The traders and old citizens said so much about the difficulties and toils of these northern portages that we did not know but what we, ourselves, were to be put in bags; but we escaped that process. This delay gave us the opportunity of more closely examining the island. It is about three and a half miles long, two in its greatest width, and nine in circumference. The site of Fort Holmes, the apex, is three hundred and twelve feet above the lake. The eastern margin consists of precipitous cliffs, which, in many places, overhang the water, and furnish a picturesque rocky-fringe, as it were, to the elevated plain. The whole rock formation is calcareous. It exhibits the effects of a powerful diluvial action at early periods, as well as the continued influence of elemental action, still at work. Large portions of the cliffs have been precipitated upon the beach, where the process of degradation has been carried on by the waves. A most striking instance of such precipitations is to be witnessed at the eastern cliff, called Robinson's Folly, which fell, by its own gravitation, within the period of tradition. The formation, at this point, formerly overhung the beach, commanding a fine view of the lake and islands in all directions, in consequence of which it was occupied with a summer-house, by the officers of the British garrison, after the abandonment of the old peninsular fort, about 1780. The mineralogical features of the island are not without interest. I examined the large fragments of debris, which are still prominent, and which exhibit comparatively fresh fractures. The rock contains a portion of sparry matter, which is arranged in reticulæ, filled with white carbonate of lime, in such a state of loose disintegration that the weather soon converts it to the condition of agaric mineral. These reticulæ are commonly in the slate of calcspar, crystallized in minute crystals. The stratum on which this loose formation rests is compact and firm, and agrees in structure with the encrinal limestone of Drummond Island and the Manitouline chain. But the vesicular stratum, which may be one hundred and ten or twenty feet thick, has been deposited in such a condition that it has not had, in some localities, firmness enough permanently to sustain itself. The consequence is, that the table-land has caved in, and exhibits singular depressions, or grass-covered, cup-shaped cavities, which have no visible outlet for the rain-water that falls in them, unless it percolates through the shelly strata. Portions of it, subject to this structure, have been pressed off during changing seasons, by frosts, and carried away by rains, creating that castellated appearance of pinnacles, which gives so much peculiarity to the rocky outlines of the island.