45 



3. Iron. 



The iron is reported as ferric oxide in table 3*^. The distribution 

 is quite uniform from type to tyjie and from drift to drift. On the 

 Kansan, all three types show a his/her content than on the Late Wiscon- 

 sin, and, on the latter, the averap^e percentai::es are almost identical. 

 The difference between drifts is c^reatest on the Carrinqton silt loam 

 where, in the second and third foot-sections, it amounts to 1.0 per cent, 

 and least on the Carrington loam, which exhibits a remarkable parallel 

 ism also in the case of practically all other constituents. On the 

 Kansan, the maximum on two of the three types is shown in the second 

 foot-section, while on the T.ate Wisconsin it is found in the third foot. 



Table 39. — Ferric oxide in the different sections. 



4. Alumina. 



The total alumina (Table 40) is very uniformly distributed on the 

 two drifts as well as from type to type, on the Kansan showing a mini- 

 mum of 9.50 per cent and a maximum of 12.43 per cent and, on the Late 

 \\'isconsin. a rancfe from ^\52 to 12.54 per cent. 



Table 40. — Alumina in the different sections. 



Carrington silt loani Fargo silt loam Carrington loam 



Late Wis. Kansan Late Wis. Kansan Late Wis. 



per cent per cent per cent per cent per cent 



10.46 10.29 10.18 9 50 9.52 



10.87 11.46 10.62 10.54 10.66 



11.35 12.43 11.57 12.01 11.81 



12.13 12.28 12.54 10.46 11.77 



11.38 11.86 11. .50 10.83 11.22 



In the vertical distribution the maximum, as in the case of the 

 ferric oxide, on the Kansan, is to be found in the second foot and on 

 the Late Wisconsin in the third foot, the opposite of what was found 

 for silica. The percentat^^es in the upper sections are not as large as 

 those in the lower ones, which is to be explained by the downward 

 translocation of colloidal clay. 



The similarity in the alumina content on the two drifts is evident 

 from the averages for the three-foot sections on all three types, viz.. 

 11.46 per cent on the Kansan and 11.37 per cent on the Late Wisconsin. 



