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 Rh traced the river Coppermine to the sea, while it was not till 1793 that Mr. (after Sir A.) Mackenzie discovered the river now named after him, and crossed the continent of North America from Atlantic to Pacific. One of the reasons for this late exploration of the north-west of North America was a geographical myth started by a Spanish voyager named Juan de Fuca as early as 1592. Coasting as far as Vancouver Island, he entered the inlet to the south of it, and not being able to see land to the north, brought back a report of a huge sea spreading over all that part of the country, which most geographers assumed to pass over into Hudson Bay or the neighbourhood. It was this report as much as anything which encouraged hopes of finding the north-west passage in a latitude low enough to be free from ice.

As soon as the United States got possession of the land west of the Mississippi they began to explore it, and between 1804 and 1807 Lewis and Clarke had explored the whole basin of the Missouri, while Pike had investigated the country between the sources of the Mississippi and the Red River. We have already seen that Bering had carried over Russian investigation and dominion into Alaska, and it was in order to avoid her encroachments down towards the Californian coast that President Monroe put forth in 1823 the doctrine that no further colonisation of the Americas would be permitted by the United States. In this year Russia agreed to limit her claims to the country north of 54.40°. The States subsequently acquired California and other adjoining states during their war with Mexico in 1848, just before gold was discovered in the