dential advice, in all cases of difficulty, of those men of science who are most competent to decide upon them, and finally to promote, by an active and extensive agency, the introduction into general use of every patent or other invention and improvement which they shall be the means of bringing forward.

It must be obvious, that an association like this can never be influenced by any of those motives which occasionally tempt individuals to defraud those whom they pretend to assist and patronize. It must depend for its prosperity on attaining and upholding such a character for honour and liberality, that all may, without the slightest hesitation, entrust it with the most candid disclosure of their designs, in the perfect assurance, that if these designs merit support, they will obtain it to the fullest extent.

The Society will depend for its remuneration entirely on the success of each plan in the prosecution of which it may embark; it will expect no indemnity in case of failure, and stipulate only, that when an inventor begins, through their agency, to derive profit from his invention, he shall make a suitable return for the benefit he has received.

As the Society, however, is established equally with a view to public as private good, it is proposed, that as soon as the dividends to the shareholders exceed eight per cent., they shall be limited to one-half of the further profits, and that the other half shall be devoted, in the first place, to the establishment of a National Museum of Machines and Models, and next to the promotion of scientific knowledge among those classes engaged in our arts and manufactures.

In order that mechanics, who are likely to contribute most to the business of the Society, may be still further participators in its profits, it is proposed to call for the capital required by instalments, so moderate in amount, and on such long notices, that even persons of very humble means may find it an eligible medium for the investment of their savings. It is intended that not more

173

From the sketch which has been now given of the objects of the Society for the Encouragement of Inventions, it will be seen that it will interfere with the interests of no class of persons, and ought therefore to excite the jealousy of none. It will supply exactly what has been long much wanted, and what will be alike beneficial to all: to the ingenious and industrious mechanic, whose only impediment is his poverty, it will afford all the advantages of a large capital and powerful connexion; to the gentleman of scientific or mechanical pursuits it will furnish facilities which few can at present command; while the public at large will be essentially benefitted by a combination of these advantages, since it will bring to an earlier maturity the fruits of genius, and every improvement in the arts will be more rapidly followed by an increase of production. It will, in short, become the connecting link between genius and fortune.

STEAM ENGINE,

SIR-Among the various improvements which have marked the progress of scientific information in the United Kingdom, none are more calculated to fix the attention of the British public, or to excite that spirit of inquiry which necessarily precedes and accompanies all speculative projects, than that powerful facilitator of commercial intercourse, the Steam Engine, when applied to the purposes of navigation.

That this spirit of inquiry has been most successfully directed to that important branch of our national enterprise, is strikingly apparent in the rapid advancement towards perfection which has been made in that almost "all-powerful" machine.

Surely, then, it must have been a subject of regret with others, as well as myself, that the application of this extraordinary power should not have

succession of them) is graduated through the whole are, 90 degrees excepted, that, being the only point at

the

allude particularly to the adoption of paddle-wheels, as the mode by which the propelling force of steam vessels is applied.

That the process of rowing originally suggested the idea, and that the paddle-wheel, by its rotatory motion, and consequent facility of application, should have appeared and been adopted in the first instance, as not only the most simple, but the closest and most effective copy of that process, I can readily imagine; but that it really is a close and effective copy, I shall endeavour, in the briefest manner I can, to disprove.

For example, suppose the paddlewheels to be 15 feet in diameter, three of which are immersed in water (and, I believe, they are often much more than that), each float, at the time it strikes the surface, would be at the angle of 34 degrees, and from thence to 44, it must necessarily act upon the vessel more as a lifting than a propelling power. At 45 the force is equal; from 45 to 134, therefore, are the only degrees through which the propelling power predominates. At 135, in rising, it is again equal; from thence, until it leaves the water, at 146, its tendency must be to depress the vessel aft; and although the resistance becomes less as the float ascends towards the surface, yet a considerable power is required to overcome that resistance, which does not contribute its share to the progress of the ship

"

It may be objected, that as the lifting and depressing power predominates only in 20 out of 110 degrees, through which the floats pass, and that the principal force through the remaining 90 degrees is a propelling one, the balance must be strongly in favour of the latter. So it is; yet it will be well to recollect, that this sacrifice of power (independently of the shock which the machinery must sustain when the float first strikes the water, and the deafening roar occasioned by the rapid

Add to this the resistance of the air, which the headway of the ship very much increases, for it is of no use to sing out, Feather your oar, Jack!" and another strong objection to the paddle-wheel will present itself.

Perhaps, by going to extremes, I can give a more decided character to the argument. Suppose, then, the vessel was laden so that the axle of the paddle-wheels was at the water's edge, in that case, the whole lifting and depressing force would be equal to the whole propelling; so that if an engine of twenty-horse power could, on the simple rowing principle, move a vessel at the rate of eight knots per hour, it would require one of forty to gain the same velocity by such an application of the paddlewheel.

And now, to put conviction within the reach of that portion of your readers who will be convinced of the disparity of power only demonstration, I wont by practical the following experiment in rowing. Instead of taking the water with the blade or paddle of your oar at right angles, passing through and leaving it the same, as all good rowers do, suppose you feather it to the angle of 34 or 35, the consequence would be, that it would either skim the surface, or fly out of the tholes, unless secured by a clasp, or something of that kind, and even then it would require the force of two men to make it take and leave the water, at the same angles which the floats of the paddle-wheels do, and the requital for all your extra labour will be a loss of speed.

My object in addressing this paper to you, is merely to show that a considerable loss of power does take place in the operation of paddlewheels; but should these remarks be thought worthy of a place in your interesting Magazine, I will, at an early period, explain myself more fully, by sending drawings of an apparatus, which appear to me calcufated to increase the velocity, by ren

Top diameter and per-3,1158 pendicular depth. S

To find the thickness of the metal at top, take half the difference between the top diameters of the enclosed and enclosing vessels, and you have the thickness required. Thus, the top diameter of the two-quart measure has been found to be 6,231 inches, and the top diameter of the quart 4,9458 inches; difference 1,2852, which, divided by 2, gives 6426, the thickness required.

4

To find the thickness at the bottom, take the difference between the top and bottom diameter of the enclosing vessel, and the difference of the depths of the enclosed and enclosing ones, and thus say, as the depth of the enclosing vessel is to the first difference, so is the second to the difference of the diameter of the bottom of the enclosing vessel and its diameter at the bottom of the enclosed one, which difference, added to the bottom diameter of the

former, will give the diameter at the bottom of the latter; from which take the bottom diameter of the enclosed vessel, and half the difference will be the thickness required.

Thus the top and bottom diameters of the two-quart measure have been found to be 6,231 and 4,362 inches; consequently their difference is 1,869; the depths of the quart and two-quart measures have been found to be 4,9458 and 6,231 inches, difference 1,2852; therefore 6,231: 1,869::1,2852: 3,855, added to 4,362, gives 4,7475, from which take 3,4621, and you will have 1,2854, half of which will give the thickness of the metal, at the bottom of the quart measure, 6427. The difference of the depths of the enclosed and enclosing vessels will be the thicknesses of the

bottoms.

Тор

Bottom

Of Bottom . . .8097

The thickness of the sides of the vessel are calculated perpendicular to the axis of the cone, not perpendicular to the blank sides..

I am, Sir,

Your obedient servant,

WILLIAM LAKE. '.

Bulbourne, near Tring, March 22, 1825.

[In a former communication of mine (Vol. 11. No. 78, page 350) I find one first column, for" and that the variaor two typographical errors. In the tions of a degree in latitude," read "although the variations," &c. Second column, for "consequently the descent of a heavy body from within one second," read "consequently the descent of a heavy body, for rest, is one second," &c. &c.]

The Managers of the Mechanics' Institutions are respectfully informed, that they may, on application to our Publishers, be supplied, gratis, with proof copies, framed, of the Portrait of their distinguished friend and advocate, Mr. BROUGHAM; and that our Publishers will make a liberal deduction from the price of all Books purchased for the use of the Mechanics' Institutions and Schools.

Notices to Correspondents in our next.

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