Little or nothing is known of the dreary solitudes beyond Lake Superior; enormous muddy ponds and marshes are succeeded by open, dry, sandy plains; then forests of hemlock and spruce arise, again swamp, bog, windfalls, and stagnant water succeed; in the course of many miles there may not be one dry spot found for a resting-place. The cold is intense in this desolate region; in winter spirits freeze into a consistency like honey; and even in the height of summer the thermometer only shows thirty-six degrees at sunrise. Part of the north and east shore of this greatest of the lakes present old formations--sienite, stratified greenstone, more or less chloritic, and alternating five times with vast beds of granite--the general direction east, with a north or perpendicular dip. Great quantities of the older shell limestone are found strewn in rolled masses on the beach. Amygdaloid occupies also a very large tract to the north, mingled with porphyries, conglomerates, and various other substances. From Thunder Mountain westward, trappose greenstone is the prevailing rock: it gives rise to some strange pilastered precipices near Fort William. Copper[155] abounds in this region to an extent, perhaps, unsurpassed any where in the world. At the Coppermine River, three hundred miles from the Sault de St. Marie, this metal, in a pure state, nearly covers the face of a serpentine rock, and is also found within the stone in solid masses. Iron is abundant in many parts of Upper Canada; at Charlotteville, eight miles from Lake Erie, the metal produced is of a very fine quality. The Marmora Iron Works, about thirty-two miles north of the Bay of Quinte, on the River Trent, are situated on an extensive white rocky flat, apparently the bed of some dried-up river; the ore is found on the surface, and is very rich, yielding ninety-two per cent.: the necessary assistants, lime and fuel, abound close at hand. Various other minerals have also been found there; among the rest, small specimens of a metal like silver. There are many strong mineral springs in different parts of Canada; the most remarkable of these is the Burning Spring above Niagara; its waters are black, hot and bubbling, and emit, during the summer, a gas that burns with a pure bright flame; this sulphureted hydrogen is used to light a neighboring mill. Salt springs are also numerous; gypsum is obtained in large quantities, with pipe and potter's clay; yellow ocher sometimes occurs; and there are many kinds of valuable building stones. It is gathered from the Indians that there are incipient volcanoes in several parts of these regions, particularly toward the Chippewa hunting grounds.