CHEMICAL STUDY OF DOLOMITES 
45 
PER CENT 
SiO, 
2.16 
FeA 
0.00 
AlA- 
24.24 
CaCOg 
72.83 
MgCO. 
0.31 
Cu 
0.86 
100.40 
The specimen is in no sense a dolomite, but a limestone contain- 
ing only a small amount of magnesium. 
Professor LeRoy D. Weld has called our attention to “a solu- 
ble white incrustation sparsely deposited in some of the crevices 
in one of the Oneota dolomite caves on the Mississippi.” The cave 
is situated near Marquette (North McGregor), Clayton Coun- 
ty. On bringing to his laboratory and testing a portion of the in- 
crustation, he finds it to be magnesium sulphate. Professor Weld 
accounts for this soluble sulphate by the action of sulphuric acid 
in the atmosphere on the magnesium carbonate of the rock. The 
cave is near the Milwaukee railway, and it is exposed to the smoke 
from the coal which usually contains a small quantity of sulphuric 
acid. 
Cornell College, Mount Vernon. 
