32 [Assembly 



broken through the latter. Such an instance occurs at Little- 

 Falls, where the hard red and gray gneiss has been lifted up in a 

 ridge across the Mohawk, and appears in the gorge protruding 

 through the fossil-bearing slates and limestones. Most of New- 

 England is covered by rocks of this character; their broken, 

 bent, and upheaved position bearing witness to their having 

 been subjected to enormous pressure in every direction. Even 

 there, in some localities there are portions of these rocks which 

 show traces of fossils, to prove that they are only altered or 

 changed masses of the same strata which in Western New- York 

 appear in horizontal and unchanged layers of limestone ; a'lld it 

 is believed that the coarse crystalline rocks of the White and 

 Green mountains are in fact extensions of the same masses, 

 which have undergone a similar transformation. 



Still below these metamorphic rocks are found what are known 

 as Hypogene or Plutonic * rocks. These include granite, f trap, 

 greenstone, porphyry, and many other varieties of hard crystal- 

 line rocks, the great peculiarity of which is that they are not 

 found in layers or strata, but in shapeless masses, and appear, 

 instead of having been formed by deposition from water, to have 

 been upheaved from below. They bear evidences of having been 

 intensely heated, and in many instances have calcined or baked 

 other rocks with which they come in contact as before mentioned. 

 Though in their original position the lowest of all rocks, they 

 have in many places been upheaved far above others ; and in 

 most high mountain ranges, the cone or central ridge is formed of 

 these rocks, which have been thrust upward, splitting through 

 and tilting up all which lay above them. They form the central 

 mass of the Adirondacks, and masses. of them are found in the 

 Highlands and in many parts of New-England, the well known 

 Quincy sienite being one form of hypogene rock. They were 

 once generally called "primary" or "primitive," as it was 



* Hypogene, signifying born from below. Plutonic, from Pluto, king of the infernal 

 regions in Pagan mythology. 



f Granite is a hard crystalline rock, made up of crystals of quartz, felspar and mica. 

 There are many varieties of rocks of similar nature, varying by having some other minerals 

 replacing or added to these, such as hornblende, garnet, steatite, etc. etc. The rock varies 

 much in color, being often red, but not uncommonly grey or dark. The frequent use of the 

 term ** granite " in popular speech to signify any hard and massive rock, is entirely incor- 

 rect. Sienite, which is quarried at Quincy (Mass.) in great quantities, and has been so 

 extensively used in building in Boston and for the Exchange in New-York, is granite with, 

 the mica replaced by hornblende. 



