The origin of treeless prairies seems to be referable to annual prairie fires, by the growing consent of those who patiently investigate the matter, and thus one of the great philosophical questions of the past age is being finally set at rest. Up to, say, a couple of years ago the belief of Professor Whitney prevailed that there was' something in the finely comminuted soil of the prairies which so firmly enveloped the seed as to prevent the necessary action of the atmosphere in inducing germination. Other hypotheses - all, however, tending to the physical impossibilities of tree growths - were in favor. In the "Proceedings of the Academy of Natural Sciences of Philadelphia," for February, 1881, probably the first philosophic attempt to show the futility of all these hypotheses appeared. It was there shown that there was no more reason why the seeds of strong herbaceous plants should grow and form the well-known flora of the prairies than the seeds of ligneous plants; that herbaceous plants or annuals which could flower and commit their seeds to the earth before a fire flew over them, could spread in spite of prairie fires; but that ligneous plants, which required several years of growth before seeding, could not spread when annually burned down; that, as a matter of fact, trees were being raised by the million on the prairies by nurserymen, and that wherever prairie fires were prevented from occurring, the woodlands did actually encroach on the grassy prairie.

This view now receives all the confirmation that is necessary from a paper by Robert Ridgway in the " Proceedings of the National Museum," wherein he shows that the forest area of the Wabash basin has extended to such an extent that numerous small grassy prairies, which were common at the first settlement of the country, have become transformed to woodland, and that, owing to this encroachment, the forest area of the valley is greater than it was fifty years ago. There are now huge trees of oak and hickory, eighty feet high, on what certainly was grassy prairies fifty years ago. The question of the origin of these prairies being definitely settled, the anthropological one connected with it derives a new interest. As the natural condition of the North American continent is to be covered by a forest growth and this forest growth has been kept down by the agency of annual Indian fires, the Indians must have been here before the subsidence of the waters which covered the prairies, and the annual fires following the regular subsidence alone kept the forests from springing up.

It is an excellent illustration of the fact that the settling positively of one important question only leads to the introduction of other and often greater ones. - Independent.