ON THE MANAGEMENT OF FURNACES AND BOILERS. and revolving rod as before described, and for the purposes aforesaid, and with a cover or cap to place over the lime as aforesaid." ON THE MANAGEMENT OF FURNACES AND BOILERS. BY C. W. WILLIAMS, ESQ. Sir,-In my last, I enumerated the several kinds of combustible gases which are produced in a furnace, and for which a supply of atmospheric air will be required. The following tabular view of their relative quantities, as generated from each charge of coal, with the periods of their respective development and length of flame during the varying stages of the process, will convey a fair practical estimate of the effects produced in a well regulated furnace by the admission of fresh supplies of air-in the right place, and the right manner. These results (and which may be tested by all, without the aid of a laboratory or chemical professor) cannot fail to convince us how we have been led astray on this subject, by the oversight of practical as well as theoretic men; among whom may be mentioned Tredgold and his followers. Not possessing, or adopting, the means of internal inspection, such men, notwithstanding their unquestionable talent and scientific acquirements, have, themselves, been led to form very erroneous notions on the power and length of flame, and the admission of air to furnaces-giving precise rules for the proportions of furnaces and boilers, with even the appearance of mathematical precision. distance," says Tredgold, "to which the flame and heated smoke of a fire will extend, so as to be effectual, will depend on the draught of the chimney and the nature of the fuel; from three to six feet will be about the range in a wellconstructed fire-place: that is, about six feet with coal and a good draught, and about three feet with coke and slow draught. This, of course, will regulate the length of the boiler." What connexion those six feet, or three feet, have with the length of the boiler, it would be very difficult to define on any rational or scientific grounds; and I am prepared to show-that the dictum of Tredgold (which has recently been republished under high sanction) is unsound and wholly unwarranted in every particular. The 291 I am aware that I have been much censured for presuming to question the engineering skill of those who are connected with boiler-making. When, however, we find those engaged in this important department so misled, the want of some more practical details will not, I trust, be disputed; and I may here observe, that I have already had abundant proof from many of the highest standing in this branch of business, that I have not laboured in vain. I have already characterized the gases evolved in a furnace, by the general terms of coal gas and coke gas, (see Mech. Mag. No. 961,) as well for the sake of brevity, as of directing attention to the peculiar nature of the difference between the former, as generated from the coal, during the early part of the process, and the latter kind of gas, as produced, during the later stages, from the clear red, or glowing embers on the bars, as they progressively approach to the character or appearance of a coke fire. As there are many important considerations arising out of these two states of the charge of coal, which are intimately connected with the admission and action of the air, it is of the last importance that we keep this distinction in mind-many of the practical and chemical errors of "smoke burning" inventors being clearly traceable to its neglect. I will here, then, briefly observe, that, by coal gas, is meant the hydro-carbon gases (composed of carbon and hydrogen) evolved from the coal, before it assumes a red or ignited appearance; whereas, by coke gas, is meant the carbonic oxide, (composed of carbon and oxygen,) formed from the carbonic acid, in its passage through the glowing ignited mass on the bars, in the form of coke, and after the coal gas has been expelled. The quantity of this coke gas will then be in proportion to the thickness or body of such ignited mass-the current of air passing through it, in its state of incandescence. "Carbonic oxide," observes Professor Graham, (in common with all the other authorities,) "may be obtained by transmitting carbonic acid over red hot fragments of charcoal contained in an iron or porcelain tube. The combustion is often witnessed in a coke or charcoal fire. The carbonic acid, produced on the lower part of the fire, is converted into car bonic oxide as it passes up through the red hot embers." I here make this special reference to the process by which this carbonic oxide (which I call coke gas) is produced, as I perceive some practical men err by considering it to be an original formation arising out of the glowing matter, after it has been reduced in temperature; whereas the fact is the reverse, as practice, and the highest authorities, prove: namely, that carbonic acid, being first generated, takes up, "as it passes up through the red-hot embers," an additional portion of carbon, aided by the intense heat of the incandescent mass: the incombustible carbonic acid being thus converted into combustible carbonic oxide. To this latter, air must therefore be admitted, by some other quarter than through such fuel itself from the ash-pit; since, instead of effecting its combustion, such air, so admitted, would only increase its quantity, (by increasing the quantity of carbonic acid,) and make the evil worse. Having detailed this process more at length in my Treatise on Combustion, I need not here dwell on it. We will now further consider our charge of coal on the furnace, and the following table will present a view of the relative quantities of those two gases produced from it during the progress of its combustion. bustible gases evolved and entering into combustion, (if supplied with air,) as far as can be estimated by the length of the flame passing from the furnaces over the bridge, and into the flues. It is possible the generation of the coke gas may, to a certain extent, continue longer than the first five minutes, and begin sooner than at the end of thirty five minutes, as expressed in the table-the brilliant light from the coal gas preventing the feebler light from the flame of the coke gas from being perceived. These, however, are minor and insignificant details. I have aimed solely at giving a general description of what is seen; in all cases, however, the quantity and length of the flame are un derrated, rather than overrated. The state of the fire at the time of the charge, and many other circumstances, tend to alter the quantities and times: the above, however, may be considered as a correct general view of the matter. By the table, it will be seen, that the flame, which, according to the dictum of Tredgold, would be but six feet, actually reaches to a length of twenty-two feet, (and even that is by no means the maxi. mum,) while its minimum is not less than ten feet. Tredgold speaks also of the "flame and heated smoke," yet, in my furnace, from which the above table was drawn, and where the largest quantity of gas was produced, there was no smoke whatever, not even as much as would dull the bulb of the thermometer, the flame being of a clear and brilliant white colour. Another writer on boilers (adopting Tredgold's views) observes, "With boilers whose fire grates are square, and whose lengths are not less than four times that of the grate, we have never met with an instance of the flame reach. ing to the end of the boiler, provided there was a good draught and the fire properly managed." Now the boiler from which the above table was taken, falls in with these proportions, being fifteen feet long, and the fire-grate square (three feet). Yet the flame not only reached the end of the boiler, but passed above ten to twelve feet beyond it -often extending along one of the side flues, and even illuminating the second In a score of other boilers, to which have introduced the air in the proper manner, the flame may be seen, during ON THE MANAGEMENT OF FURNACES AND BOILERS. large portion of an hour's charge, reaching from twenty to thirty feet in length, and not an "imperfectly developed and dull reddish flame," but of a brilliant and well-developed character. These are the errors to which engineers are exposed, and by which manufacturers are led astray, from the want of adequate means of observing what passes within the furnace and flues; and the supplying the necessary air in the right place and manner. For, in the cases above named, when the air-admission orifice is closed, the flame is not only shortened, but nearly extinguished -its length is reduced to the Tredgold standard-and instead of the interior atmosphere of the flues being clear and transparent, it becomes dark, with a cloud of black smoke, which renders internal inspection impracticable, and sightholes of no avail. By the above table, we see that before the charge was thrown on the furnace, the coal gas had ceased to be produced : the fire being then clear and of a glowing red, and the flame necessarily confined to that of the carbonic oxide, or coke gas. Of this there could be no doubt, from its peculiar colour and character, as well as from the appearance of the ignited mass on the bars. ́ ́On the charge, however, being thrown on, the coal gas, we see, takes its place; the former ceasing to be evolved, or nearly so. easily accounted for, when we consider the great cooling effect of the fresh coals on the ignited mass, and which thus destroys the very cause of the production of such coke gas, namely, the high temperature and state of incandescence. This is The coal gas then goes on increasing in quantity and length of flame, until, at the end of twenty minutes, we see it has reached its maximum of 22 feet from the bridge. Continuing in this state for some time it gradually decreases, while that from the coke gas simultaneously increases, until the former has entirely ceased, and the latter alone prevails. This progression, and even the existence of the two flames at the same moment, is quite perceptible, until the entire of the solid fuel on the bars has become clear with a glowing appearance. Should there be any irregularity in expelling the coal 293 being evenly spread, the appearance inside will present many interesting and instructive proofs and illustrations, which we cannot now stop to describe. Towards the close of the charge, and when the flame from the coke gas has sensibly diminished, it will be perceived that the time has arrived for a new charge, and this without opening the fire-door to look in. If the proper time be suffered to pass, or, should the next charge be thrown on too soon, in either case the efficiency of the process will be materially affected the appearance in the interior will vary-the quantity, rate of progression, and even the nature of the evolved gases will, in a great degree, be altered, and the question of time and economy considerably influenced. There is no difficulty in understanding all this. The observer cannot be deceived by the misrepresentations of interested parties, or the truth obscured by plausible theories. By such means of observation, the owner soon becomes his own master, and his eyes are opened to the truth or fallacy of what he is called on to believe or practise. This is, in fact, making the chemistry of combustion on the large scale, an easy, intelligible, and practical science. It is now to be observed, that during the process of the entire charge, the atmosphere, as it were, of the flues, will be perfectly transparent. This all-important fact is at once ascertained by looking through them, as from S 1 to S 2;-(see engraving in No. 971;) should any cloudiness appear, or the flame assume a reddish or murky colour, we are at once warned that something is wrong, and called upon to rectify it. This subject, however, will be considered more in detail as we proceed. Thus, we perceive, that at no stage of the process, from the beginning to the end of a charge, is there a flame of less than 10 feet from the bridge, and even extending to above 20 feet in lengththus at once negativing Tredgold's hypothesis. This flame being perceived to be in immediate contact with the boiler bottom, against which it impinges; where then, it may be asked, can we find any ground for asserting that the length of the flame should "regulate the length of the boiler?" But with still greater force do I ask, where is the foundation for the assertion that there is no combustible gas produced, and therefore, no demand for air, when the fire in the furnace has become clear, red, or incandescent? Or, that the air so introduced could have, not a heating, but so cooling an effect, as actually to affect the boiler plates injuriously? Nothing can be farther from the fact. Such assertions could only be the result of mere conjecture, in the absence of internal inspection, since, with such aid, it would be impossible to deny or resist the evidence of our senses: yet, such theoretical absurdities are still palmed on the unsuspecting manufacturer, and even by those who affect to be practical men. Let such assertors bring their theoretic reveries to the test of observation. Let them examine a furnace thus furnished with the means of internal observation, and they will then be in a position to appreciate, by both seeing and feeling, what are the results from the admission or exclusion of air. The value of the admitted air, in effecting the combustion of the evolved gases will, however, be more fully illustrated when we come to consider the actual temperature and actual condition of the flues, which shall be the subject of my next communication. I am, Sir, yours, &c. Liverpool, April 8, 1842. C. W. WILLIAMS. only begun to be understood within a few years, and is even now much better known, and more scientifically acted on, in certain parts of the Continent than with ourselves. Until ammonia was known to be the really important matter of all manure, this, its very essence, was every where permitted to be volatilized in the process of violent fermentation, and is even still so in most parts of our own country. A better system, prevails, however, over a large portion of Germany, in Alsace, and in Holland and Switzerland. In the latter country they wash the dung by repeated watering at intervals. The washings are collected, rich in ammoniacal salts, and are saturated with a solution of sulphate of iron, (green copperas) or with sulphuric acid direct, to change the volatile salts of ammonia into fixed sulphates, and in this state the liquid manure is applied to the soil. It produces the most vigorous vegetation, and the sul phate of ammonia being fixed, is all assimilated by the plants, in place of being volatilized in the state of carbonate of ammonia, as with us, when crude fermenting manure is lavishly spread over our lands. Gypsum is often used in place of sulphate of iron, and is readily decomposed by organic matter in certain stages of decay. In Great Britian, where sulphate of iron from refuse pyritose coal and gyp sum may be had almost for nothing, it is singular to find its use thus almost unknown amongst us, while practised by those to whom both these articles are scarce and dear. A M. Schattenmann, of Bouxmiller, in Alsace, has greatly distinguished himself in this branch of agriculture. As director of some great chemical works, and having had under his disposal the manure produced by two hundred artillery horses, cantoned for four years at Bouxmiller, he has had opportunities of practically expe rimenting upon a great scale, and has com municated his methods and their results to M M. Dumas and Peligo. His dungheaps are made on a great square space, paved or puddled, and with a fall from all sides inwards. The stable dung is heaped all over to the height of about 12 feet; a well, sunk at one side, supplies a large quantity of water, which is at intervals distributed by wood shoots over the PROGRESS OF FOREIGN SCIENCE. heap, which is never permitted to get into a state of violent or heated fermentation; the mass is stratified with powdered gypsum, or copperas, and the drainage from it, with all the washings, are collected in a large underground tank in the centre, where they are saturated further, if requisite, with gypsum, or sulphate of iron. This latter fluid is used, as requisite, by watering the surface with it, and such are its potent effects, that he says, a name traced out by watering with it in the grass, can be distinctly traced in a few weeks by the dark coloured and vigorous vegetation produced where it was touched. The effects of this treatment on the stable dung, are to produce, in about three months, a mass (aussi gras et pâteux) as fat an pasty as cow-dung, and, according to his experience, fully as powerful. For a journal not professedly agricultural, the full details of this intelligent gentleman's methods would be out of place; but to those interested in the perusal of the original paper ("Comptes Rendu," No 7, for February last) would be important. The theoretic grounds on which this successful practice depends, have been fully developed in a form accessible to the English reader by Dr. Leibig, in his report on organic chemistry, applied to agriculture, &c., addressed to the British Association. Effects of Tide upon Artesian Wells. An Artesian well, which has been some time sunk at the military hospital of Lisle, has been observed to vary considerably in the force and volume of its supply. M Bailly, captain of engineers, has made a long continued series of accurate observations upon the variation, and has arrived at the following conclusions. == The maximum supply is 63.55 lit. per min. The minimum 33 lit. The mean of all the experiments 48:55 lit. The maximum height to which the water will rise (above the surface namely) when prevented from flowing off is 2-385 metres, the minimum 1956 metres, the mean of all 2·253 metres. The greatest variations, both in supply and height of column, correspond with the periods of the moon's syzygies, and the minima of both correspond in an equally constant manner with the time of quadratures. It may hence be concluded that the phenomena are due to the tides. The periods of maximum supply were 295 found to be eight hours after high water at Dunkerque and Calais, so that it would appear that it takes that time to transmit the pressure of the tidal column from these ports, or from the nearest point of coast, to Lille. Some connexion between the tides and the level of well waters has long been conceived, or observed, in various parts of Great Britain, but heretofore never identified with the actual periods of rise and fall. Some extremely curious questions of a geological character arise from this result. How does the tidal water act on that of the well, without gradually making it brackish? Is the fresh water merely contained between beds of clay, or rock, which partly float upon it, and are compressed by the advancing tide, and forced to yield up their watery store, like wine pressed from a skin; or do the columns of salt and fresh water actually mingle? And if so, does the sea water lose its salt in the bed through which it passes, by decomposition, and become fresh? It is quite conceivable that such re-actions might take place as resulting in nearly insoluble salts, would leave the sea water as fresh as many spring waters are found. Metalliferous Deposits of Sicily. An able report has been made to the Academy of Sciences on this subject, by M. Adrien Paillette. From this it appears, that some time ago an English company obtained from the Neapolitan government, authority to work mines in Sicily, and full of expectation from the boasted historical accounts of its ancient riches, both mineral and agricultural, had, without any previous research, but merely on inspection of some old work. ing, prepared means of opening mines, and working them on a large scale. The results were unsuccessful, like many others of the same sort, begun in the same reckless way, on both sides of the Atlantic; and they were now so discouraged, that the pumping engines, and stampers, &c., brought at an immense cost from Wales, lie to this day in store at Messina, or abandoned on the shore. Under these circumstances, some of the principal parties concerned determined to send a commission of mining engineers to learn what were the real mineral riches of the country. M. Juncker, ingenieur en chef of the Royal School of mines, and M. Paillette, civil engineer, were ap |