1866.] 29 [Shaler. 



A glance at the whole length of the section shows the interesting fact 

 that the upper surface of the lower, or fossil bed, is exceedingly irregu- 

 lar, sinking downward, passing out of the exposed section towards the 

 northern extremity of the cliff. At other points in the section, irreg- 

 ularities of surface, such as could hardly originate beneath the level of 

 the sea, are found, nor does it seem possible that they are to be attrib- 

 uted to land slides, or other confusing agents. 



The syenite bed-rock, which is bared at the southern end of the 

 section, exhibits unquestionable proof of ice-wearing, being thoroughly 

 polished. The exposed surface being small, it is not possible to de- 

 cide whether the striation is uniform in direction, and thereby to 

 determine whether the agent which effected the wearing was land- 

 ice, or iceberg. However this be, there is no doubt that the whole 

 extent of the section rests on a true ice-ground surface. 



The record of changes, as given by these beds, seems to admit of 

 but one interpretation. The first condition there recorded is that of 

 glaciation, during which the bed-rock received its smoothing ; following 

 this came a period of comparative repose, during which the deposi- 

 tion of the fine sediment constituting the fossil bed began. A conclu- 

 sion based on negative evidence is always dangerous, but from the 

 examination which has been made it would seem, as if at first the sea- 

 floor was quite barren of life, and that many feet of the accumulation 

 had taken place before the life, which we find recorded in the fossils 

 there found, had gained a footing on the bottom. After the accumu- 

 lation of the fossil bed, there must have been an elevation of the sea 

 bottom sufficiently extensive to bring the present summit of this bed 

 above the water level. This elevation admitted of the formation of 

 the irregularities of surface of the fossil bed from weathering actions. 

 It does not seem likely that this elevated condition could have been 

 long continued, for in the soft state of the material constituting the 

 beds, degradation would have gone on very rapidly, and a compara- 

 tively brief period would have caused the destruction of the whole 

 mass. 



The next stage of the conditions seems to have been brought about 

 by the subsidence of beds for the second time, so that the highest 

 point of the fossil bed must have been many feet under water. It 

 would seem from the section that this subsidence was immediately fol- 

 lowed, if not attended, by the deposition of the ordinary stratified 

 drift which borders the New England coast. For If any considerable 

 time had elapsed between the depression of the shore and the laying 

 down of the boulder drift, it is likely that there would have been 

 some fine sediment laid down upon the weather worn surface, which 

 is manifestly not the case. 



It is most probable that the subsidence was accompanied by the 



