388 Scientific Intelligence. 



Connecticut border, is believed to be the metamorphic represen- 

 tative of a Cambrian sandstone. 



" During- the Ordovician period the conditions for the deposi- 

 tion of sediments continued, and sandstone and shales and calca- 

 reous deposits were formed. The calcareous material is now 

 represented by the upper part of the limestone of western Con- 

 necticut and Massachusetts, and the shales and sandstones are 

 believed to have been the originals from which certain schists 

 were developed by metamorphism. The accumulation of these 

 sediments implies the wearing down of the adjacent lands, per- 

 haps to a plain. 



" In western Connecticut no definite record is left of the long 

 interval of time between the Ordovician and the Triassic. The 

 absence of known Devonian and Carboniferous strata, and the 

 facts which are known in regard to the geological history of 

 eastern North America in general, suggest the belief that the 

 state during these ages was part of a land mass bounded on the 

 west by a salt-water sea and on the east by the ocean. More- 

 over, it is believed that Devonian time saw western New England 

 molded into mountain ranges, and witnessed their disappearance 

 into land of less relief. The inference that an area of dry land 

 existed in western New England during Devonian time, rests 

 upon the fact that the fossils found in Maine are unlike those of 

 corresponding age found in New York, thus indicating the pres- 

 ence of an isthmus separating two water bodies in the northeastern 

 United States. Then again, the sediments of Devonian age both 

 east and west of Central New England show a retreating shore 

 line, as if the land were rising along a northeast-southwest axis. 

 The great thickness of Devonian sediments in the region to the 

 west — 5,000 to 10,000 feet — indicates that the land area of New 

 England constituted a mountain range comparable in height to 

 the southern Appalachians and perhaps rivaling the Alps. 



" Between the Ordovician and the Triassic occurred the univer- 

 sal metamorphism of the sedimentary deposits, with the intrusions, 

 of igneous rock and the formation of the numerous veins of quartz 

 which form such characteristic features of the metamorphic crys- 

 tallines. The portions of the intrusive masses now exposed to 

 view cooled and crystallized beneath the earth's surface ; but it 

 is reasonable to assume that pan, of the molten rock reached the 

 surface, and gave rise to volcanic phenomena, all traces of which 

 have now disappeared. The date of these intrusions and details 

 of their character are unknown. All that can safely be said is that 

 they represent different periods of igneous activity and occurred 

 between the Ordovician and the Triassic. Metamorphism of 

 the pre-Triassic rocks occurred at some date or at several dif- 

 ferent dates later than the original deposition of the rocks. The 

 exact time when these great changes took place cannot be stated, 

 but the metamorphism in large part seems to have been associated 

 with the mounlain-making movements which were so marked 

 near the close of the Carboniferous. A wide extent of territory 



