MATERIALS EXAMINED • ^^1 



5. Clay like the Kaiisan, section 2, Crescent townsliip, Pottawattamie County, 



Iowa. 



6. Yellow bonlder-clay, Dimmick, Illinois. 



7. Pinkish yellow boulder-clay on top of a yellow boulder-clay from a railroad 



cut one mile south of Oglesby, Illinois. 



8. Boulder-clay, one-half mile east of Hillsdale, Illinois. 



WATER DEPOSITS 



General discussion. — Deposits belonging to this class are many and 

 various. A considerable number of analyses have been made, and while 

 some important classes of sediments are not as well represented as they 

 should be, it is believed that the data secured will give a general idea of 

 the composition of most sediments excepting coarse beach material. 

 They will be designated as sediments in glacial waters, terrace materials, 

 sediments in small streams, sediments in large streams, and marine 

 sediments. 



Sediments in glacial waters. — The material examined was taken from 

 deposits somewhat closely associated with till, and in situations indicat- 

 ing that the waters in which they were laid down drained glaciers. In 

 some cases they were pockets in till, suggesting intraglacial water cur- 

 rents (number 10). In other cases they are from terraces produced in 

 proximity to margins of glaciers (samples 9, 11, 12, 14, 16, 17, 18). 

 Owing to the nearness of the unassorted glacial material, we expect to 

 find deposits in such situations imperfectly sorted. The samples 9 to 

 18, inclusive, were taken across several layers of sand and gravel repre- 

 senting, as nearly as possible, uniform conditions of deposition. It will 

 be seen that in these samples there are materials present in from seven 

 to twelve different grades, averaging nine grades. Excepting one sample 

 (15), the percentages exceed one in from five to nine grades. The maxi- 

 mum ingredient ranges from 20 per cent (sample 9) to 53.9 per cent 

 (sample 14). 



It will be noticed that the admixtures vary considerably, one extreme 

 sample having only one grade of coarse admixtures (sample 15), while 

 it has five grades of fine admixtures. In an average showing the general 

 distribution of the quantities in all the grades in this class of sediments, 

 this distribution appears decidedly askew, as the coarse admixtures, dis- 

 tant from three to four grades from the maximum, are present in much 

 larger quantities than the corresponding fine admixtures. They produce 

 a second maximum. This is a distinguishing feature of some other sedi- 

 ments and its significance will be discussed later. It must be considered 

 a characteristic of poorly sorted material transported by drifting cur- 

 rents on the bottom under water currents and under winds. 



