manure, as compared with the use of equivalent applications of
ground limestone; and, as an average of the sixteen years, every ton
of caustic lime applied liberated seven dollars' worth of organic
nitrogen, as compared with ground limestone. That this much
liberated nitrogen was essentially wasted and lost is evidenced by
the fact that larger crops were produced where ground limestone was
used than where burned lime was applied.

"The limestone must be quarried whether used for grinding or for
burning, and the grinding can be done for twenty-five cents a ton
where a large equipment with powerful machinery is used and where
cheap fuel is provided, as near the coal mining districts. It need
not be very finely ground. If ground to pass a sieve with twelve
meshes to the linear inch, it is very satisfactory, provided that
all of the fine dust produced in the grinding is included in the
product. You see the soil acids are slightly soluble and they attack
the limestone particles and are thus themselves destroyed or
neutralized. If, however, you ever wish to use raw rock phosphate,
insist upon its being sufficiently fine-ground that at least ninety
per cent. of it will pass through a sieve with ten thousand meshes
to the square inch, this being no finer than is required for the
basic slag phosphate, of which several million tons are now being
used each year in the European countries. Like the raw rock
phosphate, the slag gives the best results only when used in
connection with plenty of decaying organic matter."

"That reminds me," said Mr. West, "of what one of the fertilizer
agents said about raw phosphate. He said the use of raw phosphate
with farm manure reminded him of 'stone soup,' which was made by
putting a clean round stone in the kettle with some water. Pepper