RIPPLE MARKS EPRY. 315 



to a marsh (fig. 16) that occupiesj between Ploimeour-Trez and 

 Goulven, the head of the bay. If our theory be correct, one ought 

 from the existence and direction of these ridges to conclude that the 

 waters of the bay do not retire in a direction perpendicular to the 

 beach, but are diverted more or less obliquely to it and toward this 

 outlet. This is what I have always noted. One day especially, when 

 hidden in the thicket on a sandy bar of the swamp in pursuit of 

 herons, I killed one of these birds. The tide was high and conse- 

 quently close at hand, and the bird fell into the water. As I had 

 just eaten, it was impossible to swim out in order to recover it, and 

 I was obliged to abandon it. The tide being high, it floated past me 

 in a tantalizing manner. It was my first heron ! ^Mien the tide 

 had receded a little, however, the bird floated away quickly and 

 obliquely toward the right in the direction of the creek, the outlet of 

 all the waters of the bay. When it had arrived there it passed quickly 

 outward and in a few minutes was lost to sight. At the same time 

 the existence of a transverse current combining its efl^ects with those 

 of the ebb was revealed to me, the formation of ripple marks was 

 demonstrated, and their direction explained by the course which the 

 bird had followed. I had lost the specimen, but not my time. 



One can understand also that ripple marks are always found en 

 the bar of a river, like that of the Belon, for example, which is bare 

 during the spring tides. The mass of water which flows down from 

 the ravine, striking against an obstacle in its path, is forced to turn 

 laterally to seek toward the shore an easier passage ; on the left, the side 

 of the small bay of Kerfany, the real channel of the Belon; at the 

 right, a small depression resulting from the washing out of the sands 

 by the eddy in front of the rocks of the point of Eiec. 



We may now return to the furrows in the dry sand of the dunes, 

 or in the snow on the mountains. It will be observed that whatever 

 the agency, air or water, the process is always the same. The ripple 

 marks are never formed on the surfaces exposed to the full current, 

 but always in the gullies, or on the side of slopes over which the cur- 

 rent of air descends obliquely. Their direction indicates the course 

 of the current (fig. 17). 



On the contrary, where no transverse current intervenes ripple 

 marks are lacking in the places in which one might have expected to 

 find them. Our angle of the beach at Fort Bloque (fig. 6) is without 

 them, because the peninsula which serves as an embankment to the 

 fort prevents the access of all currents parallel with the shore, that 

 of Coureau passing between the Lorient section of the mainland on 

 the east, and the island of Groix. The ebb is produced there nor- 

 mally. The ripple marks appear solely at a point lower down and 

 farther from the shore, outside the protected zone. Can it be said 



