Page:Popular Science Monthly Volume 49.djvu/19

Rh escarpment, where there is a sudden descent of two hundred and forty feet to the lower plain, that gradually slopes for eight miles farther to the present shores of Lake Ontario, whose waters are three hundred and twenty-six feet below the surface of Lake Erie.

The features of the plain which have a bearing upon the development of the Niagara River are, a low ridge crossing the river just north of the outlet of Lake Erie; a comparatively level plain underlaid by soft rocks, extending thence to near the head of the rapids above the falls, north of which, to the brow of the escarpment, the country rests upon hard limestones, with underlying strata of soft shales and occasional layers of more persisting rocks. These softer shales form the foundation of the country between the end of the gorge at the brow of the mountain near Queenston

 (Pohlman). The buried channel or valley from the falls to the edge of the mountain at St. Davids is about a mile and a half broad, but it is not anywhere nearly as deep as the Niagara gorge.

(and Lewiston) and Lake Ontario. The work of the river has been to remove the soft rocks and undermine the thick and hard capping limestones. The chasm of the Niagara River is simply chiseled out of an elevated table-land, whose surface is a remarkably level plain, covered with towns, villages, and farms, extending apparently without a break until one is surprised at coming suddenly upon the brink of an abyss, without meeting with the sloping features which constitute the usual approaches to deep valleys. The feature of the gorge with unbroken perpendicular walls is shown in Figs. 6 and 7, which are characteristic forms of modern canons. If the valley were of great antiquity it should have been two miles or more in width, in place of a gorge of a quarter of a mile wide, and it should have had scarcely any fragments of perpendicular walls standing. Indeed, an old valley, buried beneath some ninety feet of drift, does cross the course