pumps.This once done and attended to, no algebra, and very little arithmetic, would be wanted to set all contentions at rest.P

I am glad, however, that I have not interfered with the mode of showing the great increase of duty; they are at liberty to generate their steam as cheap as they cans to raise it as high as they choose, and afterwards to allow it to expand to the uttermost point, and at last condense it in any way, being always clothed in their own garments, with all these appliances, if they can prove what they have asserted, it would be a great national benefit, an honour to Cornwall, and I should be satisfied with being the means of causing others to perform a meritorious task. With these sentiments I leave this subject in the hands of those to whom it belongs; and when these proofs are forthcoming, they will of course be published in the Mechanics' Magazine.

Your obedient servant, J. DICKSON, C.E. 9, Charlotte-street, Blackfriars-road, August 5, 1836.

FALLACY OF JONES'S MERCURIAL STEAM

"

WHEEL.

Oh wonders, sure, will never cease, While works of art do so increase." Song-THE STEAM ARM. Sir, I have lately commenced taking in your periodical, and from the excellent articles I have observed in it, I have regretted that I did not begin at an earlier period. I have particularly noticed the readiness you manifest to give publicity to any remarks on any inventions at all calculated to forward the interests of me. chanical science in the world; and as I apprehend your columns are equally open for strictures upon such inventions when they are not valuable, I have troubled you with a remark or two upon one, I perceive, in your last Number, viz. "Jones's rotary mercurial steam-wheel,” which is stated there to possess sume marvellous advantages over the common steam engine; indeed, I was induced to look at it more closely than I otherwise should have done, by observing towards" the end of the article the startling assertion (startling, at least, as I think it must be to all who have been accustomed to take the acknowledged rules of me-chanics as their guide), that this wonderful discovery completely overturns the old and absurd notion, that to produce a

certain effect an equal power must be applied in some shape or other; or, as Mr. Jones expresses it, "if we wish to raise five tons at one end of the beam, a corresponding pressure must be made on the other end or pistou ;" and this notion, I say, has been completely exploded; for now we have only to raise 112lbs. to increase the mechanical effect nearly sixteen times.

Surely, Mr. Editor, this invention must put to the blush all the paltry little improvements which have been made in steam-engines heretofore; and Messrs. Watt, Trevithick, Murray, Maudslay 66 cum multis aliis" with their contemptible 25, 50, or 75 per cent. saving," may now hide their diminished heads, and own themselves out-shone by the resplendent lustre of this new light in mechanical science. Why, even the perpetual motion, that great ignis fatuus of mechanists, has at last been overtaken and fairly run down by "Mr. Jones's rotary steam-wheel;" for it is evident, that if we apply two or three of the "sixteen times power gained" to "raise the 112lbs.," we shall have the remainder at our own disposal "to have and to hold for ever," or at least "so long as the machine" endureth."

And, sir, can sufficient be said in praise of the philanthropic discoverer of this great" wheel of fortune," who, instead of aggrandising himself by patenting his invention, generously throws it open "pro bono publico ?"-ought he not to be classed with Howard and other individuals who have disinterestedly devoted their time and talents to the public weal, and to have his memory immortalised by a monument (surmounted, I would say, with a figure of Mercury,) in Westminster Abbey ?

But, Mr. Editor, lest these honours should be surreptitiously obtained, it may be worth while to inquire whether "Jones's rotary mercurial steam-wheel do in reality possess such surprising properties as those attributed to it;-I think upon investigation we shall find that it does not-and that in point of fact, it falls woefully behind even the common engine of the old construction. We will pass over the merits or demerits of the steam-wheel as a machine, and suppose it in action, in order that we may examine the calculation of its effect. And here I would observe, that Mr. Jones has committed two great errors; first, in sup

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not have so great effect to turn the spin. dle O, as if it were constantly acting for the same length of length at the point A. (To illustrate this latter case, the circle in the figure may be supposed a pulley, over which a cord passes, having a weight hung at its extremity, the weight descending through a space equal to the length of the arc ABC-see the dotted lines.) The force, on the contrary, must be continually diminishing, as the versed sine of the arc passed through increases, and the real measure of such power will be obtained by considering the weight to have moved through a space equal to OC or AD; for as gravity is the motivepower, the distance traversed in a vertical direction is all that can be estimated as effective, and not the whole length of the are, as given by Mr. Jones. The real effect, therefore, will be 1121bs.-moved

Then, secondly, the space through which the weight is raised ought to have been taken into consideration in estimat ing the effect of the wheel. Mr. Jones has stated his calculation in so compli cated a manner as to render it a complete mystification (which, by-the-bye, Mr. Editor, your Mephistophiles has in some degree assisted by making one or two mistakes, as 1.1416 for 3·1416, and 1,780 feet for 1,780lbs). He certainly introduces something about 7 feet-112 fa thoms, 672 feet-864 revolutions, and a number of other figures, which do not seem to have any thing to do with the subject in question; but from all this he deduces (in a manner which he does not explain) an inference, which is, that a cubic foot of steam will raise 445lbs. True, and so it might be made to lift 445,000lbs., but how high? His 445lbs. (as far as I can make out the calculation) is not raised 672 feet, nor 7 feet, nor even 1 foot, but only about 9.4 inches! being the circumference of the axle 3 inches diameter. This ought to have been noticed, otherwise Mr. Jones might increase the power of his or any other wheel ad infinitum by merely diminishing the diameter of the axle; but it is one of the first principles in mechanics, that nothing is in reality gained in that way, as although a greater weight may be raised on the smaller axle by a given power, the said power must pass through a proportionately greater space in raising it, or, as the adage says, "What is gained in power is lost in time"the momentum (or force X space passed through) of the power raising being always equal to that of the weight raised.

Let us now try if we cannot find out the power of the steam-wheel in a more simple way, and we will take the data furnished by Mr. Jones himself, viz. the wheel 4 feet diameter, each vessel to be of the capacity of 1 cubic foot, and 112lbs. of mercury to be used; we will also supply something he has omitted, viz. the pressure of the steam, which, as the mercury is to be raised something above 2 feet vertical height, must be at least 14 or 15lbs. effective force per square inch, say 14lbs. Mr. Jones has nobly allowed 12lbs. (!!) for the friction of his machine; but we will go further, and, in order to give him the full benefit

of his invention, suppose no friction at all.

We have seen a little way back, that the effect produced by one quarter of a revolution of the wheel (or the action of one arm) is equal to raising 112ths. through 2 feet; and as 1 cubic foot of steam is consumed in the operation, the mechanical effect of the said foot of steam in this wheel will be represented by 112 x 2 = 224. Now, let us see what the same quantity of steam of equal pressure will do in the common engine, constructed according to the principle of “making a corresponding pressure on one end of the beam to raise a certain weight at the other." Suppose a cylinder 144 inches area, and let the piston move through a space of 12 inches, this will evidently consume 1 cubic foot of steam; and multiplying the area by the pressure per square inch, we have 144 X 14 2016lbs. raised 1 foot, for its effect in the " present engine" being 9 times as much as in the "rotary mercurial steam-wheel."

of

I think, Mr. Editor, this result will be sufficient to dispose of the invention (and I very much doubt whether it will ever be disposed of in any other way), without saying any thing of its mechanical defects; but I would recommend Mr. Jones, if he wishes to apply the power steam in conjunction with the action of a heavier fluid, to look at a wheel for that purpose described in either Stuart's or Partington's "History of Steam-Engines" I think the latter-which is a much better thing than his may ever hope to be, but which has not yet superseded the " present engine," nor do I think it ever will do so.

In conclusion, I would warn any unlucky wight," who has got a spirit of mechanical inquiry and speculation," from laying out much money in trying this wheel, as instead of (as he may fondly hope) his advances returning to him sixteen fold-he will most assuredly, sooner or later, find himself in the same predicament as a brother mechanic in Germany, of whom we read in the companion song to the one quoted in our motto, that

"No cash did the artist e'er réquite,
He never got paid-and it served him right."
Your obedient servant,
WILLIAM POLE.

Winsley-street, Aug. 10, 1836.

A NEW THEORY OF THE TIDES. Sir, I have noticed the several articles on the tides in your late Numbers, and cannot help thinking the double diurnal rising of the waters of the ocean may be explained on very simple principles, notwithstanding the apparent difficulty of the subject, and in perfect accordance with the Newtonian theory of universal gravitation and the central forces.

ing idea occurred to me. It is eight or ten years since the followI had not then met with any satisfactory explanation or theory of the tides, and the idea appear ing to my mind so clear, I mentioned it to some of my scientific friends. The notice recently taken of the subject of the tides in your valuable Magazine, has not only recalled that idea to my methory, but has suggested the possibility of making a machine to give ocular demonstration of the double diurnal tide.

For the purpose of literal demonstration, let us suppose that the distance of the earth's centre from the centre of the moon is 240,000 miles, that the diameter of the earth is 8000, and that of the moon 2000 miles, and that they are dense in proportion to their sizes. Then as globes are to each other as the cubes of their diameters, the density of the earth will be sixty-four times that of the moon, and the centre of gravity of both sixty. four times nearer the former than the latter. This point is within the body of earth, or about 3750 miles from its centre. The moon is said to revolve round the earth, in which saying there seems no but for our purpose it is impropriety; necessary to state that, strictly speaking, these two bodies revolve on the above point, which is the centre of gravity both combined. The above numbers are not correct, but they are sufficient for our purpose.

The centrifugal force, created by the revolution of the earth in this small orbit round the combined centre of gravity of the earth and moon, will have a constant tendency to make the earth fly off from that centre, which she would do if it were not for the attraction of the moon acting with equal force in a contrary direction. The earth is therefore between tivo forces, and being partly fluid, the fluid parts are elongated in the direction of these forces. This elongation constitutes the double diurnal lunar tide, which flows in a contrary direction to the diurnal

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motion of the earth on its axis. Now for the solar tides!: v

1 เง

According to the law of universal gravitation, every particle of matter of the terrestrial globe will attract every particle of matter in the lunar globe, and vice versa The attraction between these bodies may be compared to a chain binding them together, every link of which sustains the same strain, for a chain freely suspended between two points cannot have a greater strain at one part than another (barring weight, which in this case it is supposed to be devoid of). The attraction at the moon must therefore be exactly equal to that at the earth, and as the centripetal and centrifugal forces are always equal and contrary, they must produce results on the moon's surface similar to the terrestrial tides, provided that luminary be surrounded with fluids like the earth. Apply this doctrine to the earth as influenced by the sun, and the effect must be a double diurnal solar tide on the earth.

The spring tides are caused by the central forces acting parallel and in unison at the fulls and changes of the moon, and the neap tides by acting at right angles or in opposition to each other at the quarters.

From what I have said it might be supposed we have four diurnal tides, viz.

two solar and two lunar; but this is (not the case, the sun's influence being much smaller than that of the moon, perhaps in the proportion of 1 to 5. The solar tide combining with the lunar, becomes evanescent, and will be best shown by figures as follows:-Supposing the lunar tide at any particular place to rise 15 feet, aid that at the same place the solar tide rises 3 feet, then when the moon is at the full or change, and her attraction acts in conjunction with the sun's, we shall have 15+3 18 feet, or a spring tide; but when the moon is at the quarters and acts e in opposition to the sun, we shall have 15-3 12, or a neap tide.co.n

W 943

ing-breech, which may be fired six times in twenty seconds by only lifting the striker each time. So far it corresponds in principle with the one described in your valuable Magazine (No. 601, vol.

xxin) and of which your correspondent thought himself to be the inventor. This gan was purchased at the sale of an old gentleman's effects in Gloucester many years ago, and he had used it for about half a century. I am informed that it is of Continental manufacture.

Fig. is a longitudinal section of the piece; A is the barrel, which is of brass, with a bore of about three-eighths of an inch B is the stock; c is the breech, about six inches long and two inches and a half diameter, made of brass; into it are drilled seven holes, six round near the ring for containing the charges, and one in the centre bored quite through to allow a kind of arm to the barrel marked h to enter the stock, to which it is fastened by screws. d is the main-spring, which operates on the striker f by means of an offset near its bottom. In firing the breech is turned round one-sixth of its revolution, and consequently one of its six holes, which are previously charged, is brought opposite the barrel every time the striker is raised by means of a small lever projecting from its lower extremity, and coming underneath a small springcatch, as shown in fig. 2, the catch entering a recess in the breech when the striker is falling. e is the hen, or steel; it does not remain up after being struck, as in common guns, but rises a little, and is pressed down again by the spring g. There is a case of sheet brass, about two inches long, shown at 1, fig. 3, with a prime-pan cut in it at top, in which the breech turns air-tight, and by this means the priming is not lost, and a communication prevented between one prime and another, which would be of serious consequence, and a deficiency on this point is, in my opinion, the greatest objection in applying the revolving-breech to cannon, and is, no doubt, the cause of their not coming into general use. I am aware this gun may be greatly improved in detail, but still the principle preserved. I remain, Sir, Your obedient servant, JOHN THOMAS.

Redlak, near Wellington, Salop,

2.72

Aug. 3, 1836.

BRITISH MUSEUM.

We have already noticed the valuable labours of Mr. John Millard in reform- › ing our National Museum, in rendering it worthy of the country, and in extend

ing its public utility. The following petition, presented by the Chancellor of the Exchequer on Saturday last, will, we trust, secure for Mr. Millard that reward which bis incessant and successful exersa tions so well deserve. Palmam qui me-ruit ferat! Many parts of the plan alluded to in the following petition have been recommended for adoption by the: Committee in their recent Report to the House.*

To the Honourable the Commons of the United Kingdom of Great Britain and Ireland in Parliament assembled.

The humble Petition of JOHN MILLARD, of No. 34, Arlington-street, Camden Town.

Showeth,-That your petitioner is the author of a letter to the Right Honourable the Chancellor of the Exchequer, containing a plan for the better management of the British Museum; by the adoption of which your petitioner humbly conceives the public utility of this national establishment would be greatly extended, and the prosperity of our arts and manufactures materially improved.

That your petitioner, with a view thus to adapt the British Museum to the present advanced state of human science and learning, has, for the last three years, at considerable personal sacrifices, devoted the greater part of his time and attention to the collection of information both at home and abroad, which might tend to facilitate the labours of the Committee appointed by your Honourable House to inquire into the condition, management, and affairs of the British Museum; and your petitioner has reason to believe, that, without such aid on his part, the Committee could not have been put into possession of many important facts, the disclosure of which could not fail of producing the most beneficial results to the public.

Your petitioner, therefore, humbly represents these circumstances to your Honourable House, in the hope that your Honourable House will take such notice of his petition as to your Honourable House may seem meet. And your petitioner will ever pray, &c. JOHN MILLARD. July 11, 1836.

SCHOOL OF DESIGN.

Our readers will be gratified to hear that, through the influence of the Chancellor of the Exchequer, a grant of 1500%. has lately passed the House for the establishment of a School of Design for the improvement of our national manufac tures; and the following correspondence

See Mechanics' Magazine, p. 285.