now EXTINCT MO NS TEES ARE PRESERVED, 19 
are much more likely to contain the remains of land animals, 
than those that were formed in seas, and they are more likely 
to be in a complete state of preservation. Within the last 
century, five or six small lakes in Scotland, which had been 
artificially drained, yielded the remains of several hundred skeletons 
of stags, oxen, boars, horses, sheep, dogs, hares, foxes, and 
wolves. There are two ways in which these animals may have 
met with a watery grave. In the first place, they may have got 
mired on going into the water, or in trying to land on the other 
side, after swimming across. Any one who knows Scotch lakes 
will be familiar with the fact that their margins are often most 
treacherous ground for bathers. The writer has more than once 
found it necessary to be very cautious on wading into a lake 
while fishing, or in search of plants. Secondly, when such lakes 
are frozen over in winter, the ice is often very treacherous in 
consequence of numerous springs ; and animals attempting to 
cross may be easily drowned. No remains of birds were dis- 
covered in these lakes, in spite of the fact that, until drained, 
they were largely frequented by water-fowl. But it must be 
remembered that birds are protected by their powers of flight 
from perishing in such ways as other animals frequently do. 
And, even should they die on the water, their bodies are not 
likely to be submerged ; for, being light and feathery, they do 
not sink, but continue floating until the body rots away, or is 
devoured by some creature such as a hungry pike. For these 
reasons the remains of birds are unfortunately very rare in the 
stratified rocks ; and hence our knowledge of the bird life of 
former ages is slight. 
The Imperfection of the Record. 
A very little consideration will serve to convince us that the 
record which Nature has kept in the stratified rocks is an incom- 
plete one. There are many reasons why it must be so. It is 
