We must, however, guard ourselves against
too literal an interpretation of the word "contemporaneous,"
and we must bear in mind the enormously-prolonged periods of
time with which the geologist has to deal. When we say that two
groups of strata in different regions are "contemporaneous," we
simply mean that they were formed during the same geological
period, and perhaps at different stages of that period, and we
do not mean to imply that they were formed at precisely the same
instant of time.
A moment's consideration will show us that it is only in the former
sense that we can properly speak of strata being "contemporaneous;"
and that, in point of fact, beds containing the same fossils, if
occurring in widely distant areas, can hardly be "contemporaneous"
in any literal sense; but that the very identity of their fossils
is proof that they were deposited one after the other. If we find
strata containing identical fossils within the limits of a single
geographical region--say in Europe--then there is a reasonable
probability that these beds are strictly contemporaneous, in the
sense that they were deposited at the same time. There is a
reasonable probability of this, because there is no improbability
involved in the idea of an ocean occupying the whole area of
Europe, and peopled throughout by many of the same species of
marine animals.
Pages:
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100