Loess Soils of the Transition Region g 



box and the cylinder containing the standard supported on a stand 

 at a height of 6 to 12 inches above the former. After lighting 

 the candle and darkening the room as much as possible, the stop- 

 cock of the higher cylinder is opened wide. While the operator 

 has one hand on the stopcock of the lower cylinder and has one 

 eye over the latter, watching the candle flame, the solution is 

 allowed to slowly enter until the flame just disappears. Then 

 the stopcock is closed and the height of the column of solution 

 recorded, after which the lower cylinder is raised and the stop- 

 cock opened so that part of the solution flows back into the other 

 cylinder. Then the determination is repeated until two or three 

 successive readings give approximately the same height, the aver- 

 age of these being used in the calculation. After thus determin- 

 ing the depth of the column of the standard extract required to 

 hide the candle flame, similar determinations were made with all 

 the extracts. It much simplifies the calculations if in all cases 

 equal weights of soil have been extracted and the extracts have 

 been made up to the same volume. . , . Where the same graduated 

 cylinders, both of the same internal diameter, are used in all cases, 

 it suffices to record the volume of the extract required to hide the 

 candle flame. Otherwise, it is necessary to measure the depth of 

 the column of solution. . . . Provided that the same weight of soil 

 has been used and that the humus extracts have been made up to 

 the same volume, the percentages of humus will vary inversely as 

 the heights of the columns of extract required to hide the candle 

 flame." This method was tried only in the case of some of the 

 soils of high humus content, and with indififerent success. 



The above, in brief, are the methods tried, and as indicated 

 before, the Rather method was adopted for the preparation of the 

 humus extracts. 



DETERMINATION OF TOTAL NITROGEN 



But very few total nitrogen determinations were made, since 

 the totals on both the individual fields and the composites of the 

 transition series had previously been made by Mr. McDole, of this 

 station, and his figures were made use of in calculating the humus- 

 nitrogen ratios. Any nitrogen determinations that were made, 



119 



