know all that he knows of his own self; but were those letters from
his mother? The handwriting was very modern. Even her father made an
old-fashioned C and W in signing his own name. Had he not looked at
the writing on both those letters before he noticed the others? and
why did he remain so long in his room before coming down to dinner?
Had he not been in college--in a great University where there were
hundreds of the brightest girls of his own State? But why should any
girl be interested in farming? Teaching is such a cultured
profession.

Only a moment--just while he was sorting the papers upon which they
had made the computations, but a hundred thoughts had passed through
her mind. Now he was speaking.

"You remember we took a sample of the subsoil on the sloping land.
This soil is evidently residual, formed in place from the
disintegration of the underlying rock. The soil may represent only a
small part of the original rock, because of the loss by leaching.
Here are the amounts of plant food found in two million pounds of
the subsoil:

590 pounds of nitrogen
1,980 pounds of phosphorus
37,940 pounds of potassium
24,808 pounds of magnesium
31,320 pounds of calcium

"A splendid subsoil," Percy continued. "I know of none better in
Illinois, except that we sometimes have more calcium in the form of
carbonate, and even somewhat more potassium in places; but this must