COPPER AND ZINC AS ANTAGONISTIC TO "ALKALI " SALTS 169 
General Discussion 
It may be stated without qualification that the data submitted 
above are evidence of the antagonistic action of the heavy metals to 
alkali salts for crop plants grown in pots. Moreover, our evidence 
appears to be the first of the kind ever published. If, as now seems 
likely, the principles thus adduced may be applied to field conditions, 
a new factor of safety may be introduced into alkali problems which 
may possess major importance in competent hands. From the scien- 
tific standpoint, on the other hand, the facts which we have obtained 
are equally interesting and important and indicate a field of investiga- 
tion of great promise with regard to the mechanism of the antagonistic 
action which we have noted. 
That the effects noted are, in a sense, certainly not ephemeral ones 
may be gleaned from the data submitted for the adobe soil in which 
three crops were grown in succession in some of the series and antago- 
nism was shown to obtain in all cases. It is unfortunate that similar 
results were not obtained for the Oakley soil which could be submitted 
in this paper, but the results of certain series which were not complete 
and therefore could not be given here indicate, as one would expect, 
that the facts adduced in the case of the adobe soil are of equal cogency 
in their application to the Oakley soil. 
Other general features of our experiments, which may demand 
special attention here, are the following: The small quantities of the 
metals which are sufficient to antagonize large quantities of alkali salts 
render the economics of the applications of the scientific principles 
involved fairly simple. If it should prove possible to employ refuse 
from metallic ores for the purpose, the task of antagonizing the alkali 
salts in soils should prove particularly simple. The fact, also, that 
zinc is nearly as effective as copper in the direction noted may be 
indicative of possibilities in the same line with other and cheaper 
metals, a point which we shall hope to determine in future experiments. 
The reproductions of photographs of some of the grain yields in 
vials as containers will serve to emphasize the data for the yields which 
are given in the tables. 
In the discussions given herewith, the authors have been fully 
cognizant of the differences which obtain between the amounts of salts 
applied to the soil and those which remain actively in solution in the 
soil water. We have not attempted, therefore, to give in the tables 
