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witnessing her extraordinary speed, together with the entire absence of vibration in the vessel and disturbance of the water, although going at the rate of about sixteen miles per hour.

After landing their Lordships at Woolwich Dock-yard, her owners directed that her speed should be at once tested, by putting her in competition with about the fastest, if not the very fastest vessel on the River, namely, the Railway. This the party in command, (the wellknown Captain Turner, for many years commander of the Mercury,) at once proceeded to do. The Queen met the Railway about three miles below Woolwich, turned round, and beat her considerably into Blackwall. She started

again with her for Gravesend, at halfpast four, and it was soon evident that the Railway had no chance; but as this was in some measure to be attributed to the number of passengers on board the latter, the Queen went on to Gravesend, with the view of trying the Railway on her return passage, conceiving that, at half-past six o'clock on Saturday evening, there would not be many going up. So, in fact, it turned out; and the people of the Railway, which started from the Terrace Pier, when passing the Queen, lying at the Town Pier, gave her the challenge of" come on, we are ready for you now." The Queen started some minutes after the Railway, so as to give her time to call at Gray's Pier; but when the former got up to Gray's, the latter was about two miles ahead. The Queen then made all haste after her, making from 34 to 35 revolutions per minute, and got into Blackwall neck and neck with the Railway, thereby establishing, without question, her much superior speed.

Having stated so much, Mr. Editor, allow me to remark, that I have read, from time to time, a great deal about the speed of this and that vessel; but in no one instance do 1 recollect noticing any statement whereby we might come at the cost of obtaining these high speeds, which, after all, is the question of most interest to the scientific reader. The cylinders of the Queen are 29 inches in diameter, and the length of stroke 4 feet 5 inches; the average number of strokes per minute, 34; pressure of steam in boiler, 8 lbs.; the condenser vacuum, equal 27 inches mercury; the diameter

of paddle-wheels, 16 feet 6 inches width of ditto, 8 feet.

I enclose a diagram, taken on the 16th of July, by which your readers will see at what portion of the stroke the steam is cut off, and that the effect indicated was produced at an expense of about 64 cwt. of coal per hour, being, I believe, less than the average of steamers of her class.

INDICATION DIAGRAM OF "THE QUEEN," 16TH JULY.

Starboard.

I am, Sir, your obedient servant,

August 9, 1842.

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PERFORMANCES OF WATER WHEELS.

The Midland Counties Herald contains a letter from "A Miner," in which, adverting to a statement made at the Institution of Civil Engineers that Wheal Friendship and Wheal Betsy water-wheels were, in July 1841, performing 69, 51, 54, 56, 72, 67, and 57 per cent., or on an average 61 per cent. the writer makes the following remarks:

"I have been frequently at these mines in the course of the last thirty years, and have paid particular attention to the duty performed by the wheels, in order to make correct calculations for erections of my own; but at no time, could the best of these pumping engines perform 40 per cent. A recent practical trial to a wheel, proved that 200 gallons of water cannot be pumped 20 feet high with a 50-foot water-wheel, using 200 gallons to peform one revolution.

"The tables in the Practical Miners' Guide may be depended on, found on page 88, made up as follows, viz. :—

18,750 lbs. of water performing a revolu tion on wheel 46 feet diameter will draw a 12-inch lift 113 fathoms 6-feet stroke. Thus-113 fms. of 12-inch pumps,

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About 234 per cent. "I should be glad to know-How the was measured? Particularly the Old Sump Wheel,' 51 feet diameter, 10 feet broad, the water poured into its buckets 5,632 gallons per minute.

"The mode of measuring running water by width, depth, and time, is not a satisfactory way. The most correct way for measuring water is to measure the contents of a reservoir in number of cubic feet. When ascertained-First, Fill the same with water, observing the required time by minutes and seconds, which will give the number of cubic feet per minute. Secondly, Work the water down by counting the number of revolutions performed by the wheel until the reservoir is empty, which will give the number of cubic feet to each revolution.

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head of the lift, by having a small cistern or some other vessel prepared for the purpose."

THE CRANK QUESTION.

Sir,-Although I feel much obliged to your correspondent, R. W. T., for saying he does not doubt my veracity, in relating the experiments made by me, connected with the inquiry into the action of the crank, particularly the last experiment; nevertheless, the nature of that experiment, the limitations within which it was confined-the very terms of it rendering a practical trial unnecessary-makes me doubt whether I am much indebted to his kindness for this courtesy. The more so, that I find he has not changed some of his bad habits, and does not hesitate, when it answers his purpose, to give garbled extracts from my papers, and make believe he cannot understand me (as I before had occasion to remark), when he thinks it more convenient to do so than to refute my arguments. For example, had he not unfairly stopped short in the extract which he makes respecting the first matter he touches on, it would have been seen that I contended for a loss of power equivalent to 20; and have not, as he alleges, abandoned that point, as untenable. Would it not

have been more to his credit, to use his best endeavour to prove I was in error in doing so?

R. W. T. is beating a retreat, I perceive. He wishes, like some others of your correspondents, when hard pressed, to shift his ground, and to make it appear that there is some misunderstanding between us about the meaning of words. He pretends that we are not agreed on the proper meaning which should be given to the words "Loss of power," when applied to the mechanical contrivance of a crank. Now, as the concluding part of his letter is altogether confirmatory of my views, it is very necessary, to prevent cavilling about words, to explain, in language which cannot be misunderstood, what my meaning of the term "loss of power" is; and I shall expect equally as explicit an explanation from my opponent.

Let us suppose two steam-engines, one on the rotative principle, but, speaking theoretically, without friction, the other with a crank, also without friction; and let the boilers and daily consumption of coals be perfectly equal; and let the proportions of each engine (again speaking theoretically) be such that the quantity of work done by each with the given boilers shall be a maxi

mum.

Further, let the work required to be done be of the same description in both cases, and involve a considerable degree of fric

tion, such as grinding corn, spinning, &c. If the rotative engine, under these circumstances, is found to do more work,-if the larger quantity of work performed by that engine shows that the whole power is not given out by the crank, which it receives from the first mover,-then, I say, there is a loss of power in the crank. I think it unnecessary to answer those who require to know what becomes of the loss; that loss as certainly takes place, whether it be from loss of effect or destruction of power and this is clearly the meaning of the term "loss of power" made use of by Mr. Russell, Mr. Sang, and many others, whose writings on the subject are to be found in your Magazine. If the case were otherwise, why should these gentlemen contend that a person who would endeavour to contrive a machine for ordinary works, such as grinding corn, &c. &c., without the intervention of a crank, must be ignorant of the first principles of mechanics? When I mentioned the circumstance of drawing a spike out of a piece of timber, the pulleys, screws, levers, wedges, or any other mechanical contrivance to effect that purpose might be assumed to have no friction; but your correspondent cannot dispense with the friction of the spike; one pound might lift the spike, but it might require one ton to draw it! Now your correspondent is disposed to turn round and to cavil with me about this friction, on the ground of a misunderstanding about words, and that this friction was excepted,—that is, the very work required to be done was excepted. How else am I to understand him, when he says, in the latter part of his letter, that the work must be such as will answer for a crank engine? Does he mean that grinding corn is not proper work? He admits, almost in as many words, that such work cannot be well done without a fly,-his crank will not move without momentum. And thus he supports my argument, which is corroborated by the experiment. The spring in my experiment did not require momentum.

Your correspondent objects to my experiments because there is no similarity between them and a crank; but I need not remind him, that if the doctrine of virtual velocities applies to the crank, in cases where there is much friction, it must equally apply to my experiments. Moreover, he objects, that in

The word friction, as used in all these papers, is not confined to the rubbing surfaces of the machinery, but embraces every thing connected with the work to be done that retards or opposes motion. The resistance of paddle-wheels is as much an element of friction as the axle friction of the wheels, according to the view taken of it in these papers, and by such unscientific authorities as Smeaton,

these experiments I jump from an angle of 90 degrees to one of 30 degrees. Now it is surprising to me that he could not perceive that my doing so was a circumstance in his favour, and against myself; for had the leverage of the cross-bar been gradually reduced, as it is in the crank, from 90 to 30, the weights which, to support his views, should have moved over a greater space, would, in that case, have moved over a less space.

I will give another example of my meaning of the term "loss of power," and one which, I presume, will not be found fault with as being of an imaginary character. I allude to the experiments described by your Aberdeen correspondent, published some time back in your Magazine, where the same boiler was made use of, and the same quantity of fuel to work the engine at one time with a crank, and at another time without it. Your correspondent's admission that the crank-engine did not do one-half the work of the other, I call "loss of power." I call that loss of power also (though your correspondent seems to be at a loss to comprehend it) where, in the experiment with the non-momentum apparatus, as well as in the other experiments, 37 lbs. could not be drawn over a space of six inches. "Get

a suitable apparatus," says your correspondent," and it can be done." Very trueor take away the crank, he might have said, and almost any other contrivance would do it. 74 x 3 will not answer the conditions, as your correspondent will discover, if he will examine these experiments a little more particularly. Moreover, the space required to be passed over was 6 inches, not 3 inches.

R. W. T. observes, that he might safely undertake, with the addition of another cross-bar (so as to suit it to the work to be performed), to make it re-produce the lost power (What lost power, if none had been lost?) and make it move the 36 lbs. six inches. And he thinks I could easily find out how this could be done. There could be no contrivance of the kind placed between the cross-bar and the power, or between the crank and the first mover, in any case, that would have the effect he alludes to, without changing the principle altogether of the action of the crank.

Your correspondent complains that I do not notice his experiment with a model, which he thinks more like a working crank, and affects not to understand what I mean, when speaking of its limited effect. It was not its dimensions which I alluded to, but the impossibility of trying the necessary experiments with different descriptions of work with sufficient accuracy, and with the same facility, as in my experiments.

I will now allude, in a few words, to some other circumstances connected with these experiments. It will be observed that, in these experiments, the crank is represented as moving in one of two quarters of its revolution, and that its motion in that quarter is from a state of the greatest leverage to the dead point; and, consequently, a quarter of its revolution most favourable to the action of the crank. The other two quarters of its revolution, namely, from the dead point in the circle to the point of greatest leverage, would have been one more in my favour, and against the crank; as the destruction of momentum in the first case was applied in performing the work, whereas the restoring the momentum was done at the expense of the power. Moreover, it will be observed, that at the termination of all these experiments, where the cross-bar was made use of to represent the crank, the power would not have been sufficient to move the weight the smallest quantity beyond the assigned distance on the table, even had it been able to reach it, which it was not. But in all the cases where the crossbar was removed, the power would have been sufficient to carry on the motion beyond these points, if required. Again, it will be seen that the spaces passed over on the table by the weight, are not equal on each side of the line drawn across the table, although the work done on each side was equal; there was, consequently, unequal work done in equal times, but the uniform motion of the fly-wheel must interfere, and cause an approach to what, under the circumstances, would be impossible-equal work to be performed in equal times; and therefore must injuriously interfere with the action of the crank.

I am, Sir, yours, &c.
M.

PHOTOGRAPHY-AND SOMETHING MORE.

A very remarkable discovery, with respect to the self-transmitting property of figured surfaces, under certain circumstances, has been recently made by Dr. Moser, of Konigsberg, which would seem to indicate that there is something else than light concerned in the production of such effects, and that we must look for some fitter term than Photo-graphy to designate the branch of science or art to which they belong. The following is the account of this discovery, brought to this country by Professor Bessel, as communicated by him to the late meeting

of the British Association, through the medium of Sir David Brewster, and published in the Athenæum.

A black plate of horn, or agate, is placed below a polished surface of silver, at the distance of one-twentieth of an inch, and remains there for ten minutes. The surface of the silver receives an impression of the figure, writing, or crest, which may be cut upon the agate or horn. The figures, &c. do not appear on the silver at the expiration of the ten minutes, but are rendered visible by exposing the silver plate to vapour, either of amber, water, mercury, or any other fluid.

Sir D. Brewster stated that he had heard Prof. Bessel say, that the vapours of different fluids were analogous to the different coloured rays of the spectrum; that the different fluids had different effects, corresponding to those of the spectrum; and that they could, in consequence of such correspondence, produce a red, blue, or violet colour. The image of the camera obscura might be projected on any surface-glass, silver, or the smooth leather cover of a book-without any previous preparation; and the effects would be the same as those produced on a silver plate covered with iodine.

This paper gave rise to an animated conversation, in the course of which M. Bessel said that he had seen some of the pictures taken by this process, which were nearly, but not quite, as good as those obtained by Mr. Talbot's process. - Sir D. Brewster said, this was the germ of one of the most extraordinary discoveries of modern days; by it there seemed to be some thermal effect which became fixed in the black substance; and not only so, but M. Bessel informed him, that different lights seemed to affect different vapours variously, so that there seemed to be something like a power of rendering light latent; a circumstance which, if it turned out so, would open up very new and curious conceptions of the physical na ture of light; on the emission theory, it would be easy to account for this; on the undulatory theory, he could not conceive how it could be possible. Prof. McCullagh said, he believed Newton had somewhere thrown out a suggestion, that luminous particles, as they entered into bodies, might be caught and retained, within certain bounds, by continual attractions.-Sir D. Brewster said, that the experiments which he had performed with nitrous gas seemed to strengthen some such view as this, for, at certain temperatures, we had here an instance of a gaseous body as impervious to light as a piece of iron.-Sir J. Herschell thought it a pity to encumber this new and extensive

field of discovery now laid open to them by any speculations connected with the theory, either of undulations or emissions. He had found that paper could be so prepared, as that the impressions of some colours might become permanent upon it, while others were not; and thus it became possible to impress on it coloured figures by the action of light. He exhibited a piece of paper so prepared, which, at present, had no form or picture impressed on it, but which was so prepared, that, by holding it in strong light, a red picture would become developed upon it. He wished much he could prevail on Sir W. Hamilton to explain to the meeting a metaphysical conception, which he had disclosed to him, and which seemed to him, though darkly, he owned, to shadow forth a possible explanation of many difficulties.— Sir W. Hamilton said, that, appealed to by Sir J. Herschel in this manner, he could not avoid placing before the meeting the theory alluded to, however imperfect and obscure. He then explained it; but we regret our inability to express it adequately. It appeared to depend on the conception of points, absolutely fixed in space, and endowed with certain properties and powers of transmission, according to determined laws.-Professor McCullagh had indulged in speculations allied to, and, as he conceived, involving this very conception of Sir W. Hamilton, and had even followed out some of its consequences, by reducing it to a mathematical form-the conception was of double points, or poles, transmitting powers-but he had abandoned it as a mere speculation.-Sir D. Brewster thought these speculations tended to repress experimental research, and to turn men's minds from what was solid to what was fanciful. He conceived, also, that indulgence in them, and mere abstract mathematical research, by rendering men averse from the more humble and laborious pursuits of experiment, absolutely produced a distaste for these subjects; and to this he attributed the fact that, while learned societies frequently overlooked, and even refused to publish in their Transactions experimental papers, the transcendental flights were always sure to find a welcome place.-Sir J. Herschel considered that there could be no true philosophy, without a certain degree of boldness in guessing; and such guessing, or hypothesis, was always necessary in the early stages of philosophy, before a theory has become an established certainty; and these bold guesses, in their proper places, he conceived, should be encouraged, and not repressed. Sir W. Hamilton's conception he thought perfectly clear in its metaphysics, and should not be thrown overboard, merely because it was metaphysical. The President

hoped that Sir W. Hamilton would develope and publish this speculation, in order that it may be sifted, scrutinized, and rejected, if merely ideal; or established and adopted, if solidly founded in nature and fact.

RECENT AMERICAN PATENTS. [Selected and abridged from the Franklin Journal.] METHOD OF WETTING FLANNELS AND OTHER CLOTHS PREVIOUS ΤΟ SCOURING

OR MILLING; Joseph W. Hale.-A colander, pierced with numerous small holes, is attached to a reservoir, or tank, of water, by means of a pipe, the orifice of which is regulated by a valve, to which a cord is attached, having a weight at its opposite end, for the purpose of keeping the valve opened when desired. A roller is placed at one end of the frame, and two at the other end, and the cloth, in going from the single roller to the double set, by which it is drawn through regularly, passes under the colander, and receives the spray from it.

IMPROVEMENT IN THE JOINTS OF SPECTACLE FRAMES; Thomas Eltonhead." It has heretofore been the practice, in forming the frames of spectacles of metal, to divide the end-pieces, which are soldered to the rims containing the glasses, into two parts, and to connect these two parts together by means of a screw. The joint-pin has been affixed to one of these parts, and the side, or temple pieces, have had the tubes through which the joint-pin passes soldered to them.

In my improved construction, I make the end-pieces solid, instead of dividing them into two parts, and into this solid piece I file a notch, to receive the end of the temple piece, which is to be adapted thereto, and a hole drilled through for receiving the jointpin."

ROTARY STEAM ENGINE; Isaac N. Whittlesay. "The general construction of my improved engine," the patentee says, "is similar to that of some others which have been heretofore constructed, but I have made such improvements thereon as are intended and calculated to obviate some of the difficulties which have been experienced in its action. The principal of these improvements consist in the employment of the steam to open and close the sliding valves, and in the arrangement of some of the other parts by which its action is governed."

Within a hollow case, of the usual construction, "revolves a drum, which carries two valves, to be operated by the action of the steam, which action causes the said inner drum, with its shaft, to revolve in the ordinary way. The valves, which are connected together by a rod, slide into recesses made

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