Page:Popular Science Monthly Volume 19.djvu/247

Rh deposits. The Norian rock is distinguished by the abundance of labradorite, a feldspar possessing iridescent tints, and is found in Essex County, New York, Labrador, extensively along the St. Lawrence, upon Lake Huron, while "bowlders of it are occasionally found along the eastern shores of Maine and Massachusetts, and also in northern New Jersey."

The Huronian era succeeds, and is a name applied to the upper layers of the Huron Mountains, Lake Superior, to the Green Mountain series, and to detached areas along the coast of Newfoundland, eastern New England, and southward upon the flanks of the Blue Ridge. The Mont Alban series marks the fourth period, so named after the White Mountain layers in New Hampshire, where the aggregated display of crystalline schist is assigned to this province. New York, Philadelphia, Baltimore, and Washington occupy this terrain, and these rocks occur throughout the Blue Ridge, as far as Georgia, of more than passing significance, as they form the gold-bearing strata ia Virginia, North and South Carolina. In these rocks the garnet, staurolite, cyanite, and chiastolite, favorites of the mineralogist, are almost exclusively found.

Instinctively we ask: Did no living thing exist through all these ages; did the mechanical wear and tear of rock-masses and their redeposition by mechanical means solely occupy the desolate centuries? The proofs of organic activity, involving the functions of life, are numerous, but the exact character of that life and the special conditions under which it flourished are greatly if not entirely wanting. In the first place, we find in Canada important, indeed inexhaustible deposits of carbon under the form of graphite, and graphite occurs in our coal measures as the direct product of alteration from coal. These huge masses, distributed in pockets, sheets, and nodules through the archæan rock, indicate the presence of vegetative forces, doubtless exhibited in plants of a low order, but on a scale of tropical exuberance.

These carbon pockets occupy the shrunken areas of what were once vast, waving, and deeply matted beds of algæ, sea-weeds, building up, through innumerable generations amid the gathered detritus of shore and cliff, dense piles of carbonaceous remains. Or else they are attributable to a fertile growth of lichens which spread, possibly with an almost arborescent vigor, over plain and mountain. These organisms are low in the vegetable hierarchy, and along with them may have lived allied families: the microscopic Desmids and Diatoms, whose siliceous tests showered down through the still oceans; beside them the Corallines and Nullipores, forming calcareous fringes and coral-like thickets; the minute Protophytes and the delicate Charæ. Doubtless this age marked the climax of these plants, and, through multiplied species and in vast numbers, they represented one phase of the ever restless evolution of vital forces.

The great deposits of iron-ore, though affording no direct evidence