Ch. II.] 
SUBAQUEOUS DEPOSITS. 
9 
them having thinned out and given place to others, or some- 
times one of the masses, first examined, is observed to increase 
in thickness to the exclusion of other beds. Besides this 
limited continuity of particular strata, it is obvious that the 
whole assemblage must terminate somewhere ; as, for example, 
where they reach the boundary of the original lake-basin, and 
where they will come in contact with the rocks which form the 
boundary of, and, at the same time, pass under all the recent 
accumulations. 
In almost every estuary we may see, at low water, analogous 
phenomena where the current has cut away part of some newly- 
formed bank, consisting of a series of horizontal strata of peat, 
sand, clay, and, sometimes, interposed beds of shells. Each of 
these may often be traced over a considerable area, some ex- 
tending farther than others, but all of necessity confined within 
the basin of the estuary. Similar remarks are applicable, on a 
much more extended scale, to the recent delta of a great river, 
like the Ganges, after the periodical inundations have subsided, 
and when sections are exposed of the river -banks and the cliffs 
of numerous islands, in which horizontal beds of clay and sand 
may be traced over an area many hundred miles in length, and 
more than a hundred in breadth. 
Subaqueous deposits. The greater part of our continents are 
evidently composed of subaqueous deposits ; and in the manner 
of their arrangement we discover many characters precisely simi- 
lar to those above described ; but the different groups of strata 
are, for the most part, on a greater scale, both in regard to depth 
and area, than any observable in the new formations of lakes, 
deltas, or estuaries. We find, for example, beds of limestone 
several hundred feet in thickness, containing imbedded corals and 
shells, stretching from one country to another, yet always giving 
place, at length, to a distinct set of strata, which either rise up 
from under it like the rocks before alluded to as forming the 
borders of a lake, or cover and conceal it. In other places, 
we find beds of pebbles, and sand, or of clay of great thick- 
ness. The different formations composed of these materials 
