Page:Popular Science Monthly Volume 25.djvu/610

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involves. Among these results there is of course much that is fanciful, but there is also a very large substratum of established truth; and if the student thoroughly comprehends the symbolical language of chemistry, and understands the facts it actually represents, he will be able to realize, so far as is now possible, the truths which underlie the conventional forms.

The study of the structure of molecules naturally leads to the study of their stability, and of the conditions which determine chemical changes, and thus opens the recently explored field of thermo-chemistry. To be able to predict the order and results of possible conditions of association of materials, or of chemical changes under all circumstances, is now the highest aim of our science, and we have already made very considerable progress toward this end. But I have detained you too long, and I must refer to the "New Chemistry" for a fuller exposition of this subject. My object has been gained if I have been able to make clear to you that it is possible to present the science of chemistry as a systematic body of truths independent of the mass of details with which the science is usually encumbered, and make the study a most valuable means of training the power of inductive reasoning, and thus securing the great end of scientific culture.


THE Missouri River, as is well known, is the larger of the two great branches which unite to form the Lower Mississippi, discharging at its mouth 120,000 cubic feet of water per second, while the Upper Mississippi discharges only 105,000 cubic feet per second. It is therefore itself properly the Upper Mississippi. The perpetually turbid character of its waters is a familiar fact to the ordinary reader, even if he has never seen them.

It is proposed to state a few facts, derived from a season's personal observation in the valley of the Upper Missouri and of its nearly equal tributary, the Yellowstone, which may account for this condition, and serve to explain the peculiar form of erosion that characterizes this river system.

The upper portion of these rivers, where they flow through mountain-gorges, form deep cañons, and leap over wild cascades, is, of course, more interesting than their lower portions, where the flow, though rapid, is tolerably uniform through valleys of considerable width and among low sand-bars and islands of their own creation. As a consequence of this, we find that it is this upper portion that has received the chief attention by writers and explorers, who hasten through the