344 CONTEMPORANEOUS DEPOSITION [cHap. xvI. 
the terraces at Coquimbo (to a height of 250 feet), but are em- 
bedded in a friable caleareous rock, which in some places is 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 con- 
taining 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 Jand 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 escarp- 
ments 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 Pa- 
tagonia 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 con- 
