Cotton, Charles Philip (1832–1904), civil engineer, was born 19 January 1832 in Dublin, son of Henry Cotton (qv), archdeacon of Cashel, formerly of Bucks., England, and his wife Mary Vaughan, youngest daughter of Richard Laurence (1760–1838), archbishop of Cashel. Educated at Stackallan, Co. Meath, and St Columba's College, Rathfarnham, Co. Dublin, Cotton received his junior moderatorship in experimental and natural science before entering TCD (1848), where he earned a BA (1853), a diploma in civil engineering (1854), and several certificates in practical engineering. His credentials guaranteed him a prestigious apprenticeship: William Richard Le Fanu (qv) took him on as a pupil (1855–63), and under him Cotton acted as resident engineer in the construction of the Bagenalstown & Wexford and the Mallow & Fermoy railways and in the completion of the Roscrea–Nenagh line. He was eventually appointed Le Fanu's chief assistant.
With such a promising start, it was not surprising when Cotton went on to become one of the most successful and well-respected engineers of Victorian Ireland. When Le Fanu retired from private practise in 1863, Cotton and his partner B. F. Fleming were appointed his successors, and together as engineers-in-chief they ensured the completion of the above-mentioned railways, the Wicklow–Wexford railway, and the Shillelagh branch line. Cotton diversified into other areas of engineering: he served as consulting engineer (1863–7) to the Port of Dublin corporation, the body created in 1854 to manage Ireland's lighthouses, where his main duty was to supervise the reinforcement of the Fastnet lighthouse. However, he was perhaps best known for his role as chief engineering inspector to Ireland's local government board (1869–99), where his services were deemed so valuable that when he reached the mandatory retirement age in 1897, the board convinced the treasury to allow him to carry on for two more years.
Throughout his career, Cotton strove to make engineering and sanitary legislation simple and accessible, thus facilitating implementation. He wrote a Manual of railway engineering in Ireland (1861), a practical guide for young engineers that clarified railway legislation and outlined the various steps required in preparing and letting railway contacts. It was so well received that a second edition was published in 1874. In the area of public health, he cleared up much of the confusion created by dozens of overwhelming, complex, and permissive statutes by writing a Loans manual (1890) that explained borrowing rules to local authorities. He also published three explanatory compendiums of Irish public health legislation – A manual of procedure by provisional order under the sanitary acts (1887), The Irish public health acts, 1878–1890 (1891), and its supplement The Irish sanitary acts (1892) – that simplified much of the legal jargon and highlighted the sections relevant to sanitary officers. The last was lauded by the Irish press, which complimented him on his valuable compilation. In recognition of his commitment to sanitary matters, Cotton was appointed to the royal commission on sewage disposal (1898) and was later named chairman of the viceregal commission on the health of the city of Dublin (1900).
During his life, Cotton was an active member of the Institution of Civil Engineers of Ireland, presenting papers on various scientific and engineering topics. He was given full membership in 1861 and made an honorary life member in 1902; he held the posts of honorary treasurer (1871–2) and president (1873–4). Most noteworthy and representing the esteem in which he was held by his peers, he was listed as one of five founding members of the institution when it was recreated under royal charter in 1877. Cotton's reputation extended beyond Ireland: he was a member of London's Institution of Civil Engineers from 1864, and just before his death was granted an honorary life membership (1903).
He married (1878) Marion Louisa, eldest daughter of Sir Maltby Crofton of Longford House, Co. Sligo, somewhat late in life; they had no children. Cotton died 10 March 1904 at his residence in Bray, Co. Wicklow, at the age of 72. His death was met with great sadness by the profession, who regarded him ‘with the highest esteem and respect’ (Transactions of the Institution of Civil Engineers of Ireland, xxxii, 1904–5, 27).
As well as his work on engineering and sanitary topics, Cotton's publications include the 1878 supplement to Henry Cotton's six-volume Fasti ecclesiae Hibernicae, which Cotton completed for his father when he went blind.