Lansing Pleistocene Geology. — WinchcU. 275 
A similar examination was made of the stratified silt layer, 
with similar results. If casually examined this silt would be 
pronounced highly calcareous — and so it is en gros. But it 
is apparent, on closer inspection, that this carbonate of lime is 
largely confined to loess-kindchen formed in it, or to encrusta- 
tions and fillings that occupy the numerous fissures by which it 
is cut. These fissures are very numerous and very tortuous. 
They cause the dry silt, when excavated, to crumble into a 
thousand polygonal masses that roll out almost spontaneously. 
They are abundantly coated with a white deposit of carbonate 
of lime. When thoroughly washed and freed from this second- 
ary deposition of carbonate of lime, these masses do not effer- 
vesce freely on the application of hydrochloric acid, but if 
they be immersed in such acid there appears a languid attack 
of the acid in the escape of a few fine bubbles of gas, showing 
that the secondary deposition has also penetrated the inter- 
ior of the silt. There is another sli^it difiference observable 
in the microscopical mounting, viz : the silt contains also round- 
ed or angular grains of quartz of much greater size than anv 
seen in the clay underlying. But with those two exceptions 
this silt is, microscopically and chemically, identical with the 
clay that underlies it. The character of those two la vers. 
taken together, seems to indicate a common origin for the 
bulk of the material of which they are composed ; and also 
that the silt is referable to a washing action from the under- 
lying clay ; such action having also introduced some coarser 
quartz particles pot derivable from the immediately underlying 
clay though probably from the surface adjacent. The absence 
of drift materials from the clay and its scantiness in the silt 
indicate that they originated in pre-Iowan time. The addition 
of lime in excess to the silt is due to the downward leaching 
from the overlying loess. The sample of the silt examined by 
the writer w^-s obtained near the entrance to the tunnel. He 
is not able to affirm that the little fissures arc as frequent, and 
as calcareous, at the other end of the tunnel, Init he noticed no 
difference. His sample from the underlying clay was obtained 
near the place of the skeleton. 
The writer is under obligations to Dr. C. P. l>crkey for tb.e 
determination of the percentages of carbonate of lime in Nos. 
I, 3 and 4. He has made the following statement: 
