308 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



which I have arrived that I present here. Although it is simply that 

 of an amateur who can only bring to his researches a measure of 

 curiosity and much patience, I believe that it will impress itself on 

 others with the same force that it has on me, if they will consent to 

 accompany me, stage by stage, along the road which has led me to 

 it. In order to simplify the explanation and clarify the text, I shall 

 present in connection with each argument the most convincing of a 

 number of photographs which I have taken on different beaches. 



In the first place, then, where are these ripple marks formed? 

 Broadly speaking, ridges of this kind are produced beyond the 

 reach of the waves on the dry sands of the interior of dunes (fig. 2) 

 and likewise on the sandy slopes of Sahara, or the snow carpet of 

 Alpine heights. Due without question to aeolian action, these do not 

 interest us, at least for the present, though we shall have occasion 

 to return to them later. 



In the area in which the ebb and flow of the tides manifest them- 

 selves it is necessary to distinguish between an upper and a lower 

 beach. The first presents a particularly steep slope, and the water 

 only reaches it during the neap tides. But then the water possesses 

 a much greater force, because it must, during the same number of 

 hours, traverse a longer course. For these two reasons the layers of 

 water which are spread out, however thin they may be, are carried 

 about with such velocity that no other force can counteract their ef- 

 fects. But their action is vertical. The grains of sand are energetically 

 propelled from below upward and from above downward, but solely 

 in a vertical direction. Consequently, children's modelings, foot- 

 prints, or ridges raised perhaps by the wind during the time when 

 the sand is drying, all inequalities indeed, whether depressions or 

 elevations, are erased or thrown down, as the smoothed-out slope 

 takes on the regular surface of a glacis (fig. 3). Figure 3 shows 

 the sea at work ; fig-ure 4 enables one to judge of the final result. 



On the upper beach ripple marks are never found. They occur, 

 in contrast, in great abundance on the lower beach, as shown 

 in figure 1 — in great abundance, but not always, nor everywhere. 

 Figure 5 is a view taken in the Bay of Goulven on the same day and 

 at the same hour as figure 1, and scarcely a hundred meters to the 

 right of the place where the latter was taken and toward nearly the 

 same point of the horizon. The two photographs placed side by 

 side constitute a panoramic view of the same landscape. The ridges, 

 which are so beautifully shown at the left, are irregular and scarcely 

 outlined at the right, presenting merely a wavy appearance. 



Let us go elsewhere. Here is a beach in the region of Lorient. 

 that of Fort Bloque, quite ideally flat, and apparently well suited for 

 the formation of ripple marks. (See fig. 6.) A fisher woman is 

 walking toward the rocks, which begin to appear above the water, 



