8 
Bulletin 65. 
Most of our analyses, for instance, have to do with only one phase Of 
the subject and that almost exclusively a mineralogical one which 
may practically be designated as a somewhat indefinite study of the 
decomposition products of feldspar, principally a red orthoclase. It 
may be a little humiliating at this juncture to make so uncompli¬ 
mentary a statement concerning this part of our work, but it is 
scarcely more. This is very plainly suggested by the results of the 
mechanical analysis which, as already stated, shows this mineral to 
be the principal one from which the potash can be derived. The 
small amount of mica in the soil would, even if the mica were 
easily attacked and altered, contribute but a very small amount of 
potash or lime, it being very subordinate in quantity. The analyses 
of the separate parts of the soil as obtained in the mechanical 
analysis will be shown to suggest the same fact so forcibly that it 
amounts almost to absolute proof that in our samples we have to do 
with an altered feldspar. 
THE EXPERIMENTS COVER TOO SHORT A PERIOD. 
What the effect of growing three crops on this soil may 
have been is scarcely shown by so short a series of experiments; 
that is, the results are not large enough to be measured by the 
means at our command. Even if we should confine the effect to 
the clay this would still be true. This, however, cannot, as we will 
show, be justly done, for the feldspar certainly yields fresh quantities 
of potash to the soil. This mineral is so finely divided, or enough 
of it is, that even the rain water can and undoubtedly does take a 
perceptible quantity of this compound into solution. 
POTASH IN FELDSPAR AVAILABLE. 
§ 12. We shall show by direct experiment that the oat plant, 
for instance, can appropriate potash from this mineral when it is 
finely powdered, even in cases in which the mineral is perfectly 
fresh and the whole work of decomposition has to be done during 
the period of growth of the plant, perhaps by the roots of the plant 
itself. The theory of the formation of zeolitic minerals, to serve as 
the conveyors of the potash, etc., from the more stable minerals to 
the plant, cannot very well be appealed to, at least as necessary. 
My experiments do not show that zeolitic compounds are not formed, 
but they do show that if they are formed, their formation takes 
place so rapidly that perfectly fresh, but finely pulverized, feldspar 
becomes an available source of potash in the short period required 
for the growth of the oat plant. I do not mean to say that finely 
powdered feldspar will yield potash so rapidly that it will furnish a 
supply adequate to the production of a crop, but that it will furnish 
in the aggregate a very considerable quantity of this element. It is 
a well known fact that this mineral yields potash to water and it 
