Arsenic in the Soil. 375 
the soil?—With the action of the rains and the fall- 
ing of the leaves, most of the arsenic which is 
applied to trees finally reaches the soil. What then 
becomes of it? If lime has been used with the 
spray, the arsenic will be insoluble when it falls 
upon the soil. It is possible that the organic acids 
in the soil, and also carbonic acid, may dissolve some 
of the arsenic, but it would be almost surely made 
immediately insoluble again by combination with lime 
or other soil constituents. If soluble arsenic is placed 
on the soil, it probably almost immediately goes into 
insoluble combinations, and remains where it was 
placed unless slightly washed down by mere mechan- 
ical means. Now, some plants appear to have the 
power to take up very minute quantities of arsenic 
and still thrive—probably so minute that the nicest 
chemical test can scarcely discover it,—but any appre- 
ciable quantity of soluble arsenic in the soil quickly 
destroys the roots. If, therefore, the grass and other 
plants under sprayed trees continue to live, there 
need be no fear that the arsenic will injure the soil. 
A study of the destination of arsenic which has 
been applied to the soil in the form of Paris green 
was made at the Cornell Station (Bulletin 101), from 
which the following conclusions were drawn: “The 
gist of the whole matter then, if we may generalize 
_from these tests, is that the arsenites do not leach 
from the soil. They remain where they fall, the 
same as sand does, and are carried down only when 
there are erevices or other openings in the soil, and 
they then go down as insoluble compounds, and to 
