The actual surveys of the island began with the arrival of Captain George Vancouver, in his sloop "Discovery" and armed tender "Chatham." Captain Vancouver's explorations on the Pacific were to occupy nearly three years. In July 1793, he sailed northward between Haida Gwaii and the mainland, sighting them several times in the distance. In September he was again in their vicinity, and coasting down the west shore he made observations and outlined the general contour. The navigators were to too great a distance, however, to allow for a more exact delineation, nor had they the time to make a complete sketch of the numerous bays and inlets. The sketch Captain Vancouver was able to make did not consider sufficiently accurate to be depended on, yet the first charts made by Admiralty in later years were based chiefly on his surveys. In the years 1852 to 1866 a number of the larger inlets and bays were charted: Port Kuper during the visit of "H.M.S. Thetis" in 1852; Cumshewa Inlet by Captain T. Sinclair of the Hudson's Bay Company; Virago sound, the entrance to Massett Inlet, and Houston Stewart Channel in 1853 when "H.M.S. Virago" visited those sections of the coast; and Skincuttle Inlet in 1862 by the officers of "H.M.S. Hecate." Skidegate Inlet was surveyed in part by D. Pender as part of his extensive charting of the whole coast in 1866.