120 Dr Fleming on the Revolutions in the Animal Kingdom , 
conclusion, that, along with the increase of dry land, there must 
have been a proportional diminution of aquatic animals and 
plants, and a corresponding increase of those which inhabit the 
land. There is likewise reason to conclude, that, amidst these 
vast revolutions, so many alterations must have taken place in 
those physical conditions, on which the life of animals depends, 
that multitudes must have been annihilated with every succes- 
sive change. The increase of land, by this process of upfilling, 
and the reduction of the number of mountains supporting gla- 
ciers, must have altered greatly the temperature of the globe; 
and, in every region, increased the difference between the heat 
of summer, and the cold of winter, by promoting the intensity of 
each. This change of temperature may have been somewhat 
modified by the progress of vegetation in the different periods, 
by the formation of volcanic land, and the heat communicated to 
the air by volcanic fire. It is impossible to estimate all the ef- 
fects which these changes may have produced on different spe- 
cies of animals, but little doubt need be entertained that they 
were of considerable extent. 
In consequence of these changes which have taken place on 
the earth’s surface, corresponding alterations must have been 
produced in its condition, as a residence for animals. Every 
lake, as it was filled up, would receive the remains of all those 
of its inhabitants, the locomotive powers of which prevented 
them from shifting to a more suitable dwelling. If a number 
of these lakes were filled up nearly at the same time, over the 
whole, or a large portion of the globe (and the universality of 
many of these upfilling formations justify the supposition), the 
total extinction of a race of animals may have taken place; and 
each succeeding deposition may have been equally fatal to the 
surviving tribes. 
If every physical change which can take place on the surface 
of the earth, whether it be an alteration of temperature, of the 
quantity of land or water, of moisture or dryness, is detrimental 
to some animals, we need not be surprised, that, amidst the vast 
number which has occurred, many species have disappeared, 
whole races become extinct, and the general features of the ani- 
mal kingdom undergone successive changes. 
When we trace the characters of the different depositions 
which have taken place, from the newest alluvial beds, to the 
