dimensions; and it is now generally kept clear from accumulation by the land floods, but in dry seasons by the sluices in the lock-gates. The bed of the channel is stated to form a regular inclined plnne of more than a mile in length, free from a shoal or any other impediment.

The confluence of the two channels has been rendered permanent, by a pier of copper slag, with an active slope of five to one. When finished, this pier will extend full half a mile in length.

The paper then describes generally the ordinary modes of construction adopted in the works, and more particularly the lock, the cill of which is 23 feet below the level of an ordinary spring tide the coping is 2 feet above that level, and the gates are 25 feet 6 inches high.

The fabric of the lock is composed of hard silicious sandstone, cemented with blue lias lime mortar. The ashlar work of the walls is 4 feet in thickness, with counterforts, and the spaces. between them are filled with rubble, grouted with lime and sand. The whole thickness of the walls may therefore be taken at 8 feet, excepting at their bases, where they are 10 feet. The walls rest in part upon an inverted arch, three feet in thickness, and the whole mass, including the invert, rests upon a concrete of large and small rubble.

The harbour is stated to be in immediate connexion with extensive copper and tin-plate works, and also with a great extent of coal-beds bordering the valley of the Avon, and the trade is rapidly increasing, its position in the Bristol Channel being highly favourable to a foreign trade.

A plan of the harbour, with the streams and channels, and a transverse section of the lock, accompanied the paper.

"Description of the Calder Viaduct, on the Wishaw and Coltness Railway, with the Specifications, Estimates, and a series of Experiments to ascertain the Deflection of two of the Strutted Beams."-By John Macneill, M. Inst. C. E.

When first the author was called upon to carry out the extension of the Wishaw and Coltness Railway, he found that the funds for that purpose were very limited, and that it was necessary to construct the works in the cheapest manner possible. To accomplish this it was necessary to design and lay out a single line of railway, which would be sufficient to carry on the trade

by horse power, but if possible, and consistently with limited funds, to construct the viaduct over the valley of the Calder (the principal work on the railway) in such a manner as to be able to widen it hereafter, and to make it suitable for locomotive power, in the event of the trade being increased, or of the railway forming a part of the great line of communication between England and the West of Scotland. Having these objects in view, and being so restricted in funds, he was obliged to lay out the works in the first instance, very differently from what he otherwise would have done, if there had been ample funds.

The valley of the Calder, which the railway had to cross, was nearly half a mile in length, and the elevation of the line over the surface of the ground, varied from 50 to 130 feet. The first intention was to construct a viaduct, 480 feet in length, of stone arches, 60 feet span and 12 feet wide between the parapets; but as this mode of construction would have been the cause of much expense, when it became necessary to widen the viaduct for a double line of railway, and would also have involved an embankment of nearly 60 feet in height, composed of clay and marl, which was considered unsafe and likely to slip, an effect which subsequent experience on other portions of the line, has since fully proved would have been the case, it was determined to extend the viaduct to about 1200 feet in length, and to construct it of timber resting on stone piers, which allowed the means of widening and strengthening it hereafter, without stopping the trade or incurring more expense than would have been necessary in the first instance, if built to the full dimensions.

The piers and abutments are built hollow, of grey freestone, from the adjoining quarry of Dalziel; the trussed wooden beams rest in metal sockets, and the springing plates are laid, for supporting the under arches of bent timbers, which are now in progress of construction, to render the viaduct capable of supporting safely the weight of locomotives and heavier trains than now pass along it by horse power. The usual load for horses is four waggons, each weighing 1 ton, and carrying 3 tons of coal; there are frequently three of these trains on a single arch of the viaduct at the same time, and thirty loaded waggons weighing 120 tons, exclusive of the engine and tender, have frequently been taken over; on one occasion, a train consisting of sixty-five loaded waggons, of 4 tons each, making a gross load (including the engine and tender) of 279 tons, was taken over the viaduct,

but the usual load is restricted to 30 tons, until the under arches are fixed.

The details of the construction of the general work are then given, and the total cost of the single width is stated to be about £15,000; this sum includes the metal castings for the future widening, and when the strengthening and widening of the whole will be completed, the total cost will not exceed £25,000, which is stated to be a low price for a viaduct of 1200 feet long, and varying from 50 to 130 feet in height.

A description is then given of the experiments upon the deflection of a trussed beam. Two stone piers were erected 100 feet apart, with metal caps and sockets built into them; two beams were laid and strapped together and the struts fixed, precisely as they would have been in the bridge; along each side of these beams, but quite unconnected with them, posts were driven in the ground, to which a horizontal beam was attached; six rods of deal, carefully divided into inches and tenths, were then screwed to the outside faces of the beams. The beams were, in the first instance, brought as near as possible to a horizontal line, by means of a spirit level, and the zero point on the rods made to correspond with a fixed line on the horizontal bar. When the beams were loaded, and the deflection from the original level took place, it was marked by the divisions on the index rods, which being firmly screwed to the beams, rose or fell with them, and showed the quantity of deflection as marked by the line on the horizontal bar; after each load was put on the beams, it was allowed to remain an hour or two before the deflection was measured; and after the load was taken off, the deflection was again measured at an interval of some hours to ascertain the permanent set, before another load was put on. The load made use of was railway bars; they were distributed over the beams in various situations, and in various quantities, varying from 1 to 60 tons; the results of which are stated in a series of elaborate tables: and a large collection of diagrams show the situation and form of the load and the space covered at each experiment. By examining these diagrams, the situation of the load, its weight, and the deflection caused by it, will be at once seen; the results of these weights are given in the tables in feet and decimals, which will be more satisfactory than the diagrams alone would be, to those who may wish to make any calculation, or to form a practical rule upon them for their own guidance.

The appendix contains the specifications for all the artificers' work, with the dimensions of the several parts and the priced estimates; the drawings accompanying the paper were executed by Mr. Macniel's assistant, George Ellis, Assoc. Inst. C. E.

Description of the mode adopted for sinking a Well, at Messrs. Truman, Hanbury, Buxton, and Co.'s Brewery."

By Robert Davison, M. Inst. C. E.

The author commences this communication, by stating that one of the principal objects of the brewers, is to obtain a constant supply of water at a low temperature, for the purpose of cooling the worts, particularly during the summer months. The quantity of water to be obtained from the land-springs has (he says) been represented as not to be depended upon; this would probably be correct, if required, as frequently proposed, for the supply of all the wants of a city; but if a well is properly sunk, there can be no doubt of obtaining a supply of 80 to 100 gallons per minute.

With regard to the quantity of water obtainable from the chalk stratum, the author believes it to be more precarious; for while instances occur occasionally, where a considerable opening is found in the chalk and a plentiful supply is obtained,—the cases it is believed are as frequent, where fissures are not met with and a failure ensues.

He then proceeds to give a narrative of the facts which occurred during the progress of an attempt to sink a cast-iron cylinder from the surface down to the chalk, a depth of about 200 feet, intending to admit the springs at the different levels, as might be considered most advisable.

The well was commenced in the middle of a land-spring well, 16 feet diameter, and in order to avoid the usual inconveniences of pumping and excavating, Mr. Clark, of Tottenham, performed a large part of the work with the " Miser," instead of by the usual methods of well-sinking.

The land-spring well was drained January 25, 1839, and the excavation of a well, 11 feet diameter, was commenced; this was carried down of a clear diameter of 8 feet 6 inches inside the brick steening, and when it had arrived at the depth of 115 feet 3 inches, the first cast-iron cylinder was lowered, and others were gradually added, shutting out the springs as they were

passed, until April 3, when, at the depth of 135 feet, in a bed of yellow clay and pebbles, the water overpowered the excavators, and after trying many methods of continuing the excavation, the use of the "Miser was resorted to, when the cylinders had gone down to 144 feet. On the 11th of May, the oyster bed was reached, at 163 feet depth; and after some deliberation, it was resolved to continue sinking down to the chalk. For seven days the men were employed in "jumping" a heavy chisel bar to break through the hard rocky crust of this oyster bed; at length, between the 25th and the 27th of May, the cylinders suddenly sunk 5 feet 6 inches; the misering was continued until the depth of 189 feet 10 inches was attained, and the cylinders were found to be completely fixed. A pressure of nearly 100 tons, applied by powerful screws, was tried, without producing any effect; it was therefore determined to fill all the space between the steining and the exterior of the cylinder with concrete, although a portion of the steining was discovered to have given way; it was supposed that the cylinders would have been held up by the pressure against the steining and the earth; the pumpwork was therefore fixed, and after a time the pumping commenced. On the 21st October, after no more than the usual pumping, (the water generally containing sandy sediment,) it was observed that the pavement around the well had given way; the machinery was stopped, and immediately there occurred a rumbling noise within the cylinders, which lasted probably four or five minutes; on examination, it was found that the cylinders had sunk 4 inches, the main girders, across the top, were broken, and on sounding the well, it was discovered that an extensive "blow" of sand had taken place, and filled the bottom of the well for nearly 28 feet; this was cleared out by misering, and after recommencing pumping for some time, on the 14th December a separation of the cylinders, about 2 inches wide, was discovered at about 73 feet from the surface. Mr. J Braithwaite and Mr. J. Simpson were consulted as to the best method of proceeding; the former was of opinion that there was such a subsidence behind the cylinders, as would endanger the safety of the surrounding buildings. The latter did not take so serious a view of the matter; but he suggested the sinking of an internal cylinder, if the original one could not be forced down.

After this examination, a portion of one of the cylinders was 2 s

VOL. XXII.