his profession. The history of engineering in this country showed that the works which reflected the highest honour upon the profession had been carried out, to a great extent, by men who had not any large amount of special theoretical education, but who, being possessed of great natural powers, were enabled to take advantage of the national resources and peculiarities in such a way as to command for English engineers universal respect. He thought that this result would not have been attained, if they had relied upon a technical theoretical education, and systematized rules, cut and dried by others, instead of their own energy and originality of mind and action.

Mr. MALLET was far from wishing to disparage the achievements of those who had been the great fathers of English engineering; but he would ask, how much greater would those achievements have been if these undoubtedly great men, the Brindleys and the Stephensons of engineering history, in place of having to employ their grand intellects in hammering out imperfectly, and as best they could, the information they needed, had had that educational training that would have placed at their command, in orderly array, the accumulated stores of knowledge of all mankind in all time past, and the power that such confers?

Mr. CRAWFORD observed, through the Secretary, in reference to a remark that the works between Verviers and Liège, on the line from Cologne to the Prussian frontier, had not been described in the Paper, that that railway was in Belgium, and being beyond the Prussian frontier, was not within the limits treated of in the Paper. The principal works of interest on the railway from Cologne to the Prussian frontier, namely, the incline at Aix-laChapelle and the large tunnel, one of the first constructed in Germany, were alluded to.

November 18, 1862.

JOHN FOWLER, Vice-President,

in the Chair.

THE Discussion upon the Paper No. 1,071, on "The Railway System of Germany," by Mr. R. CRAWFORD, was continued throughout the evening to the exclusion of any other subject.

November 25, 1862.

JOHN ROBINSON MCLEAN, Vice-President,
in the Chair.

No. 1,058.-"The Hownes Gill Viaduct, on the Stockton and Darlington Railway." By WILLIAM CUDWORTH, M. Inst. C.E. THE Stockton and Darlington Railway has been no exception to the system of gradual extension, which appears to be so commonly the policy, or the necessity of railway management. Its length, at the time of its opening in 1825, was 25 miles. It has now spread out, by numerous ramifications, to 183 miles. The branch upon which the Hownes Gill Viaduct has been erected was formerly the western part of the Stanhope and Tyne Railway. After the dissolution of that Company the part referred to came into the hands of the Stockton and Darlington Railway Company, in the year 1844. On account of the mountainous character of the country traversed by this branch, which has a summit level of about 1,450 feet above the sea, the adoption of steep gradients, worked by stationary engines and ropes, though diversified with occasional intermediate lengths comparatively level, was unavoidable; but it was carried to a greater extent than would be consonant with modern ideas. Thus, Hownes Gill, a dry ravine 800 feet wide and 160 feet in depth, situated near the Consett Ironworks of the Derwent Iron Company, in the north-western part of the county of Durham, was crossed by a descent and ascent corresponding with the contour of the Gill; the gradient on the west side being 1 in 2, and that on the east side 1 in 3. A small traffic, conveyed in chaldron waggons, was for some years taken over these gradients with little difficulty, although encumbered with what subsequently proved to be a needless contrivance, for preserving the waggons in a horizontal position. This consisted of cradles, or carriages, one for each incline, having front and hind wheels of unequal diameter, upon which the waggons travelled side foremost. Only one waggon could be passed across in each run, and. delay and expense were incurred, by each having during its transit to be turned upon four turntables. It was, however, arranged that both inclines should be in operation at once, by which means the gravitation of the descending waggon aided the engine in drawing up the ascending one.

Soon after the connection of this branch with the Stockton and

Darlington Railway, the increased traffic was objectionably retarded at the Gill, and greater facility of transit became imperative. This was obtained by the simple removal of the cradles and turntables, and by allowing the waggons to travel upon their own wheels, when three could be linked together in a train, and passed across in less time than was previously occupied by one. This alteration was satisfactory, and the Gill was worked well for a time; but a large accession of traffic, consequent upon the discovery of the Cleveland ironstone, and its purchase by the Derwent Iron Company, at length demanded further accommodation. The trains were necessarily limited to three waggons, to avoid putting undue strain upon the couplings, and various methods of obviating this restriction were considered; but nothing less than the erection of a high level viaduct seemed to offer a satisfactory solution. The idea of a viaduct had been a favourite one with the Directors of the Stockton and Darlington Railway Company from the first; but for some years the traffic was insufficient to warrant the necessary outlay. As early as the year 1844, with the view of ascertaining the probable cost, the Directors issued advertisements offering premiums for the two best designs of viaducts, to be accompanied with estimates of cost. This met with a ready response, but the estimates attached to the premium drawings exceeded £17,000. When, in 1853, the subject became more pressing, the remembrance of the premium experiment was sufficiently encouraging to induce the Directors to repeat it. Upon this occasion their attention, and that of their engineer-in-chief, Mr. John Dixon (M. Inst. C.E.), was attracted by a design sent in by Mr. John Anderson, then of Edinburgh, now of Middlesbro'-on-Tees, contractor, and prepared by Mr. Thomas Bouch (M. Inst. C.E.), as it was accompanied by a tender to erect the viaduct, and to uphold it for twelve months after completion, for the sum of £11,697 if built of common brick, or of £13,237 if built of firebrick. The design represented twelve arches each of 50 feet span. Although the ability of Mr. Anderson was well known to the Directors, and although they had also great confidence in Mr. Bouch, it was thought desirable to consult the late Mr. Robert Stephenson, M.P., as to the sufficiency of the design. In the interview which Mr. Dixon had with Mr. Stephenson, when Mr. G. P. Bidder (Past-President Inst. C.E.) was present and gave his advice, a general approval of the plan was expressed, with some limitations and recommendations, as the proportions of the viaduct were considered to be such as to leave no margin for inferior material, or workmanship.

Nearly three years elapsed before further action took place. At length, in 1856, Mr. Anderson's offer was accepted, to erect the viaduct in fire-brick, set in hydraulic mortar, the arches to be in

cement, for the sum of £14,100. As the premium drawing, with the modifications suggested by Mr. Stephenson and Mr. Bidder, was the basis of this contract, the sum required to be readjusted, when the circumstances of the foundation, site, &c., had been considered. In December, 1856, a revised contract was entered into, referring to a duly matured working drawing and specification. Mr. Anderson then undertook to erect the viaduct in eighteen months, and to uphold it for twelve months after completion, for the sum of £14,614. To avoid interfering with the traffic over the inclined planes, a deviation of the line was an obvious necessity. The piers in the slopes of the Gill found a firm foundation on the shales and stone of the coal measures. The only difficulty was the occurrence of abandoned iron-stone drifts, the entrances to which were concealed by a thick cover of débris. A careful probing of the doubtful foundations, with boring-rods, was therefore resorted to. Some of the drifts were entered and explored, and eventually both the abutments were sunk through the strata in which the mines occurred. In the bottom of the Gill there was a thick bed of heterogeneous material, consisting of the débris of the slopes, into which a bore-hole was put down for 30 feet, without indicating a change of stratum. Although this bed was by no means of a soft nature, it was not deemed firm enough to sustain the great weight of the structure with ordinary foundations. At the suggestion of Mr. Stephenson, the bases of the three central piers were extended, by the application of inverts, until the weight scarcely exceeded 1 ton per superficial foot. The choice of firebrick, in preference to common brick, was made with the view of having the best material, the common bricks of the neighbourhood being inferior both in strength and regularity of shape. Large quantities of fire-bricks are made at the collieries in the district, for the linings of the coke ovens and of the iron furnaces of Cleveland.

The extreme length of the viaduct (Plate 1) is 730 feet, and its greatest height, from the bottom of the inverts to the level of the railway, is 162 feet, or from the surface of the ground about 150 feet. There are twelve semicircular brick arches, each 50 feet span, 14 feet in length, and 2 feet 6 inches in thickness, set in Portland cement. The inverted arches in the foundations, four in number, have a versed sine of about 14 feet, and are 38 feet in length, and 3 feet in thickness. The brickwork in these, as well as in the piers, and in the whole of the viaduct, with the exception of the arches, was set in hydraulic mortar. The height of the five loftiest piers, measured from the springing of the inverts to the springing of the arches, ranges from 114 feet to 110 feet; that of the six remaining piers diminishes' rapidly towards each end. Their length is 14 feet at the top, and 38 feet at the bottom, in the case

of the high ones, the latter dimension corresponding with that of the inverts. The piers down to within about 15 feet of the inverts are stayed with buttresses, which are transverse to the line of the viaduct. At this point they are only 17 feet 6 inches in length, but below this level the buttresses merge into the piers, when they together present a rectangular horizontal section 38 feet in length. The buttresses are 3 feet thick at the top and 5 feet thick at the bottom; their projection from the piers being increased by offsets at intervals of about 35 feet. The piers, although light in their proportions, are reduced by recesses 7 feet 3 inches wide, and averaging 3 feet 9 inches deep, in each side, so that the horizontal section of the pier and buttresses is in the form of a double cross, the brickwork left in the middle being only 2 feet thick. These recesses are not continuous throughout the pier, but are divided into three compartments, the solid parts between affording facility for the introduction of two bond courses of stone, the continuation of which through the buttresses forms a finish and protection to the offsets. The amount of brickwork abstracted from one pier by the adoption of the recesses is 142 cubic yards, or about 14 per cent. of the contents of a solid pier without recesses.

Between the spandril walls, which are of brick 3 feet thick, two internal parallel walls of stone 2 feet thick were introduced, to sustain a platform of flagging 6 inches thick, upon which the waybeams' and ballast are carried. The arches between these walls are kept dry by a layer of puddled clay, which conveys the water to discharging-pipes over the piers in the usual manner. The waybeams are of Memel fir, 12 inches by 12 inches. They were at first fixed to the flagging with bolts secured to the internal walls; but it was soon found that there was an objectionable rigidity in the permanent way, indicated by the working of the ballast and the occasional fracture of a joint chair, and accompanied by an unpleasant amount of vibration. These evils were remedied by simply removing the nuts from the locking-down bolts, lifting the way-beams 6 inches, and interposing that thickness of the common coke ballast of the district, between the way-beams and the flagging. The external walls were covered with a simple projecting string course, 3 feet 6 inches by 1 foot 9 inches, and upon this was fixed a substantial cast-iron railing, forming the parapet. The choice of iron was more than a mere question of taste, it effected a considerable saving of brickwork; for if a brick or a stone parapet had been adopted, the upper part of the viaduct, including the arches, must have been about 16 feet wide, instead of 14 feet.

The fire-bricks, which were of excellent quality, were obtained chiefly from Pease's West Fire-brick Works, near Crook, about 14 miles from the viaduct, but having railway communication with