alternating processes. 
121 
this difficulty. Sir Charles Lyell, in his ob¬ 
servations on Nova Scotia, says, that at a 
place called ''The Joggins,” there is a range 
of perpendicular cliffs on the coast, composed 
of regular coal measures, and including about 
nineteen beds of coal, all parallel, varying 
from two inches to four feet in thickness. 
At more than ten distinct levels in this series, 
there are stems of trees, each originating in 
a coal seam, all upright, with reference to 
the floor on which they grew, all cut off by 
the layers of mud and coal above. The 
trees were hollow, and the bark has become 
coal, the interior filled with sand. Here 
are then the unequivocal remains of ten 
distinct forests which grew at distant inter¬ 
vals on the same spot, and between the 
interval each in succession covered with 
clays and sands, which were deposited un¬ 
der water and have become solid stone. 
Such instances might be cited from nearly 
all the known deposits of coal; the latter 
evidently owing much of its present cha¬ 
racter to alternate changes of dry land and 
water: the ocean, or lake-bed, becoming a 
vegetable soil, sustaining its noble burden 
L 
