142 
THE GROWTH OF CONTINENTS. 
are mostly formed of sand from the New-England 
granites. Such deposits are the local work of 
one period, containing the organic remains be- 
longing to the time and jilace. From the geo- 
logical point of view, I would call them Forma- 
tions ; from the naturalist’s point of view I would 
call them Zoological Provinces. 
Of course, in urging the application of these 
names, I do not intend to assume any dictator- 
ship in the matter of geological nomenclature. 
But I do feel very strongly the confusion arising 
from an indiscriminate use of terms, and that, 
whatever names be selected as most appropriate 
or descriptive for these divisions, geologists should 
agree to use them in the same sense. 
There is one other geological term, bequeathed 
to us by a great authority, and which cannot be 
changed for the better : I mean that of Geologi- 
cal Horizon, applied by Humboldt to the whole 
extent of any one geological division, — as, for 
instance, the Silurian horizon, including the 
whole extent of the Silurian epoch. It indicates 
one level in time, as the horizon which limits our 
view indicates the farthest extension of the plain 
on which we stand in space. 
We left America at the close of the Carbonif- 
erous epoch, when the central part of the United 
States was already raised above the water. Let 
