The Atlantic border may be considered as the threshold of the continent. It was among its dense, gloomy forests of hard wood and pine that European nations planted their colonies; here those colonies grew into States, which were the nucleus of the American Union. The Appalachians are not high enough seriously to affect the climate or landscape of the region. Their flanks slope gradually down to the sea, furrowed by rivers which from the first gave character to the colonies. In New England, where there is an abundance of good harbors, the coast is narrow and the streams are short and rapid, with stretches of navigable water between the waterfalls which turn the wheels of industry for a busy, ingenious, and thrifty people. The long, broad rivers of the South, flowing lazily through a wide base-plain, the coast of which furnishes but little safe anchorage, served as avenues of traffic for the large, isolated colonial estates strung along their banks; the autocratic planters taking pleasure in having ports of entry at their doors. The Hudson and the Potomac lead far inland,--paths to the water ways of the interior,--and divide the Atlantic slope into three grand natural divisions, the New England, the Middle, and the Southern, in which grew up distinct groups of colonies, having quite a different origin, and for a time but few interests in common. The Appalachian mountains and their foot-hills abound in many places in iron and coal; works for the smelting of the former were erected near Jamestown, Virginia, as early as 1620, and early in the eighteenth century the industry began to be of considerable importance in parts of New England, New York, and New Jersey; but the mining of anthracite coal was not commenced until 1820. The soil of the Atlantic border varies greatly, being much less fertile in the North than in the South; but nearly everywhere it yields good returns for a proper expenditure of labor. The climate is subject to frequent and extreme changes. At about 30° latitude the mean temperature is similar to that on the opposite side of the Atlantic; but farther north the American climate, owing to the divergence of the Gulf Stream and the influence of the great continent to the west, is much colder than at corresponding points in Europe. The rainfall along the coast is everywhere sufficient. Sidenotes: The Mississippi basin. The Pacific slope.