16th of August) will bear witness, to the fact that the Great Western arrived early in the morning of the 14th of August, and the Queen early in the morning of the 15th." The former part of this statement is correct enough as relates to the Great Western, but how "Observator" has fallen into the error of saying the British Queen was 24 hours after the Western, I cannot conceive. I will merely quote the British Queen's log to prove the falsity of this assertion. Captain Roberts says, under the date of August the 14th not 15th: "One o'clock, P. M., Falmouth pilot-boat alongside; two o'clock, the Lizzard and its lighthouse, in full view; four o'clock, took a Cowes pilot alongside-12 days and 19 hours from pilot to pilot; 13 days to Portsmouth." And this is what " Observator" calls arriving early in the morning of the 16th. Now I I remain, Sir, yours, sincerely, London, Oct. 8th, 1839. SELECTIONS FROM THE PROCEEDINGS OF THE BRITISH ASSOCIATION-NINTH MEETING AT BIRMINGHAM. [Abridgement of Athenæum Report.-Continued from page 462 of last volume.] Sir John Herschel on the non-action of the Red Rays of Light on Photogenic Paper. [Extract of letter read to the Mathematical and Physical Section.] Slough, August 28, 1839. My dear Sir,-May I take the liberty of requesting that you will mention to the physical section of the British Association a very remarkable property of the extreme red rays of the Prismatic Spectrum, which I have been led to notice in the prosecution of my inquiries into the action of the spectrum on paper, rendered sensitive to the chemical rays by Mr. Talbot's process, or by others of my own devising. The property in question in this: That the extreme red rays, (such I mean, as are insulated from the rest of the spectrum by a dark blue glass coloured by cobalt, and which are not seen in the spectrum unless the eye be defended by such a glass from the glare of the other colours,) not only have no tendency to darken the prepared paper, but actually exert a contrary influence, and preserve the whiteness of paper on which they are received, when exposed, at the same time, to the action of a dispersed light sufficient of itself to produce a considerable impression. I have long suspected this to be the case, from phenomena observed in taking photographic copies of engravings; but having at length obtained demonstrative evidence of the fact, I think this may not be an improper opportunity to announce it. When a slip of sensitive paper is exposed to a highly concentrated spectrum, a picture of it is rapidly impressed on the paper-not merely in black, but in colours, a fact which It is impossible in this climate to form a brilliant and condensed spectrum without a good deal of dispersed light in its confines ; and this light, if the exposure of the paper be prolonged, acts of course, upon every part of its surface. The coloured picture is formed, therefore, on a ground not purely white, but rendered dusky over its whole extent, with one remarkable exception,―viz. in that spot where the extreme red rays fall, the whiteness of which is preserved, and becomes gradually more and more strikingly apparent, the longer the exposure and the SELECTIONS FROM THE PROCEEDINGS OF THE BRITISH ASSOCIATION. greater the consequent general darkening of the paper. * * * * The above is not the only singular property possessed by the extreme red rays. Their action on paper already discoloured by the other rays is still more curious and extraordinary. When the spectrum is received on paper already discoloured slightly by the violet and blue rays only, they produce, not a white, but a red impression, which, however, I am disposed to regard as only the commencement of a process of discolouration, which would be complete if prolonged sufficiently. For I have found that if, instead of using a prism, a strong sunshine is transmitted through a combination of glasses, carefully prepared, so as to transmit absolutely no ray but that definite red at the extreme of refrangibility, a paper previously darkened by exposure under a green glass has its colour heightened from a sombre neutral tint to a bright red; and a specimen of paper rendered almost completely black by exposure to daylight, when exposed for some time under the same glass, assumed a rich purple hue, the rationale of which effect I am disposed to believe consists in a very slow and gradual destruction, or stripping off as it were, of layers of colour deposited or generated by the other rays, the action being quicker on the tints produced by the more refrangible rays in proportion to the refrangibilities. It seems to me evident that a vast field is thus opened to further inquiries. A deoxidizing power has been attributed to the red rays of the spectrum, on the strength of the curious experiments of Wollaston on the discolouration of tincture of guaiacum, which ought to be repeated; but in the sensitive papers, and still more in Daguerre's marvellous ioduretted silver, we have reagents so delicate and manageable, that every thing may be expected from their application. J. F. W. HERSCHEL. Mr. Frodsham's Compound Pendulum.— It is an ordinary pendulum, with a steel rod, over which Mr. Frodsham slips a zinc tube, which passes through a brass bob, and rests on the adjusting screw at the lower end of the rod, the bob being fastened at the centre by two connecting rods of steel to the tube, at the point at which the expansion of the tube is the same as that of the rod; so that, as the steel rod expands downwards, and is lengthened by heat, the zinc tube expands upwards in the same degree; and therefore, if the lengths of the rod and the tube be rightly proportioned, the pendulum may be regarded as of invariable length. But, as it is seldom found that different specimens of the same metal have precisely 29 the same expansibility, Mr. Frodsham proposes to have several small pieces, or rings of different lengths, cut from the same tube, as correcting pieces, which are to be slipped on or withdrawn, until the length of tube is found that will compensate the pendulum for change of temperature. Mr. Frodsham stated, that the whole in the bob through which the zinc tube passes, is larger than the tube, but there are brass fillets at both ends, with a hole in each exactly fitting the tube; these fillets are perforated with several small holes to admit the air, so that any change of temperature may not be prevented from affecting the part of the tube which is within the bob. The zinc tube is larger than the steel-rod of the pendulum, fillets being also placed at each end of the tube, with a hole in each, just large enough to let the rod pass through. The tube is pierced with small holes throughout its whole length, to allow the air access to the rod. In the suspending part of the pendulum, Mr. Frodsham directed attention to what he called an isochronal piece; it is a brass tube about five inches in length, with a slit about an inch in length at the bottom, to form a spring, so as to slide rather stiffly on the rod. At the upper end of the tube is a clasp, which, by means of two screws, is made to embrace the suspending spring; so that after the pendulum has been adjusted to the length for time, the acting part of the suspending spring may be varied at pleasure, without altering the length of the pendulum, by sliding the isochronal piece up or down the rod, and tightening the screws of the clip. Previously to tightening the screws of the clip, the suspending spring must be allowed to assume its natural and unconstrained position. The rod and the spring being thus united, there can be no wavering motion of the rod, such as is generally found, in a greater or less degree, when the rod and the spring are simply pinned together. Instead of the fork which embraces the pendulum, and connects it with the clock, being a fixture, Mr. Frodsham uses a rod about eighteen inches long, attached to the pallets of the clock, and on this rod is slid a moveable fork, which is fastened by a screw to the rod, at such distance from the axis of the pallets, as is found by experiment to have the greatest power over the pendulum, and thereby cause it to vibrate through the largest arc. Mr. Frodsham stated that by a series of experiments, he had discovered that to any given weight of the bob of a pendulum, some particular length and strength of the suspending spring is better adapted than any other to produce isochronism, and with such spring the pendulum will vibrate through a larger arc with a given weight, or will vibrate as far with a less weight than with any other, and that, unless the pendulum is first isochronized, anomalies may be imputed to imperfect compensation, which have their origin in a very different source. Strength of Woods.-Mr. Hodgkinson stated the results of some experiments to ascertain the power of different species of wood to resist a force tending to crush them. The specimens upon which trials have been made were turned into right cylinders, about one inch in diameter, and two inches long. The apparatus used to crush them has been described by Mr. Hodgkinson in an account of his experiments on cast iron, published in the Transactions of the Association. The crushing surfaces were perfectly parallel, and the body to be crushed had its ends bedded firmly against them, the force being applied in the direction of the fibres. The specimens broke by sliding off in a given angle, dependent on the nature of the material, as the writer had found to be the case in cast iron and other bodies, showing that the strength in any particular species of bodies, is directly as the area of the section. Great discrepancies were found when the woods were in different degrees of drynesswet timber, though felled for a considerable time, bearing, in some instances, less than one-half of what was borne when dry. These experiments were made at the expense of Mr. Wm. Fairbairn. The following were some of the results :Description of wood. Mean force which crushed the specimen. 4306 lb. 2514 Yellow Pine Cedar 4456 4157 inches asunder, and had different weights, as two and a-half, three, three and a-half, and four cwt., laid upon the middle of each; the last weight being within a few pounds of the breaking weight. The intention was to ascertain what effect would arise from each of these weights lying constantly upon the bars. The results are, 1st. The bars are still bearing the loads, and apparently may do so for many years. 2nd. The deflections, which are frequently measured, the temperature being observed at the time, are constantly increasing, though in a decreasing ratio, a fact, which shows that, though cast iron may be safely loaded far beyond what has hitherto been deemed prudent, still it is extremely probable that the bars are advancing, by however slow degrees, to ultimate destruction. Mr. Cottam's new Railway Wheel.-The wheels suggested are made on the following principles: 1st. They are wholly of wrought iron, so welded together, that, independent of screws, rivets, or any other kind of fastening, they form one piece with the spokes. 2nd. The spokes of the wheels are placed diagonally, and act as trusses, thereby giving the greatest possible support to the rim, or tire, and, at the same time, being in the best position for resisting lateral pressure. 3rd. Iron in a state of tension or compression, as is usually the case with the tires of the wheels, is easily broken by sudden shocks, or by vibratory action. The wheels in question are so constructed, that the fibres of the iron employed are neither compressed nor stretched, but remain in their natural condition. 4. The strength of iron being as the square of its depth, then the flanged tires of these wheels, which offer sections twice as deep, are, consequently, four times as strong as those of any wheels at present in use. This increase of strength is attributable solely to the peculiarity of their construction, and not to any increase in the weight of the material. 5th. The spokes strike the air edgewise, and thus offer the least possible resistance. Wheels where the spokes present a flat surface may be said to act as blowing machines, and, as such, require a greater propelling power. 6th. These wheels, by simply varying the curve of their spokes, become either rigid or flexible, or, in other words, they may be made to any degree of elasticity. 7th. When worn by friction, the rims or tires may be turned down, and have hoops of railway tire shrunk on them. Thus repaired, these wheels are very strong and durable, and more advantageous than those of other constructions. Mr. Roberts spoke to the successful use of cast iron wheels, which, properly manufactured, he had never found to fail. The MUNTZ'S YELLOW METAL SHEATHING. most important consideration to be attended to was the absence of oxide of iron, and if any was on the metal it must be removed by a file. If this precaution were attended to, there would be little fear for the stability of cast iron wheels. Mr. Woods stated, that on the Liverpool and Manchester Railway cast iron wheels were much used. They had employed wheels with wooden tires at the opening of that line, some of which were still in use; and so satisfied were the Directors, that it was their intention to have some new wooden wheels made, and to submit them to the test of experiment. MUNTZ'S YELLOW METAL FOR SHEATHING A few years ago, a patent was obtained for a metal wherewith to cover the bottoms of vessels, and which promised all the advantages of copper, with at least equal durability in any climate, and a considerable saving in cost. It is manufactured in sheets in the same manner as copper, and from its resemblance to yellowish tinted brass, has obtained the name of "yellow metal." Several vessels belonging to this port, and others of London, were plated with it some years ago; but it was found to be less ductile than copper, and therefore less suitable for being laid round angles, or into the grooves or hollows of the stern-post or rudder, where the rudder-irons (or rather coppers) are attached. In some instances, too, when it required renewing, it was found, on taking it off, that it had, to a considerable degree, perished, having become so brittle, and full of minute pores, that, to use the word of a seaman, who examined it, "it broke in the fingers like a piece of gingerbread." This was, however, in the comparative infancy of the invention, and before proper proportions of materials, of which the metal was composed, had been proved by the test of experience; and the friend of science and of commerce will, doubtless, be gratified to learn that such improvements have since been made, as will, in all probability, ere long, render the use of the "yellow metal" almost universal in our mercantile marine, as at once combining economy with durability. The metal is now made sufficiently ductile for sheating; several fine large ships have been bottomed with it within the last few months, and it is so rapidly gaining ground in the estimation of navigators, that we are informed Messrs. Pascoe Grenfell and sons, copper dealers, have, during the last half year, done much 31 more business in the article than in copper itself. The captains who have lately given it a trial, speak highly of its good qualities; and one vessel plated with it has made three successive voyages from London to India without requiring any renewal in that particular-showing a durability considerably beyond the copper generally used. The price is 1d. per lb. cheaper than copper, and it is 63 per cent. lighter than that metal. It is also found to retain its weight to a greater extent, and the old metal is taken back in exchange by the manufacturers. Another, and perhaps an equally important, use of this metal is, for the bolts or fastenings of ships. From its hardness, when manufactured for this purpose, it is vastly superior to copper, inasmuch as being nearly as hard as iron, it can be driven into a much smaller augur-hole than copper, and to a greater depth in dead wood; forming, consequently, a tighter and stronger fastening, and not so liable to draw, on this account, as well as from the absence of verdegris. From all, indeed, that we can learn, the "yellow metal" may be considered one of the most useful discoveries of modern times in a commercial country like this. The works are situated within about a mile of the town of Swansea, immediately in the neighbourhood of the copper works, and are at present capable of manufacturing a considerable quantity of sheathing and bolts -there being four pair of rollers, with the machinery necessary for drawing rods, worked by an angine of 544-inch cylinder, 8-feet stroke. The metal is a combination of copper and zinc, the best admixture being found to be 60 per cent. of the former, and 40 per cent. of the latter. The metal is delivered on the works, and is then submitted in these proportions to the action of a reverberatory furnace, or melted in pots, from which it is cast in plates or bars, according to the object for which the metal is required, whether "bolts" or "sheathing." It is subsequently submitted to heat, and when, as it appears to us, of a "cherry red," is worked in the cylinders or rollers, or drawn out in rods. The process is in itself exceedingly simple, and affords little novelty to any one accustomed to the manufacture of iron.-Mining Journal. this table were hollow. Down the hollow legs wires were run to the floor, and along the floor in grooves made for the purpose, to the wall, then up the wall to the third story, thence to a point immediately above the centre of the table, The wires were communicated from the table to the point above, in the manner used in bell hanging. The grooves through which they ran were inlaid with the softest buckskin, so as to prevent a noise in pulling them; the grooves were then covered over with thin copper, and a carpet screened all from view; the grooves in the wall were papered over so as to prevent detection. Immediately above the card table, the ceiling was ornamented with a circular painting, after the fashions of some parlors. In the centre of the painting was a hook as if to suspend a lamp. The ceiling was cut into small holes, which could not be detected from below, because they represented certain portions of the figures of the paintings. When a party was engaged at play, a person above could look down upon the hands and by pulling the wires give his partner at the table any intimation as to the strength of the opposing hands, which an agreed signal might indicate. The room above was kept dark, which also prevented the players from ascertaining the cheat, particularly at night. We hear that such a piece of machinery is erecting in one of our fashionable gambling establishments. Is it so? Mileage Duty.-A table appended to the Report of the Railway Committee, shows the amount of mileage duty received from railways in England, that have not compounded for the duties. From this table it appears, that the London and Birmingham Company have paid, from July, 1837, to January, 1839, the sum of 10,9957. 12s. 1d.; the aggregate number of miles travelled during that period being 24,111,560.-The Grand Junction, from 4th July, 1837, to January, 1839, 17,0327. 19s. 10d.; number of miles, 32,702,384. The Liverpool and Manchester, from January, 1836, to January, 1839, 21,3971. 28. 84d.; number of miles, 41,082,500. The London and South-Western, from May, 1838, to January, 1829, 1,524. 19s. 3d.; number of miles, 2,927,928: and the Great Western, from 4th June, 1838, to January, 1839, 2,2297. 10s. 1d.; number of miles, 4,280,648.-Railway Times. The Typoface.-The Bordeaux papers mention that a young sculptor of that city has discovered a method of taking casts of the human face, which, without requiring that the features should be reduced to a state of perfect rigidity, allows them to preserve all their natural play, and thus produces an exact resemblance with the animation of life. His name is Pellet, and he designates his apparatus the Typoface. Aerostation.-M. Garnerin, according to the Paris papers, is constructing a balloon at the Ecole Militaire, which he hopes to direct through the air as he pleases. On each side of the car he has adapted four palettes, resembling the wings of a wind-mill, which he puts in motion by the means of a secret internal mechanism. The resistance of the air to every palette that strikes it is reflected upon the balloon and carries it forward, just like the flying bird or swimming fish. M. Garnerin, it is added, has already made some experiments which proved perfectly successful. Street-Sweeping Machine.-A new system of sweeping the streets by means of a machine was tried on Friday at the Barrière des Fourneaux, in presence of a committee appointed by the Municipal Council of Paris. M. Arago was one of the commissioners. The experiment is said to have succeeded.-Capitole. Preserving Beer.-A patent has been taken out in America for preserving beer from becoming acid in hot weather, or between the temperatures of 74 degrees and 94 degrees. To every 174 gallons of liquor the patentee, Mr. Storwell, directs the use of 1 lb.. of raisins in the following manner:-" Put the raisins into a linen or cotton bag, and then put the bag containing the raisins into the liquor before fermentation; the liquor may then be let down at 65 degrees or as high as 70 degrees. The bag containing the raisins must remain in the vat until the process of fermentation has so far advanced as to produce a white appearance or scum all over the surface of the liquor, which will probably take place in about 24 hours. The bag containing the raisins must then be taken out, and the liquor left until fermentation ceases. The degree of heat in the place where the working vat is situated should not exceed 66 degrees nor be less than 60 degrees." "The Atlantic" Steam Ship.-This fine vessel may now be seen, in all her proportions, in the buildingyard of the Messrs. Wilson, north side of the Clarence Dock. She is building for the Transatlantic Steam Company, and intended as a companion to the Liverpool in the New York trade. Her tonnage exceeds that of the Liverpool by nearly 500 tons, and she will be ready for launching in the course of six weeks or two months.-Liverpool Albion. Natural Flowers in Winter.-To produce these, some of the most perfect buds of the flowers it is wished to preserve, such as are latest in blowing and ready to open, must be chosen. Cut them off with a pair of scissors, leaving the stem about three inches long; cover the end immediately with Spanish wax, and when the buds are a little shrunk and wrinkled, wrap them up separately in paper, and place them in a dry box. When it is desired to have the flower to blow, take the buds overnight, cut off the sealed end of the stem, and put the buds into water wherein has been infused a little nitre or salt, and the next day you will have the pleasure of seeing the buds open and expand themselves, and the flowers display their most lively colours, and breathe their agreeable odour around. New Mode of Marking Linen.-A celebrated German chemist, Mr. Hoenle, has invented a new plan for marking linen without ink. This is effected by simply covering the linen with a fine coating of pounded white sugar. The stamp of iron, very much heated, is impressed on this material. Two seconds suffice for the operation. The linen remains slightly scorched, but the mark is indelible. Mr. Hancock's Steam Carriage.-In continuation of the account of Mr. Hancock's steam trip to Cambridge described in our last number, we are informed that the Automaton made several trips in the neighbourhood of Cambridge, until the carriage was taken almost forcible possession of by a mob who clambered upon it, on all sides, until it contained nearly forty persons-Mr. H., unaware of the great load with which he was honoured, on attempting to move his steering apparatus at a turn of the road, had not strength to do so, and although the steam was immediately shut off, the impetus carried the fore part of the Automaton into a ditch. Several spokes of the forewheels were broken, the axle bent, and other damage done, but none to the passengers. In a few hours, fresh spokes were put in the wheels, and every thing repaired, and the steamer returned to the inn yard. On the next day Mr. H. ran the carriage to Newmarket and back-each journey of about 13 miles, in a little more an hour. On Friday the Automaton returned to London. LONDON: Printed and Published for the Proprietor, by W. A. Robertson, at the Mechanics' Maaazine Office, No. 166, Fleet-street.-Sold by A. & W. Galignani, Rue Vivienne, Paris. |