144 HOW CROPS FEED. 
action of moving ice (glaciers) or water (rivers), and de- 
posited as sediment in their present positions. 
Drift Soils (sometimes called diluvial) are characterized 
by the following ;articulars. They consist of fragments 
whose edges at least have been rounded by friction, if the 
fragments themselves are not altogether destitute of 
angles. They are usually deposited without any stratifi- 
cation or separation of parts. The materials consist of 
soil proper, mingled with stones of all sizes, from sand- 
grains up to immense rock-masses of many tons in weight. 
This kind of soil is usually distinguished from all others 
by the rounded rocks or boulders (“hard heads”) it con- 
tains, which are promiscuously scattered through it. 
The “ Drift” has undoubtedly been formed by moving 
ice in that period of the earth’s history known to geolo- 
gists as the Glacial Epoch, a perio: when the present sur- 
face of the country was covered to a great depth by fields 
of ice. 
In regions like Greenland and the Swiss Alps, which 
reach above the line of perpetual snow, drift is now ac- 
cumulating, perfectly similar in character to that of New 
England, or has been obviously produced by the melting 
of glaciers, which, in former geological ages and under 
a colder climate, were continuations on an immense scale 
of those now in existence. 
A large share of the northern portion of the country 
from the Arctic regions southward as far as latitude 39°, 
or nearly to the southern boundaries of Pennsylvania and 
to the Ohio River, including C:nada, New England, Long 
Island, and the States west as far as Iowa, is more or less 
covered with drift. Comparison of the boulders with the 
undisturbed rocks of the regions about show that the 
materials of the drift have been moved southwards or 
southeast wards to a distance generally of twenty to forty 
miles, but sometimes also of sixty or one hundred miles, 
from where they were detached from their original beds. 
