NO. 23.] CENTRAL CONNECTICUT IN THE GEOLOGIC PAST. 15 



system which stretches through Massachusetts, Connecticut, New 

 Jersey, and southeastern Pennsylvania to central North Caro- 

 lina. To a lesser degree the history has corresponding stages in 

 those belts of the Appalachians to the east and west. The local 

 description, besides giving details of local interest, serves, by 

 concentrating the attention, to bring out sharply the magnitude 

 of the changes which mark the passage of geologic time. It is 

 thought, therefore, that such a discussion may serve for more 

 than local interests. 



The Surface Features. The surface of the land is the prod- 

 uct of erosion. The erosion of the portions above sea level during 

 each period has furthermore been carried to varying degrees of 

 completion. The result has been to divide Connecticut into three 

 geographic provinces, the Central Lowland, and the Eastern and 

 Western Highlands. The Central Lowland trends nearly north 

 and south across the central part of the State and extends north- 

 ward across Massachusetts. On the northern boundary x of Con- 

 necticut it has a breadth of twenty miles, but narrows southward 

 to about eight miles at the latitude of New Haven. It constitutes 

 throughout most of its length the broad valley of the Connecticut 

 River, but the latter abandons the Lowland at Middletown and 

 has carved from that point a gorge diagonally across the Eastern 

 Highland to Long Island Sound. The southern end of the Cen- 

 tral Lowland is consequently drained by several small rivers which 

 flow into New Haven harbor. With the exception of the narrow 

 belts of marble which occur in the western part of the State, the 

 Triassic shales and sandstones which underlie the Lowland are 

 the rocks least resistant to decay and erosion, and have, therefore, 

 been worn low, rapidly from the geologic standpoint. The 

 Eastern and Western Highlands are, on the contrary, with the 

 exception of the small Pomperaug Valley lying west of the map, 

 Figure I, underlain wholly by metamorphic rocks; these are 

 crystallized sediments or mashed and recrystallized igneous rocks. 

 With the exception of the marble belts the metamorphic rocks 

 are hard and insoluble and therefore slow to decay into soil. But 

 this means slow erosion, as discussed under a previous heading, 

 save where the stream currents, carving with the sand and gravel 

 of their beds, wear out narrow valleys. Thus it is perceived that 



