MARINE MARSHES '^H 



which the water enters and leaves the area occupied by the 

 marine marshes. . 



As orcHnary tides cover salt meadows to the depth of a foot 

 or more it is evident that if the area of these fields be extensive 

 the quantity of water which enters upon and departs from them 

 twice each day may be large in amount. The movements of 

 this flux and reflux are in a spontaneous w^ay accurately organ- 

 ized. Lookine over an extended field of marine marsh when 

 the tide is low we observe a system of channels in areal extent 

 proportionate to the surface occupied by the water at high tide, 

 the whole appearing, as before remarked, like a condensed map 

 of a great river system. At many points on the marsh, rarely 

 separated by more than a few hundred feet, we note shallow 

 drain ways, often from ten to twenty feet wide and only a foot or 

 two dee[). Close observation will show that the general surface 

 of the area about these troughs slopes with a very gentle inclina- 

 tion toward their margins. Following the w^ater in the ebbing 

 tide we note that it drains into these grooves which, as they 

 extend, become deeper and with more distinct banks, the natu- 

 ral result of the additional energy of the streani occupying it. 

 One of these grooves coalesces with another, the united chan- 

 nels become deeper, until, in a distance of a mile, the gathered 

 waters are strone enoucjh to cut a channel extendin^r to below 

 low-tide mark. If a number of these permanent waterwa)'s 

 unite they may form a broader tidal river. 



Where the process of development of a marsh growth in 

 a harbor basin is complete, the whole of its area which is 

 not required for the ingress and egress of the tide is occupied 

 by the mat of vegetation or by the decayed vegetable matter 

 that forms beneath it. In this condition the marshes can no 

 longer extend themselves either in a vertical or horizontal 



