Through the second half of the century much of the more southerly regions of Canada and the Mackenzie-Yukon systems were re-explored and examined by the discerning eyes of scientific personnel attached to British, colonial, and, later, Canadian expeditions. The most important investigations occurred on the Great Plains and in the Cordillera south of the Peace River, and along the arc of the Precambrian Shield from the Athabasca River to the north shore of the St Lawrence. The first large-scale scientific expeditions focused on the southern plains; the John Palliser and Henry Y. Hind surveys of 1857-60 added major information on their hydrography, terrain, vegetation, soils, climate, and geology.