Geology of Lincoln Co., S. D. — Bcndral. 83 
including the upper sand and gravel stratum, varies within the 
limits of ihe region from 80-125 ^^c^- 
Even the till yields water, although it is of inferior quan- 
tity and quality, being sometimes impregnated with HoS. It 
is probably due to the joint-structure of the till, that the rain 
sinks below the surface in fissures and cracks, so that, for in- 
stance at Tea. water is struck in digging cellars and cisterns at 
at depth of about 8 feet. 
Whether the red clay, which is at points more or less free 
from sand, but at others hardly to be distinguished from the 
till, so far as its constituents are concerned, and which overlies 
the yellow and the blue till or underlies the blue till, has to be 
considered an independent member of the drift or represents 
only another phase of the till, must be left undecided for the 
present, k has been found by the writer to crop out to the sur- 
face in sec. 25 of Delapre township, S.W. quarter, where it de- 
velops a thickness of 40 feet ; and also within one foot from the 
top of the blufifs, facing Fairview. where it forms thin layers 
above and below a band of calcareous concretions, which stand 
with their axes vertical. It has been found by boring east of 
Tea to underlie the blue till and also the fine sands underneath 
at a depth of 134 feet, 40 feet thick, while at Worthing it is 
found to underlie the black loamy soil at a depth of only 2 feet, 
w'xth a thickness of 5 feet, overlying the blue till. 
Especial attention may be called to the exceptional occur- 
rence of clay of "bufif-creani"' color, mottled by a greenish sand, 
which is intermixed with the clay. It has been met with by the 
writer only at one locality, i.e. eleven miles south and within 
a third of a mile east of Canton, in a cut on the northern side 
of the road, w^liere it occupies the very base of the exposure of 
about 6 feet of the yellow bowlder-clay. It is also laid bare in 
the road itself. The writer suggests here a rearrangement of 
clays and greenish sands from above, washed down to the foot 
of the cut and spread over the road by rain. 
c : The Occurrence of the Loess. 
The Loess, which is still the subject of much dispute among 
geologists, so far as its origin is concerned, occupies, as already 
indicated, only limited portions of the area. It is met with less 
in continuous sheets, but rather in isolated patches, cladding 
preferably the highest parts of the region, although it descends 
