314 MARKINGS, FOOTPRINTS AND FUCOIDS 



by the next tide ; but when carefully filled up by gently de- 

 posited new material, and hardened into stone, there is no limit 

 to their duration. 



Let us inquire how this may take place, and the tidal flats 

 of the Bay of Fundy and Basin of Minas may supply us with, 

 the information desired. In the upper parts of the Bay of 

 Fundy and its estuaries the rise and fall of tide, as is well 

 known, are excessive. I quote the following description of 

 the appearance they present from a work of earlier date : — 



"The tide wave that sweeps to the north-east, along the 

 Atlantic coast of the United States, entering the funnel-like 

 mouth of the Bay of Fundy, becomes compressed and elevated, 

 as the sides of the bay gradually approach each other, until in 

 the narrower parts the water runs at the rate of six or seven 

 miles per hour, and the vertical rise of the tide amounts to 

 sixty feet or more. In Cobequid and Chiegnecto Bays these 

 tides, to an unaccustomed spectator, have rather the aspect of 

 some rare convulsion of nature than of an ordinary daily 

 phenomenon. At low tide wide flats of brown mud are seen 

 to extend for miles, as if the sea had altogether retired from 

 its bed ; and the distant channel appears as a mere strip of 

 muddy water. At the commencement of flood a slight ripple 

 is seen to break over the edge of the flats. It rushes swiftly 

 forward, and, covering the lower flats almost instantaneously, 

 gains rapidly on the higher swells of mud, which appear as if 

 they were being dissolved in the turbid waters. At the same 

 time the torrent of red water enters all the channels, creeks 

 and estuaries ; surging, whirling, and foaming, and often having 

 in its front a white, breaking wave, or * bore,' which runs 

 steadily forward, meeting and swallowing up the remains of 

 the ebb still trickling down the channels. The mud flats are 

 soon covered; and then, as the stranger sees the water gaining 

 with noiseless and steady rapidity on the steep sides of banks 

 and cliffs, a sense of insecurity creeps over him, as if no limit 



