THE LOST VOLCANOES OF CONNECTICUT. 229 



in Fig. 7. When tliis first volcanic disturbance was over, the 

 accumulation of sandstones went on again, the sands were washed 

 in from the shores of the estuary and crept out over the back of 

 the lava-sheet ; the finer sediments settled down into the irregular 

 crevices in the surface of the flow, even filling little half-open 

 vesicles. A microscopic examination of specimens from these 

 contacts of lava and overlying sandstones brings back vividly the 

 condition of their deposition. Loose fragments of the lava, car- 

 ried a little way by the waves and more or less water-worn, were 

 mixed with the sands 

 for a few feet above 

 the lava, but they 

 were soon all buried. 

 Then things went on 

 for a long time about 

 as before the erup- 

 tion. The supply of 

 sediments seems to 

 have become finer 

 after a while, for a 

 bed of black shale is 

 found, with numer- 

 ous impressions of 

 fossil fishes and 

 plants, one of the 

 few traceable fos- 

 siliferous layers of 

 the entire forma- 

 tion. Then came 



more barren sandy shales again. It is impossible to measure the 

 time of this quiet work in years, but after three or four hundred 

 feet of strata had been formed, another outburst of lava (M) took 

 place, and on a greater scale than the first. The lava-sheet formed 

 by this eruption is three or four hundred feet thick — thick enough 

 to have in all probability filled the shallow estuary wherever it 

 ran, transforming it into a level lava plain, like the plain of the 

 Shoshone River of to-day Bat the depression of the estuary 

 trough continued ; if the lava surface was at first above water 

 level, it was soon submerged and buried in sands and mud, repeat- 

 ing all the significant phenomena of contact that have been men- 

 tioned above. Then came another long period of quiet, broken by 

 a third lava outpouring (P) ; and after that, still more sandstones 

 and shales, until aqueous and igneous rocks had accumulated to a 

 thickness of perhaps two miles. At some time during this long 

 history a sheet of lava was driven in or intruded between the 

 sandstones near the bottom of the formation (marked I in Fig. 8) ; 



Fig. 8. 



