64 J. D. Dana on the origin of some of the 



(2.) The outfloxoing iinder-currents of bays are produced, especially 

 when the broad opening has a comparatively narrow principal chan- 

 nel with other passages, among or over reefs ; and they are strongest 

 when the waves and currents occasioned by a storm drive heavily to- 

 ward and into the bay ; and still more so if a river add its floods to 

 the waters which the storm waves and cm-rents pile up within the 

 bay. I do not know of any observations about the bays on the Sound 

 tending to show where such under-currents exist, or what in any par- 

 ticular bay is their force or direction ; and we are at a loss as to the 

 effects to be attributed to this cause, 



(3.) The actual configuration of the rocky substratum of the great 

 basin in which the waters of the Sound rest is also little understood. 

 Long Island has no rocks at surface, or about its points ; and the 

 Sound east of Hurl Gate, except quite near its shores, is also without 

 any projecting rocks. Some of the prominent sand-spits of the 

 shores, as those of New Haven and Stratford Point, may be traced 

 far southward by means of the soundings. But it is not always easy to 

 decide whether they have resulted solely from the detritus of the riv- 

 ers to the west of whose mouths they lie, or whether a rocky base- 

 ment has determined the form of the projecting spits. On the 

 sand bed ofi" the west point of New Haven harbor there are sur- 

 faces of bare rock, giving evidence of a rocky basement. Off 

 Stratford Point, west of the mouth of the Housatonic, soundings have 

 discovered no such rocks ; and yet it is probable that the form of the 

 bottom is here determined by the rocks underneath. On Eaton's 

 Point the map says " rocky " at one spot ; and the existence of this 

 spit may also have been determined by the rocky basement below. 

 But even when the spits or projecting sand-bars are proved to cover 

 a ridge of rocks, it is not certain that this ridge may not have been a 

 result of the excavations of the glacier, and of sub-glacier streams. 



The shoals and deep holes in the vicinity of " Eaton's Neck " are 

 directly south of the mouth of Norwalk river, and those about " Mid- 

 dle Ground " are south of the mouth of the Housatonic ; and the 

 question arises : Were they partly made by the rivers when the land 

 was more elevated, or may they have been determined solely by the 

 rocky configuration beneath and existing currents ? It is apparent 

 that without some direct investigations our conclusions can only be 

 uncertain probabilities. 



Yet notwithstanding all the doubts from the above mentioned sour- 

 ces, there are so many examples of depressions leading from the bays 

 at the mouths of rivers over the bottom of the Sound, so many in 



