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342

FALLACY OF JONES'S MERCURIAL STEAM-WHEEL.

posing that he would have a power of 112lbs. constantly acting at the horizontal extremity of his wheel; and secondly, in not taking into calculation the space through which his weight is raised, when he estimates the useful effect of his machine. These points, I think, will require very little explanation. With regard to the first, it must be evident that if a weight descend through the quadrantal arc of a circle, in the direction of A B C, it will

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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 arc, as given by Mr. Jones. The real effect, therefore, will be 112lbs.-moved

through two feet for each arm of the wheel-supposing it to be four feet dia

meter.

Then, secondly, the space through which the weight is raised ought to have been taken into consideration in estimating the effect of the wheel. Mr. Jones has stated his calculation in so complicated 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 fathoms, 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

A NEW THEORY OF THE TIDES.

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 112lbs. through 2 feet; and as 1 cubic foot of steam is consumed in the operation, the mechanical effect of the said foot of

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steam in this wheel will be represented by 112 × 2224. 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 142016lbs. raised 1 foot, for its effect in the "present engine" being 9 times as much as in the " rotary mercurial

steam-wheel."

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 of 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 requite,

He never got paid—and it served him right.”
Your obedient servant,
WILLIAM POLE.

Winsley-street, Aug. 10, 1836.

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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.

It is eight or ten years since the follow. ing idea occurred to me. I had not then met with any satisfactory explanation or theory of the tides, and the idea appearing 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 memory, but has suggested the possibility of making a machine to give ocular demonstra tion 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 sixtyfour 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 impropriety; but for our purpose it is 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 two 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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ANCIENT GUN WITH REVOLVING BREECH.

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

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 hodies 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, nd 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; bat when the moon is at the quarters and acts in opposition to the sun, we shall have 15-312, or a neap tide.

Should the machine I have planned answer the purpose of ocular demonstration agreeable to what has been stated, you will hear from me again. I shall proceed to have it made and tried forthwith, and if it should appear worthy of being introduced into the schools of education, I will manufacture it for that purpose.

I have endeavoured to be as concise as possible, which is consistent both with your pages and my avocations.

I am, &c.

ALEX. CLARK, Engineer.

7, Nelson Terrace, City-road, London, August 5, 1836.

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BRITISH MUSEUM.

xxii.) and of which your correspondent thought himself to be the inventor. This gun 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. 1 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 I, 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,

Aug. 3, 1836.

BRITISH MUSEUM.

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

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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 his incessant and successful exertions so well deserve. Palmam qui meruit 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 15007. 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.

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which has lately taken place will explain the views of the Government on the subject:

"Office of Committee of Privy Council for Trade, Whitehall, July 11, 1836. "Sir,-The attention of the Lords of the Committee of Privy Council for Trade has, for some time, been directed to the propriety of establishing in this country a School of Design in the arts connected with our manufactures. It has been, in some degree, a subject of reproach to this country, that although its manufactures have, in so many respects, excelled those of others, yet that in the beauty of design they are often inferior. This defect has been, in some measure, removed by the rivalry which the competition with foreigners has naturally excited. But from this class of art having been neglected, the progress of improvement has been less rapid, especially in the silk manufacture, than is to be desired; a fact which is chiefly to be attributed to the difficulty of obtaining suitable instruction in the principles of design and colouring, in relation to objects of manufacturing art. In consequence, their Lordships are informed, the supply of pattern designs for the use of the manufacturer would be very inadequate, if our artists did not copy the designs from articles of foreign manufacture, a practice which may be necessary as a substitute for original talent, but which is to be avoided if possible.

"But it is not only in the art of design, as connected with our manufactures, that we are inferior to some other countries; we are perhaps still more so in those accessaries of the art-viz., in the knowledge of the pictorial effects of colours, and the chemistry which it is necessary that the designer should be acquainted with, in order that he may not employ such as it will not be safe for the manufacturer to adopt.

"Their Lordships have had frequent consultations with numerous parties conversant with this subject, and they have come to the conclusion that it is desirable to establish in this country a Normal school of design, in connexion with a museum, and with provision for a scheme of lectures which shall embrace the art of colouring, and the chemistry of colours. They have many reasons to think that private subscriptions will be raised, in order to extend, and ultimately, perhaps, almost entirely to support, such an establishment; but, in the first instance, they consider that it will be necessary to apply to Parliament for assistance, in order to give the undertaking a more national character, as well as to cover the extraordinary expenses which must attend its first formation. They, therefore, submit to the Lords

of the Treasury their request that the sum of 15007. may be applied for to Parliament in this year.

"The manner of carrying the plan into effect, their Lordships propose to intrust to a body of persons of competent judgment in the arts, subject to such regulations as their Lordships may think most proper to impose, for the due administration of the grant which may be made out of the public revenue.

The

"Their Lordships are of opinion that the establishment of the proposed school should consist of the Curator or Director, and two masters, with one or more attendants. duty of the Curator will be to select proper objects for the museum, and to submit estimates of the expense to the Lords of the Committee of Privy Council for Trade to take charge of such objects, whether purchased or presented, and, above all, to give, at stated periods, by way of lecture, instruction on the specimens to the scholars generally, to which lectures the public shall have the right of admission on paying a small fee. "The two masters should be of a different order of attainments, and employed accordingly.

"It is proposed to divide the school into four classes, of two of which the initiatory teacher should have the charge, the principal teacher having the charge of the others.

"The classes of the initiatory teacher will be,

"1st. Of drawing in outline perspective, and drawing-board practice.

"2nd. Of the same, with the addition of light and shade.

"The classes of the principal teacher will be,

"3rd. Of the above, with the addition of water and body colour.

"4th. Of composition and imaginative design generally.

"It is supposed that the scholars who will apply for admission in the first instance will draw moderately well, and that of them there will be a sufficient number to make at once a class of each description.

"But it may be necessary, in addition to the above provision of two teachers, to provide for the appointment of a lecturer, occasional or otherwise, to give special instruction in the chemistry of colours, as well as other necessary arts.

"The amount of the grant at first, though it may not be required for the remuneration of teachers on the scale of the Institution in its complete state, should be on that scale, as at the outset the outlay upon articles for the Museum will be considerable.

"It should be supplied with a proper collection of books, with casts of the best ornamental works, and a collection of accurate

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