The margin of the Red Sea itself consists, on the Arabian side, of a strip of low plain backed by ranges of barren hills of coral and sand formation, and here and there by mountains of considerable height.
It is surrounded by (I) a thin-walled, smaller-celled hydrom mantle; (2) an amylom sheath; (3) a leptom mantle, interrupted here and there by starch cells.
Trap appears here and there in intrusive dykes.
It was common to those tribes east of the Rocky Mountains, in the south-west and upper Columbia; but unknown apparently among the Eskimo, along the northwest coast, and on the Pacific coast west of the Cascade range and the Sierras, except among some few Californian tribes, or here and there in Mexico and southward.
Seen from Strathmore or the Firth of Clyde the Highlands present well-defined masses of hills abruptly rising from the Lowland plains, and from any of the western islands their sea front resembles a vast rampart indented by lochs and rising to a uniform level, which sinking here and there allows glimpses of still higher summits in the interior.