59+ THE POPULAR SCIENCE MONTHLY. 



involves. Among these results there is of course much that is fanci- 

 ful, but there is also a veiy 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 chemi- 

 cal 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 induct- 

 ive reasoning, and thus securing the great end of scientific culture. 



-♦«♦- 



THE UPPER MISSOURI RIYER SYSTEM. 



By LESTER F. WARD, A. M. 



THE Missouri River, as is well known, is the larger of the two 

 great branches which unite to form the Lower Mississippi, dis- 

 charging 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 mount- 

 ain-gorges, form deep canons, 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 conse- 

 quence of this, we find that it is this upper portion that has received 

 the chief attention by writers and explorers, who hasten through the 



