100 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, NO. 6 
even among soils of similar aspect. But it indicates at the same time 
that it is impracticable to calculate lime-requirement from specific 
acidity without knowing exactly what soil is under consideration in 
each case. 
Data on cranberry bog soils—It now seemed desirable to ascertain 
whether other types of soils would yield results similar to the foregoing; 
and certain of the data presented by Joffe® were used for this purpose. 
This author plotted active acidity against lime-requirement in some 
cases, but as he used exponential values for the former, his correlations 
are not directly comparable with those of the present paper. On 
recalculating his data, the specific acidity was found to range from 
1 to 1259, the lime-requirement from 0.1 to 7.5 and C from 0.004 to 
0.200. There is a decrease in C with depth in the soil at a given spot. 
The relations thus correspond to those shown in the gravelly loam 
soils. 
Data on a silt loam soil.—To obtain still further information upon 
the way in which the features in question vary from one soil to another, 
some data on an Ohio silt loam, published by Knight,’ were used. 
(In this connection the writer wishes to state that he does not agree 
at all with the majority of Knight’s conclusions.) The specific acidity 
observed ranged from 100 to 1140, the lime-requirement from 0.9 to 
2.2, and C from 0.0015 to 0.0091. As in the other soils, the range 
in C is wide; but in this series of results it is brought out with special 
clearness that liming results in a marked increase in the value of C, 
although the effect varies to some extent with the differently fertilized 
soils, evidently because of the different ways in which the lime reacts 
with the compounds present. 
Classification of soils on the basis of C-—The values of the correla- 
tion coefficient © for the whole series of soils above considered are 
collected in Table 1. They are arranged in a number of “classes,”’ 
the typical value for each of which is made for convenience about 
twice as great as for the preceding one.’ There are, of course, all 
gradations between these classes. It is evident that only if the class 
into which a given soil falls could be determined by some simple proce- 
dure, would it be practicable to obtain its lime-requirement from its 
specific acidity. 
6 Soil Sci., 9: 261. 1920. 
7 Journal Ind. Eng. Chem., 12: 559. 1920. 
8 In order to bring the values close to numerals the relationship of which is obvious, 
the multiple actually used is ¥/ 10 or 2.154. . . The rounded-off numbers obtained 
thereby, in all decimal places, are 1, 2 and 5. 
