_KINDS OF SOILS. 145 
+ 
The surface of the country when covered with drift is 
often or usually irregular and hilly, the hills themselves 
being conical heaps or long ridges of mingled sand, gravel, 
and boulders, the transported mass having often a great 
depth. These hills or ridges are parts of the vast trains 
of material left by the melting of preadamite glaciers or 
icebergs, and have their precise counterpart in the moraines 
of the Swiss Alps. Drift is accordingly not confined to the 
valleys, but the northern slopes of mountains or hills, whose 
basis is unbroken rock, are strewn to the summit with it, 
and immense blocks of transported stone are seen upon 
the very tops of the Catskills and of the White and 
Green Mountains. 
Drift soils are for these reasons often made up of the 
most diverse materials, including all the kinds of rock and 
rock-dust that are to be found, or have existed for one or 
several scores of miles to the northward. Of these often 
only the harder granitic or silicious rocks remain in con- 
siderable fragments, the softer rocks having been com- 
pletely ground to powder. 
Towards the southern limit of the Drift Region the 
drift itself consists of fine materials which were carried 
on by the waters from the melting glaciers, while the 
heavier boulders were left further north. Here, too, may 
often be observed a partial stratification of the transported 
materials as the result of their deposition from movmg 
water. The great belts of yellow and red sand that 
stretch across New Jersey on its southeastern face, and 
the sands of Long Island, are these finer portions of the 
drift. Farther to the north, many large areas of sand 
may, perhaps, prove on careful examination to mark the 
southern limit of some ancient local glacier. 
Alluvial Soils consist of worn and rounded materials 
which have been transported by the agency of running 
water (rivers and tides). Since small and light particles 
are more readily sustained in a current of water than 
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