span of 128 feet (39 metres), combined with a rise of only 24 feet (7 metres). The flatness of the arches had been deemed necessary to avoid creating a raised "hump" on the deck of the bridge, which would have gone against Brunel's accommodation of early locomotives and his practice of maximising operational economy by building lines with flat or very gentle gradients (locally 1 in 1,320, which is less than 0.1 per cent), which had the benefit of reducing the running costs of the trains. Construction On 31 August 1835, the Great Western Railway Act was passed by Parliament, authorising the building of the line. Work commenced on its construction during the following year. The resident engineer who oversaw the building of Maidenhead Bridge was John Wallis Hammond, while a William Chadwick was appointed as the contractor for the construction of the structure. As originally built, the Maidenhead Bridge possessed a length of 235 metres and a width of 9.1 metres. It was visually symmetrical about the central river pier, which was founded on top of an existing small island sited roughly midstream in the river. The two main arches had a semi-elliptical shape, each having a span of 39 metres with a very low rise of 7.4 metres. The approach viaducts featured four round-headed flood arches; the short arches nearest the river bank having a span of 6.4 metres while the six flanking arches having an 8.5 metre span each. The elevations were identical and had Doric pilasters positioned between the river and bankside arches and corniced parapets throughout, while the deck comprised a series of stone slabs. The brickwork, both on the elevations and under the arches, was executed in London stock brick. The innovative low-rise arches over the Thames became subject to considerable controversy concerning their stability or purported lack thereof. During the construction of the bridge, the timber centring used to build the arches was eased; on the eastern arch, the three lowest rings of brickwork began to settle, separating from the body of the arch across a section of between 7.6 metres and 9.1 metres. Critics were keen to hold this up as proof that the design of the arches was flawed. However, it was soon established that the problem had been a product of the mortar having not been fully hardened, while also appeared worse on the spandrels than midway underneath the arches.