tinuous; but it is the continuous effort of one man, and against the tempest and the surge the boat stirs not a foot from the shore. But change the plan of operation; adopt the aggregate and concentrated plan, instead of the separate and continuous. Let the ten men pull all at once, and the boat bounds over the wave and makes head against the storm; a pause for a moment ensues after the first stroke, and the tempest seems likely to drive back the boat; but after a brief interval, another pull-'a long pull, a strong pull, and a pull altogether,' (the principle has become a proverb,) the boat again springs forward with quickened speed; its own momentum now keeps it moving during the intervals of the strokes, and by the united and repeated efforts of the ten rowers judiciously applied, finally reaches its destination. "No single and separate efforts of the ten men, however rapidly applied, in succession, one after the other, could have accomplished the object. And in what does the continuous splashing of the ten floats of the paddle wheel during every stroke of the engine-in what does this differ from the disjointed and separate efforts of the ten men in the life boat? The ordinary paddle wheel distributes the power of the engine equally over the whole circumference of the paddle wheel, say 100 feet. I propose to concentrate the whole power of the engine into a strong pall of ten or twelve feet, wherein the reserve power is accumulating for the next stroke."-p. 33. Mr. Booth proceeds, in the second place, to explain how he would accumulate or store up the power not made use of during the nine-tenths of the stroke when his propeller is inactive, and give it out when wanted in aid of the efficient tenth. The following is the plan which he proposes for this purpose: "Q, Fig. 1, is a pneumatic cylinder, closed at each end. The stroke of the piston will be to the same extent as the motion of the upper end of the upright lever L to which the piston is attached by a chain and wheel, as shown in figure 1, or other efficient mode of connexion. The reserve power is brought into action as follows:-The cylinder Q is to be filled with air more or less compressed by a small force pump. If the stroke of the pneumatic piston is 2 feet 6 inches, the length of the cylinder space should be 5 feet. When the piston is at the bottom, the air must be forced into the cylinder, to the density, I will suppose, of 100 lbs. per square inch (the exact amount of compression to be at the option of the engineer). As the cam wheel, No. 2, moves the propellers slowly back with the valve plates open, the pneumatic piston will be slowly raised, and when the stroke is finished, the area above the piston will be diminished one-half, and the density of the compressed air will consequently be double, or 200 lbs. per inch, which, on the return of the upright lever L will powerfully assist the steam-engine or principal moving power in effecting the forward or main stroke of the propeller. If found desirable a small portion of air may be admitted underneath the pneumatic piston, which, being compressed on its descent, will act as an air cushion, to prevent any shock at the end of the stroke. The diameter of the pneumatic cylinder as well as the degree of compression on the air, must be left to the judgment of the constructing engineers. In the drawing (figure 1) the cam of the wheel No. 1 is represented in the position of having just completed its action on the lever L, and propeller P in the principal movement propelling the vessel forward; and the cam of wheel No. 2, just about to commence the slow backward movement by which the reserved power is raised, and the levers or propellers quietly brought back and placed in position for the next effective stroke."p. 27. Mr. Booth calculates that the gain which may be effected by this double concentration of power is actually as ten to one! "We will suppose that it is desired to make the forward stroke of the propeller equal to the pull of a thousand horse. If the concentration be ten-fold, a steam-engine of a hundred horse power should suffice; or, to cover extra friction, &c., say, 200 horse may be required. The pneumatic cylinder and cam wheels will effect the rest. A cylinder 3 feet diameter with a stroke of 2-6 and charged with air at 100 lbs. per inch pressure, and slowly compressed into about onehalf its bulk, would answer the purpose."p. 40. Mr. Booth anticipates that people may wonder how he is to get a valve plate or paddle-board large enough to act as a fulcrum to his thousand horse pull or lever; but he gives the following reasons for believing that one of corresponding dimensions will not be at all required; that, in fact, a very small" one will answer every purpose. "I will admit that in the proposed scheme it will be desirable to have valve plates large enough to meet a far greater resistance in the water during the main stroke of the propeller, than the resistance at present offered to the paddle wheel during the same extent of motion. But a small valve plate or paddle board will accomplish this object. I shall suppose that on the proposed plan the pad dle board will be three times as deep in the water as the floats of the ordinary paddle wheel. By the law of hydrostatics, this condition would give five times the power to the water as a fulcrum of resistance, which is its proper function in relation to the paddle board. Consequently a paddle board of three square feet area would be as efficient at the increased depth as one 15 feet arca at the lesser depth; but that is not all. The vibrating propeller may, in its principal movement, be made to move twice as fast as the paddle wheel, which will increase the efficiency again of the fulcrum probably two-fold additional, making the 15 feet equal to 30. I think there need be little apprehension, therefore, respecting a very small valve plate being sufficient to give out the requisite power, the comparison being between deep water and high velocity in the valve plates, and shallow water and a slower motion in the ordinary paddle boards.”—p. 41. Assuming that Mr. Booth is right in his new theory of concentration, and the new practice which he seeks to found upon it, this grand practical result would follow, that the whole marine steam power of the country might be at once multiplied tenfold; or, to make allowance, as he says, for such matters as "extra friction, &c.," say fivefold. Every vessel of 100-horses power might at once be converted into one of 500, and the Penelope, of 650, now on the stocks, might have her unparalleled magnitude increased to the prodigious amount of 3250-horses power! You have but to adopt Mr. Booth's reciprocating valve propellers, cam wheels, and pneumatic cylinders, and behold the prodigy achieved! But can such things really be? Can the true principles of steam navigation have remained so long hidden from the anxious scrutiny of the many eminent men who have devoted themselves to their elucidation, that it should have been reserved to Mr. Booth to pour, all at once, such a flood of light upon them? Mr. Booth who knows so little of the science of his own particular business, railway transit, as to suppose that double power, double speed, is the rule by which it is regulated? However possible, it is assuredly not very probable. We do not hesitate to state our own strong impression to be, that the whole affair is a delusion-very ingeniously conceived, and most skilfully and plausibly advocatedbut still a delusion. We have not left ourselves room to refute in detail Mr. Booth's various positions, but we shall add a few general observations, which may serve to indicate the grounds on which we rest our opinion. The concentration of effort which Mr. Booth proposes to accomplish by his reciprocating-valve propeller, though treated by him as something quite new, is no more than has been tried to be accomplished many times before; it is the object of all the feathering paddle-wheels which have ever been invented; and the object also of every sort of wheel in which it is endeavoured to place the floats so that they shall only act against the water when they can act with advantage. A paddlewheel, the floats of which act only during the front half of each revolution, is just as good an example of intermitted action, as the case of the boat with its ten rowers, so much dwelt upon by Mr. Booth. The paddles, it is true, act one after the other, while the rowers act all together, but the difference in time between the two operations is so extremely small, as, in all probability, to reduce them, in point of efficiency, to a very near equality. Between the single reciprocating propeller of Mr. Booth, however, and the boat with its ten rowers, there is really no analogy whatever. Mr. Booth proposes to do by one stroke what the rowers do by ten, and he talks as confidently of doing it as if it were a thing of the greatest ease imaginable, whereas, in point of fact, it would be found just as difficult to throw the power of a thousand horses into one pull, as for ten men to apply their hands to one oar. Numerous experiments, of unimpeachable authority are on record, which show that it is impracticable to obtain from one arm or propeller the same degree of velocity which is obtainable from a number. What the best numbers are, according to different circumstances, such as area of floats, power applied, &c., may not have been ascertained with perfect exactness; but there has been enough, at all events, determined, to justify us in pronouncing Mr. Booth's single propeller to be altogether out of the question. Nor do we think he will mend his case much, either by the greater depth or the greater velocity which he proposes to give to his propeller, (on the former of which points he evinces some strange notions,) since that would still leave the distribution of force as it was before, and it is there, the fallacy of his system appears to us chiefly to rest. ON MR. HOULDSWORTH'S PYROMETER-BY C. W. WILLIAMS, ESQ. Sir, I have now to lay before your readers the results obtained from one of the simplest, yet most valuable adjuncts to a furnace that has yet been applied. So vague have been our modes of testing the comparative values of what are ignorantly called "Smoke Burning" Plans, that, (probably from the want of something practically more efficient,) we seem to have quite overlooked the object of which we are in search. Having adopted the boiler, with all its varieties and imperfections, and its fluctuating power of evaporation, as the instrument for testing the heating powers of the various descriptions of coal, or the efficiency of the several modes of constructing and managing our furnaces; we thus take one, and a very imperfect class of vessels, mechanically considered, as an index of the efficiency of a wholly different class, chemically considered. seems to be dependent on no better ground than that, practically speaking, we have none other. This may be admitted as a reason for its adoption, but can be none for its justification, or for our apathy in searching for a more trustworthy one. In treating of combustion, as regards the use of coal, our object manifestly is, to discover the best construction, arrangement and management, of a furnace towards obtaining the greatest quantity of heat from any given quantity of the fuel. Instead of endeavouring to ascertain this measure of heat in the furnace, or flues leading from it, we inconsiderately apply ourselves to measuring the quantity of water evaporated from the boiler placed over such furnace; and this without the slightest reference to the good or bad faculty of such boiler, in absorbing and applying the heat, or even endeavouring to ascertain whether more or less heat is so absorbed, or how much is lost by the chimney shaft. Thus, instead of applying ourselves directly to the object of our enquiry, we refer to a class of secondary, and manifestly uncertain data. So prevalent, indeed, is this mode of testing the heating properties of different kinds of coal, or arrangements of the furnace, in promoting combustion, by reference to the quantity of water evaporated by the boiler, that we fall into this erroneous practice, and yield ourselves up to a fallacious mode of reasoning and experimenting, which would not for a moment be sanctioned in any other mechanical or scientific pursuit. This most fallacious test of the chemical process of combustion by reference to the mechanical process of evaporation, I am now, however, enabled to state, that there is a simple and direct mode of obtaining the desired results, and of testing the boiler and the furnace by reference to their respective functions and modes of action. Let it be understood, that in testing the value of any mode of constructing or managing a furnace, and particularly as regards the admission of air to the fuel in effecting the most perfect combustion, our object is to ascertain by which method we obtain or generate the largest measure of heat-leaving it to another, and different class of experiments, as to the best means of applying such heat. In a communication made by me at the Victoria Gallery, Manchester, and to the Mechanical Section of the British Association, I stated, that in pursuing the enquiry, on the large scale, as regards combustion, and the modes of producing the greatest quantity of heat from any given weight of coal, I found it absolutely necessary to discard the boiler in toto-that the uncertainty which exists as to the evaporative powers of the various kinds of boilers in use was such, that no reliance could be placed on the results obtained through their means. I asked what test, rationally and mechanically considered, can boilers, with their peculiar and variable faculties of absorbing heat and generating steam, furnish, towards ascertaining the proportion of the furnaces in generating heat, or the various descriptions of coals in their combustible proportions? And who can determine how much of the heat generated does this or that kind of boiler absorb or apply? My eyes were thus opened to the defective mode of obtaining results, by applying the evaporative economy of a boiler, as a test of the heat-generating power of any kind of coal or mode of managing the furnace. I found a large evaporative economy from one kind of boiler, when combustion was manifestly imperfect in the furnace, and a great deficiency of evaporation in another, where combustion was nevertheless complete, and a much larger measure of heat ob MR. HENRY HOULDSWORTH'S THERMOMETRIC DIAGRAM, SHOWING THE FLUCTUATIONS OF TEMPERATURE IN THE FLUES OF A BOILER, ON THE NEW AND OLD SYSTEM. Scale of Temperature in Degrees. tained from the fuel. I saw, in fact, that the error lay with the boiler, and was forced to the conclusion, that in treating experimentally of the furnace and its management, particularly as regards the admission of air, the furnace alone, and its heat-generative powers, must be tested, and apart from the boiler. How then was this heat-generative economy to be ascertained? I suggested three modes. 1. By means of thermometric bars, the heat being conveyed to the thermometer by the conducting power of the metallic bar. 2d. By the use of a series of metallic alloys, introduced into the flues, and which, being fusible at varying and ascertained temperatures, would indicate the temperature existing in the flue. 3d. By means of a pyrometer constructed of a number of metallic bars, united by a system of compound levers, the expansive power of the bars being transferred to an index placed outside the boilers. These several modes of ascertaining the internal heat in the flues had their inconveniences, on which I need not here dwell. At the late Meeting of the British Association in Manchester, Mr. Henry Houldsworth described his very simple and useful Pyrometer. He is reported to have said (see the last number of the Mechanics' Magazine, page 32,) that "he had that morning fitted up a contrivance for ascertaining the comparative temperature of the flues under different circumstances which had not previously been very satisfactorily ascertained. Mr. Williams had used a thermometer, inserted in a bar of iron," (copper,) "which was placed in the 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 weights, and by its expansion or contraction acted upon an index, which gave a very correct measure of the relative temperature. He had tried some experiments with it, and had obtained very satisfactory results." At a subsequent Meeting of the Association, Mr. Houldsworth said, that, "Since the discussion on this subject he had made some careful experiments with the Pyrometer which he then described; and the results were, in his judgment, exceedingly satisfactory and conclusive. These experiments were made upon a furnace fitted up according to Mr. Williams's patent, by putting three cwt. of coal upon the fire two different times, the fire being each time in the same state, and the temperature of the flue, as indicated by the Pyrometer, being in each case about 700 degrees. On one occasion, the air passages were left open, in the other they were closed; in each case the experiment was continued for 100 minutes. In the experiment in which the passages were left open, the average temperature of the flue was about 1,100 degrees; in that in which the passages were closed, and Mr. Williams's apparatus thrown out of use, the temperature averaged only about 900 degrees. During the whole time of the former experiment, there was an entire absence of smoke; during great part of the latter, the flues were filled with smoke. Mr. Houldsworth exhibited a diagram, showing in a very striking manner, the results of his experiments." I now send you a copy of the diagram exhibited by Mr. Houldsworth on this occasion. (See preceding page.) So sensible was this pyrometer, that it registered the degree of cold produced by the mere act of opening the fire door. Mr. Houldsworth also stated, that he tested the effect of admitting or excluding the air every five minutes, and on each occasion the lowering of temperature in the flue by closing the air aperture was rapidly indicated by the Pyrometer. A remarkable proof of the rapidity with which this Pyrometer indicates the change of temperature in the flues, is shown in the diagram. On the charge of 3 cwt. of coal being thrown on the furnace, much carburetted hydrogen gas is of course evolved. If air be so admitted as to effect its combustion, a large flame is instantly produced and a corresponding heat. But if the air be excluded, the gas is converted into sinoke, and the temperature in the flues rises but gradually. These two changes of a sudden elevation of the temperature in the one case, and a slow one in the other, are strikingly marked in the diagram, from the starting point. So again, when, at the end of 75 minutes, as marked on the first experiment, (see the upper line,) when the fuel is levelled on the bars and the air prevented rushing up in too large masses, the temperature rises suddenly, above 100 degrees in about two minutes; |