€98 KANSAS CITY REVIEW OF SCIENCE. 



which Prof. Meehan establishes his conclusion was as familiar to my childhood as 

 the alphabet, and its extreme simplicity is virtually acknowledged by him a few 

 lines lower on the same page, where, speaking of Indians, he admits that " Low 

 as their power of reasoning may be, they could not but have perceived that while 

 grassy herbage throve in spite of fires, perhaps improved under the fiery ordeal, 

 trees could not follow on burned land. What could be more natural than 

 that they would burn the prairies with the object of retaining food for their wild 

 animals." Certainly what savages could reason out a priori, white men ought 

 to be able to account for a posteriori with all the data at hand ; and this they 

 certainly have done from the first, and refused to be befogged by any of the 

 other specious reasoning already referred to. 



But the problem of the " grassy prairies " and the problem of the Great 

 Plains are not identical. When we extend our inquiries to embrace the broad 

 expanse that stretches westward from the Missouri and the western boundary of 

 Arkansas to the base of the Rocky Mountains, we encounter a new class of phe- 

 nomena which require to be accounted for on a different principle. 



The investigation is, however, seriously complicated by the fact that between 

 the very distinct conditions that characterize the typical prairies and the typical 

 plains there is geographically no precise line of demarkation, the one passing into 

 the other by rigidly insensible gradations. 



In traveling westward from Kansas City or from Omaha, one passes through an 

 almost completely treeless region for a distance of five or six hundred miles. A 

 careful observer will, however, perceive that the eastern portion of this great plain 

 differs in many respects from the more central or western portions, and that it 

 may therefore be divided into two general areas, which, however, blend together 

 and do not admit of being clearly marked off from each other. If it could serve 

 any useful purpose to draw an arbitrary line to denote approximately the western 

 boundary of the one and the eastern boundary of the other, this line might per- 

 haps be made to coincide with the looth meridian, which passes through western 

 Kansas and central Nebraska. For a moderately limited north-and-south range, 

 this line does not fall far from that represented by an altitude of 2,500 feet and 

 an average annual rain-fall of twenty inches. 



In point of fact, as regards this latter, which is of chief importance to our 

 subject, the twenty-inch isohyetal, if followed southward from the Missouri River, 

 which it crosses at a point near Yankton, or about on the 98th meridian, bears 

 westward and touches the Kansas and Nebraska State line almost exactly at the 

 looth meridian. It continues slowly to bear westward and reaches the loist 

 meridian at the southern boundary of Kansas, crossing it, but returning to it at the 

 Rio Grande, which it follows thereafter very closely to near its mouth. 



This line as thus described would, therefore, still more nearly represent the 

 imaginary boundary of these two treeless areas. 



As we approach this line, proceeding westward, the grassy character of the 

 plains gradually disappears, the typical prairie vegetation is changed and gives 

 place to a new class of plants which are for the most part represented by three 



