Page:The Journal of geology (IA journalofgeology21894univers).pdf/413
square miles. This area has a maximum width on the south of ten miles and a minimum width on the north of four miles. The delimitation of the Pre-Cambrian as just given is only approximate, as in many localities data for its separation from overlying rocks are lacking.
The Geological Survey has lately issued topographic maps of nearly all the territory embraced in the above-outlined area; in them the pronounced relief of the country is well shown. These maps are the Rutland and Wallingford sheets. An inspection of the topography reveals a line of high elevations on the west, with steep slopes to the east, and steeper slopes commonly on the western side. This line of mountains extends from the southern limit of the Wallingford sheet to the northern limit of the Rutland sheet, and is only broken by narrow transverse valleys where lateral streams come in from the east or southeast and join Otter creek in the Rutland valley. On the east side of the area a similar range of high mountains extends the same distance, but coalesces with the western line in the northern part of the Rutland sheet. The convergence of the two lines is geologically dependent on a narrowing of the series of folds, which originally mantled over the central part of the area. North of Ludlow mountains an offset to the east occurs which carries the line slightly to the east of the Wallingford sheet.
It will be noticed on the Wallingford sheet that there is a central area between the border line of mountains of relatively much lower elevations. From Copperas hill in Shrewsbury one observes that the mountains appear to encircle him with a line of much higher elevations. In a country of strong relief one is always impressed with a sense of being in the centre of a series of elevations of greater height than those in the immediate vicinity. But from Copperas hill the impression is borne out by a glance at the topographic maps. On the east and west are the two lines of mountains just described; to the south, but farther away, the country begins to rise towards the high peaks of Stratton and Somerset; to the north, just north of the town of Shrewsbury