536 PROCEEDINGS OF THE ACADEMY OF [NOV., 



THE FORMATION OF RIPPLE-MARKS, TRACKS, AND TRAILS. 



BY AMOS P. BROWN, PH.D. 



In the summer of 1902 I spent a portion of August in camp near 

 the head of Sandwich Bay, Labrador. Our camp was located at a 

 place called Dove Point on the charts, near the mouth of Dove 

 Brook and at the mouth of the estuary of White Bear River, which 

 latter empties into this arm of the bay some three miles above the 

 Point. Dove Point extends out from the north shore of Sandwich 

 Bay for more than a mile, nearly to the channel leading to the river 

 mouth, the deep-water portion of which is here about one-third of a 

 mile wide. Extending to the northeast, towards Dove Brook and 

 the Mealy Mountains, are wide mud flats, laid bare with each low 

 tide; beginning with a breadth of a mile and a half at the Point and 

 gradually narrowing until they disappear altogether at some 4 or 5 

 miles along the shore. To the northwest of the Point they extend 

 for some three miles, beginning with a width of half a mile and 

 gradually narrowing to the mouth of White Bear River. 



The higher ground at the Point, about 20 feet above the water 

 level, is composed of sand and gravel with occasional boulders, which 

 probably represents the Saxicava sands or Upper Boulder deposits 

 of Canada, although no fossils were found in the sands. At their 

 base and underlying these sands is the clay deposit, in which is found 

 numerous shells of the Leda clays, such as Saxicava arctica Desh., 

 Serripes groenlandicus (Chem.), Astarte elliptica McGill, Macoma 

 sabulosa Morch, etc., and scattered over the surface of the clay flats 

 are many large boulders left by the erosion of the clays by the water. 

 As the tide is not very high here, about three feet on the average, 

 these flats are gradually covered by a shallow layer of water, which 

 ripples in over the flat with each rising tide. It is generally accom- 

 panied by wind, which makes little wavelets that break on the shore 

 when the water finally reaches it. The level of the flats is so nearly 

 perfect that when they are completely covered by the rising tide 

 this layer of water is in general but a few inches deep near the shore, 

 though at some distance from the shore it may be three feet deep 

 over some parts of the flat that were laid bare at low tide. The 

 clay is particularly firm and compact, and retains impressions made 

 upon it for many succeeding tides. As the bay freezes to the bottom 



