34 AI orris J. Blish 



in the west, although, on the whole, it is fairly constant through- 

 out the loess region. 



8. The nitrogen content of humus is slightly higher in the west 

 than in the east, although it also is fairly constant throughout the 

 entire loess area. 



9. The so-called '' humus ash," as determined by the Rather 

 method, shows a tendency to run a trifle higher in the western 

 soils than in the eastern. 



10. With regard to the comparison of soil colors, and the rela- 

 tion of soil color to humus content, it is concluded that the color 

 of the soil may be associated fairly closely with the humus content 

 when the soils under inspection are from the same locality, but 

 when soils of dift'erent localities are brought together the ex- 

 treme differences in types of color, caused by substances other 

 than humus, such as lime and iron, made a satisfactory and 

 reliable comparison by this method impossible. 



11. An arrangement with regard to color intensity, using the 

 humus extract instead of the soils themselves, may be made with 

 a fair degree of accuracy without the colorimeter. 



12. The photometric determination of humus was attended 

 with only indifferent success and did not give satisfactory results 

 in the case of soils containing under one per cent of humus. 



13. In preparing humus extracts for colorimetric determina- 

 tions, solutions prepared by the Rather method give a clearer and 

 more transparent solution than than do those prepared by the 

 Hilgard method, due probably to the fact that a slight amount 

 of clay is carried through the filter in using the Hilgard method. 



144 



