Ch. IV.] 
PROVED BY ORGANIC REMAINS, 
43 
shown to have been contemporaneous, if we suppose the rivers 
flowing from those three countries to carry the remains of 
different species of the animal and vegetable kingdoms into the 
Mediterranean, 
In like manner, the sea intervening between the northern 
shores of Australia and the islands of the Indian ocean, con- 
tains a great proportion of the same species of corallines and 
testacea, yet the land animals and plants of the two regions are 
very dissimilar, even the islands nearest to Australia, as Java, 
New Guinea, and others, being inhabited by a distinct assem- 
blage of terrestrial species. It is well known that there are 
calcareous rocks, volcanic tuff, and other strata in progress, in 
different parts of these intermediate seas, wherein marine 
organic remains might be preserved and associated with the 
terrestrial fossils above alluded to. 
As it frequently happens that the barriers between differ- 
ent provinces of animals and plants are not very strongly 
marked, especially where they are determined by differences of 
temperature, there will usually be a passage from one set of 
species to another, as in a sea extending from the temperate to 
the tropical zone. In such cases, we may be enabled to prove, 
by the fossils of intermediate deposits, the connexion between 
the distinct provinces, since these intervening spaces will be 
inhabited by many species, common both to the temperate and 
equatorial seas. 
On the other hand, we may be sometimes able, by aid of a 
peculiar homogeneous deposit, to proVe the former coexistence 
of distinct animals and plants in distant regions. Suppose, for 
example, that in the course of ages the sediment of a river, like 
that of the Red River in Louisiana, is dispersed over an area 
several hundred leagues in length, so as to pass from the tropics 
into the temperate zone, the fossil remains imbedded in red 
mud might indicate the different forms which inhabited, at the 
same period, those remote regions of the earth. 
It appears, then, that mineral and organic characters, although 
often inconstant, may, nevertheless, enable us to establish the 
