The water during the hottest summer months sustains a uniform temperature of forty-five degrees, and is as clear as crystal. The outflow from this lake furnishes the great river passing through the Sault Ste. Marie, through which passes a greater tonnage of vessels than through the Suez canal, and most of them of very large draft. This river with the combined waters of Lake Michigan and Lake Huron passes on through the Detroit River and Lake Erie and over Niagara Falls. It is also claimed that from Lake Superior a large subterranean stream flows into Lake Ontario from which lake the stream in junction with Niagara river forms the St. Lawrence, the river so copious in its flow as to be immune from floods. This question is in point: Where does this enormous supply of water come from to supply Lake Superior? Without taking single witnesses, we will call up groups. Take the various great lakes of the world, Europe, Asia and Africa, where all great rivers seem to have their sources in some lake. As to rainfall if that originates these streams, and if so, how is their flow kept so uniform, or is it from a steady, unfailing source, as would come from the inside ocean of supply? Lakes of enormous depth exist in the Sierra Nevada, and Rocky Mountains, as Pyramid Lake, Donner, Tahoe and Crater Lakes. In our Adirondacks are thousands of lakes, in Vermont and New Hampshire, and in the White Mountain region, throughout the mountain portions of Maine, in West Virginia, and the Carolinas, and in other high and mountainous sections lakes abound. As we come to the low country there are few witnesses to call, as the only body of water worth mentioning is in Utah, that lake being salt and below the level of the ocean. While the subject of this chapter is introduced under the heading of springs, it may seem out of place to bring in these great lakes, assuming that they are of the same class. But there is no doubt whatever of their being nothing more or less than mammoth springs. Next to the great lake system of the world, may be called in evidence the atolls so prevalent in the southern Pacific Ocean and growing also in other places on the globe. These peculiar features appear to have been built up from the tops of submarine mountains or old craters that have been filled with fresh water, from which structures of coral have grown till they reached the surface. The formation of these atolls being generally elongated, or in chains like mountain ranges, is suggestive of the same influence in their inception as the upheaval of mountain chains on land surfaces by hydraulic pressure.