94 
PETRIFIED FOREST. 
in others in an estuary, in the greater num¬ 
ber in the ocean bed. There have ])een 
periods during which the sea and the lake 
have had alternate prevalence in some lo¬ 
calities, as in central France. In Southern 
Europe, in Asia, in South America and 
elsewhere, the tertiary formations exist in a 
more solidified form, as rocks of imposing 
magnitude. 
As a fitting accompaniment to Mr. 
Ansted’s picture of the groves which at this 
era adorned the eastern shores of our own 
island, we extract from Darwin’s Journal 
his account of the petrified forest found 
amidst the volcanoes of the Cordilleras in 
South America. 
‘^The Uspallata range is separated from 
the main Cordillera by a long narrow plain 
or basin, like those so often mentioned in 
Chili but higher, being six thousand feet 
above the sea. This range has nearly the 
same geographical position with respect to 
the Cordillera, which the gigantic Portillo 
line has, but it is of a totally different 
origin ; it consists of various kinds of sub¬ 
marine lava, alternating with volcanic sand- 
