A Critic of my paper on “The Winding of Rivers” writes to me that I and others “do not take into account the nature of the soil traversed by a stream,” which “must materially affect its course.” Let me call attention to the two figures (117 and 118) on p. 499, vol. i, of Sir A. Geikie's Text Book of Geology, ed. 1903. The one is entitled “ Meandering course of a Brook,” and resembles that which is often seen in meadows. The other represents the “Winding of the Gorge of the Mozelle above Cochem.” There is no essential difference between them. Without knowledge of the scale I could not say that either had been formed in alluvium and not in hard rock. Both are based on the same principle; each is an adaptation, evolved from a more extended network of streams, formed to meet the requirements of the area to be drained. Lateral streams, even though they do not now exist—the growth of turf or of timber may have rendered them unnecessary—have united with that line in the network best adapted both for the longitudinal and the lateral drainage. In detail this may differ; in principle it is always the same.