three or four feet; so that the use of lighters has become unnecessary, and vessels of every description can get up to the quay. The other improvements of our author consisted in constructing a great extent of new wharfs; in forming a new channel for the river, constructing capstern towers and jetty, with a bulwark and embankments. These works, including a communication bridge of cast iron to the Inches, cost about L.61,000, the whole of the improvements amounting to L.160,590. To these valuable works the trustees have added a building slip, according to the patent of Mr Thomas Morton of Leith, capable of receiving the largest class of steamers for the purpose of repair; and we are glad to find that another of these slips has been recently laid down.* Improvements of nearly a similar extent were made by Mr Telford on the harbour of Dundee, a seaport on the Tay of great commercial activity, and now possessing a population of upwards of 60,000 souls. Previous to the commencement of the present century, the excellence of the roadstead, aided by a very imperfect wharfage on the shore, enabled her enterprising citizens to carry on a considerable trade. The growing prosperity of the city, however, rendered it necessary to have a considerable addition to its harbour accommodations. The harbour dues, which in 1765 produced only L.126, amounted in 1800 to L.1300; and though the corporation had, in ten years previous to 1815, collected and applied promiscuously with the town revenue, no less than L,13,817, yet they had expended only L.1193 on the harbour and wharf. The landowners, however, and the agricultural capitalists of the rich and fertile district which lies in the vicinity of Dundee, began to feel an interest in its prosperity as a seaport, and, finding it vain to rouse the corporation to a sense of their duty, they succeeded in placing the exclusive management of the harbour in the hands of public commissioners. The conduct of the Dundee corporation,' says Mr Telford, 'forms a striking contrast with that of Aberdeen. The management of the port was No Mr Telford has given, in his Appendix, the Report of the Select Committee of the House of Commons on Mr Morton's valuable invention, which the writer of this article had repeated opportunities of examining from its earliest stage, till it was brought to its present perfect state. fewer than fifty-four of these patent slips have been laid down at different ports, and licenses have been granted for the construction of several others. Notwithstanding the high encomiums which the Select Committee had passed on the value of this invention, they refused to grant an extension of the patent, but recommended a small parliamentary reward, which Mr Morton received. VOL. LXX. NO. CXLI. C taken out of the hands of the former, because their views did not keep pace with the growing demands of commerce; whereas the latter have been exposed to obloquy and parliamentary persecutions for proceeding on too extensive a scale of improvement.' Under this more enlightened management, there was completed a floating-dock 750 feet long, and 9450 broad; having an entrance lock 170 feet long, 40 feet wide, and a graving-dock 265 feet long, 68 feet wide at top, and 40 at bottom; having 16 feet of water on the sill of the entrance lock at high water of ordinary spring tides. These works cost L. 119,855 and in November 1834, there was completed, at an expense of L.12,000, a new wet-dock, called Earl Grey's Dock,' fitted to accommodate the splendid steam-packets which ply between Dundee and London. It is 55 feet wide, 210 feet long between the gates, with 19 feet depth of water on the sill at high water of spring tides, and 14 in ordinary neap tides. Notwithstanding the unfavourable prediction of the corporation, the effect of these improvements on the trade of Dundee exceeded the most sanguine expectations. The annual tonnage, which in 1800 was 63,000, was in 1831 189,326, and in 1837, 286,662. In 1830, the raw material of the linen trade imported into Dundee was 18,577 tons, and in 1837 it was 34,149; while in 1831 the coals imported were 271,431 bolls, and in 1837 529,061 bolls. The increasing communication between Ireland and London had at various times directed the attention of the public to the necessity of making extensive improvements on the roads and harbours by which this communication was effected. Previous to 1815, the sailing packets which plied between Dublin and Holyhead were often tossed for several days in a stormy sea; and, when the passengers had completed their miserable voyage, they were landed upon rugged unprotected rocks, from whence they proceeded by miserable tracts of road, composed of a succession of circuitous and craggy inequalities, for twenty-five miles, across the island of Anglesea to the Menai strait-a troublesome and dangerous tidal ferry, over which the mail and other coaches could not be passed in boisterous weather. After various ineffectual attempts to improve this untoward line, Sir Henry Parnell succeeded in having a Board of Parliamentary Commissioners appointed for this purpose; and this Board chose Mr Telford for their engineer. We shall not detain our readers by any account of the skilful and judicious improvements which Mr Telford made upon the roads and harbours between Dublin and London, but shall pro ceed at once to give an account of the Menai bridge—that magnificent design, by which he surmounted the most formidable obstacle in the whole line of communication. The Menai ferry, which had been leased by Queen Elizabeth to John Williams, of Plas Isa, at an annual rent of L.3: 6:8, produced now a yearly revenue of L.878; and it was decided by a jury, that Lady Erskine of Cambo, to whom it had descended, should receive a compensation of L.26,954, or thirty years' purchase. Mr Telford recommended a bridge of wrought iron, on the suspension principle, which, after much discussion, was adopted by Parliament. A Parliamentary grant of L.20,000 was obtained in 1818 in preparation for this work; but it was not till 1819, when a new Act of Parliament was passed, that the foundation stone was privately laid on the 10th of August. The work advanced with such celerity, that during 1821 from 300 to 400 men, and from five to seven vessels were employed on it; and in the beginning of 1826 it was completed and opened to the public. The following is Mr Telford's account of this interesting event: On 'Upon my report of the state of the works, the Commissioners determined that the passage over the bridge should be opened on the 30th of January 1826, The weather about that time proved very stormy; and, previously to the opening day, Sir Henry Parnell and myself examined the entire structure, and found all necessary arrangements made. Monday morning, at half-past one o'clock, the London mail-coach passed across the estuary, at the level of 100 feet above that tideway which herctofore had presented a decisive obstruction to travellers. The Chester mail passed at half-past three o'clock, and Sir Henry Parnell with myself drove repeatedly over; about nine o'clock, and during the whole of the day, was an uninterrupted succession of passing carriages, horsemen, and pedestrians, who had assembled to witness and enjoy the novelty and in the evening all the workmen were regaled with a joyous festival.' The total length of this magnificent bridge is 1710 feet, or nearly one-third of a mile. In its breadth there are sixteen chains, each chain being composed of 935 bars of wrought iron. The number of suspension rods affixed to each series, of four chains each, is 199, and the total number is 796. The total number of trussed bearing bars is 444, and the total weight of iron work 4,373,282 lbs., or above 2186 tons: the iron work is protected from the weather by paint, a single coat of which weighs about two tons and a half. The total expense of the bridge, including the toll-houses and half a mile of road, and the embankment on the Anglesea side, was L. 120,000. The tolls, in 1827, amounted to L.1200.. The perfect security of this gigantic undertaking, and the scientific skill by which it was planned, were put to a severe test by the storms of 1838 and 1839, in which similar works were laid prostrate. A slight disturbance of the suspension bars which carry the roadway, was the only damage which the Menai bridge sustained. Its iron ribs and sinews defied the tempest, and justified the encomium of the Poet-Laureate TELFORD! Who o'er the vale of Cambrian Dee, The success of this work directed the attention of other nations to the erection of similar bridges upon the suspension principle; but though some of these may be nominally of larger dimensions, yet none of them with which we are acquainted can bear any comparison with the Menai bridge-in the grandeur of its conception, in the difficulties to be overcome, in the massive lightness of the fabric, and in the elegance and perfection of the workmanship. The longest suspension bridge in the world, is, we believe, that at Freyberg in Switzerland, which was begun in 1831, and finished in three years, in 1834. The roadway is suspended on four cables of iron wire, each containing 1056 wires; and they are capable of supporting three times the weight which the bridge is ever likely to bear, or three times the weight of two rows of waggons extending entirely across it. The cables enter the ground on each side obliquely for a considerable distance, and are then carried down vertical shafts cut in the rock, and filled with masonry, through which they pass, being attached at their extremity to enormous blocks of stone. The following are its dimensions, compared with those of the Menai bridge. 580 feet. 905 do. 25 feet. 28 do. Height. 130 feet. 174 do. Menai Bridge, Freyberg Do. The bridge of Freyberg was constructed under the direction of M. Chaley, of Lyons, and cost 600,000 francs, or about L.25,000. We cannot conclude this account of the Menai bridge without calling the attention of our readers to the original design of a great iron bridge, which Mr Telford proposed in 1811 to the Lords of the Treasury, as the best method of crossing this arm of the sea. Mr Telford does not mention the reason why the plan was not adopted; and we are therefore led to believe that its estimated expense, viz. L.127,331, was the only obstacle to its The Pontcysylte aqueduct, already described. adoption. The bridge was to consist of a single arch of 500 feet span; its breadth was to be 40 feet, almost double that of the present bridge, and its height 100 feet at high water spring tides. The difficulty of erecting a centering-foreseen, and dwelt upon by Mr Rennie as almost an insuperable one-Mr Telford proposed to remove by a contrivance altogether new, and exceedingly simple and ingenious; namely, by suspending the centering from above, in place of supporting it from below. This method consists in erecting on the top of the abutments, frames (we presume of iron) 50 feet high-the purpose of which is to receive strong blocks, or rollers and chains, by means of which, by the aid of windlasses or other mechanical powers, each separate piece of the centering is to be raised into, and suspended in, its proper place. Each piece of centering being about 50 feet long, 10 of them are necessary for the whole arch; so that five suspending chains, passing from a frame on each abutment, will support the whole of the centering. Mr Telford regarded this mode of constructing centres as applicable to stone as well as iron arches; and he states that the operations which it involves are more capable of correct demonstration, than those of the former mode of supporting from below. He justly remarks, also, that if this method should be successfully practised on so large a scale at the Menai, all difficulties with regard to carrying bridges over inaccessible ravines or turbulent streams, will in future be done away, and a new era formed in bridge building. From the general introduction of suspension bridges, owing no doubt to their comparative cheapness and facility of execution, this reasonable anticipation of Mr Telford has not yet been realized; but we venture to look forward to its general introduction when arches of iron or stone shall replace, as we believe they ultimately will, the less firm and substantial fabrics of suspension bridges. Our experience of stone and iron arches has now been extensive, and they have been found to resist, with equal efficacy, the slow corrosion of time and the occasional assaults of the storm and the hurricane. They are, therefore, in their very form and elements, fixed and enduring structures, calculated, like our dwellings and our fortresses, to last for ages. United by cement as tenacious as themselves, or by bolts and bars of the same material, the voussoirs of an arch, whether of stone or of iron, are indestructible. The elements have no power either to disintegrate their mass, or to disunite their combination; and the force of gravity, the only one to which they are exposed, tends but to consolidate their strength, and press them into a state of more permanent stability. This, however, is not the character of suspension or chain bridges, or of chain piers, |