experience and practice, as derived from experienced and practical
men themselves, and not as given by those who profess to speak for
them. That which has been done by a practical man, can best
be explained by him in his own words and in his own language;
the statements of many practical men can best be simplified and
reduced to value by one having a familiar acquaintance with their
mode of thought and expression; a wide field must be carefully
examined before we can lay down special rules; the testimony
of many men being competent to give testimony, in various
places and at different times, must all be collected and com-
pared before the most correct practice can be determined and
decreed. That which is true of tradition or transmitted testimo-
ny, whether oral, by means of medals, manuscripts or any other
kind of evidence, save that of revelation, is true as to the value
of the lessons taught by experience. The same principles must
be taught at all times, in all places, and by all men, otherwise they
cannot be taken as a rule of action and of right, as directions to
be followed or practice to be recommended.

The true theory of Agriculture then must depend upon a knowl-
edge of the nature of crops grown for the wants of men; of the
substances which enter into their composition; the sources whence
obtained, the modifying circumstances to which they are sub-
ject by human art; the nature of the soil as to its mechanical and
physical as well as its chemical composition.

These being known, then the testimony of practical men must
be obtained, and from them must be learned the results of their ob-
servation; and then, and not till then, can a general and universal,
and at the same time a local and special system be recom-
mended.

To carry out these views, I shall therefore proceed to give, in
the first place, a description of all the substances found in our
crops, specifying those obtained from the air, those from the earth,
and those common to both, and afterwards the nature of the soils
as to their mechanical and chemical composition; the nature and
composition of various manures or fertilizers, the best mode
and proper places for their application, as furnished by the testi-
mony of observant practical men, and a knowledge of the several
properties of each as far as these have been ascertained.

I deem this of more consequence at the present time, as I have
received very many applications for my former Reports, each con-
taining only a part of the above matter; advertisements have ap-
peared in the papers for them, and numerous applications have
been made to me in person. But there is another and a strong
reason: there has lately appeared a Report from a high source,
commending itself to public belief by reason of the place from
whence it emanates, containing so many errors on the subject

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