of sound and practicable improvement, to the development of which a small portion of our time may be usefully devoted.

As the subject has been involved in much confusion, and, to many of our readers, must be altogether new, we shall first endeavour to state, in a brief and popular way, the chymical composition of coal, before we detail the new applications that are proposed to be made of its ingredi

ents.

Pit-coal exists in this island in strata, which, as far as concerns the hundredth generation after us, may be pronounced inexhaustible; and is so admirably adapted, both for domestick purposes and the uses of the arts, that it is justly regarded as a most essential constituent of our national wealth. When exposed to heat, as we see it every day in our grates, it is manifestly composed of a fixed base of carbonaceous matter, and a variety of evaporable substances, which are driven off in the form of smoke and flame. But, instead of being consumed in this open way, the coal may be distilled, and these evaporable matters collected in proper vessels, and examined. They are then found to contain, besides a considerable quantity of matter, which is condensed by cold into tar and alkaline liquor, an invisible elastick fluid, or gas, which no cold nor effusion of water can condense or absorb. It is a compound of two highly inflammable gases, which chymists call the light hydrocarbonate, and the heavy hydrocarbonate, or olefiant gas; ⚫ and this mixture burns with a very brilliant and beautiful light. It is this gas which furnishes the flame in our common fires;* but its beauty is there

There are, in fact, according to Mr. Davy, three inflammable gases given out in our fires-the two we have mentioned, and the gaseous oxide of carbon, which is known by its blue flame. They are all distinctly perceptible. The light hydrocarbonate forms the main body of the Bare; the olefiant appears in brilliant

impaired by the unavoidable alloy of smoky vapour. A separation, however, may be effected by the distilling process, which leaves the pure aërial fluid such as we have described. All the new plans for lighting with coal gas, proceed upon the principle of purifying this fluid, collecting it in reservoirs, and distributing it in tubes. From the furnace where the coal is distilled, a main pipe may convey all the evaporable matter into a large reservoir or gasometer, where, by various means, chiefly, we believe, by washing with water, it may be freed from impurities, and propa gated through the tubes in every direction by its own elasticity. If nothing confine it, it will issue from the extremities in an equable flow, but still invisible, till a lighted taper be applied, when it bursts into flame, and continues to burn as long as the gas is supplied. Mr. Accum found, by a comparison of shadows, in the manner suggested by count Rumford, that the light of a gas flame is to that of an equal-sized flame of a candle or lamp as 3 to 1; * or, in other words, that to light up a certain space, one gas flame will give as much light as three candles burning with a flame of equal size. The products of the combustion are in both cases the same-water and carbonick acid gas; but with this mate

jets; and the gaseous oxide is occasionally seen near the root of the flame, or in contact with the coal. It is possible that a small portion of this oxide may mix with prepared gas.

We should have suspected the proportion was overrated, had not the same accurate experimenters assured us, "that 500 cubick inches of gas, burnt from the orifice of a jet, so as to produce a flame equal in size to that of an ordinary candle, consumed 1076 cubick inches of oxygene gas in the same time that a candle kept burning in the best possible manner, consumed only 279. And we know, that the intensity of any artificial light depends on the rapidity with which oxygene is absorbed. See Appendix to Report of the Committee, &c.

rial difference, that candles frequently, and lamps always, give out a quantity of smoke and soot; whereas the combustion of the gas is perfect, and leaves no sensible residuumnothing that can soil the most delicate white. Its effects on the air of a room are, therefore, less insalubri ous than those of a candle, since the only noxious substance it yields is carbonick acid gas; and this it produces in smaller quantity than our common lights. From the inflammable properties of the gas, explosions, bursting of tubes, and other dangers might be apprehended. But there is no ground for such fears. On the contrary, nothing can be more simple or easy in the management. The gas may be confined by a stop-cock with perfect safety, and issued as Occasion requires. When it is exhausted, the flame goes out as quietly as the flame of a candle does, when the tallow is spent.

Such are the nature and properties of this curious and beautiful substance, when examined in a small way in the laboratory of the chymist. But it frequently happens, that theories perfectly just and elegant in themselves, and confirmed by expements on a small scale, with a nice apparatus and skilful management, are yet, when attempted in the large and wholesale way, utterly incapable of being reduced to practice; and thus, many a promising plan has ended with performing nothing. But, in the case before us, there are facts, of the description we want, to be collected from different quarters, and furnished by individuals unconnected with each other, which fully verify the anticipations of theory, and the conclusions of more limited experi

ment.

The first, and by far the most valuable of these facts, is contained in Mr. Murdoch's paper; the chief object of which is to describe the mode of lighting the cotton-mill of Messrs. Philips and Lee, at Manchester. From this account we learn, that

"the whole of the rooms of this, the most extensive cotton mill in the kingdom, with the counting house and store-room, and the adjacent dwelling house of Mr. Lee, are now, and have been for several years, lighted up with the gas from coal, to the exclusion of all other artificial light." The manner in which the gas is procured and distributed, we shall quote in his own words.

"The coal is distilled in large iron retorts, which, during the winter are kept constantly at work, except during the intervals of charging; and the gas, as it arises from them, is conveyed by iron pipes into large reservoirs or gasometers, where it is washed and purified, previous to its being conveyed through other pipes, called mains, to the mill. These mains branch off into a variety of ramifications, forming a length of several miles, and diminish in size as the quantity of gas to be passed through them becomes less. The burners, where the gas is consumed, are connected with the above mains by short tubes, each of which is furnished with a cock, to regulate the admission of gas to each burner, and to shut it totally off when requisite. This latter operation may likewise be instantaneously performed throughout the whole of the burners in each room, by turning a cock, with which each main is provided, near its entrance into the

By a comparison of shadows, the whole light of the gas flames used was found equal to that of 2500 candles of 6 to the lib. We cannot enter into all the items of expense: they are given with the most scrupu lous accuracy; and the economical statement for one year stands thus. The cost of the cannel coal which he used to furnish the gas, is 1257. and of common coal to carbonize it, 201. in all, 145. from which deduct the value of the coke, 93%. and to 527. The interest of capital sunk in the whole expense in coal is reduced the apparatus, with a liberal allow. ance for tear and wear, is stated at 5501. making the total expense of lighting the manufactory about 6001. a year. That of candles, to give the

* Vide Nicholson's Philosophical Journal for October last.

same light, would be about 2000/. If the comparison were made on the average of three hours a day, which, in most cases, would perhaps be nearer the truth, the advantage would be still more in favour of the gas lights. The interest of capital and tear and wear, remaining nearly the same as in the former case, the whole

cost would not exceed 650/. while that of the tallow would be 3000l. Here, then, we have a saving of three parts in four; and it is not likely, as we shall see hereafter, that Mr. Murdoch has reached the utmost point, either of economy in his process of distillation, or of simplicity in the construction of his apparatus. "The peculiar softness and clearness of this light," says Mr. Murdoch, under whose direction the whole was completed, "with its almost unvarying intensity, have brought it into great favour with the work people: and its being free from the inconvenience resulting from the sparks, and frequent snuffing of the candles, is a circumstance of material importance, as tending to diminish the hazard of fire, to which cotton mills are known to be much exposed."

The next fact we shall bring forward is important, inasmuch as it shows, that the superiority of gas lights is not confined to great manufactories, but is equally apparent in those on a small scale; thus opening a much wider range for the possible application of the new mode. We

are indebted for this fact to a Mr.

Cook, a manufacturer of metal toys ⚫ at Birmingham; a clear headed, practical man, not apt to be dazzled by a fanciful theory, but governed in his transactions by a simple balance of profit and loss. There is a naïveté in his own account of this process,

which will amuse as well as instruct the reader.

"My apparatus is simply a small cast -iron pot, of about eight gallons, with a

cast iron cover, which I lute to it with sand. Into this pot I put my coal. I pass the gas through water into the gaso meter or reservoir, which holds about 400 gallons; and, by means of old gun barrels, convey it all round my shops. Now, from twenty or twenty-five pounds of coal, I make, perhaps, six hundred gallons of gas; for, when my reservoir is plus in waste, unless we have work to full, we are forced to burn away the overuse it as it is made: but, in general, we go on making and using it, so that I cannot tell to fifty or a hundred gallons. And, in fact, a great deal depends on the coal, some coals making much more than others. These twenty-five pounds of coal put into the retort, and say twenty-five pounds more to heat the retort, which is more than it does take one time with another

but I am willing to say the utmost, are worth four pence per day. From this four pence we burn eighteen or twenty lights during the winter season."

In this manner are the candles which he used to employ, and which cost him three shillings a day, entirely superseded. But, besides his expense in candles, oil and cotton for soldering used to cost him full 30%. a year, which is entirely saved, as he now does all this soldering by the gas flame only. For "in all trades in which the blowpipe is used with oil and cotton, the gas flame will be found much superiour, both as to The flame is sharper, and is constantquickness and neatness in the workly ready for use; while, with oil and cotton, the workman is always forced is, till it is sufficiently on fire to do to wait for his lamp getting up; that his work. Thus, a great quantity of oil is always burned away useless; stopcock is turned, the lamp is ready, but, with the gas, the moment the

and not a moment is lost." We must refer to Mr. Cook's letter, for the details of expense, which he gives with faithful minuteness, and always the gas. The result of the whole is, leaning to the side unfavourable to

that he saves 301. out of the 50%. which his lights formerly cost him. And, when we consider that his calculation allows the gas lights to be burnt the whole year, and the candles only twenty weeks, there can be little

doubt, that the savings in this case follow nearly the same proportion as in the former. If the apparatus be erected on a still smaller scale, "the saving," Mr. Cook assures us, "will be equally great for the poor man who lights only six candles, or uses one lamp, if the apparatus is put up in the cheapest way, will find it only cost him 107. or 124. which he will nearly, if not quite, save the first year."

The last trial of gas lights we shall mention, though not the most satisfactory, has made the greatest noise in the world, and was, indeed, what first led us to think upon the subject, During one of those excursions to the metropolis, with which we occa sionally treat ourselves, after a long period of northern rustication, our attention, at such a time alive to every thing, was arrested by a new and singular spectacle. The whole range of Pall Mall, from St. James's to Cockspur street, was lighted up by means of lamps, fed with gas instead of cotton and oil, and certainly in a style of much superiour brilliancy. We found, upon inquiry, that the conductor of this remarkable illumination was a Mr. Winsor, acting under the auspices of a committee of subscribers; and that it was executed by them as a grand experiment to convince parliament and the publick of the national importance of their intended Light and Heat Company. Subscriptions had been collected, to a very large amount, to carry into effect Winsor's discovery; and 20,000l. vested in a committee, to assist him in his experiments, and make application to parliament for a charter of incorporation. In prosecution of these objects, we afterwards learned, that a correspondence was opened with the chancellor of the exchequer in the month of March last; but he, alleging partly the advanced state of the session, which did not allow a private bill to be presented, and partly his own doubts as to the utility of its object, declined promis

ing his support to the measure. Since that time, a general meeting, it seems, has resolved not to regard the answer of Mr. Perceval as a final rejection, but to come forward with their claims for a charter, during the present ses sion. On what grounds these claims are founded, it is not very easy to discover. It is possible that government, foreseeing that the new mode of lighting would render less productive the taxes raised on the common materials, might think it wise to sanction some publick establishment, by way of securing to itself a share in the profits. But it is the title of Mr. Winsor and his friends to an exclusive privilege, that puzzles us. We attempted to look for it in his pamphlets; but encountered, at every step, such ignorance, quackery, extravagance, and false calculation, that we had scarcely patience to wade through them. As, however, we are in search of facts, we shall, in mercy to a foreigner and an enthusiast, who talks about his new light with all the ferver of a fanatick, pass over his wild reasonings in bad English, and state briefly whatever there is of value in his plans and processes.

We must premise, however, that we cannot allow him the credit of being a great discoverer-a name which he is suspiciously fond of arrogating to himself. That coal yields an inflammable gas has been long known; and its nature is particularly described by Dr. Clayton. in the Philosophical Transactions for

avail him little, and that it is impos sible to give him or his friends the monopoly of a practice, which is already adopted by several persons who pretend to no secret or mystery in the art. We cannot discover that there is any decided superiority in Mr. Winsor's gas lights over those of Mr. Murdoch. It is asserted, indeed, in "Considerations," &c. that it is necessary to take to pieces, now and then, the tubes in Mr. Lee's manufactory, to clear them from impurities; while those of Mr. Winsor contract no soil by any length of use. But Mr. Murdoch expressly assures us, in his paper, that all inconveniences of this kind are now entirely done away. Winsor's Analysis of New Castle Coal is certainly very complete. The gas flames he exhibits in the different apartments of his house are extremely brilliant; and the variety and neatness of their application worthy of praise.

He deserves credit too, we think, for calling the publick attention, more than had been done before, to the peculiar advantage of coke as a cheap and agreeable fuel. This substance is the residuum that is found after all the evaporable matter has been expelled from the coal by heat. It comes out from the distilling process in large, spongy masses, greatly diminished in weight, but increased in bulk nearly one third. Though somewhat more difficult of ignition than coal, it burns longer, and gives out a steadier and more intense heat. That it should do so, will not appear strange to our chymical readers (and who is there now that does not know something of chymistry?) when it is considered that the quantity of matter, which, in the combustion of coal, is changed from a solid to a state of elastick fluidity, must necessarily carry off much calorick in a latent state; while the glow of the coke radiates with an intensity unimpaired by any demand of this kind. The same respectable chymist we formerly mentioned, bears testimony to the supe

riority of coke. "I have learned," says Mr. Accum,*"that the heat produced by coke, when compared with that which can be obtained from coal, is at least as 3 to 2." Thus he found, that it required three bushels of coal to distil a given quantity of water, and only two of coke. He tried the two substances also by combustion, with a certain measure of oxygen gas, by the fusion and the reduction of metals, &c. and the same result was obtained; a result certainly not unimportant; since it proves that, by being forced to yield the material of a beautiful light, coal is actually improved very considerably in its power of giving heat. We have not the least doubt that this coke, as Winsor produces it, and as we have seen it used in his house, might be introduced to form, if not the whole, at least four fifths of our common fires, with a very great addition of comfort, cleanliness and economy. Let it be observed, however, that we possess no facts that warrant us in pushing this conclusion any further than regards the coke of Newcastle coal. Mr. Murdoch, though he makes proper allowance for the coke produced in his process, does not enlarge at all on its qualities; and it is probable, that some species of coal generate coke too dull and difficult of ignition for consumption in our grates, and only fit to be used in stoves and furnaces where there is a strong draught. But we are persuaded, that the greater proportion of the other varieties in the island will be found, on trial, to yield the same sort of coke as Winsor's, and that it can never be produced in such quantity, by the extended use of the gas lights hereafter, that the demand will not fully and rapidly absorb it. Its merits have long been acknowledged in many processes of art; and it is prepared from coal with the loss of all the volatile ingredients in the great manufacturing districts; and if the

* Appendix to Report of the Committee.