cultivate.

"I wrote to the Illinois Experiment Station before I left Washington
to see if I could get the average composition of the heavier prairie
soil, which occupies the very flat areas that were originally
swampy, and one of the letters you had received for me gives 8000
pounds of nitrogen and 2000 pounds of phosphorus as the general
average for that soil. That is our most productive land, and it
contains about five times as much of these two very important
elements as your poorest land.

"Our more common Illinois prairie contains about 35,000 pounds of
potassium, 9,000 pounds of magnesium, and I 1,000 pounds of calcium.
This is more than twice as much potassium and nearly three times as
much magnesium as in your poorest land, but the calcium content is
about the same in your soil as in ours. However, as you will
remember, your soil is distinctly acid and consequently markedly in
need of lime, the magnesium and calcium evidently being contained in
part in the form of acid silicates with no carbonates; whereas, our
brown silt loam is a neutral soil and our black clay loam contains
much calcium carbonate, the same compound as pure limestone."

"I am anxious to know about our best land," said Mr. West. "What
did the chemist find in the soil from the slope where we get the
best corn after breaking up the old pastures?"

"He found the following amounts in the surface soil," said Percy.

800 pounds of nitrogen