VAOLHORSE MAES PRAGES 
The Loess of Western Illinois and Southeastern Iowa. By FRANK 
LEVERETT, Denmark, Iowa. 
The north border of ‘the loess both in western Illinois and eastern 
Iowa appears to have been determined by the ice-sheet. The loess is 
apparently an apron of silt spread out to the south by water issuing 
from the ice-sheet. It is loose textured at the north and becomes 
finer textured toward the south, showing a decrease in the strength of 
depositing currents. The wide extent of the loess over the uplands 
has led to a consideration of the influence of the wind as well as water 
in its distribution. It is thought that wind-deposited loess may be 
distinguished from that which is water-deposited. The wide extent, 
however, appears to be due to water-distribution rather than wind. 
Wind action apparently came into force subsequent to the water dis- 
tribution and is of minor importance. 
Possible Depth of Mining and Boring. ALFRED C. LANE. Geol. Society 
of America, Philadelphia, 1895. 
The paper was prepared for the forthcoming volume of JZzxeral 
Industry. ‘The possible depth of mining was studied from the con- 
struction of a curve representing the minimum cost of mining at vari- 
ous depths. The chief factors in increasing the cost were found to be 
the increased length of time required for a hoist, and the increasing 
temperature. Stress was laid on the efficiency of the escape of com- 
pressed air in neutralizing the increasing rock temperature, and the rate 
of increase in temperature in the Lake Superior copper mines was dis- 
cussed, with the result that an increase in temperature of not more 
than 1° F. in 100 feet could safely be assumed and that in all proba- 
bility a depth of 10,000 feet could be reached without insuperable dif- 
ficulty. A shaft is now down 4800 feet, and another one started which 
will not reach the lode until it is down 5000 feet. In the discussion 
following Professor Shaler suggested that the low temperature gradi- 
ent might be due to the cooling effect of the use of compressed air 
in the mines, and Mr. Lane suggested that it might also be due to a 
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