At a more recent period Mr. Stevenson experimented at the Bell Rock Lighthouse in the same way on twenty-five different kinds of malleable iron, with the result that all of them were soon affected, and that galvanised specimens resisted oxidation from three to four years, after which the chemical action went on as quickly as in the others.
CHAPTER X.
BRIDGES.
1811–1833.
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.