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of persons now living it was an open strait, by which small 

 vessels passed through the island. Its waters are now en- 

 tirely fresh, and contain fresh water animals, such as Emys 

 pieta, E. punctata, and Emysaurus serpentina ; and fresh 

 water plants, among which is the Valisneria. It is the resort 

 of myriads of water fowl, such as are usually found on fresh 

 water. To a great distance from the shore this pond is 

 very shallow, but becomes deeper towards the centre in the 

 probable situation of the old channel. Within twenty years, 

 oysters could be obtained here, and their shells are still 

 abundant. In the vicinity of this pond are smaller ones of 

 a similar character. In other places the process of trans- 

 formation may be seen now going on. The sea washes up 

 a sand bar across a bay, and in time stops up its entrance. 

 Sometimes this obstruction is broken through by storms, and 

 the sea again enters until the passage is once more closed. 

 Sometimes the barrier is removed by the neighboring inhab- 

 itants, to permit the entrance of the herrings. It is an in- 

 teresting question how the water in these ponds becomes 

 changed from salt to fresh. 



Mr. Desor mentioned several similar facts in confirmation 

 of Dr. Cabot's statements. 



Mr. Ayres said that he was very familiar with the region 

 which was the subject of Dr. Cabot's observations. He 

 stated, that in the pond to which he had particularly refer- 

 red, there are still to be found specimens of the Striped 

 Bass, Lahrax lineatus, which had been shut in when it 

 was cut off from the sea. 



Mr. Whitney suggested as an explanation of the change 

 from salt to fresh water in these ponds, that, as the bottom 

 is sandy, all the water originally enclosed had escaped by 

 percolation, and its place has been gradually supplied by 

 rains and neighboring springs. 



Mr. Ayres stated that in the neighborhood of these ponds 

 there exist, on the sea-shore, the remains of a pine forest, 

 which has been submerged. At low tide, a strip of this 



