GKOIvOGY OF IvA SAIvIvE COUNTY. 



41 



duce it to a level and polish it as we find has been 

 done ag-ain and ag^ain. 



Now wherever we have a surface of hard rock, 

 that is covered with a foot or more of earth, we 

 g-enerally find the face of the rock, where uncov- 

 ered to be smooth, more or less polished and trav- 

 ersed by striae or scratches, with an occasional 

 g-roove straig-ht as a line can be drawn, and run- 

 ning* in g-eneral from some point between northwest 

 and northeast to some point between southeast and 

 southwest. These grooves may be a foot or more 

 wide and are often more than six inches wide and 

 foui rnches deep, and the causes which produced 

 the drift must have formed these. 



Various theories have been advanced to account 

 for these widely different phenomena. In all of them 

 water and ice are the important ag-ents, and we believe 

 these causes to be amply sufficient to produce the 

 really wonderful effects which we find g-raven in 

 the rocks and testified to by beds of sand, gravel 

 and clay. 



This is not wholly theoretical. A study of 

 glaciers has showm us that these immense masses 

 of slowly moving ice are today producing- just such 

 results as we find everywhere recorded in the drift. 

 They are doing the same work, smoothing- and pol- 

 ishing- hard rocks, scratching their surfaces with 

 multitudes of fine lines or stri«, transporting larg-e 

 blocks of stone, g-rinding- and crushing- much rock, 

 and forming sand and a mud which becomes clay, 

 and more than this the deposits formed by g-lacial 

 streams, streams which flow from a glacier, are in 

 every respect like those we find in the drift. 



Moreover, these deposits are not found every- 

 where. There are no such strata in the southern 

 part of our State, and all through the country 



