Nimmo [q. v.], who was then occupied with piers and harbour work in Ireland.
In July 1832 he went to Venezuela to take charge of the Bolivar Mining Association's mines, about two hundred miles from Caracas. He spent three years there; but bad health, brought about by the unhealthy climate, forced him to return to England in 1834. In 1838 he published a book describing his life in Venezuela, entitled 'Reminiscences of South America' (London, 1838). After his return he was employed for a time by Jesse Hartley [q. v.] on the Liverpool docks, and then on railway surveys in Germany for J. Walker; he also superintended the completion of the Manchester, Bury, and Bolton railway line. About this time, in 1838, at the request of the Great Western Railway Company, he reported as to the advisability of the continuance of the broad gauge on that system. In his report he opposed the continuance of the broad gauge, and all through his life he fought strenuously against a break of gauge on railway systems; he took a very prominent part in the opposition in 1872–3 to the proposals of the Indian government for altering the gauge of the railways in India.
In 1845 Hawkshaw was appointed engineer to the Manchester and Leeds Railway, the nucleus of the present Lancashire and Yorkshire railway system, and he remained consulting engineer to the latter company until 1888. His most noteworthy work in connection with this company was the introduction in the new lines of steeper gradients than any which had been adopted down to that date, and although his action was strongly opposed by Robert Stephenson [q. v.], Hawkshaw's sound judgment on this matter has been attested by the adoption since then of similar gradients on similar railways throughout the world.
In 1850 he came to London, and set up in practice as a consulting engineer, and from 1870 onwards he was in partnership with his son and his old assistant, Harrison Hayter.
It is not possible to deal even in outline with the numerous schemes in all branches of engineering for which Hawkshaw was responsible; only a few of the leading and more important ones can be referred to here. In connection with railways perhaps his most famous works were the Charing Cross and Cannon Street railways, with their large terminal stations and bridges over the Thames; the East London Railway, with its utilisation of the old Thames tunnel, constructed by the elder Brunei; and the great tunnel under the Severn for the Great Western Railway Company, which at the time of its completion in 1887 was one of the most noteworthy of such pieces of railway work, the tunnel being four and a third miles long, two and a quarter miles of this being under the tidal estuary of the Severn (see Walker's The Severn Tunnel: its Construction and Difficulties, London, 1891; also Proc. Inst. Civil Engineers, cxxi. 305).
Hawkshaw was also, with Sir John Brunlees [q. v. Suppl.], consulting engineer to the original Channel Tunnel Company; before preparing his plans for this work he had very careful geological surveys made on both coasts, and he also made detailed marine surveys. During his later years, however, he refused to have anything to do with the proposed tunnel, having come to the opinion that the construction of a tunnel would be a distinct national disadvantage.
In bridge work, in addition to those already mentioned across the Thames, Hawkshaw designed the Nerbudda bridge in India, nearly one mile long; and was responsible, with W. H. Barlow, for the completion of the famous Clifton suspension bridge, utilising for this work the old chains from the Hungerford suspension bridge, which had been pulled down to make room for his new Charing Cross railway bridge.
In 1863, at the request of the then viceroy of Egypt, Hawkshaw visited Egypt and carefully examined the site of the proposed Suez ship canal. It was the extremely favourable report which he sent in on the scheme, and on the proposed site, which finally led to the adoption of M. de Lesseps's plans. The khedive had made up his mind that if Hawkshaw should report against the scheme he would have nothing more to do with it. Richard Monckton Milnes, lord Houghton [q. v.], who was present at the time, says that when Hawkshaw landed at Port Said to take part in the opening ceremonies of the completed canal, M. de Lesseps presented him to the engineers who were present with the words : 'This is the gentleman to whom I owe the canal' (Reid's Life of Richard Monckton Milnes, first Lord Houghton, 2nd edit. ii. 217).
Hawkshaw was also a member of the international congress which met at Paris in 1879 to consider the proposed inter-oceanic ship canal across Central America. He was opposed to the Panama canal scheme because he did not believe it could be constructed at a reasonable cost, and so retired from the congress.
In 1862 he became engineer to the Amsterdam ship canal, which was eventually opened by the king of Holland on 1 Nov.