OF ZOOLOGICAL FOCI. 143 
churc into the Mississippi, and more than fifteen hundred 
miles from any maritime port, Mr. Say discovered it in 
considerable numbers. Its existence in this case involves 
some important consequences, for, if we consider it to 
be of foreign origin, and take the period of its introduc- 
tion to have been some time since the first permanent 
colonization of this continent by Europeans, and suppose 
the point at which it was introduced to have been upon 
the sea-coast, it is necessary that the animal should have 
travelled more than twenty thousand times its own length 
every day while in motion, and to have been in progres- 
sive motion one fourth of the whole time for two hundred 
years, in order to have reached this locality; and if its 
progress has been aided by accidental transportation to 
some point on the Mississippi River, the result will not be 
the less improbable. Now when we reflect, that it is 
only sixty or seventy years since the first settlements of 
white men were made west of the Alleghany Mountains, 
and that it is scarcely forty years since the country 
beyond the Mississippi River was reached in their pro- 
gress, and bear in mind that the accidental transporta- 
tion of such animals could only have occurred by the 
merest chance, and that in their natural progress they 
must have overcome numerous and steep mountains, and 
crossed wide and rapid rivers, the difficulties in the way 
of this mode of explanation seem to be insuperable. It 
is true, that the historical period within which this con- 
tinent has been known, comprises probably but a small 
part of its whole existence, and that the action of known 
