VELOCITY OF WATER IN PIPES. as the continued product of the arms of the levers presented towards the weight is to that of those turned from the weight or towards the power. But although this may be one way, yet it is not the practical method. The number of teeth in the wheels and the leaves in the pinions are found; and then the power is to the weight, as the continued product of all the leaves is to that of all the teeth. (To be continued.) VELOCITY OF WATER IN PIPES. Sir, It seems from the communication of your correspondent Aqueduet, that I mistook his meaning inrespect to the pipe having a slopethis, however, makes no material difference in the result obtained. This your correspondent seems to admit, as he observes, that "he cannot think it would matter much whether the insertion were into the bottom of the reservoir or not!" Otherwise, who would suppose him to be so ignorant as to think that the water in the reservoir being below the horizontal level of the pipe, can have any effect on the velocity of the water passing through it? Every body knows that the velocity of the water in the pipe depends on the altitude of the head of water above it, which generates its initial velocity; the greatest velocity being at its entrance into the pipe-the pipe being horizontal-the water evidently acquires no further increase in its velocity from the effects of gravity, but is retarded by the friction of the pipe in proportion to the ratio of the square roots of their lengths nearly. Now, according to the result obtained from the formula of Du Buat, we find that the retardation occasioned by the friction of the pipe is very nearly equal to the initial velocity. If we suppose the pipe to be plugged up at the extremity, and a small hole to be made in the top of the pipe near the reservoir-it is well-known both from theory and practice, that the water will spout nearly to the height of the head of water in the reservoir. But this will not be the case in a pipe of 200 miles in length, when a small hole is made 429 in the pipe at this distance from the reservoir. The water will acquire the same level, it is true; i. e. suppose the pipe at the end to be turned up in a vertical position, the water will rise in it to the same level as that in the reservoir at 200 miles distance; but it will be a considerable time in acquiring that level. The height to which the water would spout would in each respective case be equal to the,, and part of an inch only. Now, if we suppose the pipe plugged, and a hole drilled part of an inch in diameter, and the same quantity of water to pass through the adjutage, as that which passes through the pipe, according to Du Buat's formula, the water will in this case issue with a velocity equal to that in the pipe X area pipe area adjutage or in each case equal to 133, 196, 156, and 35 inches per second. And the height to which the water would spout would be nearly equal to 23, 50, 32, and 16 inches respectively, neglecting the resistance of the air and aperture of the adjutage. In respect to the quantity of the discharge, I did not, as your correspondent supposes, mistake the drift of the inquiry. And in respect to my taking the discharging orifice at an inch in diameter-I took it as stated in the inquiry; no mention being there made as to the pipe being plugged up at the end, or an aperture being made in the side of the pipe, the answer was therefore quite as consistent as the question in which the marrow and substance, mind you, was wanted! As to Du Buat's formula, I am quite aware that it is empirical; but in its application to the present inquiry, it will admit of its greatest accuracy, the results in pipes of considerable lengths being nearly the same as those which are found to obtain in practice. It is principally in pipes of short lengths in which this formula fails, where the slopes are very considerable. Suppose, for instance, the length of the pipe is 50 feet, and the height of the upper above that of the lower end of the pipe 30 feet. Now it is evident that the pipe is the hypothenuse and 430 PROFESSOR ALDINI'S INCOMBUSTIBLE DRESS FOR FIREMEN, the altitude of the upper end, the perpendicular of a right-angled triangle; therefore the value of s, or slope of the pipe, is equal to & nearly: hence whatever may be the length of the pipe, the value of s in this formula will always be the same. Here then this formula fails of giving a correct result, and other formulas are therefore substituted in similar cases; but I know of no formula which is allowed to give a more correct result than that of Du Buat in the present inquiry. If your correspondent can point out one, that one will be the marrow and substance, mind you, and will determine the drift of the inquiry at once. Mr. Editor,-Secure in the ultimate result, I am quite content to draw upon my stock of patience, and permit the Practical Engineer-the spirited vizor-covered champion of Legion and exposer of imposition-to run at the end of his tether until my leisure permits me to attempt to break a lance with him: knowing full well, that in the mean time there is no fear his practical knowledge will impose upon any one. It matters little whether the Practical Engineer knows me or not; my observations are not the less applicable to him on that account. In my last letter to the Magazine, I purposely touched on the subject of the joints and bolts, knowing by the tenor of his first letter that it would produce an amusing display of his abilities; and hence we see that because he cannot comprehend how such joints can be made, he assumes, as a necessary consequence, that my narrative must be altogether an imposition; and is induced to break out into the exclamation of "Mr. Gilman, Mr. Gilman, how can you have the effrontery to make such assertions!" Mr. Gilman begs to assure the Practical Engineer that he is perfectly easy about the matter, and has nothing to fear, notwithstanding the Practical En gineer's confidence; and that there really are more things in heaven and earth than the Practical Engineer appears to have yet dreamed of in his philosophy. Verily this Practical Engineer seems quite as much puzzled about these joints, as Peter Pindar represents the King to have been, when he attempted to discover how the joints of apple-dumplings were made. Yours, &c. WM. GILMAN. FARTHER PARTICULARS OF PROFESSOR The following additional particulars respecting Professor Aldini's incombustible dress for firemen, of which we gave a brief notice in our last Number, are chiefly derived from a Report of a Commission recently appointed by the Royal Academy of Paris to investigate the merits of the invention. The Reporter to the Commission was M. Gay Lussac: The dress of M. Aldini consists of two garments;-one a thick tissue of amianthus, or of wool rendered incombustible by being steeped in a saline solution; the other, an iron wire-gauze dress covering the former. The idea of the latter was suggested to him by the chain-armour of the ancients, which he found to be impervious to flame; upon the principle first discovered by Sir H. Davy, and employed by him in the construction of his safety lamp. This wiregauze dress, however, would not alone be sufficient to protect the body from the action of heat, though it might ward off the flames: but the dress of amianthus, or wool, by its thickness and non-conducting power accomplishes this, and forms with the wire-gauze an efficient defence, for the time at least that the exertions of the firemen require. The head-piece consists of a stout cap of amianthus-cloth, fitting close to the skull, and covering the throat, having holes made in it for the nose and mouth: spectacles are also provided for the eyes, lined with fine brass wiregauze. The metallic dress consists of five different pieces: the helmet, between considerable space, and which is morewhich and the amianthus cap there is a afford additional security to the face; over furnished with a mask in front, to a cuirass; arm and thigh pieces, the PROFESSOR ALDini's incombuSTIBLE DRESS FOR FIREMEN, latter joining the cuirass over the hips; a pair of boots; and a shield of an oval form, five feet and a half long, and two and a half wide. This shield is useful in stopping or turning any strong jet of flame, and thus enabling the fireman to see his way; and it is proposed to construct frames on a similar principle, to intercept the flames issuing through a door or other aperture. The whole of this dress is composed of iron wire-gauze, the meshes of which are about one twenty-fifth of an inch in diameter: the weight of it altogether is about 15lbs. The fireman has likewise a basket, covered with wire-gauze, strapped to his back, for the purpose of transporting a child through the flames; ropes and double gloves also of amianthus have been made, with the latter of which, red-hot bars of iron may with safety be carried in the hand. A fireman, with the double protec tion of the incombustible cloth and wire-gauze, subjected his face to the flame of a straw fire held in a chafing. dish, for the space of 1 minute and 30 seconds. Another, armed as the former, with the addition of a sheet of amianthus in front, supported the heat during 2 minutes and 37 seconds without any symptoms of suffering. The pulse of the first rose during the experiment, in the space of a minute, from 80° to 120°, and that of the second from 72° to 100°. 431 The next experiment was still more satisfactory. Two parallel hedges, about three feet distant from each other, were formed of straw and brushwood, piled upon bars of iron. When these were set on fire, the flames from the two rose in a body to the height of at least nine feet, and filled the entire space between ; while the heat was too great to approach nearer than eight or ten paces. At this instant, six firemen, accoutred with the dress of M. Aldini, and following each other at a slow pace, traversed the flames between the hedges many times in succession. One of them carried an osier-basket covered with wire-gauze, containing a child eight years old, protected only with a mask of incombustible cloth. This experiment, which the bystanders witnessed with apprehension, had a most satisfactory result; and had the smoke been more dense, it would have been entirely decisive. The firemen were unhurt; the one with the child retreated from the fire in the space of a minute, on account of the cries of the child, who was frightened at a sudden movement of the man in shifting it on his shoulder. The child was also uninjured, and when taken from the basket its pulse had risen only from 84° to 98°. The other firemen sustained the experiment 2 minutes and 22 seconds; and on coming out, were in a profuse perspiration. The pulse of the fireman who carried That of the fourth..... The main question was, the possibility of supporting respiration in the midst of the flames: and if we suppose the men to be completely enveloped in them for two three minutes, their situation certainly appears most perilous. M. Gay Lussac observes, that when a furnace is heated so as to flame and smoke, the air within is entirely deprived of oxygen; and therefore it is certain, that if the immediate action of the flames were guarded off by the wire-gauze, still it would be impossible to sustain respiration in the midst of them. We must therefore conclude that if the firemen did not experience the difficulty of breathing which we should naturally expect, they must have been supplied in some way with pure air. There are several ways of account ing for this; and one, which M. Gay Lussac suggests, appears the most probable: viz. that the men were supplied الي 92° to 116° 88° to 152° 84° to 138° 78° to 124° by a current of fresh air from the space between the two garments. Besides this, we cannot suppose that their heads were constantly enveloped in the flames, and they would of course find favourable moments for breathing; but the power of suspending the breath is also an excellent resource, which every fireman ought by practice to acquire. The fireman has another difficulty to contend with, in the dense volumes of smoke, which prevent his breathing, blind his sight, and consequently retard his exertions. To obviate this, it has been proposed to furnish a supply of air from a portable reservoir; or by means of a flexible tube, rising from the feet to the mouth, through which the fresh air would naturally rise, as the heated air escaped above. There is little doubt that amianthus may easily be manufactured: M. Aldini has succeeded in weaving a stout cloth of it, 9 feet 5 inches long, and 5 feet 3 inches wide, being nearly equal to the celebrated one preserved in the Vatican. But the cost of this material cannot admit of very general use; and on this account M. Aldini is endeavouring to substitute for it a manufacture of wool. Wool is naturally but little inflammable, and when steeped in a solution of sal-ammoniac and borax, or alum, burns to a cinder without inflaming; it is also slowly penetrated by heat. It appears from an experiment of M. Flourens even to have an advantage over amianthus. That gentleman presented a finger covered with amianthus cloth to the flame of a wax candle, and afterwards repeated the experiment, substituting a covering of the prepared wool of the same thickness. In the first case he experienced the effect of the heat sooner than in the latter. In point of economy, facility of preparation, and convenience, from its greater lightness and weaker conducting power, the preparation of wool has the preference over THE NOVELTY." amianthus; and though its resistance to fire is less than the latter, it is still suffi-" cient in all ordinary cases, and may form a very sufficient substitute. FURTHER EXPERIMENTS WITH "THE NOVELTY" STEAM-CARRIAGE ON THE LIVERPOOL AND MANCHESTER RAIL WAY. Extract of a Letter from a Correspondent. Liverpool, Jan. 28, 1830. * "On Tuesday, the 26th, a series of very interesting experiments were made with "The Novelty" on the two miles level at Rainhill, under the direction of Mr. Vignoles, the engineer; which had chiefly for their object, to ascertain the weight which this engine is capable of drawing, and at what expenditure of fuel. I have but time to send you a brief abstract; the results are most satisfactory. The steam was kept up for 6 hours and 16 minutes, or 6-26 hours. The coke consumed during that time was 526 lbs. To which add for getting up the steam, which was done Total-588 lbs.=5} cwt. in 32 minutes, 62 lbs. The load drawn was 28 tons, 1 cwt, and about 10 passengers, say 28.5 tons in all; equal to 960 tons drawn during the experiment: 28.5 tons carried 30.813 miles viz. 878.7 tons. 7.5 17.5 do. 3.224 do.. 24.18 58.11 960 46 tons carried one mile. The blowing apparatus being constantly at work, the average consumption of coke was 84lbs. per hour: viz. 526 lbs. S3.9lbs. Now, the average of the speed 6.26 hours. of the engine between the quarter mile-posts, was 8.05 miles per hour, with a load of 28.5 tons; therefore 285x8-05-229-425 or 229 tons, carried 1 mile with S4lbs. of coke. Consequently 83.9 lbs. coke 229.425 tons 365 or of a pound per ton per mile. The distance from Liverpool to Manchester being 31 miles, the quantity of coke necessary to convey a ton that distance, will be 365×31-11315 lbs. which at 10s. per ton, is 6106d. or ths of a penny per ton for the whole distance. If we add one-fifth for stoppages at each end, and getting up steam, the amount will be 6106+1221=*7327, or under d. per ton for 31 miles!" INTERIM NOTICES. Mr. Lubbock has published in the last No. of the Philosophical Magazine, a paper "On the tides in the port of London," which is intended to confirm the accuracy of his investigations and computations in the Companion to the Almanac. It bears the most unequivocal marks of that gentleman's wonted philosophical acumen and correctness. We hope to give it a cursory examination early enough for our next Number. Errata. Page 405. col. 1. in the sirth descrip tion of lines the word cuspidated should have beennodated. Page 406, fig. 6, the parabola marked 'E' should have been B.' S. Y.-Yes. Communications received from G. C.-Lancaster-Mr. Dowling-S. P. B.-Dr. Fox-Mr. Ilarvey-Mr. Hayter-Littoralis--A Naturalist -Mr. J. Gilbert. LONDON: Published for the Proprietor, by M. SALMON, at the Mechanics' Magazine Office, No. 115, Fleet Street; where Communications for the Editor (post paid), are requested to be addressed. M. SALMON, Printer, Fleet Street. |