292 The Age of this Earth. [ May, 
now. We cannot tell when the water was separated from the 
atmosphere, or how long the atmosphere retained in itself the 
elemental constituents of water and of earth. The mathemati- 
cian and geologist have nothing to do with the subject before 
this event took place; there is nothing visible or tangible, no 
data for a single figure. The moment dry land is created the 
physical geographer begins his labors. They are not difficult ; 
he knows the uncertain forces that work under cosmical laws on 
forever changing materials; by knowing the results at present, 
he can tell those of the past. Far be it from us to suggest in- 
fallible action ; we can but give a faint outline of the whole, but 
we give nothing that cannot be verified by the law and its actions 
at the present moment. 
The geographer looks through time upon the face of the first 
dry land; he sees the water-sheds giving out their, little trickles 
all running down the slopes, all wearing away something in their 
course, all depositing some atoms on their way, and all carrying 
on to their little estuaries or deltas a constant succession of mi- 
nute atoms. He sees the deltas constantly extending by the 
addition of atoms, and constantly rising in consequence of the 
retiring of the waters. He sees constant additions to the dry 
land made by the water in one place, and constant abstractions 
in another; he knows that every atom taken from the water-bed 
makes that bed deeper, and every atom taken from dry land 
helps eventually to extend its shores. 
Under these actions he comprehends that the dry land must 
have gone on growing, and that the undulating ocean bed must 
have grown deeper where its currents ran, and shallower where 
they did not; he traces the gradual growth of these shallow 
places, not by any forcible elevation of the mass, but by the slow 
departure of the water, by the sediments left upon them, by the 
eventual growth of vegetation, by the creation of life, by the 
elemental forces forever returning to their dusts, in some regions 
or another, to the extending deltas and the growing dry land. 
He looks upon the mud and sand-banks of to-day and sees the 
same forces at work under the same laws; he knows that these 
forces acted under the same laws at the beginning, and he knows 
that they acted on the materials then available as they act on 
the materials of to-day. He marks through legends, history, and 
his own experience the denudations and the additions of the sea- 
shores ; he finds that in thousands of years the general contour of 
the dry land has remained the same; he finds that localities have 
