6S 
FIFTEENTH REPORT. 
we displace the soil solution. We may congratulate ourselves on the 
choice of paraffine oil as a medium. With the most refined instruments 
that were at our service, we were unable to detect any change in the 
solution when it was brought into intimate contact with the paraffine 
oil. A e found then, that the inactive paraffine oil did not change the 
electrical conductivity of the soil solution, while the chemical analysis 
also showed that there was no change brought about by the action of 
the paraffine. 
The third method which we employed was the measuring of the surface 
tension. We might expect that when only slight traces of the paraffine 
oil were dissolved in the soil solution, this would have its marked effect 
on the surface tension of this liquid. However, we were unable to detect 
any change in the surface tension of the liquid after it had stood for 
a long time covered with the paraffine oil. So far. the results obtained 
have demonstrated the permissibility of the use of the method employed. 
In regard to the amount of the soil solution that can be extracted 
by the application of our method, I must say in advance that even slight 
modifications even of the apparent details of our process caused large 
variations in the amount of water obtained. 
If we record only the values obtained, by the use of those conditions 
which we knew to be most satisfactory, then we must record the amount 
of solution obtained as a percentage of the total water capacity. 
But, at present, there exists in a few fields of soil physics such con- 
flicting interpretations of the meaning of the term “water capacity.” 
In the different text and laboratory books, we find the most diverse 
definitions and the most conflicting methods for the determination of 
this total water capacity. Because we suspected that this value would 
vary quite markedly with the application of the differently devised 
methods, we undertook some experiments which proved that our suppo- 
sition was correct. The total water capacities of the same soil as de- 
termined by the different methods varied over thirty per cent. From 
the soils containing the maximum water capacity we were able to ex- 
tract over seventy per cent of the total water. As an example, I will 
cite in this connection the data of an average extraction. 
From eight kilograms of soil (clay) which contained 11.3% water 
(figured on the basis of dry soil) was obtaned 330 cc. of soil solution. 
It is evident that such results can not be obtained by the use of a 
simple suction pump where the maximum difference of pressure is neces- 
sarily less than one atmosphere. 
However, we have secured larger differences in pressure by using 
several hundred pounds of pressure by means of a hydraulic press. 
We now have the soil solution and will analyze it. There are two 
ways in which we may investigate such a solution which require a 
short explanation. 
I. The chemical analysis. 
II. The physiological analysis. 
A chemical analysis seeks through its results a determination of soil 
fertility. However one can not claim that this method has been suc- 
cessful. The only thing which we can say with surety about its results 
is that if a certain nutritive element is found to be not pres- 
ent in the soil, then it is lacking for the nutrition of the plant. The 
