water and naphtha in the fittings. The only wonder is, that this obstacle did not take place long before. I warned him of its probability the first time I inspected his arrangements in the roof of the House. Again and again have I explained to him the cause of this temporary difficulty, arising solely from his placing the gasmeter, charged with water, in a very hot situation, instead of the cellar, a very cold one. The youngest apprentice in a gas-fitter's establishment could have told him that meters, so placed in bakers' shops, or other warm situations, are liable to have their "fittings," or tubes of conveyance, charged with deposited moisture, and where a more convenient situation cannot be obtained for the meter, then, syphons or receivers, for this water, are placed at proper intervals in the fittings. Here then, is "the head and front of my offending," as blazoned forth in the REPORT,' and of which, even to this very day, the most unwarrantable use is endeavoured to be made at the numerous club-houses which have adopted my patent, during the last year and a half, with perfect success and satisfaction. Here, Mr. Editor, I close my case, trusting very safely as to the verdict likely to be returned by your readers and the public. I will not tire them with extracts from letters through the years 1841 and 1842, up to the very time of Mr. Gurney giving his evidence on May 2d, when he stated his reasons for discontinuing what, without much vanity, I might call 'Lowe's Improved Bude Light,' to be the difficulty at times of procuring manganese, whilst on May 12th, he ascribes it to the formidable obstacle' of deposition; the real fact being, that the Gas Company would not accede to his unreasonable request of a special, instead of a general licence.

Believe me to remain,

Dear Sir, yours, &c.

GEO. LOWE.

Scientific Notices.

REPORT OF TRANSACTIONS OF THE INSTITUTION OF CIVIL ENGINEERS.

(Continued from page 403, Vol. XXI.)

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 been 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 2 s

VOL. XXI.

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 stonework 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 vertically, 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 shewn 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.

April 19th, 1842.

The PRESIDENT in the Chair.

"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 sidedrains 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