1892.] 
455 
[De Geer. 
was accumulating. Again, as the continents in certain instances 
for long periods of time have not lost in height, and this notwith- 
standing their immense denudation, they must have been gradu- 
ally rising. It is also very generally admitted, that many of 
the abundant alternations of strata deposited during different 
bathymetrical conditions, as well as the breaks between them, 
were caused by the oscillations of the earth’s crust. In many in- 
stances, however, it can not be decided whether the change of 
level was really due to movements of the land, or whether it was 
only the surface of the sea that rose and fell. Since the eminent 
Austrian geologist, E. Suess, in his grand work u Antlitz der 
Erde ” has in a very ingenious way tried to refer most of the 
oscillations to the latter cause, denying the rising of the conti- 
nents altogether, and since his views have been adopted by many 
geologists, it seems particularly desirable to get more positive 
facts for the final settlement of the question. 
For the present at least it is hard to get such facts concern- 
ing the older formations, as they are very often eroded away 
to a greater or less extent and concealed by younger deposits. It 
is thus in most cases impossible to determine the original extent 
of a certain layer and especially of the sea in which it was formed. 
Consequently we cannot determine with sufficient accuracy in 
what way the corresponding geoid-surface has been deformed. 
In regard to the Pliocene and Pleistocene formations it is of 
course less difficult, but in many parts of the world it seems as if 
the old shore-lines, which once marked the limit of these forma- 
tions, were not very well developed or easily recognized. It may 
sometimes be due to the fact that when the shores are low and 
consist of loose marine deposits, it is often very difficult to distin- 
guish the new from the old formations, and also to ascertain the 
depth of the last submergence. The beach is also easily effaced, 
partly perhaps through wind-blown sand. 
In the glaciated regions, however, the conditions are often dif- 
ferent and more favorable for the formation of enduring shore- 
lines, as the land is there generally covered with till and angular, 
stony debris, forming an excellent material for recording the action 
of the waves. Most of the old shores are described as situated 
in the glaciated regions, though this may perhaps depend upon 
another and deeper cause. 
Although a great many marine shore lines, shell deposits, and 
