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Mechanics' Magazine,

MUSEUM, REGISTER, JOURNAL, AND GAZETTE.

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WEATHERDON'S ROTARY SAW-CRANK. Sir,-On perusing some of the earlier numbers of your instructive Magazine, I observe in vol. vi. a plan for a new rotary motion by a Mr. De Tir. Should you consider the drawing and description of the one I have sent you, which I completed some time since and called a "rotary saw-crank," likely to interest your readers, I without further apology give it.

The following is a brief description of the drawing, the model of which was made of wood, and worked extremely well. A A is part of the framework C, which passes through the blocks B B, and works in grooves to keep the frame in place. L F is a half-toothed wheel (or rather less), strongly fixed to the shaft or axle D; the dotted lines, showing the hold which the teeth has on crossing its centre at right angles. SS are the side frames or saws, the teeth of which are on either side, directly opposite to the spaces on the other; so that the impulse given to the last teeth LS, at the conclusion of the upstroke, will press forward the first tooth F, on the half wheel, into the first opposite space FS, as shown by the drawing; when the frame will descend on the tooth F, in gear with the half wheel, and transfer it by the impulse of the teeth LH, at the conclusion of the downstroke, into the space G at the top of the frame, completing with the up and down-stroke, one revolution of the shaft D, and so on, thereby producing a uniform rotary motion.

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turned to his native country, spent his time and a considerable proportion of his income in scientific and in practical researches. To a high degree of talent and great practical skill, Mr. Waddell joined sagacity and perseverance, and as he grudged no outlay in his experiments, he seldom took up a subject without pursuing it until he was satisfied that he had achieved what he had attemptedor that success was unattainable. Few persons have made more numerous or better devised experiments on the dif. ferent modes of propelling steam-vessels; among other plans, he tried that now proposed by Mr. Taylor, which he varied in many different ways, and ultimately thought he had succeeded in putting it into a useful working form.

On this he prepared a small vessel, in which he made a voyage from Leith to the Western coast of Africa; this voyage satisfied him that he was mistaken, and it is understood, that latterly he had come to the conclusion, that no form of propeller was equal in effect to a well made paddle-wheel: provided the diameter was large, and the immersion of the floats not too great.

It might not have been worth while to advert to the above circumstances, had it not been that the last modification which Mr. Waddell gave to his stern propeller, included a great improvement over the form it had previously, which was that now employed by Mr. Taylor. Instead of having the vanes at the extremity of a rigid shaft, Mr. W. applied an universal joint immediately outside the stern of the vessel. The part of the shaft beyond the joint was supported by a collar hanging from an outrigger, and from this collar, chains passed to the quarters of the vessel; by this arrangement he dispensed with a rudder, as by applying the quarterchains as tiller-ropes, the shaft and its vanes were made to traverse sufficiently to alter the direction of the ship's course as required. By means of the pendulous support, the shaft was capable of adjustment to the most favourable angle of depression, and might also be elevated entirely out of the water when in harbour, or exposed to injury from other vessels.

I regret that it is not in my power to supply a detailed account of Mr. Waddell's labours in this matter, because

MR. UTTING'S ASTRONOMICAL TABLES.

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The intricacy of water-closet machinery in the plans upon which they have hitherto been fitted, has been a great drawback upon the comfort of these conveniences. Upon any part getting out of order, no one but a practised plumber understands the various connections, and the apparatus remains for a time useless mayhap, from something breaking or getting out of place, a whole house is flooded with water, and furniture damaged or destroyed. A water-closet has recently been brought into use, invented by Mr. F. Roe, of Chamberwell, in which nearly all the old and intricate apparatus of wires, cranks, box-valves, spring boards, springs, and such like, are dispensed with.

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B

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A is the handle; B, weight to bring down handle; C, lever, to open D, the ship cock or valve; E, pipe to arm of basin; F. basin; G, recess in basin to to supply the basin; H, fan; I, cistern. This simple arrangement, may, of course be modified in a variety of ways to suit different situations. One particular advantage of the plan is, that the apparatus being all in the closet, and none in the supply cistern, any number of closets may be supplied from one cistern, situated at any part of the house, so that it is at a level high enough to produce a strong current of water.

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PP and P-P

Tt ; but I will candidly inform him, T-t that any assertion the Scotch Dominie has made, is worth a waggon load of such demonstrations as he has thought proper to give, and if I fail in proving this, then let it be said, that Kinclaven is one of the most ignorant pretenders that ever attempted to impose upon the In the above figure of Roe's closet, readers of the Mechanics' Magazine.

Nautilus seems to have a horror at arithmetical calculations (which the Cambridge Student designated, "the drudgery of science,") in this I perfectly agree with him, and to prevent one having occasion (in the following investigations) to allude to that vulgar branch of science, I shall here premise, that the symbol a, in what follows, is understood to be the measure of four right angles, or three hundred and sixty degrees.

Let P and p represent the siderial, and T and t the tropical periods of any two planets; x and y the measure of the precession of their equinoxial points (Nautilus designates it recession, and I agree with him) in terms of a, for a troTy. That The ty: T:

pical year.

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that the recession of the equinoxial points of any two planets for the time Tare equal, or, finally, if the recession of the equinoxial points of the earth for any time whatever be x, the recession of the equinoxial points for all the planets in the system for the same time will also be x. They have now nothing more to do but to consult their astronomical books, to cure them of this blunder.

Nautilus has made a most unwary attack upon the Cambridge Student. In "thumbing over" (this expression I borrow from N. himself) the pages of "Maddy's Principles of Plane Astronomy," he finds Very likely he may

that t

=

also find p

TS T+S

=

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PS

P+S

; from which we

may easily deduce, that in the case of the earth and moon, there is an equality between the expressions

;

PP

and

P-p

Tt T-t the earth and moon; but the Cambridge Student in none of his letters has made the slightest allusion to these bodies. The truth is, Nautilus having found, that in the case of the earth and moon, that Pp Tt he very unwisely con

and all this I allow to be true, of

P-p

=

T-t

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Tt+pt-p T Tz (p-t)

py and this equation, by reduction,

p-t

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t

becomes to x=Ty .. x= Ty; that is, the recession of the equinoxial points of the first planet is Ty But the recession of the equinoxial points of the

second planet was proved to be

Ty

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t

Hence, we arrive at this startling result:

Oct. 31, 1838.

KINCLAVEN.

THE MECHANICAL CLOCK-PUZZLE

CORNHILL.

Sir,-This clock, placed in the window of Mr. Savory, seems to have caused some little noise and wonderment; some of the papers state that even clock-makers themselves are puzzled to account for

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THE MECHANICAL CLOCK-PUZZLE.

the motion of the hand in front of the glass dial-plate.

I think the thing can be managed simply enough in the following way :— The stand contains, no doubt, all the works necessary for the movements of an ordinary clock, and these are set in motion, either by a pendulum or spring. The circular dial-plate of glass is firmly fixed upon this stand, upon which the figures are written; behind this is another circular plate of glass; this plate has the hour-hand fastened to it by a small arbor projecting through the front plate.-Now it is evident, that this second, or back plate, may rotate with the hour hand without the motion being seen; there is a small train of wheels leading up the branch of the stand terminating in a small drum; upon this drum the periphery, or edge of the back plate of glass (which carries the hand) rests; it is therefore evident, that any motion may be given to this invisible glass-wheel, or roller, by the motion of the drum, in exactly the same manner as the motion is now given in ordinary clocks by a small pinion driving the large wheel, which carries the hour hand. Indeed, the clock might be made more complete by introducing another plate of glass behind the second one; this could carry the minute-hand upon a hollow spindle, which would pass through the other two to the front, and which third plate of glass might receive its motion by another hidden train of wheels and drum like the former. I have no doubt, whatever, that this is the way the movement is effected, and not by any galvanic or magnetic agency. I am, Sir,

Your obedient servant.

[Two other correspondents suggest somewhat similar plans to the above.]

It appears to me that there are two glasses (of which I annex a sketch in section) and the following is my explanation of the mechanism: :

Let A A represent the section through the centre of the front plate, on which the figures for the hours are painted. This is fixed in the outer frame, or ring, CC; BB is another plate of glass cemented into a ring of brass D D, which ring has teeth cut on its outer edge; E

B

F

B

A

D

A

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