s, with the rain which falls on the ground, satisfies, under
ordinary circumstances, the requirements of the clover-crop. This crop
causes a large accumulation of nitrogenous matters, which are gradually
changed in the soil into nitrates. The atmosphere thus furnishes
nitrogenous food to the succeeding wheat indirectly, and, so to say,
gratis.

"10. Clover not only provides abundance of nitrogenous food, but
delivers this food in a readily available form (as nitrates), more
gradually and continuously, and, consequently, with more certainty of a
good result, than such food can be applied to the land in the shape of
nitrogenous spring top-dressings."

"Thank you Charley," said the Doctor, "_that is the most remarkable
paper I ever listened to_. I do not quite know what to think of it. We
shall have to examine it carefully."

"The first three propositions in the Summary," said I, "are
unquestionably true. Proposition No. 4, is equally true, but we must be
careful what meaning we attach to the word 'accumulate.' The idea is,
that clover gathers up the nitrogen in the soil. It does not _increase_
the absolute amount of nitrogen. It accumulates it--brings it together.

"Proposition No. 5, will not be disputed; and I think we may accept No.
6, also, though we can not be sure that allowing clover to go to seed,
had anything to do with the increased quantity of clover-roots.

"Proposition No. 7, may or may not be true. We have no proof, only a
'probability;' and the same may be said in regard to propositions Nos.
8, 9, and 10."

The Deacon seemed uneasy. He did not like these remarks. He had got the
impression, while Charley was reading, that much more was proved than
Dr. Voelcker claims in his Summary.

"I thought," said he, "that on the part of the field where the clover
was allowed to go to seed, Dr. Voelcker found a great increase in the
amount of nitrogen."

"That seems to be the general impression," said the Doctor, "but in
point of fact, we have no proof that the growth of clover, either for
hay or for seed, had anything to do with the quantity of nitrogen and
phosphoric acid found in the soil. The _facts_ given by Dr. Voelcker,
are exceedingly interesting. Let us look at them:

"A field of 11 acres was sown to winter-wheat, and seeded down in the
spring, with 13 lbs. per acre of clover. The wheat yielded 40 bushels
per acre. The next year, on the 25th of June, the clover was mown for
hay. We are told that 't