GEOLOG Y. III 
remote parts of the earth have very different animals; 
the preservation of organic remains at the mouth of the 
Mississippi being no index of what is going on at the 
mouth of the Ganges. While it is possible, it is certainly 
not proved by the structure of the rocks, their deposition, 
and organic remains, that the whole earth has passed at 
the same time successively through the Primary, Secondary, 
and Tertiary Ages. The limits of this essay do not admit 
of the further discussion of this subject; nor, indeed, is it 
necessary, as the question has been thoroughly argued 
by Herbert Spencer in his *Illogical Geology." The dis- 
putes of the Neptunists and Plutonists ought to be a 
warning to Geologists not to apply generalizations, drawn 
from limited data, to the whole earth. In the present state 
of Geology we should receive all conclusions with great 
caution, being prepared at any moment to have them 
modified or even disproved by future research. Notwith- 
standing the difficulty of obtaining fossils, the injuries they 
often have received in being removed from the rocks, that 
many are lost or destroyed through the ignorance of the 
workmen who are often the first to find them, together 
with the fact that the chance of plants and animals being 
preserved is very small, remembering how the remains of 
an animal, dying at the present day, are picked to pieces, get 
separated, and are often finally destroyed,—yet the museums 
in different parts of the world contain numerous organic 
remains on which is based the science of extinct plants 
and animals, or Paleontology, the conclusions of which 
science are important proofs of the truth of the theory of 
the evolution of the higher forms of life from the lower. 
The opponents of the transmutation of species argued 
` fifty years ago, If the higher forms have descended from 
the lower, where are the missinglinks? Paleontology has an- 
swered that objection by supplying the missing links, such as 
the intermediate forms which bind together the Rhinoceros 
