One of his earliest inventions, patented in 1838, was
railway points, which superseded the sliding rail used up to that time. In 1837
Robert Stephenson appointed him as one of the engineers on the
London and Birmingham Railway, where he was responsible for Watford tunnel and the incline down from
Camden Town to
Euston. He presented an important paper on the correct principles of
skew arches to the
Royal Institution. In 1837 the future philosopher of evolution
Herbert Spencer, whose father George Spencer had been Fox's tutor when young, joined him as an assistant engineer. Fox then entered into partnership with the contractor Francis Braham to form the company Braham, Fox and Co., which when Braham retired became Fox, Henderson and Co., of London,
Smethwick, and
Renfrew. The company specialised in railway equipment, including wheels, bridges, roofs, cranes, tanks and
permanent way materials. It also experimented with components for
suspension and
girder bridges, with Fox reading a paper before the
Royal Society in 1865. The company was responsible for many important station roofs including
Liverpool Tithebarn Street, (1849–50),
Bradford Exchange (1850),
Paddington and
Birmingham New Street. One notable employee of Fox, Henderson & Co. was
William Siemens, a pioneering mechanical and electrical engineer. His designs for an energy-saving boiler led to financial losses for the company, but his electrical telegraph recovered the losses. ==Crystal Palace==