58 



E. COLOR. 



A color coni])arison was made of all the samples, incki<lin£^ those 

 of both sets from each field. For this purpose a 25-i^ram portion of 

 each soil passed through a 2mm. sieve, was placed in a porcelain dish 

 of 100 cc. capacity, moistened and allowed to temper for an hour. 

 Then all the moistened samples were arranged in order of color, the 

 darkest being placed at one end and the lightest colored at the other. 



It was found possible to differentiate the soils into eight groups 

 (Tables 59 to 62), the shades of color in which were fairly distinct. 

 The graduation from one group into another, however, was not abrupt, 

 nor did every member of any of the groups possess exactly the same 

 shade as all the others. While eight shades of color were distinguish- 

 able, there were only three basic colors, viz., black, white and red. 

 The members of group 1, the darkest, and of grou]) 2 were black to 

 black with a brownish tint, those of group 3 brownish black to dark 

 brown, of 4 dark brown, of 5 dark reddish brown, of 6 light reddish 

 brown, of 7 brownish red, and of 8 brownish gray to light trray. The 

 color subsoils, as has recently been pointed out (1, p. 253). is not 

 dependent upon the amount of organic matter, being due in large 

 part to other coloring material. The degree of oxidation of the iron 

 affects the color as illustrated by groups 7 and 8, which have relativeh' 

 the same intensity of color but the former has the more pronounced 

 reddish shade because of a higher degree of oxidation of the iron. 



Carrington Silt Loam. Considerable variation in color was found 

 between sets within the same field as well as from field to field, this 

 being as great on one drift as on the other (Table 59). 



On the Late Wisconsin the soils in the first 6-inch section have, 

 in general, a relatively darker color than those of the corresponding- 

 level on the older formation. There is qtiite a marked difference in 

 the shade of color between the soils from the third foot level on the 

 two drifts, those on the Kansan having a distinctly reddish tint, while 

 on the younger drift browns, grays, and grayish browns predominate. 

 This would indicate that the oxidation of the iron has not proceeded 

 as far on the latter. The averages for the five fields, with the excep- 

 tion of the first six inches, are the same. 



Fargo Silt Loam. With the exception of Fields I and II on the 

 Late Wisconsin, there is little variation between the two sets within 

 the same field (Table 60). The average for the three foot sections 

 on the Kansan are the same, while a wider variation is shown on the 

 Late Wisconsin. On the latter the color of tlie soils in the second 



