310 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



to attribute the formation of ripple marks to the violence of the 

 current of the tide that sweeps this very flat area, or to the indirect 

 action of the wind, or in some measure to the combined action of the 

 two elements, the air and the water. 



The second h3rpothesis has been very generally adopted. At first 

 sight, we repeat, it appears very convincing. In reality, it does not 

 bear serious examination, and should be resolutely rejected. What- 

 ever the state of the atmosphere, indeed, one will observe that on a 

 beach there are certain points where at all times, or at least with very 

 great regularity, ridges are formed. At other points on one day 

 they will disappear, though the wind may blow a gale, while on the 

 morrow they reappear, though the sky may be calm and the sea like 

 glass. 



Not only is there no correlation between the movements of the 

 aerial ocean and the wrinkling of the sandy surfaces submerged 

 under a very thin stratum of water, but, on looking closely, one 

 observes that it is particularly in those places where the bottom is 

 especially protected from the influence of the wind that these marks 

 attain their largest dimensions; for example, where the ground is 

 accidentally sunken, in the depths of pools, or on the banks of small 

 streams, or at low-water mark ; again, where the force of the current 

 of the tide, as well as that of the wind, whatever it may be, remains 

 comparatively negligible, and is actually without effect, for example, 

 on the sands of bars, which are exposed only a few minutes, and then 

 only at the equinox, at the mouth of rivers and streams. 



One should not have a shadow of a doubt on this point. Ripple 

 marks are the work of the tide, and of that alone, as they are nowhere 

 so numerous and conspicuous as where the sands are best protected 

 from the effects of the wind. 



This first point settled, it remains to harmonize this assertion with 

 what we have said of the effects of the tide on the higher part of 

 the beach, where far from producing a greater wrinkling of the 

 bottom, the increase of its speed, owing to the great inclination of 

 the beach, causes a general leveling. 



In order to explain this apparent contradiction, and find the 

 solution of the enigma, which of the two factors is it necessary to 

 consider, the inequalities of the two slopes, or the difference between 

 the dynamic effects of a breaking wave and those of a regular cur- 

 rent? It is, in fact, neither the one nor the other. They are of no 

 importance. All research in this direction leads to nothing. Here 

 again is an impasse to be avoided. The solution of the problem is 

 to be sought elsewhere. In order to discover it without further 

 delay, we must transfer ourselves to a point on the shore where the 

 ripple marks always, or nearly always, form; that is, to the line of 



