SUE-FACE DEPOSITS. 95 



usually the case, perfectly parallel with their fellows, distinct 

 and straight. 



An exposure of the same limestone on the Nebraska side 

 of the Missouri river, opposite Council Bluffs, and only some 

 six or eight feet above the ordinary stage of water in the 

 river, shows similar scratches. These, however, have a very 

 different direction from any of the others, it being south, 

 forty-one degrees west. Those observed upon the Sioux 

 quartzite in southwestern Minnesota and the adjacents parts 

 of Iowa and Dakota, have various directions, usually east of 

 south, from ten to twenty degrees. 



It is of course not supposable that the glaciers had a uni- 

 form movement to the south, even if we had no evidence to the 

 contrary, for it is evident that their currents would be more or 

 less deflected from that direction by the inequalities of surface 

 over which they passed. On the contrary, we have abundant 

 evidence that the currents of the glaciers were numerous and 

 various in their directions, even in so flat and open a country 

 as ours ; but what was the cause that actually did determine the 

 direction of those currents in every case we may never know. 

 Our observations, however, show certain coincidences that are 

 worthy of mention, but they are not presented as anything 

 like conclusive evidence. By referring again to the degrees 

 of divergence of each of the sets of striae just described, it 

 will be seen that those of the set near Burlington coincide 

 pretty nearly in direction with the general direction of the 

 streams of the eastern system of Iowa drainage. Those of 

 the set which were observed opposite Council Bluffs coincide 

 quite as nearly with the general direction of the streams of 

 the western system; while the two sets observed upon the 

 same surface in Mills county, represent currents which, at that 

 point at least, are approximately coincident in direction res- 

 pectively, with the general course of the Missouri and Platte 

 rivers. 



It is not impossible that these currents of the great wide- 

 spread glacier, which it is assumed in former times, spread 

 over the surface of the State, and the currents of the present 



