18 GEOLOGICAL SURVEY 
5. Resting upon these are other rocks, for the most part composed of the same materials as 
granite, but differing from it in presenting evidence of mechanical origin, and in having a structure 
apparently the result of deposition from water. They are more or less crystalline, which is 
supposed to be the result of subterranean heat, and the alterations produced by this cause have 
obtained for them the name of metamorphic rocks. Besides their stratified structure, the result of 
deposition from suspension in water of the materials of which they are composed, they are often 
intersected by planes, (supposed to be produced by contraction.) This is called joimted structure. 
Some of them are divisible into laminze whose planes do not coincide with the planes of stratifi- 
cation. This structure has received the name of slaty cleavage. 
6. That the metamorphic rocks have been elevated from their originally horizontal beds by a 
force acting from below; and hence the inclined position in which they are always found. The 
phenomena produced by this elevation have given rise to the terms dip, strike, outcrop, anticlinal 
and synclinal axis, §*c. 
7. That no organic remains have hitherto been found in these strata, and hence they are some- 
times called non-fossilliferous stratified rocks. 'This can only be explained by supposing that they 
were deposited before the beginning of life on the earth; that they were deposited under cireum- 
stances unfavorable to the preservation of animal and vegetable remains; or that these remains 
were obliterated by the intense heat to which the rocks have been subjected during their consoli- 
dation. 
CHAPTER IIL 
Palaeontology. — Classification. — Vertebrata—Mammalia.— Characters of the class.— Orders.— 
Birds.— Reptilia Characters of the class.—Fossil Reptiles — Orders.—Enaliosauri.—Ichthy- 
osaurus. —Plesiosaurus.— Crocodilia. —Dinosauria.—Lacertilia.—Pterosauria. —Chelonia.— 
Ophidia.— Batrachia. —Class Pisces.— Sub-kingdom Articulata.—NSub-kingdom Mollusca. 
Radiata.—Infusoria.—Fossil Plants. 
Before proceding to the consideration of those rocks which contain organic remains, it will be 
proper to take a general view of the science which has for its object the determination and descrip. 
tion of those forms which have passed out of existence in the revolutions of time, and whose ’ 
remains are entombed in the solid crust of the globe. 
For a long time these remains were considered mere “sports of nature”—the work of what was 
called a “ plastic force”—and violent was the opposition that those met with who held the opposite 
opinion, that they belonged to forms which once had life. It seems, at this day, almost incredible 
that fossil shells, presenting all the characteristics of the exuvie of living mollusks, should ever 
have been considered as mere imitative forms assumed by rocks. When observation, at length, 
gained its proper ascendency over speculation, and organic remains were viewed in their true light, 
Geology made a rapid stride towards its proper place as a science. 
