4 BULLETIN 141;. U. S. DEPARTMENT OF AGRICULTURE. 
obstructed and where considerable accumulations of organic matter 
were mingled with the surface soil. Before artificial drainage was 
supplied the majority of them existed as swamps and swales irregu- 
larly scattered through the upland. Artificial drainage has brought 
about the reclamation of the majority of these tracts, ancl^ their 
soils are now classed chiefly with the Clyde series. 
Expressed in terms of parallels and meridians, the territory within 
which some members of the Clyde series have been encountered ex- 
tends from longitude 75° west to longitude 90° west; and from lati- 
tude -10 ° north to latitude 45° north. There is some probability that 
more northern occurrences will eyentually be encountered. It 
should be understood that the larger areas of soils of the Clyde series 
are decidedly localized within these geographic limits, being con- 
fined to those portions of the territory which were at one time occu- 
pied by the glacial lake extensions of the Great Lakes, or else occur- 
ring within smaller lake beds and depressions throughout the up- 
land or upon the terraces of the glacial rivers which once furnished 
outlets for the ponded waters of the predecessors of the present 
Great Lakes system. 
THE GLACIAL LAKE AND RIVER TERRACE SOIL PROVINCE. 
The various sections of the country may be divided into major 
soil provinces within which the soil-forming materials possess a 
common general origin and have been deposited or otherwise formed 
through very similar processes. That region in the northern por- 
tion of the United States which was at one time or for successive 
periods of time occupied by the waters which resulted from the 
melting of the continental ice sheet and those portions of the lower 
lands across which these ponded waters escaped to the sea are classed 
as the glacial lake and river terrace province. Its general location 
and extent are shown upon the map. figure 1. 
GEOLOGICAL ORIGIN OF THE SOILS OF THE CLYDE SERIES. 
Within recent geological times a large proportion of the north- 
eastern and north-central States was occupied either once or repeat- 
edly by a thick covering of ice in the form of a continental glacier. 
The latest occupation by glacial ice has been called the Wisconsin 
stage of glaciation by the geologists. It took the form of a glacial 
advance in many ice lobes occupying the area now covered by the 
existing Great Lakes and the adjacent territory immediately to the 
south and west of them. 
The different lobes of ice were pushed southward from the Cana- 
dian highlands until they occupied practically all of northern and 
western Xew York, northwestern Pennsylvania, northern Ohio, and 
