The divisional line of the “Bottom Rocks” is not, however, to be placed at the point at which life first appears. This great series is naturally divided by differences of mineral conditions, by order of deposition, and in reality of age, in our own country, and in other countries both of Europe and America, and apparently also, as far as our present information goes, in Asia and Africa.

In Canada, below the equivalents of our Shropshire “Bottom Rocks” and of our lower Cambrian beds, as in the Highlands of Scotland, as we have already obtained, are still more ancient beds of sedimentary origin, which have become crystalline. In Bohemia, in Finland, and in Scandinavia we have these primeval gneissic lands below the lowermost Silurian deposits; but the geologists generally of other countries, except, the Canadian, have not yet made much progress in this investigation, and it is only in very few instances that the distinctions between the older and younger gneiss have been noticed; and so little regard as to geological age has been ordinarily paid in the case of granitic rocks, that, knowing as we do the very various periods at which some of those masses were erupted, or protruded through sedimentary strata, the mere knowledge of their existence is nearly or quite valueless as evidence.