AUTHOR OF BY ISRAEL CRUSSELL PROFESSOR OF GEOLOGY IN THE UNIVERSITY OF MICHIGAN LAKES OF NORTH AMERICA," GLACIERS OF NORTH AMERICA,' NEW YORK G. P. PUTNAM'S SONS LONDON JOHN MURRAY 1-13-41 Transportation Library GB 1213 Every river appears to consist of a main trunk, fed from a variety of branches, each running in a valley proportioned to its size, and all of them together forming a system of valleys, communicating with one another, and having such a nice adjustment of their declivities, that none of them join the principal valley either on too high or too low a level; a circumstance which would be infinitely improbable if each of these valleys were not the work of the streams that flow through them."-Illustrations of the Huttonian Theory of the Earth: by John Playfair. Edinburgh, 1802. p. 102. |