No. 6.] MATTHEW — TIDAL EROSION. 3T1 



position of these mud-beds and of the gravel banks is of great 

 practical value to navigators in the Bay, owing to the prevalence 

 of summer fogs, which make necessary a frequent use of the 

 sounding lead. 



While the tides have evidently affected the condition of the 

 surface of the sea-bottom in the Bay of Fundy they have also 

 cut deeply into its substance. At the mouth of the Bay where 

 the run of the tide is moderate and the water deep, this result 

 is not very noticeable ; but at the head of the Bay its power 

 in cutting and removing the soft mud and sand at the bottom is 

 very great. Near the mouth of the Bay, however, this scouring 

 action of the tide is seen in the shallow basin, called Passa- 

 maquoddy Bay. At all the entrances to this sheet of water the 

 bottom is very rocky, and the channels are full of deep holes and 

 pointed ledges, exposed by the constant churning of the current 

 in these narrow passages. The rush of the tide causes a roaring 

 sound that may be heard for many miles, and the whirlpools are 

 strong enough to upset boats and careen larger vessels. Its 

 great power in this shallow bay is also shown in the production 

 of channels extending from these passages nearly across the Bay^ 

 while the largest rivers which enter the bay do not show channels 

 even at their mouths, except such as the tide has helped to exca- 

 vate. The Magaguadavic River, for instance, one of the largest 

 which enters Passamaquoddy Bay, has not cut a channel in the 

 bottom of that bay deeper than the 5-fatliom contour-line ; but 

 right athwart the mouth of this stream runs atidal channel 

 that extends up into Bocabec Bay (an indentation of Passama- 

 quoddy Bay). 



None of the rivers from the Magaguadavic eastward to the 

 Saint John ha a heavy in-draft of tide, and so the work of the 

 current at the mouth of these smaller streams has been slight. 

 But at the mouth of the Saint John Biver very deep channels have 

 been made by the ebb and flow of the tide in the narrow passage 

 by which this river enters the sea. Although there is a depth 

 of 36 feet only, at low water, on the reef which causes the rapid 

 at the mouth of the Saint John called " The Falls," such is the 

 force of the current that a trench 150 feet deep has been pro- 

 duced below " The Falls," and one of 200 feet deep above them. 



But if the deeper part of the Bay of Fundy be examined, 

 evidences of tidal erosion will be observed even more remarkable 

 than those which the river mouths present. The first well de- 



