On the next day (20th) the wind abated, so as to permit us, at six o'clock A.M., to issue from our place of detention; but we soon found the equilibrium of the atmosphere had been too much disturbed to rely on it. At seven o'clock, and again at nine o'clock, we were driven ashore; but as soon as it slackened we were again upon the lake; it finally settled to a light head wind, against which we urged our way diligently, until eight o'clock in the evening. The point where we encamped was upon that long line of deposit of the erratic block, or boulder stratum, of which the White Rock is one of the largest known pieces. At four o'clock the next morning, we were again in motion, dancing up and down on the blue waves; but after proceeding six miles the wind drove us from the lake, and we again encamped on the boulder stratum, where we passed the entire day. Nothing is more characteristic of the upper lake geology, than the frequency and abundance of these boulders. The causes which have removed them, at old periods, from their parent bed, were doubtless oceanic; for the area embraced is too extensive to admit of merely local action; but we know of no concentration of oceanic currents, of sufficient force, to bear up these heavy masses, over such extensive surfaces, without the supporting media of ice-floes. The boulders and pebbles are often driven as the moraines before glacial bodies, and there are not wanting portions of rock surface, in the west, which are deeply grooved or scratched by the pressing boulders. The crystallized peaks of the Little Rocks, above St. Anthony's Falls, have been completely polished by them.--_Vide_ p. 149.