Marykirk, Annan, Stirling, and Hutcheson stone bridges—High-level bridge for Newcastle—Timber bridge of built planks—Winch Chain Bridge—American bridges of suspension—Runcorn Bridge—Menai Chain Bridge—New form of suspension bridge.

Mr. Stevenson’s stone bridges over the North Esk at Marykirk, and the Nith at Annan (Plate VI.), are good specimens of road bridges of moderate extent; and his bridge over the Forth at Stirling, and Hutcheson Bridge over the Clyde at Glasgow (Plate VII.), are structures of a larger class.

Of the latter, Mr. Fenwick, of the Royal Military Academy, Woolwich, in the preface to his work on the Mechanics of Construction, published in 1861, says,—“The London and Waterloo Bridges, in the metropolis, which rank among the finest structures of the elliptical arch, and Stevenson’s Hutcheson Bridge at Glasgow, which is one of the best specimens of the segmental arch, together with many others, have supplied me with a variety of problems for illustration.”

PLATE VI.

ANNAN BRIDGE
1824.

MARYKIRK BRIDGE
1811.

W. & A. K. Johnston, Edinburgh.

PLATE VII.

HUTCHESON BRIDGE, GLASGOW.
1828.

STIRLING BRIDGE.
1829.

W. & A. K. Johnston, Edinburgh.

PLATE VIII.

DESIGN FOR HIGH LEVEL ROAD BRIDGE
AT NEWCASTLE ON TYNE.
1828.

TRANSVERSE SECTION.

W. & A. K. Johnston, Edinburgh.

The Hutcheson Bridge was completed in 1832. The masonry of the piers was laid at the level of seven feet below the bed of the Clyde, on a platform of timber, on piles eighteen feet in length. I found by161 a section made in 1845, after a lapse of thirteen years, that the level of the river had been lowered, in consequence of the deepening of the river Clyde by the Navigation Trustees, no less than eleven feet, and even with that amount of scour the bridge was, and might long have remained, a safe structure. But immediately above its site there is a weir which dams up the Clyde and forms a lake, or almost still pool, in the river’s bed for several miles. It was determined, in the interests of navigation, to take powers to remove the weir, and on its removal the bridge could, no longer be pronounced safe; it was also resolved to take powers to replace the Hutcheson by the new Albert Bridge, designed by Messrs. Bell and Miller.
* * * * *

Mr. Stevenson has also left behind him some traces of originality of design in bridge-building.

In 1826 he gave a design to the Corporation of Newcastle for raising on the existing bridge another roadway, on a high level, to communicate with the higher parts of the town, as shown in Plate VIII., being the idea since so successfully carried out on a large scale by the late Mr. Robert Stephenson in his justly celebrated “high-level railway viaduct.” Mr. Stevenson’s design, as will be seen, consists of piers of masonry raised on the piers of the old bridge supporting a roadway of cast iron. The upper bridge being continued across the quays on either side of the river, and joining the roadways leading towards the south and north by easy gradients, avoided the circuitous and dangerous route of the old post road through Newcastle.

For timber bridges Mr. Stevenson also proposed, in162 1831, a new form of arch of a beautiful and simple construction (Fig. 16), in which what may be called the “ring-courses” of the arch are formed of layers of thin planks bent into the circular form and stiffened by kingpost pieces, on which the level roadway rests. This form of bridge was afterwards very generally employed for railway bridges before the discovery had been made that for such works, structures of iron were, in the end, more economical than timber.
Fig. 16.

In 1820, he proposed to the Cramond District of Road Trustees, with a view mainly to lessening the cost of the work, a form of suspension bridge applicable to spans of moderate width, in which the roadway passes above the chains, and the necessity for tall piers is avoided. The suspension bridge over the Rhone at Geneva, and other bridges, have since been constructed on this principle.

In 1821 Mr. Stevenson wrote an article on Suspension Bridges for the Edinburgh Philosophical Journal; and as it contains a description of163 this new form of construction, as well as some historical information relative to bridges on the suspension principle, a few extracts from the paper may not be without interest:—

    “Winch Chain Bridge.—The earliest bridges of suspension of which we have any account are those of China, said to be of great extent; Major Rennell also describes a bridge of this kind over the Sampoo in Hindostan, of about 600 feet in length. But the first chain bridge in our own country is believed to have been that of Winch Bridge over the river Tees, forming a communication between the counties of Durham and York. This bridge is noticed and an elevation of it given in the third volume of Hutchison’s Antiquities of Durham, printed at Carlisle in 1794. As this volume is extremely scarce, owing to the greater part of the impression having been accidentally destroyed by fire, the writer of this article applied for a sight of it from the library of his friend, Mr. Isaac Cookson of Newcastle-upon-Tyne. The following account is given by Hutchison at p. 279:—‘The environs of the river (Tees) abound with the most picturesque and romantic scenes; beautiful falls of water, rocks and grotesque caverns. About two miles above Middleton, where the river falls in repeated cascades, a bridge suspended on iron chains is stretched from rock to rock over a chasm nearly sixty feet deep, for the passage of travellers, but particularly of miners; the bridge is seventy feet in length, and little more than two feet broad, with a hand-rail on one side, and planked in such a manner that the traveller experiences all the tremulous motion of the chain, and sees himself suspended over a roaring gulf, on an agitated and restless gangway, to which few strangers dare trust themselves.’ We regret that we have not been able to learn the precise date of the erection of this bridge, but from good authority we have ascertained that it was erected about the year 1741.

    “American Bridges of Suspension.—It appears from a treatise on Bridges by Mr. Thomas Pope, architect, of New York, published 164in that city in the year 1811, that eight chain bridges have been erected up............