192 ELEMENTARY GEOLOGY 
or a watery muck, into which one may sink. Ireland 
and Scotland are also noted for their peat bogs, which 
furnish a kind of fuel. 
In the bogs the vege- 
tation does not decay, as 
it does where it falls to 
the ground in the air; 
for, as 1t commences to 
Fra. 101. 
Diagram showing a peat bog in section. decompose, substances 
To illustrate the extinction of lakes by are produced which give 
growth of sphagnum. 
antiseptic properties to 
the water. So, for hundreds of years, bogs may pre- 
serve the prints of the beaver teeth upon the tree 
trunks which they have cut; and the bones of ani- 
Fie. 102. 
Deposits of carbonate of lime precipitated from solution in Lake Mono, in | 
the Sierra Nevada. 
mals may resist decay, and lie in this muck well pre- 
served. 
