whereas the common Argand gas-burner has usually from 12 to 15 holes of a larger bore, to give equal light when consuming a much larger quantity of gas. In the case of the larger burners, he drills the holes at a distance from each other of about one-twentieth of an inch. As a general rule for the combustion of gas according to his improvement, he considers it necessary to observe that the quantity of gas supplied, or height of the flame, should be such that its top is just received within the lower edge of the innermost central chimney. "When this is the case, the combustion will be found very perfect, and the light brilliantly white. No carbon will be deposited within any of the chimneys, and the light will be perfectly steady, the lower edge of the central chimneys defining the upper part of the light, so that the jagged or irregular edges and flickering so unpleasant to the eye in common gas-burners does not exist, and the light appears of a permanent form, as a truncated section of a luminous cone.' 39 Although a circular form of flame alone has been previously mentioned, the patentee states that the same improvements in the combustion of gas will be attained if a form of flame, bounded by straight lines, or other form than circular, be employed, provided a corresponding change be made in the form of the chimneys and apparatus. Note.-Mr. Boccius has entered a disclaimer with the clerk of the patents, of the same date as his specification, in which he states, that having, since the date of his patent, been advised that part of the said invention is not new and useful," he disclaims the following words of the title, "in gas, and on the methods in use, or burners" -so that the title, as thus amended, stands as follows," certain improvements for the combustion of gas." ADDERLEY WILCOCKS SLEIGH, K. T. S. OF MANCHESTER, CAPTAIN IN HER MAJESTY'S SERVICE, for a certain method or certain methods of effecting and forming sheltered floating harbours of safety by the employment of certain buoyant sea-barriers applicable thereto, and which said improvements are also applicable to and useful for the formation of breakwaters, floating bridges, lighthouses, and beacons, the protection of pier-heads, or embankments, and for other similar purposes. Rolls Chapel Office, Aug. 8, 1842. Captain Sleigh states that his invention consists in the construction and adaptation of sloping or oblique platforms mounted upon, connected to, or supported by floating hollow vessels or caissons, by which the platforms are always maintained in sloping or oblique positions and are enabled to rise and fall with the tide. These floating vessels and sloping platforms, when constructed, are to be so arranged as to form sea and wind barriers for sheltering ships and other vessels, and also pier-heads, bridges, and other structures requiring such shelter from the ordinary destructive effects of heavy seas and gales of wind." The ideas of the patentee are illustrated by a sectional view of a breakwater constructed on his system. The hollow vessel or caisson is represented as consisting of ribs of timber strongly planked on the outside and made perfectly water-tight and buoyant; but it may be constructed, it is said, of sheet iron or other suitable material if desired. It is of a peculiar shape, being of the form of an oblong longitudinal wedge, with the back part rounded like the side of a vessel, and the bottom perfectly flat, whilst the upper surface or deck rises at an acute angle from the extreme edge of the bottom, forming an inclined plane, which extends longitudinally the whole length of the structure. Through the centre of this caisson and along its whole length extends a strong timber beam or keel, which will be the centre of motion on which the caisson floats. The top, bottom, and sides of the caisson are supported and strengthened by internal stays or bracings arranged in any suitable and convenient manner for the purpose of giving stability to the structure. The sloping or inclined platform is mounted upon the upper surface of the vessel and firmly secured to it by wooden or iron bracings or stays. Strong rings are attached for moving it securely in any desired place. The lower end of this platform is to be immersed in the water, and its face or inclined plane to rise therefrom at an angle of 30° (in imitation of the slope of the supposed beach) to a considerable distance beyond the top of the caisson or vessel, thereby "offering a modified resistance to the violence of the winds and waves, by which means their destructive effects will be much lessened, and the water behind screened or sheltered from the action of the tempest." These floating breakwaters may be made of any dimensions, and in order to form a sea and wind barrier or harbour of refuge, a suitable number may be moored side by side, either in a straight or curved line as may be required. They are to be connected together by universal ball and socket joints, or links and toggle joints, placed at the ends of the keel or beam, "by which they will be allowed to roll upon their centres of gravity, or yield temporarily in any other way to the violence of the winds or waves.' The manner of arranging these sea barriers or floating breakwaters, to form a harbour of refuge is shown by drawings, in which they are shown connected together in the manner before stated, and are moored to the bottom of the sea by chains or cables attached at one end to the rings before mentioned, and at the other end to anchors fixed to the ground under the water. In place of the peculiarly shaped caisson or floating vessel before described the sloping platform or inclined plane may be attached or connected to a floating frame-work, supported by a number of barrels or other hollow wooden or iron vessels, or the inclined platform may be borne by a wooden frame-work or raft. The platform may be employed even without any floating support by connecting it at one end by means of chains, cables, or otherwise to the bottom of the sea, in such a manner that the upper edge may rise from the water in an inclined direction. Claim. I wish it most distinctly to be understood, that I do not intend to confine myself to the methods herein shown, and described, of constructing and floating my improved sea and wind barrier, but claim as the invention the employment as breakwaters of portable sloping platforms, or inclined planes, partially immersed in the water, in whatever manner or of whatever materials such inclined planes may be constructed, or in whatever way they may be floated or buoyed up, in, or on, the water, and held in the required situations when such portable and buoyant inclined planes are employed for the purposes or objects above stated.' INSTITUTION OF CIVIL ENGINEERS. Colonel Jones's Observations on Breakwaters. Mr. H. R. Palmer observed that the form suggested by Colonel Jones for the faces of breakwaters did not appear sufficiently justified by observed facts; the idea was entirely of a speculative character, and was contrary to the laws of nature, which should be the engineer's chief guide. Many years ago Mr. Palmer had occasion to study very carefully the motion of the shingle beach at the harbour of Folkstone, and at several other places, and the results of his observations were published in the Transactions of the Royal Society. He found that the slopes of the surface were always regulated by the force of the waves, and the angle at which they impinged; and that when the forces were at right angles with the line of beach the whole of the pebbles were brought down below the level of the acting forces. At Folkstone, when the sand was thus left bare, the surface stood at an angle of 9 to 1, and that slope resisted the force of very heavy seas. The effect of the action of the sea upon an upright surface was observable in every cliff upon the coast, and the tendency to destruction was everywhere obvious. Shingle beaches might be considered as adjustable barriers, but in the construction of piers it was necessary to adopt some precise form. When circumstances required the walls to be nearly vertical, the line of their direction should be determined with reference to the prevailing winds. Those portions of the piers of Swansea harbour which formed even only a small angle with the prevalent winds remained firm and substantial, but that part which was directly opposed or at right angles to them has been undermined. In a design of his for a pier in Mount's Bay at Penzance, Mr. Palmer had so arranged that the angle of the main pier should be at 5° with the line of the greatest forces. Thus then a horizontal slope is in fact made as a substitute for a rising one. He attributed the failures alluded to by Colonel Jones more to defective workmanship than to faults in the principle of the structure. Mr. Palmer exhibited and presented to the Institution plans of Ramsgate, Dover, Folkstone, Swansea, and Penzance harbours. In his observations of the action of the sea upon various parts of the coast, General Pasley had remarked that the slope of the beach was exactly in accordance with the materials of which it was composed; if it was shingle or decomposed rock or soft material, the slope was gradual; but if the shore was rocky, the waves had not any serious effect upon the bluff face opposed to them, except in the case of chalk cliffs. He conceived, therefore, that a perpendicular wall constructed of large ashlar work well cemented, would assume the character of a rock, and all the prejudicial action of the receding wave would be avoided. Mr. Bull stated that the banks of the river Calder in Yorkshire, had been effectually secured from damage by means of stone pitching or setting, laid at an angle of from 45° to 50° with the horizon, and resting on a mass of stone thrown into the bed of the river below the level of the water in dry seasons. These loose stones had generally been laid at an inclination of about 25° or 30° where the depth at low-water was not great; but where the water was deep the lower part of the slope had been made at about 45°, returning at the upper part or near the surface of the water to the former angle of 25° or 30°. The pitching, composed of oblong stones, was laid in courses with nearly vertical joints, having the least sectional area exposed to the action of the flood waters. The stones were from 15 to 20 inches long, varying in their widths, and were laid on a bed of gravel, or soil, he preferred coarse gravel, as it was less liable to be washed out from behind the stones, which sometimes occurred with soil, unless it was of a strong clayey nature. Several miles of facing done by him in this manner had now being standing between seven and nine years without requiring any repairs. In a few instances when the loose stones at the foot had been either insufficient in quantity or so small as not to resist the action of the floods, and had been washed away, the pitching had slid down into the bed of the river without being otherwise disturbed; after it had settled, the top part had been renewed and the original line restored. The floods in the river Calder frequently rose from 8 feet to 12 feet, and flowed with a very rapid current, consequently the pitching had to resist a powerful action, particularly at the concave side of a bend in the river, where the action was both directly upon and along the face of the work. The loose stones below the low-water mark were seldom disturbed by the floods, and where they had been removed, no damage had been sustained beyond the sliding down of the pitching as before described; such, however, had not been the case where from peculiar circumstances a perpendicular or nearly perpendicular wall had been built instead of the pitching; in such instances a slight disturbance of the loose stones had frequently caused the destruction of the wall. Where the pitching had been backed with light soil, which was easily washed out through the joints, the stone-work had fallen into holes as might be expected, but where a good strong gravel had been used for the backing, no such instances had occurred. Mr. Bull differed from Colonel Jones's opinion as to breakwaters with a vertical or nearly vertical face, because any disturbance of the footing, however slight, must have a tendency to overthrow the wall, and that tendency would be in proportion as the angle of the wall diverged from the angle of repose; that is to say, if the wall was quite perpendicular a comparatively small disturbance of the foundation or footing would destroy the equilibrium and the superstructure would be overthrown, but the nearer the face approached the angle of repose, the greater would be the security. He did not mean to assert that the angle of repose was the best for the face of a breakwater, or that the same angle should be preserved from below low-water mark to the top of the structure; on the contrary, he was inclined to think that a curved section commencing from a few feet below low-water mark at an angle of 10° or 15° from the horizon and terminating at the top at an angle of 70° or 75° would be found a good form, and if the courses of face stones were laid nearly vertical, should the footing below low-water mark be removed by the action of the waves, the consequence would be a sliding down of the upper face which could easily be replaced at the top, as is done with respect to the river pitching. The proper angle for the loose stones below low-water mark would, he had little doubt, be that of repose, or nearly so, as Colonel Jones had shown to be the case in several existing breakwaters. The face stones should be roughly squared on the beds and joints, or what is called in the North" scappled" to the form of the curve, and laid in equal courses not quite perpendicular, but inclining a little from the direction of the prevailing wind, perhaps about 10° from the vertical line. Mr. Bull was induced to offer these remarks, for the purpose of recording a practice he had successfully applied to the protection of river banks (of which he presented drawings) and his opinion as to its applicability to the construction of breakwaters. "Description of the Menai Lighthouse." By D. P. Hewett, Grad. Inst. C. E. The Menai Strait is peculiarly fitted for a harbour of refuge for vessels entering the Rivers Dee and Mersey from the north, and the increasing number of ships frequenting this navigation, as well as the insufficiency of its beaconage, rendered it desirable that the entrance should be distinctly marked; the Corporation of the Trinity House accordingly decided, in 1834, to effect this object by the construction of a lighthouse, to be situated on a sunken rock about 200 yards from the Anglesey coast on the west side of the entrance, which is divided by the Puffin Island into two channels, defined by a beacon and two buoys. The principal novelty in the construction of the lighthouse is the base, which, instead of diminishing, like the Eddystone, with a regular curve, recedes by a series of rectangular offsets; the object of this form of structure is to break the force of an impinging wave, and prevent the whole effect of its shock being thrown upon the upper part of the building, as it is when guided up by the curved surface. The building, which was designed by Messrs. Walker and Burges, is a handsome circular tower 75 feet high, 40 feet in diameter at the base, and 20 feet 6 inches diameter at the top, terminated by a castellated parapet, and entirely constructed of Anglesey marble. The base of the building is solid to the height of 22 feet 6 inches from the rock, diminishing at intervals of 2 feet 3 inches by offsets of 9 inches each, up to 6 feet 9 inches above high-water mark, where its diameter is 22 feet. On that level is the entrance doorway (which is accessible by steps cut in the base stones). The interior contains six floors, forming rooms for the uses of the light-keepers, stores, &c. Every precaution has been taken to render the exterior joints of the courses water-tight; each stone is secured to that below it by a slate joggle, and two oak trenails, passing entirely through it, and entering 8 inches into the lower stone. On the upper bed of each course of stones is a projecting fillet, which fits into a corresponding groove in the under side of the course placed upon it, in order to prevent the water from being forced between the courses. The two upper courses project internally and externally to form a gallery which supports the parapet and the lantern, the foundation and the framing of which are of cast-iron. The wall diminishes gradually in thickness from 6 feet 9 inches to 2 feet. The communication describes minutely the construction of the floors, the partitions, the stairs, the lanterns, &c., and the proportions of the materials for the mortar, which consisted of three measures of sand, one of ground lime, and one of Italian pozzuolana. The light is a stationary, red, dioptric light of the first order, without mirrors. The burner consists of four concentric wicks, of which the largest is 34 inches diameter; its ordinary consumption of oil is one pint per hour. The various bearings are given from which the light is visible at sea. After deducting all expenses, the surpluss revenue derived from the light dues, during the year 1840, is stated to have been 3887. 138. 3d. The lighthouse is connected with the shore by a foot bridge, which consists of a platform 2 feet 3 inches wide, supported upon a series of iron columns placed 10 feet apart, secured into the rock and strengthened by stays. This slight construction has withstood the violence of the waves for three years. The paper notices the buildings which have been erected on the shore for the residence of the light-keepers, and then proceeds to describe the beacon before alluded to, which points out a dangerous ledge of rocks on the opposite side of the channel. It consists of a cone of masonry, 20 feet in diameter at the base, and 37 feet high, surmounted by a staff and globe rising 13 feet above the apex of the cone. The globe, which is 4 feet diameter, is formed of copper bands, and is 36 feet above high-water mark. The whole amount expended in these different constructions is stated to have been about £12,800. The communication was illustrated by a series of detailed drawings and a chart of the straits. April 19, 1842. "On the causes of accumulation of deposit in Sewers, and on the hitherto generally prevalent mode of removing the same; with a description of a new Flushing Apparatus used for cleansing the Sewers in the Holborn and Finsbury Divisions." By John Roe, Assoc. Inst. C. E. In the Holborn and Finsbury Divisions there are upwards of eighty miles of covered sewers, in a large proportion of which there were accumulations of deposit, which by choking the side drains and causing effluvia became sources of much annoyance. The only remedy resorted to, was to raise the deposit to the surface of the street and cart it away this was for many reasons an objectionable process, and a careful examination of the sewers was ordered, when it was found that many causes of obstruction existed. In sewers of the same form and inclination, different degrees of accumulation existed this was caused sometimes by a greater run of water in one than in the other: in other cases, although the flow of water was equal, the deposit was unequal: in some situations, openings having been made to insert side drains, bricks had been left in the sewer, against which considerable deposits had formed the admission of water from collateral sewers at right angles and at different levels had also caused obstructions to the continuous flow along the main line: an example is given, where, although the collateral sewer was 3 feet above the level of the main line, a deposit of a foot in depth was formed for several hundred feet up the stream, while below the point of junction the sewer was perfectly clear. The insertion : of gully-necks frequently caused obstructions by permitting the access of dirt and rubbish from the road. These facts being ascertained, the next consideration was how to remedy the defects, as the locality would not permit an alteration of level, which would give a flow through the sewers sufficiently strong to carry off the deposit. After a long series of experiments (by the author, who is engineer to the Commissioners) and trials upon several kinds of apparatus, an arrangement was decided upon, consisting of an iron frame set in the sewer with a hinged door half its height, fitting with a water-tight joint: it is opened and closed by means of a jointed rod, which is worked from the level of the street. A head of water is allowed to collect against the closed door until it is sufficiently heavy, when the door being suddenly opened, the whole mass of deposit is carried forward by the rush of water. The operation is repeated with a head of 3 feet of water at intervals of half a mile, until the whole of the accumulation issues at the outfall, thoroughly cleansing the sewer. After this arrangement of apparatus had been some time in use, an improved form, with a side entrance, was continued, and is now generally adopted in situations which admit of it. By this simplified arrangement the stopgate can be worked without the mechanical contrivances of the other method, and an easy access is afforded to the sewers. This latter mode is generally adopted, and the success of the plan is stated to be perfect. All the details of the construction of the stop-gates and the sewers, as well as of several improvements in the building of the gullyholes and collateral sewers, are given, with the result of the velocities of the currents of water from heads of various heights. Drawings of all the several kinds of apparatus invented by the author were presented, and the models which were exhibited were explained by Mr. Burton, the manufacturer of the flushing apparatus. Indicators for Steam-Engines. Mr. Farey exhibited and described one of a set of Indicators for steam-engines, made by Mr. Penn of Greenwich for the French Government, to be used in trying experiments on the steam vessels in their navy. The construction was the same as those made by Mr. M'Naught of Glasgow ; but the instruments were larger and better proportioned. Mr. Farey availed himself of the opportunity of describing the construction, the operation of, and the qualities required in a good Indicator, and then exhibited a series of Indicator cards, either taken by himself or by friends whose accuracy could be depended upon. They extended from the year 1817 at short intervals down to the present time, and showed a great improvement in the application of steam in engines: in fact, Mr. Farey was of opinion that the origin and progress of the modern improvements in engines might be traced by a series of cards carefully taken at various periods, and he promised to contribute a more extended communication on the subject during the ensuing session. April 26, 1842. "Description of a new arrangement for raising Ships of all classes out of water for repair; proposed to replace the Graving Dock or the Patent Slip in certain situations; with observations upon the other methods used at different periods for this purpose." By Robert Mallet, M. Inst. C.E. This communication describes an apparatus proposed by the author as a substitute for the graving-dock or the patent slip, in situations where such constructions would be too expensive, or an inappropriate locality prevents their adoption. It reviews the principal methods hitherto in use,—such as stranding by bilge-ways, careening or heeling over, lifting by the camel, the graving-dock, the floating-dock or caissoon, the screw and the hydraulic docks (both American inven. tions), and Morton's patent slip: it enumerates the localities for which each of these inventions is most applicable, and then gives the objections to them. The author then describes the general principle of his invention to be, the diffusion of the load or strain over the greatest possible number of fixed points, avoiding casual and unequal strains; that there should be uniform motion, with a power proportioned to the resistance. In providing for this, the toggle-joint is used throughout. The machine consists of a platform, supported upon a series of frames with joints at each end, attached at the lower extremities to fixed points in the foundation, and at the upper ends to the under side of the platform, which is traversed by a series of beams, to the ends of which are fastened rods connected with rollers, working in grooves along a suspended railway on the cantilevers of two jetties, which are built to form the sides of the apparatus. A chain connected with all these rollers traverses in each suspended railway groove, and the power of a steam-engine and wheel-work, being applied after the vessel is floated on the platform and made fast, the frames raise the platform and vessel together gradually out of the water, permitting free access all |