The Study of Waves

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    A CLAIM for the recognition of the study of wave structures of the earth's surface as a distinct and not unimportant branch of geography was advanced by Mr. Vaughan Cornish at the Royal Geographical Society on Monday. For the study he proposed the name kumatology, from κυμα, a wave. Mr. Cornish illustrated numerous forms of waves by means of lantern slides, and described in detail some curious waves, of which photographs were shown, which travelled up-stream, not as a “bore,“ but without change or form. These may be observed in streams which plough their way through sandy beaches to the sea. The water-wave was really controlled by a submerged sand-wave, the up-stream flank of which was exposed to a heavy shower of sand from the turbid water. The stream being shallow and its surface in waves, the crest of the water-wave was pushed up-stream as the up-stream flank of the sand-wave received additions of material. The scour of the water was thereby deflected, and the lee slope of the sand-hill was scoured away just as fast as the weather slope grew. Thus the sand-hill moved up-stream, although every particle of sand and every particle of water travelled down-stream. Mr. Cornish showed photographs of ripple-marks mimicking organic forms, and of rippled clouds, and the ripple-ridging of hill-sides, and went on to deal with the rippling of sand by wind, of which he has made a special study. Tables of measurements were exhibited which proved that the shape of these ripples was approximately constant for wavelengths from 1 to 145 inches. The shape was the same in desert sand as in the sand of the seashore, the mean length/height being 17˙6 for the blown-sand ripples of the shore, and 18˙4 for those of the desert, difference 3˙9 per cent. He had succeeded in reproducing these ripples by the action of a steady artificial blast upon ordinary heterogeneous sand, but artificially assorted sand containing no fine particles was not thrown into ripples. For this it was necessary that there should be particles fine enough to be tossed away by the eddy which forms in the lee of the larger grains. Similarly the formation of sand reefs or waves had been observed in the Mississippi when the mixed detritus begins to settle, the finer stuff being churned up from the bottom, and swept away, leaving the coarser materials arranged in ridge and furrow. Sand-dunes were built up by the wind on similar principles. Photographs of desert sand-dunes were shown, one of which exhibited the recent encroachments of sand which have buried the road between Karachi and Clifton. The sand-dunes here are advancing as a train of waves before the south-west monsoon.

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    The Study of Waves. Nature 59, 523 (1899) doi:10.1038/059523b0

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