On the north their declivities are steep and rugged.
Through these Rocky Mountains the explorers and furtraders, by ascending the streams running down the eastern declivities of the mountains, and crossing by short portages to the streams of the western slope, have succeeded in discovering passes by which the mountain chain can be crossed, the range rarely exceeding 60 m.
The experiments of Bossut were made only on pipes of a moderate declivity, but Dubuat used declivities of every kind, and made his experiments upon channels of various sizes.
The inland slope is gradual, but on the northern shore the range terminates in abrupt and almost perpendicular declivities, and here, consequently, some of the finest coast scenery in the island is found, widely differing, with its unbroken lines of cliffs, from the indented coast-line of the west.
Bounded on the south and west by the valley of the Rhine, to which its declivities abruptly descend, and running parallel to, and forming the counterpart of the Vosges beyond, it slopes more gently down to the valley of the Neckar in the north and to that of the Nagold (a tributary of the Neckar) on the north-east.