Page:Dictionary of National Biography. Sup. Vol I (1901).djvu/188

  of Sir [q. v.] By his first wife he had two sons.

His son, (1843–1890), colonial governor, was educated at Harrow, and became a lieutenant in the carabineers. In November 1866 he was nominated private secretary to his father in the Mauritius, and afterwards filled the same office at the Cape of Good Hope. In August 1877 he was appointed a resident magistrate in Basutoland. He took part in the Basuto campaigns in 1879 and 1880, and in November 1881 was appointed chief commissioner of the Seychelles. In January 1886 he became lieutenant-governor of the Falkland Islands, but returned to the Seychelles in the following year. In 1888 he was nominated governor of Heligoland, where he remained until its transfer to Germany in August 1890. He died on 27 Sept. 1890, while on a visit to Stapleton Park, Pontefract.

 BARLOW, PETER WILLIAM (1809–1885), civil engineer, born at Woolwich on 1 Feb. 1809, was the eldest son of [q. v.] In 1826 he became a pupil of Henry Robinson Palmer, then acting as assistant engineer to [q. v.] Under Palmer he was engaged on the Liverpool and Birmingham Canal and the new London Docks. In 1827 he was elected an associate member of the Institution of Civil Engineers. In 1834 and 1835 he was employed in surveying the county of Kent for the London and Dover railway, and in 1836 he was appointed resident engineer, under Sir [q. v.], on the central division of the line between Edenbridge and Headcorn. In 1838 and 1839 the sections from Edenbridge to Redhill and from Headcorn to Folkestone were placed in his hands; in 1840 he became resident engineer of the whole line; and subsequently he was appointed engineer-in-chief. In 1842 he designed and executed the Tunbridge Wells branch, a line remarkable from the fact that it was executed, with the consent of the landowners and occupiers, before the act of parliament sanctioning it was obtained. During the next eight years he was engaged on the extension of the Tunbridge Wells branch to Hastings, the North Kent, the Ashford and Hastings, and the Redhill and Reading railways, and from 1850 he was employed in connection with the Newtown and Oswestry, the Londonderry and Enniskillen, and the Londonderry and Coleraine railways. On 20 Nov. 1845 he was elected a fellow of the Royal Society.

In 1858 Barlow investigated, with the assistance of models of large size, the construction of bridges of great span, paying especial attention to the problem of stiffening the roadway of suspension bridges. It had been supposed that to make a suspension bridge as stiff as a girder bridge it was necessary to use lattice girders sufficiently strong to bear the load of themselves, and that such being the case suspension chains were useless. Barlow, however, showed the possibility of stiffening suspension bridges by comparatively light parallel girders extending from pier to pier. Barlow's conclusions have been confirmed by [q. v.] (Manual of Applied Mechanics, ed. Millar, 1898, p. 370). While investigating this problem Barlow examined the great railway and road bridge at Niagara, and on his return published 'Observations on the Niagara Railway Suspension Bridge' (London, 1860, 8vo). Shortly afterwards a company was formed for constructing a bridge across the Thames at Lambeth, of which he was appointed engineer. This wire rope suspension bridge, which was opened on 11 Nov. 1862, contained diagonal struts in connection with the vertical ties from which the roadway was suspended. In this way a sufficient degree of stiffness was attained to permit large gas mains to be laid across the bridge without any leakage. Lambeth bridge, 'the cheapest bridge in London,' which cost with its approaches 45,000l., was purchased by the Metropolitan Board of Works ( and, London Past and Present, 1891, ii. 358).

During the construction of the bridge the process of sinking or forcing into the clay the cast-iron cylinders which formed the piers suggested to Barlow the idea that such cylinders could easily be driven horizontally, and could be employed in suitable soils for tunnelling under river beds. In accordance with these theories the Tower subway was constructed in 1869 and 1870 by excavating a tunnel through the clay bed of the Thames by means of a wrought-iron shield, eight feet