ways be taken into account in gardening,
especially in the treatment of the kitchen-garden; and as much as
possible, in agriculture on a large scale, where the time occupied
in the growth of the plants cultivated is of importance.

When we have exactly ascertained the quantity of ashes left after
the combustion of cultivated plants which have grown upon all
varieties of soil, and have obtained correct analyses of these
ashes, we shall learn with certainty which of the constituent
elements of the plants are constant and which are changeable, and we
shall arrive at an exact knowledge of the sum of all the ingredients
we withdraw from the soil in the different crops.

With this knowledge the farmer will be able to keep an exact record,
of the produce of his fields in harvest, like the account-book of a
well regulated manufactory; and then by a simple calculation he can
determine precisely the substances he must supply to each field, and
the quantity of these, in order to restore their fertility. He will
be able to express, in pounds weight, how much of this or that
element he must give in order to augment its fertility for any given
kind of plants.

These researches and experiments are the great desideratum of the
present time. TO THE UNITED EFFORTS OF THE CHEMISTS OF ALL COUNTRIES
WE MAY CONFIDENTLY LOOK FOR A SOLUTION OF THESE GREAT QUESTIONS, and
by the aid of ENLIGHTENED AGRICULTURISTS we shall arrive at a
RATIONAL system of GARDENING, HORTICULTURE, and AGRICULTURE,
applicable to every country and all kinds of soil, and which will be
based upon the immutable foundation of OBSERVED FACTS and
PHILOSOPHICAL INDUCTION.

LETTER XVI

My dear Sir,

My recent researches into the constituent ingredients of our
cultivated fields have led me to the conclusion that, of all the
elements furnished to plants by the soil and ministering to their
nourishment, the phosphate of lime--or, rather, the phosphates
generally--must be regarded as the most important.

In order to furnish you with a clear idea of the importance of the
phosphates, it may be sufficient to remind you of the fact, that the
blood of man and animals, besides common salt, always contains
alkaline and earthy phosphates. If we burn blood and examine the
ashes which remain, we find certain parts of them soluble in water,
and others insoluble. The soluble parts are, common salt and
alkaline phosphates; the insoluble consist of phosphate of lime,
phosphat