Fine example of the John Meares map illustrating his theory of the Northwest Passage.
Advocating for a water course across Western Canada, Meares believed that a river passage existed from Hudson's Bay to the Slave River, then on the Slave Lake and across western Canada to Prince William Sound, as elegantly, if speculatively, depicted on the map. He notes the travels of Mr. Hearne to the west of Hudson's Bay and most fancifully, the report of "Falls said to be the largest in the known World" to the west of Slave Lake (the irony of course being that they were unknown and non-existent).
Meares presents a credible depiction of the coastline between Price William Sound and Mt. Olympius (Olympia), at the mouth of John de Fuca's Straits, including one of the earliest depictions of Queen Charlottes' Sound and some early outlines of what would become Vancouver Island.
Meare's reference to the River Oregan is a late reference to the mythical river described by Jonathan Carver, which also came to be known as the River of the West, which is the source for the name of the modern State of Oregon. Among his more remarkable claims was that an American captain Robert Gray had sailed along this inland sea in his ship, Lady Washington, in 1789, a claim which would make its way onto a number of contemporary maps.
John Meares led two commercial expeditions to the Northwest Coast of America, first in 1786-1787 and again in 1788. The results of his expedition were published in his Voyages Made in the Years 1788 and 1789 from China to the North West Coast of America, published in London in 1790.
In this map, Meares makes a case for the existence of a Northwest Passage through the interior of North America, via river communication from western Canada to Prince William Sound. While it is now understood that many of Meares most remarkable claims were more fantasy than fact, he was also a serious reporter and his explorations along the Northwest Coast of America, subsequent to Cook, are among the most important of the period.