180 NEW YORK STATE MUSEUM 



and extensively; and since they were uplifted to their present 

 elevation, the elements have unremittingly acted upon them. 



As the rocks, newer than the Carboniferous, occur in but small 

 areas within our state, it may be concluded that the greater part 

 of this region has been above water since the Carboniferous 

 period, during the countless ages while the Triassic, Jurassic, 

 Cretaceous and) Tertiary rocks were formed and during the depo- 

 sition of which the animated population of the earth has been 

 changed many times. All of these formations were made of sedi- 

 ments worn from pre-existing land. It is to be expected, there- 

 fore, that this ancient land should show the marks of vast erosion 

 and wear. Some marks of this are found in the long and deep 

 valleys which traverse the state, all of which have been worn 

 out of the solid strata, the remaining portions of which form the 

 adjacent hills. These valleys are being worn deeper where the 

 rivers are strong and their cutting action continues, and every- 

 where they are being widened and the mountains and hills re- 

 duced in height by rains and frost. Some valleys have been 

 excavated much below the level of their present outlets, so that 

 they retain the drainage and form the remarkable series of finger 

 lakes previously mentioned. 



Vast as the work may seem, the fact is plain that not only 

 have these valleys been formed by erosion, but hundreds of feet 

 of rocky strata have been removed from the summits of the hills 

 themselves and from large tracts of plain country. The whole 

 vast basin of Lake Ontario is an excavation in rocks which still 

 lie nearly as level as when first deposited; and there seems no 

 reason to doubt that the northern edges of the enormous thick- 

 ness of formations above the Helderberg limestones once over- 

 spread the present lowlands of the counties bordering that great 

 body of water. 



Such long lines of bluffs as the Niagara ' mountain ridge/ and 

 the steep escarpments of the Helderberg limestones, are evidences 

 of the great work of erosion. The existence of old beaches, such 

 as the Lake Eidge near Rochester, proves that the waters of the 

 lake once stood far higher than now. 



