ill 



iil 



1 



4 THE CHAIN OF LIFE. 



these except that marked a are very ancient marine rocks, 

 holding fossil shells and corals, but now forming part of the 

 interior of a continent, and cut through by a fresh-water 

 river. 



, , . -^ • . 



I' .— ^■'v^r-^-v- i^'-i:3\r'- 



Fir.. 1. — Bank of stream or coast, showing stratification, 



a. Vegetable soil, b, Gravel and sand, c. Clays, d. Limestone rock, slightly 



inclined. 



In deep mines and borings still more profound sections 

 may be laid open, as in Fig. 3, which represents the sequence 

 of beds ascertained by boring with the diamond drill in search 



c 

 d 

 e 



Fic;. 2, — Section at Niagara Falls, showing the strata cut through by the action of the 

 Fall. Thickness of beds about 250 feet. 



n, Boulder clay and gravel — Post-pliocene. 



^c SialarashTir'""' 1 ^Pper Silurian, with 



d, SfniTlit^Itone "'- - ^^^^"^ -^ 



e. Medina sandstone ) morals. 



of rock fait near Goderich in Canada. Here we have a suc- 

 cession of 1,500 feet of beds, some of which must have been 

 formed under very peculiar and exceptional conditions. The 

 beds of rock salt and gypsum must have been formed by the 

 drying up of sea-water in limited basins. Those of Dolomite 



