y progressive
change can be tenable; unless, indeed, it be further assumed that four
thousand years is too short a time for the production of a change
sufficiently great to be detected.

But it is no less plain that if the process of evolution of animals is
not independent of surrounding conditions; if it may be indefinitely
hastened or retarded by variations in these conditions; or if evolution
is simply a process of accommodation to varying conditions; the argument
against the hypothesis of evolution based on the unchanged character of
the Egyptian fauna is worthless. For the monuments which are coeval with
the mummies testify as strongly to the absence of change in the physical
geography and the general conditions of the land of Egypt, for the time
in question, as the mummies do to the unvarying characters of its living
population.

The progress of research since Cuvier's time has supplied far more
striking examples of the long duration of specific forms of life than
those which are furnished by the mummified Ibises and Crocodiles of
Egypt. A remarkable case is to be found in your own country, in the
neighbourhood of the falls of Niagara. In the immediate vicinity of the
whirlpool, and again upon Goat Island, in the superficial deposits which
cover the surface of the rocky subsoil in those regions, there are found
remains of animals in perfect preservation, and among them, shells
belonging to exactly the same species as those which at present inhabit
the still waters of Lake Erie. It is evident, from the structure of the
country, that these animal remains were deposited in the beds in which
they occur at a time when the lake extended over the region in which
they are found. This involves the conclusion that they lived and died
before the falls had cut their way back through the gorge of Niagara;
and, indeed, it has been determined that, when these animals lived, the
falls of Niagara must have been at least six miles further down the
river than they are at present. Many computations have been made of the
rate at which the falls are thus cutting their way back. Those
computations have varied greatly, but I believe I am speaking within the
bounds of prudence, if I assume that the falls of Niagara have not
retreated at a greater pace than about a foot a year. Six miles,
speaking roughly, are 30,000 feet; 30,000 feet, at a foot a year, gives
30,000 years; and thus we are fairly justified in concluding that no
less a per