In an address before the Academy of Natural Sciences, of Philadelphia, a couple of years ago, Mr. Thos Meehan pointed out that there was no known agent but fire which could prevent a border line of forests from gradually spreading over the grassy prairies; that only for the annual Indian fires the great prairies of the West would long ages ago have been impenetrable forests. This view seems to be coming into general favor. In a recent issue of the " Proceedings of the National Museum," Mr. Robert Ridgeway says :

"That the numerous small prairies which were common in the Wabash Basin at the time of its first settlement have become transformed into woodland, and that, owing to this gradual change of prairie to forest, the actual area of forest in Wabash and the adjoining counties in Illinois is greater than fifty years ago. Extensive woods of oak and hickory more than eighty feet high, and with trunks nearly two feet through, are now growing on what was open prairie within the memory of some of the present owners of the land. 'This is interesting as a slight indication of the solution of the mystery which involves the origin of the prairies; while the rapidity with which these new woods have sprung up shows that the reproduction of our failing forests can he accomplished in a shorter time than is generally supposed, if proper con- sideration and attention can only be given to the subject.' "