carbonic acid, if produced at once decomposes into water and carbon
dioxid. Now, the liberated carbon dioxid is a gas and the rapid
generation or evolution of this gas constitutes the bubbling or
foaming we are looking for; but since there is no appearance of
foaming we know that this soil contains no limestone."

"Then you have already found that those three elements,--calcium,
carbon, and oxygen, you called them, I think--you find that those
elements are all lacking in this soil."

"No, this test does not prove that," said Percy. "It only proves
that they are not present as limestone. Calcium may be present in
other compounds, especially in silicates, which are the most
abundant compounds in the soil and in the earth's crust; and, as
indicated by the ending _-ate, _oxygen is contained in calcium
silicate as well as in calcium carbonate."

"I see; the subject is much more complicated than I thought."

"Somewhat, perhaps," Percy replied; "but yet it is quite simple and
very easily understood, if we only keep in mind a few well
established facts. Certainly the essential science of soil fertility
is much less complicated than many of the political questions of the
day, such as the gold standard or free-silver basis, the tariff
issues, and reciprocity advantages, regarding which most farmers are
fairly well informed,--at least to such an extent that they can
argue these questions for hours."

"I think you are quite right in that," said Mr. West. "Of course, it
is important that every citizen entitled to the privilege of voting