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by Mr. Desor ; but on looking at his drawings it bad occurred to 

 him that they might have been produced by the pebbles of a 

 conglomerate rock, which had been deposited above the Sand- 

 stone but had been subsequently removed, as may be seen in 

 Roxbury. Last June he had had the opportunity, at the mouth 

 of Peticodiac River, of studying all the effects of the sea on its 

 shores. He saw marks of rain drops in the soft ooze, and fre- 

 quently on highly inclined surfaces, precisely like those described 

 by Prof. Hitchcock as existing in the Connecticut River Sand- 

 stone. On flat surfaces the drops caused an impression with a 

 raised edge, which was never seen in the indentations made by 

 bubbles bursting through the mud. If on an inclined surface, the 

 impression was deepest on the lowest side and near to the edge 

 in proportion to the inclination. The breaking of bubbles pro- 

 duced a shallow cavity, as described by Mr. Desor, but without a 

 raised edge. Another appearance noticed by Dr. Jackson in the 

 same locality, when the shores were left by the tide, was a num- 

 ber of small ridges of singular character. These he found covered 

 cracks produced by shrinking of the mud on exposure to the 

 sun and air. The return of the tide covered over the surface 

 with a thin film of sediment, which was forced up a ridge by 

 the confined air, under the pressure of succeeding waves upon 

 the mud on each side. Occasionally the air burst through, 

 producing a series of little explosions. In general, his observa- 

 tions went to confirm the views of Prof. Hitchcock. 



Dr. Gould said that he had seen similar lines on Chelsea 

 Beach, which he had found to be due, however, to a very dif- 

 ferent cause. At the end of each ridge, just beneath the surface, 

 was a small crustacean, (a species of Idotea,) which had pro- 

 duced it, making its way along from one end to the other under 

 the sand. 



Dr. Jackson said that such a groove was much more superfi- 

 cial than the cracks of the Peticodiac mud, which were as deep, 

 in many instances, as the length of a spade. 



Mr. Ayres confirmed Dr. Gould's observations. He had also 

 seen on Chelsea Beach lines, which were undoubtedly ripple 

 marks. 



Mr. Desor, in reply to Dr. Jackson's suggestion, that the 

 superincumbent pressure of a conglomerate rock might have 



