SEEFACE DEE SITS. 97 



They were probably derived by glacial action from the 

 Dubuque lead region. 



Gold. Traces of gold are reported to have been found 

 in the drift of Iowa, and such no doubt exist. If so, it 

 may be supposed to have originated in northern Minnesota. 

 It seems almost unnecessary to say, what every person may 

 be expected to infer, that the existence in the drift of any 

 of these substances is no indication whatever of the existen -e 

 in the vicinity where they are now found, of natural deposits 

 of the same metals or minerals. Neither is there any 

 reason to hope that any of them will be found in the drift of 

 Iowa in sufficient quantity to pay for the trouble of seeking 

 for them. 



Coal. Lumps of impure coal have frequently been found 

 in the drift of northern Iowa, so much to the northward of 

 the northern boundary of the Iowa coal-field, that its origin 

 in that coal-field is not believed to have been possible. It is 

 known that a bed of impure coal, a few inches in thickness, 

 exists among the Cretaceous strata of northwestern Iowa 

 and southwestern Minnesota. This bed is believed to be the 

 real origin of the coal found in the drift of northern Iowa. 

 Unless that formation extended much farther eastward in 

 pre-glacial times than it does now, the existence of these 

 lumps of coal in the drift where we now sometimes find it, 

 pre-supposes a southeasterly direction of the current whh h 

 transported it. 



Wood. Pieces of wood are frequently found in the drift 



of different parts of the State, by digging' wells and other 



excavations. They have not only been found in the Altered 



Drift and Alluvium, but also in the unaltered drift. This 



wood must have been of pre-giacial origin, because we 



cannot suppose that trees grew in Iowa during the Glacial 



epoch, any more than they now grow in the glacial region of 



Greenland. These pieces of wood are not petrified, but are 



always so far mineralized that they are but slightly, if at 



all, combustible. Every piece thus far examined by the 



microscope, shows the peculiar structure of coniferous wood 

 13 



