366 THE JOURNAL OF GEOLOGY. 
continental shelf were first excavated during the Pliocene, and then 
re-excavated —so far as filled during the Matanzas depression,—and 
deepened during the Pleistocene elevation. Later in the Pleistocene 
the land sank to a level 25 to 500 or 700 feet below the present 
elevation and the Zapeta loams and gravels were formed. Minor oscil- 
lations, not yet well worked out, have since taken place. 
The most important conclusion of this paper, z.e., the amount of 
the elevations, is based upon the assumption that the continent stood 
as much above sea level as the fjord bottoms are below it, less some ~ 
correction for unequal subsidence of the continental area. Although 
granting that a correction should be made for unequal subsidence, the 
author seems, so far as appears from his paper, to have practically neg- 
lected this point in his calculation of the former elevation of the land. 
The amounts of elevation which he gives for the various regions are 
almost as much as the amounts by which the fjord bottoms lie beneath 
the sea level. It seems possible to account for the depths to which the 
mouths of the fjords are submerged, without assuming that the continent 
stood at such heights. 
Grant that the elevation was sufficient to permit streams to cut val- 
leys across the continental shelf hundreds of feet deep, and in one 
instance, at least, to excavate a caiion comparable to the Grand Canon. 
It is probable that subsidence, once started, would be greater along 
the edge of the continental shelf than further inland. This would 
naturally follow on the doctrine of isostasy from the loading of the 
outer part of the continental shelf by sediments, deposited as the shore 
line advanced inward. It seems highly probable that the subsidence 
would be of the nature of a seaward tilting of the land and a deepen- 
ing of the ocean basins. 
Such differential motion along lines normal to the coast would 
increase the gradient of the bottoms of these buried channels. Before 
the author’s hypothesis of practically uniform subsidence along nor- 
mals to the coast can be accepted, it is incumbent upon him to show 
that the above hypothesis of subsidence with great tilting is inapplica- 
ble to the case in hand. So far as known to geologists, all epeirogenic 
movements are in the nature of tiltings and warpings rather than rigid 
uniform changes. If the subsidence were uniform or varied only along 
lines roughly parallel to the coast, the buried channels would retain 
practically the same gradient as they had when land valleys. A rough 
means of testing this hypothesis is thus at hand. 
