To ascertain by the usual computations whether any error by the omission in the registry of a bar or microscope could be detected, the line was divided into three parts, and each part was used as a base for a minor triangulation. Very great care was taken in executing this triangulation, but it failed to discover any inaccuracy in the measurement. Sergeant James Donelan and corporal William Jenkins, with the two 3-feet instruments, carried out this special service. The results of the two measurements stand on record as under:— By General Mudge with Ramsden’s steel-chains in 1794 36575·64 feet. By sergeant Steel, with Colby’s compensation-bars, in 1849 36577·95 ” Computed from Lough Foyle base 36577·34 ” The precision of the two operations by such different instruments is strikingly close and beautiful, and not only illustrates the excellence of the instruments, but the perfection of the work. On the completion of the service, corporal Jenkins was intrusted with one of the great theodolites, and removed with a camp party from the base detachment to a mountain station. The remainder were soon dispersed on the general duties of the survey, and sergeant Steel, after again comparing the bars and microscopes with the standard measures, returned with the compensation apparatus, &c., to Southampton.[46] On the 7th June, one sergeant and twenty-five rank and file were removed from Woolwich to Shoeburyness to erect temporary barracks, &c., for the royal artillery, and also to lay platforms, build batteries, and to execute the varied works which a new station might call for, both for the convenience of the ordnance troops and the interests of the service. The party was increased to thirty of all ranks in July, but in October following was reduced to six non-commissioned officers and privates. Ever since this period, a small detachment has been retained at the station to carry on the current repairs and improvements, and its strength has fluctuated from time to time, in accordance with the prevailing emergencies.