amounting to more than one-fourth of the productive power of the
land in a rotation with clover seeded every fourth year! This one
fact is the mathematical result of four hundred and eighty other
facts obtained from twenty different pieces of measured land during
a period of twenty-four years.

"As an average of these twenty-four years, the addition of mineral
plant food produced increases in crop yields above the unfertilized
land as follows:

Corn increased forty-five per cent.
Oats increased thirty-two per cent.
Wheat increased forty-two per cent.
Hay increased seventy-seven per cent.

"As a general average of the four crops for the twenty-four years,
the produce where mineral plant food is applied, was forty-nine per
cent. above the yields of the unfertilized land, although the same
rotation of crops was practiced in both cases."

"Those are some of the absolute facts of science secured from
practical application in the adoption and development of definite
systems of permanent prosperous agriculture, and they should be made
to serve this greatest and most important industry just as the
established facts of mathematical and physical science are made to
serve in engineering."

"I am glad to know about those long-continued experiments," said
Adelaide. "They are of fascinating interest. I have been so sorry
for grandma, and for papa and mamma, because of their increasing