Skew or oblique bridges are commonplace, and entrants in this category are only included if they are of particular interest

Skew bridges became an unavoidable necessity with the coming of canals and railways in the Industrial Revolution. Before that, when bridges were only built for roads and pedestrian use, it was usually much easier to align the bridge to cross the waterway normally (i.e. at right angles).

'SKEW BRIDGES. Very little is known, says the Architect, respecting the origin of skew bridges. It has been repeatedly asserted that those built by George Stephenson on the Liverpool and Manchester Railway were the first erections of the kind, but this in incorrect, there being some of earlier date even in Lancashire. A paper in Transactions of the Institution of Civil Engineers, Vol. ?, p. 185, alludes to an oblique arch erected about the year 1530 by Nicolo, called "Il Tribolo,” over the river Mugnone, near Porta Sangallo, at Florence. It appears, however, that the principle upon which such bridges should be constructed was too little understood to render an attempt at constructing them on large scale admsable. Chapman mentions oblique bridges being in use prior to 1787, when he introduced a great improvement in their construction. Down to that time, as far as he was informed, such bridges had always been built in the same way as common square arches, the voussoirs being laid in courses parallel with the abutments. This plan could therefore only be adopted for bridges of very slight obliquity, and even then with considerable risk. About the time mentioned above Chapman was employed as engineer to the Kildare Canal, a branch from the Grand Canal of Ireland to the town of Naas, on which it was desired to avoid directing certain roads which had to crossed. He was therefore led to think for some method of constructing oblique arches upon a sound principle, of which he considered that the leading feature must be that the joints of the voussoirs, whether of brick or stone, should be rectangular with the face of the arch, instead of being parallel with the abutment. One of the first bridges built on this plan, the Finlay Bridge, near Naas, crossed the canal at an angle of only 30deg., the oblique span being 25ft and the height of the arch 5ft 6in. Mr Chapman observes that the lines on which the beds of the voussoirs lie are obviously spiral lines, and to this circumstance may be attributed much of the singular appearance of oblique arches. Finlay Bridge stood well, but the ingenious designer did not think it prudent in any other case to attempt so great a degree of obliquity, although he built several other bridges on the same principle over the Grand Canal of Ireland, and over some wide drains in the East Riding of Yorkshire. He recommends carrying the masonry as equally as possible from each abutment in order to avoid unequal strains the centering.'^[1]