The Ordnance Survey, c. 1885
The headquarters of the Ordnance Survey were established in the Tower of London until the great fire of 1842, after which they were moved to Southampton. The Director of Ordnance Survey supervised seven other officers. Two of these officers divided executive duties between them, and the other five supervised the various departments, which included the secondary and tertiary triangulation, the photography, zincography, engraving, colouring, and electrotyping processes. The country was divided into ten divisional commands for England and Wales, and one for Ireland. The Survey of Scotland being finished, had no separate command. All the detailed outdoor work was carried out in these districts.
There were four survey companies (the 13th, 14th, 15th and 16th) of Royal Engineers specially raised for survey purposes. The number of persons, military and civilian, engaged in the Department in 1885 was 3,240, exclusive of temporary help - usually boys employed on taping duties.
REFERENCE:
PORTER, W. History of the Corps of Royal Engineers. Volume II. The Institution of Royal Engineers, Chatham, Kent, 1952, p.243.