NEW SPIRAL WHEEL.

Red-Lion Street, Clerkenwell,
March, 1824.

I

GENTLEMEN ;-In your 22nd Number "A Miller in the Mountains" wishes to know how the most can be made of a fall of water. have attempted a contrivance, which, although novel in its appearance, yet nevertheless will be found to possess a very considerable share of mechanical energy when acted upon by a fall of water, equal to that of the "Miller's." A Bin the prefixed figure, represents the axis of the wheel; E E its spiral floats; G H the main, which conveys the water to the wheel; Fa trough for the water, making its discharge after its action upon the wheel; C and D are two conical wheels for changing the direction of the motion from vertical circular to horizontal circular.

But as a thing in perspective only is apt to please the eye, while it deceives the judgment, it may not be amiss to enter into an investigation as to the mechanical construction and results of this curious wheel. The first part of the inquiry, then, very naturally leads us to consider the shape and magnitude of the main G H. Now, it is well known, that all bodies freely acted upon by gravity, are uniformly accelerated in their descent; consequently, since the water in its descent is moving faster and faster, the pipe or main ought to become smaller and smaller, so as to accommodate itself to the water; hence the several areas of the column of fluid will be inversely as the different velocities. Now, the velocity of any falling body is always as the square root of the depth of descent; so also the velocity of the water in any part of the main will be as the square root of the depth; consequently the areas are inversely as the square roots of the depth.

Then, let A the area of the main at bottom; B the height of the main, as measured from A; C the depth of any part of the pipe, measured from the top; D

of revolutions per second, which, if the fall were 300 feet, and the distance between the spirals 2 feet, it would be nearly 69.5 revolutions. Now, for the force acting upon the floats as this inquiry, however, is seemingly the most difficult to those unacquainted with the principles of mechanical science, it will be previ ously necessary to take notice of a few particulars upon which the calculation depends. We desire not to rank among those who are fond of clothing their deductions in a mystical garb, and sending them forth as so many oracles; for, as our excellent friend, Dr. Birkbeck, has told us (Vol. I, p. 179) although the august Temple of Science has generally been represented to be situated on a rugged mountain, accessible only by thorny paths to the privileged few, yet it ought really to be considered as situated upon a widely extended plain, approachable with ease in all possible directions, and opening innumerable doors for the admis.. sion of its votaries.

Let A B C [see the prefixed engraving] be a right angled triangle, and A B a cylinder: now, if this triangle be wrapped round the cylinder, its hypothenuse will

trace the helices or threads of a screw. And if a spherical body were to roll down upon this screw, it would have the same velocity and momentum as if it had rolled down the inclined, plane A, C (abstracting the idea of the centrifugal force which would be created); and to raise or let down a body by such a screw, would be the same as if that body were lowered or raised upon the inclined plane A C. Hence, our spiral wheel may be considered in the light of an inclined plane, whose height is equal to E, and base equal to as many times as the convolutions of the cylinder = F.

Now, it is pretty generally known, or at least it requires little judgment to understand, what power is required to take up or let down any spherical body on an inclined plane. As the length of that plane is to its height, so is the weight to the power. This being clearly understood, the difficulty in this case instantly vanishes.

It is manifest, then, that A BH is the weight of the whole column of water in the main; consequently EABH

= N, the power neces

VE2+F2 sary to support A B H, or to allow it to slide down (if we may use such an expression), if the wheel were immoveable; but since it is at liberty to revolve on its axis, the force acting upon it will be ABH Nthe force of the wheel; for it is evident, that if we push a body up an inclined plane, whose weight is 24, with a force equal to 18, the remaining 6 must necessarily rest upon that plane; and if it is at liberty to move, it will do so with a force equal to 6. Every body knows that it requires no force to move a sphere a horizontal plane, when once its inertia is overcome, and no one will deny that its whole weight rests upon that plane. If B feet; A 36 inches, or nearly 6-8 in diameter; H= 62.5 pounds; and E = F; then the force of the wheel would be equal to 1372

on

300

pounds. It must be allowed, indeed, that this is an extreme case. I am of opinion that F ought always to be less than E.

Perhaps the "Miller" may not altogether be satisfied with the physiognomy of an algebraic page, but my motive for doing so was with a view to convey the formula in a general form; however, I shall add a few practical rules for ordinary use.

Divide the square root of the whole height by the square root of any assumed height of the main, as measured from the top. Multiply this quotient by the area of the main at bottom, and the product will be the area of the pipe at the assumed depth. Multiply the whole length of the pipe by 64.3, and extract the square root of the product; divide this sum by the distance between the spirals, and the quotient will be the velocity ar revolution per second. Multiply together the whole height of the main, its area at bottom in feet, and the distance between the spirals, and this again by 62.5; then square the distance between the spirals, and add it to the square of the like number of convolutions; extract the square root of this sum, and divide the former sum by it. The quotient arising from this division being deducted from the continued product of the whole height of the main, multiplied by its area at bottom, in feet, and this again by 62.5 will detérmine the mechanical energy of the wheel. I have always been of opinion, that a wheel of this kind would be better adapted for steamboats than the common paddlewheels, for the following reasons:

1st. The paddle-wheels 'make a very disagreeable noise..

2nd. They communicate a continued tremulous motion to the vessel. ༣༠༩

3rd. They destroy a very great quantity of power to no purpose, from their oblique action to the line of motion of the vessel.

4th. They are not adapted for

inland navigation, owing to their destroying the canal embankments.

5th. Any body coming in contact with them is certain destruction to it.

Now, all these bad qualities I feel confident would be very much mitigated by the adoption of the spiral wheel, and these hints I hope will not be lost upon your readers.

Although there is a considerable quantity of power lost in this machine from the oblique action of the floats, yet this may, in a great measure, be recovered, by extending the floats to a greater number of convolutions; for, owing to the rapid motion of the water, there can be no time for any pressure acting on the under-sides of these floats, so as to balance the force acting upon their upper surface.

I am aware that in my attempt to simplify this subject, I must necessarily subject myself to the fiery ordeal of the more strict in'quirer. However, your correspondent in the "Mountains" will, upon trial, find that the deductions ́are not very distant from the truth. I remain, Gentlemen,

Your very humble servant,
J. Y.

ANALYSIS OF CONTEMPORARY SCIENTIFIC JOURNALS. (Continued regularly). PHILOSOPHICAL MAGAZINE AND JOURNAL, Nos. CCCIX. & CCCX. for January and February, 1824. PRESSURE GAUGES. The ordinary mode of ascertaining the exact pressure of highly condensed gases, is by the rising of a column of mercury in a glass tube, hermetically sealed at the top, the tube being previously filled with air at the ordinary pressure of the atmosphere; for as the mercury rises by the pressure of the gas, the air confined in the tube above the surface of the mercury, will always be compressed to the same degree as the gas itself, making proper allowance for the weight of the column of mercury.

The only inconvenience attending this method, arises from the length of which it is necessary to have the tube, where gases are compressed to from thirty to forty atmospheres. To remedy this, we have here twoimproved gauges, proposed to us by Mr. S. Seaward and Mr. Henry Russel, who have already figured (we believe) in our pages as antago nists [see pp. 232, 246, 263, Vol. I] of considerable ingenuity, but of somewhat irascible tempers. Mr. Russel makes no scruple of affirming that his gauge "will ultimately be

considered as remarkable for its accuracy and simplicity, as Mr. Seaward's will for its inaccuracy and complexity." For ourselves, we think that the advantage, in point of simplicity, must be conceded to Mr. Russel's invention; but though Mr. Seaward's gauge is certainly of most faulty complexity, Mr. R. has failed in proving its inaccuracy. We have no doubt that both gauges will be found accurate enough for practical purposes; nor would Mr. R. have lessened his claims to respect, by limiting his asserted superiority to the greater simplicity merely of his instrument. The gauge invented by Mr. Russel is described by him to consist of a glass tube, sealed at one end, with a ball blown very near the other, leaving only as much tube beyond the ball as may be necessary for connecting it with the pipe leading from the vessel, containing the condensed gas, steam, or other vapour. This ball, when the tube is filled with air, and subject only to atmospheric pressure, should be about three quarters full of mercury, and its whole capacity need not exceed that of the tubes more than as two to That the divisions on the scale may be in geometrical progression, the tube is placed in a horizontal position. To determine the degree of pressure at any given point, ascertain the distance of that point from the sealed end of the tube, and by that measure divide the length of tube contained between the sealed end and the bulb; the quotient will be the number of atmospheres. Thus, suppose the tube eight feet long, and the

one.

column of air compressed into half that length, then we have = 2 atmospheres. If this column be again compressed into half its volume, we have 8 atmospheres. If, again (8 feet 96 inches) = 16 atmospheres. And lastly, 96 = 32 atmospheres, which is the density at which the Portable Gas Company engage to supply their customers.

96

For the internal diameter of the tube Mr. Russel considers of an inch sufficient.

EFFECT OF MERCURIAL VAPOURS. -It has long been known that persons employed in the mines whence mercury is procured, as well as those who are occupied in gilding and plating, suffer paralytic and other constitutional affections from inhaling the air saturated with mercurial vapours. [We invite attention to the Safety Mask recommended in a subsequent page.-EDIT.] An event which occurred in one of our ships of the line at Cadiz, in 1820, has afforded Dr. Burnet, one of the medical commissioners of the navy, an opportunity of illustrating this subject on a very extensive scale, in a paper read before the Royal Society, and here reprinted from their Transactions. The Triumph, of 74 guns, arrived in the harbour of Cadiz, in February 1820; and in the following March, a Spanish vessel, laden with quicksilver from the mines in South

America, having been driven on shore in a gale of wind, and wrecked under the batteries then in possession of the French, the boats of this ship were sent to her assistance, by which means about 130 tons of the quicksilver were saved and carried on board the Triumph, when the boxes containing it were principally stowed in the bread-room. The mercury, it appears, was first confined in bladders, the bladders in small barrels, and the barrels in boxes. The bladders, however, having been wetted in the removal from the wreck, soon rolled, and the mercury, to the amount of several tons, was speedily diffused through the ship. The effect of this accident was quickly seen. In the space of three weeks, two hundred men were ill with ulcerations

of the mouth, partial paralysis inmany instances, and bowel com-, plaints; and, ultimately, there was not an individual on board who was not more or less affected. Almost all the live stock too, consisting of sheep, pigs, goats, and poultry, were killed by it; mice, cats, a dog, and even a canary bird, shared the same fate, though the food of the last was kept in a bottle closely corked up; mice would frequently come into the ward-room, leap up to some height,, and fall dead on the deck. Fortunately, only two out of the large number of the ship's company affected by the mercury, died. Various opinions were entertained of the manner in which the systems of the sufferers were brought under the influence of the mercury. By some it was supposed to have originated from the use of the bread and other provisions with which the mercury was supposed to have mixed itself; and the Victualling Office actually condemned 7,940 lbs. of biscuit, as unserviceable on this account. Plowman, the surgeon of the ship, and Dr. Burnet agree, however, in opinion that the ailments were produced by the inhaling of the mercurialized atmosphere. The quicksilver, being then in the most perfect state of division, was readily taken up by the absorbents of the lungs, and soon showed its influence on the system generally. The opinion of these gentlemen is fully confirmed by the fact that many fresh cases occurred after the ship had been completely cleared of the provisions supposed to be infected.

GEOLOGICAL

Mr.

OBSERVATIONS. "Remarks on the Position of the Upper Marine Formation exhibited in the Cliffs on the North-East Coast of Norfolk, by Mr. RICHARD TAYLOR, of Norwich," will be found a valuable contribution to the geology of that district. On a former occasion (p. 389, Vol. I) we endeavoured to explain to our readers in what the value of geological science consists; and we are now, by the kindness of a correspondent, enabled to add a striking instance of the practical uses to which the general results furnished