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a most extravagant waste of fuel was committed in most of the districts in which steam power is extensively used. In Cornwall, where necessity had compelled the introduction of great economy in the management of steam engines, a system of slow and complete combustion was practised which unfortunately could not be generally adopted in this district, where most of the proprietors of steam engines had subjected themselves to serious evils by a want of capacity in their boilers, and a system of overworking in every way opposed to perfect combustion, and attended with consequences equally objectionable, whether as regarded the public nuisance of smoke, or the increased expenditure of fuel. In many establishments, engines were loaded to almost double their nominal power; requiring steam far beyond the just capability of their boilers, and to be obtained only by forcing their fires, and too frequently dispersing through the atmosphere a quantity of valuable fuel, which under other circumstances, might be usefully and beneficially employed. These were evils which could be abated only by the zealous concurrence of proprietors of steam engines themselves; but it was to be hoped, that a few striking examples of great economy and perfect combustion would have considerable effect in directing the attention of these parties to a due consideration of their own interest and of the public welfare. The report then went into a minute description of the relative proportions of furnaces, boilers, flues, and chimneys, in this and other districts, from which we select the following points. In Manchester, the usual proportion of the area of the fire bars to the heating surface of the boiler is about 1 to 11, or 100 square inches to 8 square feet of flue per horse power. In a well proportioned boiler, on the plan usually adopted in this district, a pound of moderately good coal will evaporate about 7·46lb of water, being nearly the maximum duty effected here. A number of experiments had been made upon engines in this town, the results of which were given in a table exhibited to the meeting, specifying the nominal power of each engine, the power at which it was worked, the proportion of heating surface to the grate bars, the height of the chimney, the consumption of fuel per horse power, and some other particulars, none of which, however, seemed to throw much light upon the great question of economical combustion. The greatest consumption of coal (131b per horse power per hour) was in an engine of 45 horse nominal power, worked up to 76 horse, and having the grate bars in the proportion of 1 to 10.87 of the heating surface of the boilers. The smallest consumption (8.8lb per hour) was in an 80-horse engine worked to 110 horse, and having its grate bars in the proportion to the flues of 1 to 12.70. The second, in point of economy, however, (9'1lb per hour), had the smallest proportion of heating surface of the whole number experimented upon. The general average of the consumption of coal was 10.53lb per horse power per hour. That this was far beyond what it ought to be, was exhibited by the fact, that the average con

sumption of the best Cornish engines was only 2lb per hoursomething less than one fourth of the amount in this neighbourhood. The report proceeded to detail the results of some experiments on the comparative consumption of coal in a furnace to which Mr. Williams's apparatus for the consumption of smoke had been applied, when that apparatus was at work, and when it was thrown out of Some of these experiments appeared to be vitiated by the want of a perfect closing of the air passages when the apparatus was not used. Further experiments were consequently tried with the air passages open at one time, and at another closed by a brick wall. The result was, that the average consumption with the apparatus at work, was 276lb per hour, and with the air passages effectually closed, 308lb per hour; showing a difference of 32 lb per hour in favour of Mr. Williams's plan, or a saving of rather more than 10 per cent. The report stated, in conclusion, that there could not be the slightest doubt about the practicability of abating the nuisance of smoke so much complained of in this and other districts.

The reading of the report of the committee, and the explanations of the different plans of consuming fuel which followed, gave rise to a very long discussion, of which we only present a few of the leading points to our readers.

Mr. C. W. Williams said, that, in considering the questions of the most economical combustion of fuel, and the prevention of smoke, it would be well to discard all consideration of the boiler, and the generation of steam, which were apt to introduce complexity and uncertainty into the inquiry. The question first to be considered was, how the most perfect combustion could be attained; how, from a given quantity of fuel, the greatest quantity of water and carbonic acid could be produced, and the public nuisance of smoke could be best abated. The application of the heat obtained to a boiler with the view of evaporating the greatest quantity of water was a separate question, and should have an entirely separate consideration. With respect to perfect and imperfect combustion, he thought the whole subject was explained by the little instrument he held in his hand (a short piece of copper gas tubing, with an argand burner at one end). Supposing a stream of gas to pass through the tube, if he took off the burner, and set fire to the gas, there was imperfect combustion, and a large emission of smoke; if he put on the burner, so as to cause the gas to issue in a thin sheet, and thus receive an abundant supply of oxygen, there was a perfect combustion and an entire absence of smoke. He thought that patentees who came forward to ask the public to patronise their inventions should, like himself, explain the mode of their operation; and he would beg to ask Mr. Juckes what was the chemical operation of the plan which he had submitted.—Mr. Juckes said he was no chemist: he could only refer to the results of his patent.-Mr. Williams said he doubted whether mere experimental results could be at all satisfactory. He

believed there was not one of the plans for preventing smoke, which had been submitted to the public, that would not answer the purpose when it was carefully worked; and, as to the saving of fuel, the difference between a dry and a moist day, between large coal and small, between judicious and injudicious firing, would easily make a difference of ten or fifteen per cent. in the consumption. Mr. West, of Leeds, said that the great point for consideration was the prevention of the public nuisance arising from smoke: he had recently paid great attention to this subject; he had seen nine plans for effecting it in actual and successful operation; he was perfectly satisfied, that, by the adoption of any one of them, nine-tenths, if not ninety-nine-hundreths, of the smoke now made might be prevented, to the great advantage of the owners of steam-engines, as well as of the public.-Mr. Henry Houldsworth said that, for six months past he had practical experience of the working of Mr. Williams's patent, which he had applied to six different furnaces; and he could now say confidently, from the results of that experience, that without any particular trouble or care of management, it would prevent, at the very least, three-fourths of the smoke which was now made. He did not doubt that other inventions might be equally effectual when they were carefully managed; but he preferred Mr. Williams's, because of its extreme simplicity, depending as it did solely on the admission of air in a proper manner, without any of those mechanical contrivances, worked by some moving power, which many other plans contained. There was one fact connected with Mr. Williams's patent, which he considered of some importance, which he would communicate to the section. He had that morning fitted up a contrivance for ascertaining the comparative temperature of flues under different circumstances, which had not previously been very satisfactorily ascertained. Mr. Williams had used a thermometer, inserted in a bar of iron, which was placed in a flue; but he (Mr. Houldsworth) was not satisfied with that plan, and had passed a copper wire through the flue from one end to the other. This was kept in a state of tension by a weight, and by its expansion or contraction, acted upon an index, which would give a very correct measure of the relative temperature. He had tried some experiments with it that morning, and had obtained very striking and important results. It had generally been supposed, that, when there was a perfectly red fire in the furnace, and when no smoke was generated, the admission of cold air at the bridge would do harm instead of good, by reducing the temperature in the flues. He had, however, tried the experiment that morning. After having the air passages closed for some time, he had opened them when the coals on the fire were perfectly charred, and found an immediate and decided increase of temperature in the flue. The increase of temperature was certainly most striking if the air passages were opened shortly after a large quantity of fresh fuel had been put on ; but at all times he found there was an increase when the air was admitted,

seen.

and a decrease when it was excluded. If any members of the association would do him the favour to call at his works, he should have great pleasure in showing the apparatus and its working.Mr. Williams said, he was exceedingly glad to hear of Mr. Houldsworth's invention: a good pyrometer was very much wanted.-In answer to a question from Mr. E. Corbett, Mr. Houldsworth stated that, in one experiment, about three cwt. of coals were thrown upon the fire at once, so as to produce a thick black smoke; when the air passages were closed, that smoke was immediately dissipated by opening them, and the temperature rose rapidly. On closing them again, the smoke returned, and the temperature as rapidly declined. -Mr. Taylor (the treasurer of the association) said, the subject before the section was undoubtedly of great importance to the manufacturers of this district; for they had already heard from Mr. Fairbairn, that, whilst the average consumption of ten engines in Manchester was 10 lb of coal per horse power, per hour, the average consumption in the Cornish engines was only 24lb, so that they did as much work with one pound of coal as a Manchester manufacturer did with four pounds; and at the same time they made very little smoke. In the parish of Warnup, with which he was connected, there were twenty-five engines, all of very large power, from the chimneys of which very little smoke would be He did not know that they adopted any contrivance for the prevention of smoke, beyond that of admitting air at the bridge: but they gave plenty of furnace room and plenty of boiler room, and made a rule of keeping their fires bright, and of cokeing all their coal in the front of the furnace. The great source of their superiority was, however, in his opinion, to be found in the fact, that as the engines were all employed in pumping water, it was exceedingly easy to ascertain the amount of work which each engine performed with a given quantity of coal. This was invariably recorded and published, and it produced great emulation amongst the enginemakers, the proprietors, and the workmen, each of whom was ashamed of being outdone by his neighbour; and from their joint care and exertions, and most especially from those of the workmen employed, resulted that extraordinary economy of which the section had just heard.-Mr. Richard Roberts said he quite agreed with Mr. Taylor, that with due care on the part of the fireman, a sufficient area of grate, and sufficient boiler room, smoke might be prevented without resorting to any particular contrivances.-After some further discussion, in which Mr. Edmund Ashworth, Mr. Webbe Hall, Mr. Joshua Milne, and other gentlemen took part, Mr. Jeremiah Garnett said, he could not permit the discussion to close without directing attention to one fact, namely, that although they had a variety of opinions about the best mode of preventing smoke, no one among the many scientific men and manufacturers present intimated the slightest doubt that smoke might be prevented, and the nuisance which so greviously affected Manchester and its neigh

bourhood, if not entirely removed, might be exceedingly diminished. If, therefore, parties working steam-engines would neither consult their own interests nor consider the public welfare, he trusted the legislature would interfere and compel them. There was one point adverted to by Mr. Taylor and Mr. Roberts, on which he would say a few words, as it might do harm out of doors. They had mentioned an abundance of grate and boiler room, as a means of preventing the nuisance of smoke, and no doubt it was so. But there was a danger that parties who were deficient in those respects might plead that deficiency as an excuse for continuing the nuisance. It was therefore necessary to remind the section, that, though desirable, an abundance of grate and boiler room was not necessary to the prevention of smoke. He knew from Mr. Houldsworth, that the very successful experiments made by him were made upon engines which were very limited in those respects. What had been done by Mr. Houldsworth could be done by any other parties; and, therefore, those who continued to poison their neighbours with smoke were without excuse.

The section was then adjourned to the following day.

(To be continued).

Voltaic Pile of Plate Iron. By M. WÖHLER.*

PROFESSOR POGGENDORFF has shown that the expensive platinum plates in Grove's Battery, may be substituted by plates of iron, without much diminution of power: and the subsequent researches of Wöhler and Weber have shown that plates of iron may also substitute the plates of amalgamated zinc. These philosophers thought that iron in the concentrated nitric acid would operate with iron in the diluted sulphuric acid as the platinum to the amalgamated zinc in the original battery of Grove. It is said that this view of the action has been verified by means of a pile constructed with iron and these two liquids; which the projectors have found to possess great power; a circumstance of great interest, whether viewed with reference to the theory of the voltaic pile in general, or to the voltaic action of iron in particular. Every one will now be able to make a voltaic pile, of great power and constant action, at a trifling expense it being only necessary to procure a few curved plates of iron and porous earthen cylinders. The concentrated nitric acid is the only article of much expense.

The plates should be cut from strong unoxidized iron, bent into cylindrical forms, and those of each pair united by a metallic strip. The smaller cylinder is placed in an earthen pot containing the nitric acid; and the larger iron cylinder is placed in a glass goblet containing diluted sulphuric acid, in the centre of which is also placed

• Extract from Liebig's Journal.

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