368 
NORTHERN CHILE 
CHAP. 
as much as between twenty and thirty feet in thickness, but is 
of little extent. These modern beds rest on an ancient tertiary 
formation containing shells, apparently all extinct. Although 
I examined so many hundred miles of coast on the Pacific, as 
well as Atlantic side of the continent, I found no regular strata 
containing sea-shells of recent species, excepting at this place, 
and at a few points northward on the road to Guasco. This fact 
appears to me highly remarkable ; for the explanation generally 
given by geologists, of the absence in any district of stratified 
fossiliferous deposits of a given period, namely, that the surface 
then existed as dry land, is not here applicable ; for we know 
from the shells strewed on the surface and embedded in loose 
sand or mould, that the land for thousands of miles along both 
coasts has lately been submerged. The explanation, no doubt, 
must be sought in the fact, that the whole southern part of the 
continent has been for a long time slowly rising ; and therefore 
that all matter deposited along shore in shallow water must 
have been soon brought up and slowly exposed to the wearing 
action of the sea-beach ; and it is only in comparatively shallow 
water that the greater number of marine organic beings can 
flourish, and in such water it is obviously impossible that strata 
of any great thickness can accumulate. To show the vast 
power of the wearing action of sea-beaches, we need only 
appeal to the great cliffs along the present coast of Patagonia, 
and to the escarpments or ancient sea-cliffs at different levels, 
one above another, on that same line of coast. 
The old underlying tertiary formation at Coquimbo appears 
to be of about the same age with several deposits on the coast 
of Chile (of which that of Navedad is the principal one), and 
with the great formation of Patagonia. Both at Navedad and 
in Patagonia there is evidence, that since the shells (a list of 
which has been seen by Professor E. Forbes) there intombed 
were living, there has been a subsidence of several hundred feet, 
as well as an ensuing elevation. It may naturally be asked 
how it comes that although no extensive fossiliferous deposits 
of the recent period, nor of any period intermediate between it 
and the ancient tertiary epoch, have been preserved on either 
side of the continent, yet that at this ancient tertiary epoch, 
sedimentary matter containing fossil remains should have been 
deposited and preserved at different points in north and south 
