I.—The Development of River Meanders

Extract

The paper by Dr. Callaway, “On a Cause of River Curves,” in the Geological Magazine for October, 1902, suggests comment for two reasons: first, because the cause that he brings forward seems of doubtful application; second, because the habitual entrance of branch streams at a certain part of the curves of main streams is satisfactorily explained by controls which seem to be of surer and more powerful application than the control which he advocates.

In ascribing to a tributary the power to make a main stream bend in a definite manner towards the tributary, and thus determine the habitual entrance of tributaries on the convex side of the main stream's curves, Dr. Callaway argues that the detritus brought by the tributary will be deposited on the further side of the main stream and somewhat below the tributary's mouth. Various examples known to me of the deposits formed by side streams in the channels of main streams do not bear out this conclusion: the detritus is not deposited on the further side of the main stream, but as a delta at the mouth of the tributary or a little below it; and the main stream does not bend toward, but away from the tributary. The Rhine, the Colorado, and many other rivers that might be instanced, show abundant examples of this kind. Moreover, the assumption of an initially straight main river, as stated by Dr. Callaway, involves an extreme improbability. Rivers cannot be habitually straight in their initial stage, and the bends with which they begin are as a rule spontaneously exaggerated in their later development.