IOWA ACADEMY OF SCIENCES. 125 



and 26 of Howard township. The presence of loess over- 

 lying lowan drift is not unique over tlie state, but this is 

 not its usual mode of occurrence. In central and southern 

 Iowa the deeper beds of loess are found covering Kansan 

 drift at do great distance from the lowan border. It 

 seems probable that then, as now, loess materials were 

 deposited on the leeward side of obstructions to dust-laden 

 currents of air, or where, in the path of such winds, the 

 soil was covered with vegetation which would serve to 

 catch and retain the dust particles that fell upon it. 

 However, the distribution of loess over this portion of the 

 state would indicate that during the time when the lowan 

 ice prevailed the conditions were exceptionally favorable 

 for its deposition, and that probably the source of much of 

 the materials might have been the super-glacial silt from 

 the lowan ice sheet itself. 



Very often the deposits of lowan drift are found in the 

 valleys while till of Kansan age covers the hills and 

 emerges at the surface along the upper part of the slopes. 

 Examples of hills with Kansan drift exposed at the top 

 and having lowan materials flanking the base, may be 

 seen in the northern part of section 35 of Howard town- 

 ship and along the middle line of section 21 of the same 

 township. 



The lowan ice which pushed down over this area car- 

 ried quite a large number of light colored granite bowld- 

 ers. These bowlders are usually from four to eight feet in 

 diameter, but individuals ten to twelve feet in length are 

 not rare, while one specimen was seen with a long diam- 

 eter of about thirty feet. Bowlder strewn flelds, some of 

 the rocks of large size, may be seen about eighty rods south 

 of the Toledo and Cedar Rapids road, one in the eastern 

 part of section 23 and another in the western part of sec- 

 tion 24, of Toledo township. Occasional bowlders dot the 

 surface along all of the stream courses over this region. 

 They are seldom found on the higher points, but seem to 

 have been left during the process of the melting of the ice 

 which carried them either on the lower flanks of the slopes 

 or along the beds of the streams. 



