1371. The eastern parts of North America, as it appears from meteorological tables, have a much colder air than the opposite European coast, and fall short of the standard by about ten or twelve degrees. There are several causes which produce this considerable difference. The greatest elevation in North America is between the 40th and 50th degree of north latitude, and the 100th and 110th of longitude west from London; and there the most considerable rivers have their origin. The height alone will partly explain why this tract is colder than it would otherwise be; but there are other causes, and those are most extensive forests, and large swamps and morasses, all of which exclude heat from the earth, and consequently prevent it from ameliorating the rigour of winter. Many extensive lakes lie to the east, and Hudson's Bay more to the north; a chain of mountains extends on the south of the latter, and those equally prevent the accumulation of heat; besides, this bay is bounded on the cast by the mountainous country of Labrador, and has many islands; from all which circumstances arise the lowness of the temperature, and the piercing cold of the north-west winds. The annual decrease of the forests for the purpose of clearing the ground, and the consumption for building and fuel, is supposed to have occasioned a considerable decrease of cold in the winter; and if this should be the result, much will yet be done towards bringing the temperature of the European and American continents to something like a level.