Editorial 



In December, 1898, Mr. G. K. Gilbert presented to the Geo- 

 logical Society of America a paper upon ripple-marks and cross- 

 bedding in which he undertakes to explain the large ripples of 

 the Medina formation.' Mr. Gilbert became satisfied that these 

 ripples differ "in no respect except size from the familiar ripple- 

 mark of the bathing beach and the museum slab." In order to 

 account for the size of some of the large ripples upon this 

 theory he has inferred that the waves producing them were sixty 

 feet high and made in "a large ocean." 



In the July number of the American Geologist, Professor H. 

 L. Fairchild objects to the deep ocean theory of the origin of 

 these ripples, and brings evidence to show that they are beach 

 structures. "" 



Without going into the details of either of the articles men- 

 tioned the present writer wishes to call attention in this con- 

 nection to a paper upon the origin of beach cusps published in 

 this Journal (September-October, 1900, Vol. VIII, pp. 481- 

 484), and to suggest that the explanation of the giant ripples 

 spoken of by Gilbert and Fairchild is to be found in the seaward 

 extension of beach cusps. The beach cusps are from sixty to 

 eighty feet apart, from a few inches to three feet in vertical 

 height and extend oceanward in approximately parallel lines. 

 They are formed by the interference of two sets of waves of 

 translation, and are therefore to be looked for not only on the 

 beach where they appear at the water's edge, but as far out as 

 the waves drag upon the sea bottom, and always pointing away 

 from the shore. This theory appears to account readily for all 



' Ripple-marks and Cross-bedding, by Grove Karl Gilbert. Bull. Geol. Soc. 

 Amer. Vol. X, pp. 135-140. 



* Beach Structures in Medina Sandstone, by H. L. Fairchild. Amer. Geologist, 

 Vol. XXVIII, pp. 9-14. 



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