loss of the light and heat which they are capable of producing. Your quotations and remarks upon this subject must convince every unprejudiced mind of the justness of your views as to the imperfect combustion of the inflammable gases given out by coals on the furnace grate.

By experiments with Dr. Wollaston's Differential Barometer, made in several factories, where both high and low pressure steam was employed, I found that the aërial products of combustion from the boiler furnaces flew off with a velocity of fully 36 feet per second;* a rate so rapid as to

* Experimental Inquiry into the Modes of Warming and Ventilating Apartments, in reference to the Health of their Inmates. By Andrew Ure, M.D., F.R.S. (Read before the Royal Society, 16th June, 1836.)

preclude the possibility of the hydrogenated gases from the ignited coals becoming so duly blended with the atmospheric oxygen as to be burned. It is well known that elastic fluids of different densities, such as air and carburetted hydrogen, intermingle very slowly; but, when the air becomes considerably carbonated, as it does in passing through the grate, and, consequently, heavier, it will not incorporate at all with the lighter combustible gases above it, in the short interval of the aerial transit through the furnace and flues. Thus there can be no more combustion amidst these gases and vapours than in the axis of a tallow candle flame.

Your atomic representations are quite correct, and will please all those who delight in tracing the workings of nature into her formerly mysterious and inaccessible sanctuary.

You will remember, that when, about ten months ago, you laid before me the first draught of the specification of your patent furnace, with what delight I hailed your invention as the harbinger of a brighter day for steam navigation, where economy of fuel has become the sine quâ non in regard to long voyages. I rejoice, that with the ample means placed at your command, you have since prosecuted the subject, through all its ambiguities, to a clear and conclusive demonstration of the efficacy of your plan for calling forth from pit-coal all its dormant fire, and diffusing it most efficaciously over the surfaces of boilers and along the flues. I am more particularly pleased with your analysis of the combustion of the gases and vapours given out by hydrogenous coal, commonly, though incorrectly, called bituminous, for it contains no ready-formed bitumen, but merely its elements-carbon, hydrogen, and oxygen.

Having been much engaged during the two preceding years in experimental researches upon the calorific powers of different species of fuel,* I became aware that the hydrogenous constituents of coal underwent a most imperfect combustion, and found I had been misled for some time to the false conclusion that the caking Newcastle coals afforded less heat than the nonhydrogenous anthracite of Wales. When I improved my method of burning the gaseous products first disengaged from coals, I obtained a greater quantity of heat from the so-called bituminous species; a result quite in accordance with longestablished chemical data. The immortal Lavoisier and Laplace ascertained that one pound of hydrogen, when burned in their celebrated calorimeter, melted 295-6lbs of ice, while one pound of charcoal melted only 96·5lbs.— quantities very nearly in the ratio of 3 to 1. Despretz gives the same of charcoal. It deserves to be remarked, that this ratio is exactly the inverse of that in which hydrogen and carbon unite with oxygen; for 1 part of hydrogen, by

* An account of these experiments was laid before the meeting of the British Association at Birmingham, and printed in the Athenæum, of Sept. 14, 1839.

weight, combines with 8 of oxygen to form water; and 3 parts of carbon combine with 8 of oxygen to form carbonic acid gas, which is the product of the complete combustion of charcoal. From these and similar researches, chemists have been led to conclude that the heat afforded by different bodies in the act of their combustion is in the ratio of 315 to 104; thus proving beyond a doubt, that hydrogen can disengage, in its combustion, three times more heat than the same weight proportional to the quantity of oxygen which they consume; a conclusion which accords, also, with the principle, that the intensity of heat is proportional to the intensity of chemical action, as measured by the proportion of oxygen which enters into combination.

For the first accurate analysis of pit-coals, we are indebted to Mr. Thomas Richardson, of Newcastle,* who published, a few years ago, in the eleventh volume of Erdmann's Journal für Chemie, the results of an excellent series of researches on coals made in Professor Liebig's laboratory. He used the fused chromate of lead to oxygenate the carbon and hydrogen of the coals, with Liebig's new apparatus; and his results deserve entire confidence. In the earlier analyses of coals made by Dr. Thomson, myself, and others, the peroxide of copper, which was employed to oxygenate the combustible matter, always left some of the carbon unconsumed, and thus occasioned unavoidable errors.

1. Rich caking coal from Garesfield, near Newcastle, of sp. grav. 1.280, was found to contain as follows:

2. Caking coal, of excellent quality, from South Hetton, in the county of Durham, of sp. grav. 1.274, afforded,

*An account of these experiments has been since presented, by Mr. Richardson, to the Natural History Society of Newcastle-upon-Tyne, and is printed in their Transactions, vol. ii., p. 401, and in the London and Edinburgh Philos. Magazine, vol xiii., p. 121, for August, 1838.

100 parts of these several kinds of coal take for perfect combustion (subtracting the oxygen contained in the coal) as follows:

1st. 266-7 parts of oxygen: giving out heat as the number 122-56

The quantity of heat is here presumed to be proportional to the quantity of oxygen consumed. M. Regnault published, in Erdmann's Journal, vol. xiii., p. 69, the following statement of his analysis of coals, which is regarded by Professor Löwig as very correct :*

Newcastle coal, of sp. grav. 1·280, affording a much-inflated coke, (quite akin to the Garesfield coal, if not the same,) was found to consist of carbon, 87.95; hydrogen, 5·24; azote and oxygen, 5·41.

Every coal which contains much hydrogen, and, therefore, loses much weight by ignition in retorts, necessarily produces much smoke, with a great waste of heat in our common steam-boiler furnaces, for reasons which you have so well developed in your treatise. "When a carburetted hydrogen," says Liebig, "is kindled, and just as much oxygen admitted to it as will consume its hydrogen, the carbon does not burn at all, but is deposited (or separated) in the form of soot; if the quantity of oxygen is not sufficient to burn even all the hydrogen, carburets of hydrogen are produced poorer in hydrogen than the original carburetted hydrogen.'"+ The above gas and smithy coals which, from their richness in hydrogen, are capable of affording the greatest proportion of heat by thorough combustion, afford often a much smaller quantity than the Llangennock, because the carburetted hydrogen which they so abundantly evolve is not supplied with a due quantity of oxygen, and hence much of their carbon goes off in smoke, and their sub-carburetted hydrogen gas in an invisible form. These results are quite accordant with my experiments on these coals with my calorimeter. At first, from certain defects in the apparatus, whereby the coals were imperfectly burned and a good deal of smoke was disengaged, I found that the best coals imported into London, such as Lambton's Wallsend, Hetton ditto, and Pole's Main, afforded a smaller proportion of heat than the Llangennock, or even anthracite; but, when I diminished these defects, I obtained much more heat from the Tanfield Moor coal than from the Llangennock, and more from this than from the anthracite. In fact, a coal which, like the Newcastle caking coal, contains 5·239 of hydrogen, is capable of giving out in complete combustion as much heat as if it contained an extra 10 per cent. of carbon; but, instead of this additional heat, it affords in common furnaces much less heat than the Llangennock, though this is much poorer in the most calorific constituent, viz., the hydrogen.

* Chemie der Organischen Verbindungen, vol. ii., p. 88.

+ Traité de Chimie Organique, Introduction, p. 32. A 2