9 
necessarily confined to the tropical parallels. The long- 
hair mammoth found in Siberia might have lived far beyond 
the tropics, and the carcass might have been carried by 
the floods of the rivers towards the Arctic region two or 
three thousand years ago. Had Africa been connected with 
the south of Spain, as it was in former ages, Spain would 
even now be infested by tropical animals. It is neces- 
sary to bear this in mind when we discuss questions con- 
nected with terrestrial changes. The African rhinoceros is 
found as far south as the Cape of Good Hope, latitude 34° 30' S., 
and lions as far north as Algiers, about 36° lat. N. 
The fossil forest of Atanekerdluk, in latitude 70° N. (Green- 
land), is still standing erect on its native soil. When those 
trees flourished, they required a temperature of at least 30° Fah. 
higher than is now found in that parallel. This land 4,000 
years ago was within the parallel of 48° N., in which similar 
vegetation now flourishes in France. 
The Nova Scotia coal-beds contain calamites, fern-trees 
rooted in the arenaceous beds, surrounded by their fallen 
leaves, and the remains of tropical reptiles. This formation 
is now in latitude 45° N. About 4,000 years ago it was in 
latitude 23° N., and might have then received its sedimentary 
deposits, in the same manner as they are now seen forming 
in the lagoons of St. Martha, near the mouth of the river 
Magdalena. 
The south-east part of England, when the Wealden de- 
posits were formed, was in a very warm climate. It had then its 
lagoons, with palms, arborescent ferns, &c. Crocodiles, 
iguanoes, turtles, and various reptiles, infested its fens and 
rivers, and have left their remains as memorials of their 
former existence. All this might have occurred about 4,000 
years ago, when the south of England was in latitude 
30° N. 
How much more satisfactory it is to the inquiring mind to 
learn that these great geological changes are not the result of 
chance or disturbed elements, but are occurring as regularly, 
and are as uniform and exact in the rate of their movements, 
as the rotation of the earth ; and that they do not proceed 
from a series of igneous catastrophes, regulated by no laws, 
and reducible to no fixed principles, as assumed by geologists. 
I shall not refer to the theory which was propounded at the 
commencement of the last century, and attempted to be im- 
proved by IT Alembert, to account for the change referred to 
by an assumed conical motion of the terrestrial axis. This 
inconsistent hypothesis has been lately exposed and demo- 
lished by M. Poinset, an eminent member of the French Insti- 
