The glacial erosion has here cut through the slate and bitten deep into the underlying granite.

The passage from slate through porphyritic diorite into granite may, I think, be best explained by the increasing degree of metamorphism, and at the same time a change of the original sediments at this point; granite being the last term of metamorphism of pure clays, or clayey sandstones, while bedded diorites are similarly formed from ferruginous and calcareous slates.

Just at the junction of the harder and tougher granite with the softer and more jointed slates, occur, as might be expected, cascades in the river.

It is probable that the cascades at the head of Cascade Lake and Emerald Bay mark, also, the junction of the granite with the slate--only the junction here is covered with debris.

Just at the same junction, in Fallen Leaf Lake Canyon (Glen Alpine Basin), burst out the waters of Glen Alpine Springs, highly charged with bicarbonates of iron and soda.
_d.