460 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



From Schenectady to Newburg the valley of the Hudson River is 

 open and broad, and its undulating surface constitutes part of an ancient 

 base level, originating in Tertiary time. Afterward continental eleva- 

 tion led the river to eorrade its channel deeply, so thai the immediate 

 valley of the river lies several hundred i'vot below the plain of the gen- 

 eral valley. The rocks in which this plain is carved are Lower Silurian 

 in age. including the Hudson River, Utiea, and Trenton series. They 

 are greatly disturbed, and beautiful sections are shown on the eliffs 

 and in the railroad cuts. Shaly portions have received a cleavage 



Structure, and metamorphism has extended so far that through con- 

 siderable areas the several series have not yet been discriminated. 

 Uplands visible at the right are due to the superior resistance of the 

 horizontal Lower Belderberg limestone, and loftier uplands seen beyond 

 them are due to the endurance of the Catskill sandstones. The moun- 

 tain from which the name Oatskill (Kaaterskill) is derived is a con- 

 spicuous feature at the right (west). At Newburg the Trenton lime- 

 stone occurs with but little alteration, and just beyond it the train 

 enters the area of crystalline schists, to which the mountain range 

 known as the Highlands belongs. 



The train then passes through the gorge of the Highlands, keeping 

 close to the water's edge. Above it the old base level plain holds place 

 as a terrace within the gorge. 



Beyond the gorge glimpses are obtained of disturbed and altered 

 Paleozoic rocks, and then the train approaches the Palisades,* a ridge 

 of trap, originally a sheet or dike injected in the great New .Jersey 

 series of red shales and sandstones commonly referred to the Trias. 

 This ridge borders the lower portion of the Hudson on the west for 

 many miles, and at its northern end swings west ward. The railroad, 

 passing through the curved northern extremity by a tunnel, follows 

 the western base of the ridge for more than half its length, and then 

 by another tunnel reaches its eastern base and the bank of the river 

 opposite. Xew York. 



In passing from Niagara Falls to Buffalo the train crosses the south- 

 ern outcrop of the Niagara limestone, the entire width of the Onondaga 

 Salt group, and enters upon the Corniferous limestone of the Lower 

 Devonian. Turning eastward it passes over the latter formation for 

 about 50 miles, when it recrosses the Onondaga Salt group and con- 

 tinues on the Niagara limestone to Rochester. From a little distance 

 cast of Rochester it follows the Onondaga Salt group Tor over 100 

 miles, when it crosses the thin eastern extension of the Niagara lime- 

 stone and the broad development of the Clinton formation before 

 entering upon the Utiea and Lorraine shales, upon which it follows for 

 105 miles except at Little Falls, between Utiea and Schenectady, where 



