The observations were taken by sergeant James Steel with an eighteen-inch theodolite, both at Westminster Abbey and St. Paul’s. When not prevented by haze, the sergeant attended to his duty, frequently when the breeze shook his small location to a perilous degree, with a coolness, perseverance, and accuracy that were highly praiseworthy. Sometimes he and his assistant sapper—private John Wotherspoon[14]—ascended to the observatory at St. Paul’s as often as three times a-day, and this carried through a period of four months—between the 17th June and 16th October—with unflinching resolution and assiduity, made the sergeant and the sappers objects of much interest and of curious and anxious inquiry. The observations taken from this height comprised between 8,000 and 10,000. In many instances the same subject was gone over as many as six times, none less than three or four, and the utmost distance obtained was twenty-six miles.[15] The points thus trigonometrically fixed were 2,140, a vast number being church towers, spires, conspicuous public buildings, and manufactories. To carry on the survey during the day in crowded streets, with an unbroken stream of vehicles in double transit, was an extremely difficult and irksome operation; but to be free as much as possible from this interruption, the sappers went to work every morning as soon as day broke, and pushed the survey while the metropolis was still at rest. The survey was completed in January, 1850, and the mapping finished at Southampton. For the merit and talent with which the work was conducted, the periodical press frequently expressed its admiration; and Sir Henry de la Beche and Mr. Edwin Chadwick—two of the Commissioners of the highest authority—praised the survey as being one of extreme success.[16] At another time the former gentleman observed at a special court of the Commissioners, that “the Ordnance undertook the work of the surface. A triangulation of no common order, but such as they might have expected from that distinguished service, was undertaken and executed; and upon that triangulation was founded a block plan of extreme efficiency and completeness; and it was also no common map, for it always had reference to that great triangulation to which he had already referred.”[17]