ain, for instance,
more phosphoric acid than other crops, and for these a manure rich in
phosphoric acid was provided. Others contained a large proportion of
potash, and these were called 'potash crops,' and the manure prescribed
for them was rich in potash. And so with the other ingredients of
plants."

"I recollect it well," said the Doctor, "and, in truth, for several
years I had much faith in the idea. It was advocated with consummate
ability by the lamented Liebig, and in fact a patent was taken out by
the Musgraves, of Liverpool, for the manufacture of Liebig's Special
Manures, based on this theory. But the manures, though extensively used
by the leading farmers of England, and endorsed by the highest
authorities, did not in the end stand the test of actual farm practice,
and their manufacture was abandoned. And I do not know of any
experienced agricultural chemist who now advocates this doctrine of
special manures.

"Dr. Voelcker says: 'The ash-analyses of plants do not afford a
sufficiently trustworthy guide to the practical farmer in selecting the
kind of manure which is best applied to each crop.'"

"Never mind the authorities," said the Deacon; "what we want are facts."

"Well," replied the Doctor, "take the wheat and turnip crop as an
illustration.

"We will suppose that there is twice the weight of wheat-straw as of
grain; and that to 10 tons of bulbs there is 3 tons of turnip-tops. Now,
100 lbs. each of the ash of these two crops contain:

_Wheat crop._ _Turnip crop._
Phosphoric acid 11.44 7.33
Potash 15.44 32.75
Sulphuric acid 2.44 11.25
Lime 5.09 19.28
Magnesia 3.33 1.56

"There are other ingredients," continued the Doctor, "but these are the
most important.

"Now, if you were going to compound a manure for wheat, say 100 lbs.,
consisting of potash and phosphoric acid, what would be the
proportions?"

The Deacon figured for a few moments, and then produced the following
table:

100 Lbs. Special Manure for Wheat and Turnips.

_Wheat manure._ _Turnip manure._
Phosphoric acid 42-1/2 lbs. 18-1/3 lbs.
Potash 57-1/2 " 81-2/3 "
------------ ------------
100 lbs. 100 lbs.

"Exactly," said the Doctor, "and yet the experiments of Lawes and
Gilbert clearly prove that a soil