THE LOST VOLCANOES OF CONNECTICUT. 233 



Indeed, the reader must perceive that it is only because the actual 

 facts of observation are thus arranged that the existence of the 

 faults is inferred. Most of the faults are of moderate displace- 

 ment; but just north of Meriden there is one whose movement 

 amounted to two thousand feet ; it cuts off the northern end of the 

 main lava-sheet in Lamentation and the southern end of the same 

 in the Hanging Hills group of lava-ridges. In following along 

 the line between these two dislocated portions of the sheet, every 

 ridge formed by the more resistant sandstones or conglomerates 

 is cut off in a most systematic manner, precisely according to the 

 pattern shown in the beveled surface of the model. The railroad 

 crosses this great fault about a mile above Meriden, but the trav- 

 eler will see nothing there to indicate the dislocation ; its con- 

 structional effects have all been worn out. 



But the region is not now a plain. It is a rolling lowland 

 with occasional ridges formed on the resistant edges of the lava- 

 sheets. The cause 

 of this is found in 

 a moderate uplift of 

 the whole country 

 since it was reduced 

 to a peneplain, in- 

 troducing the sec- 

 ond chapter in the 

 history of its ero- 

 sion. After this up- 

 lift a new cycle of 

 erosive work was 

 undertaken, and we 

 now find ourselves 

 at a moderate ad- 

 vance in this division of the valley's history. The softer beds 

 have wasted away into lowlands, the harder ones still stand 

 up as ridges. In the adjoining crystalline areas on the east 

 and west, where most of the rocks are hard, the erosion of this 

 cycle has made comparatively little progress ; there the val- 

 leys are narrow and the interstream spaces are rolling up- 

 lands. In the Triassic belt, where most of the rocks are soft, 

 the erosion of the same cycle has made much greater prog- 

 ress and reduced the area nearly to a second peneplain, except 

 where the edges of the hard lava-sheets still hold up their crest 

 lines to give some indication of the elevation that the whole sur- 

 face once had. Here the valleys are broad and the interstream 

 highlands are reduced to narrow ridges. This stage is indicated 

 for our ten-mile-square area in Fig. 12, produced by removing 

 from the previous form of the model certain little slips by which 



VOL. XL. 19 



Fig. 12. 



