﻿144 GEOLOGICAL ACTION OF 



here of the tidal streams coming in opposite directions from Nausett Beach towards the 

 south, and from the island of Nantucket towards the north. This convergence is im- 

 mediately suggested by the fact, that, if a vessel grounds on the south side of one of the 

 shoals in this vicinity whilst the tide is running ebb, she will begin to float on the last 

 quarter of the ebb current. The shoal formations are numerous and extensive here, and, 

 according to the information given me by the inhabitants, accumulate rapidly in favora- 

 ble situations. Dry Shoal is a name given to one of them that has appeared above water 

 within a few years in a protected part of the bay formed by Monomoy Beach, and oppo- 

 site to the opening into Chatham " New Harbour." There are no shoals on the Cape 

 Cod shore north of Nausett, though some bars are deposited at the point of the cape. 

 At Cape Cod the tide rises ten feet. On the coast of Maine the tide rises from ten to 

 eighteen feet, being greatest at the north ; and in the Day of Fundy it rises to the extra- 

 ordinary height of sixty feet. On the coast of Maine and in the Bay of Fundy there 

 are no shoals. 



On the Atlantic south coast of Nova Scotia, which is lined with banks at some dis- 

 tance from it, the average range of the tide descends again to eight and six feet. Upon 

 George's Bank the tide rises seven feet, and though but little is known of the tides of 

 the open ocean, yet it may be safely assumed that at Newfoundland Bank the range is 

 not great. In all the cases cited above, there is an observable proportion between the 

 tides and the aqueous deposits, the amount of the latter being more, as the height, &c, 

 of the former is less. 



This reasoning does not imply that shoals should be found wherever the character of 

 the tide is suitable for their formation. A proportion must also exist between the amount 

 of deposit and the quantity of loose material ; and it is perhaps to the deficiency of the 

 latter that we are to ascribe the absence of shoals on certain parts of the western coasts 

 of this continent. 



Passing from the shores of America to those of Europe, we there find deposits of sand 

 of remarkable extent, giving the same character to navigation as here, and constituting, 

 in one instance, the residence of a people distinguished in arts and commerce, whose 

 national economy derives a peculiar stamp from the nature of the soil they inhabit. 

 Holland is the most interesting, in many respects, of all similar formations. It is situated 

 on the southeast corner of the German Ocean, where the tide-waves that enter through 

 the Straits of Dover are met and repelled by those which, making the circuit of the 

 British isles, return again from the north. This convergence of conflicting currents is 

 the condition already specified as the one the most favorable to a large deposit. The 

 narrowness of the English Channel, by creating rapid currents, forbids deposits there, 



