[Illustration: FIG 2] _Topography of Connecticut._ Connecticut can be said to consist of two great areas quite distinct in topography and geologic structure.[35] On the east and on the west are the crystalline uplands which rise from sea level along the Sound to 1,700 and 1,800 feet in the northwestern part of the state, and to 600 and 700 feet in the northeastern. These uplands consist chiefly of gneiss and granite, probably of pre-Paleozoic age, which are now much folded, faulted and crumpled. Between these two areas of crystallines is a lowland belt of Triassic sandstone and shale, twenty to twenty-five miles wide, extending from New Haven north through the center of the state and including in its borders New Haven, Meriden, Hartford, New Britain and many towns of lesser note. These sandstones form a monocline with an eastward dip of 10° to 30°, and in addition to being tilted they have been faulted since their deposition in a shallow, slowly-subsiding trough of crystallines. Their thickness is variously estimated--3,000 to 5,000 feet, Dana; 10,000 or more, Davis. This lowland is interrupted by a series of trap ridges, which in general present steep faces toward the west, whereas their eastward slope is gradual, less than the dip of the sandstones. _The upland plateau._ Suppose we ascend the highest point of these trap ridges, the old tower on Talcott Mt., nine miles west of Hartford; we are 900 feet above the sea level and more than 600 above the plain at our feet. A few miles to the west across the sandstone valley, rise the crystalline uplands, which extend far to the north and to the south. On the east across the Connecticut we see the eastern uplands. The first impression, which comes to one as he gazes upon these uplands and which is strengthened with each view, is that few hills rise above the general level of the plateau; the crest line is nearly horizontal, declining gently to Long Island Sound. Above this general level are a few rounded domes, but no sharp, towering peaks. Below it valleys have been cut, but they do not destroy the plateau-like appearance. A view from the western plateau across the sandstone valley shows the remarkably even crest line of the trap ridges, a crest line which approximates in height the uplands on the east and west. A nearer view of the upland corroborates our first impressions of the gently rolling character of the inter-stream surfaces, but we have a better view of the valleys which have been sunk beneath the general level and of the low rounded hills which rise above it. In popular parlance the country is “hilly.” It is uneven, not because there are high hills, but rather because there are deep valleys. If in imagination we fill up these valleys and the wide Triassic lowland to the general level of the broad inter-stream surfaces, we shall have constructed a gently undulating plateau, dipping to the south and east--a peneplain.[36]