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IOWA ACADEMY OF SCIENCES. 



The pressure is sufficient, as is known from several sources. 



There remains yet one necessary condition unsatisfied. That is geological 

 structure. 



It is well known that the strata in Iowa have a general dip to the southward— 

 the total amount of fall being probably in the neighborhood of 3,500 feet. But the 

 State of Iowa is covered everywhere with a thick mantle of glacial deposits hiding 

 from view the stratified rocks almost entirely. Numerous streams, however, have 

 corraded their channels completely through the drift debris even into the under- 

 lying indurated rocks, thus exposing in many places the arrangement of the differ- 

 ent layers. It will be sometime before anything like accurate and detailed cross- 

 sections can be made across the State in the direction of the common inclination of 

 the rocks. Yet good progress in this work has already been made. 



There is a widespread opinion that the Iowa strata have still their uninter- 

 rupted seaward tilt unaffected by deformations of any kind. Such, however is not 

 the case. Although far removed from mountainous districts orographic move- 

 ments have affected the beds to a slight extent, producing low folds. A number 

 of these low anticlines and shallow synclines have long been known, though rather 

 vaguely. According to McGee, who has indicated recently some of the chief axes 

 in a sketch map of the State, the anticlinals of the eastern part of Iowa trend south- 

 westward. Other folds have been recognized in the central and western portions 



ZiiNU 



Sketch-Map of Iowa, showing Principal Lines of Deformation, 

 of the State. The extent of this folding is at present unknown, but in some cases 

 it may prove to be very considerable; sufficient perhaps to satisfy the l-ast require- 

 ment for a flowing well. It is not then beyond all hope that when, ere long the 

 arching dome of some low anticline is pierced we may yet hear the mighty roar not 

 soon forgotten, or listen to the gushing stream of liquid amber. 



IOWA MINERALOGHCAL NOTES. 



BY CHARLES ROLLIN KEYES. 



Ptfrite—Qaite recently there have been obtained from limestone cavities in Lee 

 unty some small but very perfect pyrite crystals. The faces are brightly reflect- 



