AGRICULTURE. 139 
the iron, by means of the set screws moving the upper rollers; the iron is 
repeatedly heated during the operation, which is continued until the sheet 
is reduced to the required thickness. 
IX. AGRICULTURE. 
Agriculture is that art by which the earth is rendered capable of minis- 
tering to our necessities. It treats of the growth of plants and animals, as 
mutually dependent branches, the latter being always founded upon the 
former. Its legitimate aim is not the production of the largest and finest 
animals, the heaviest crop without regard to cost, but the reaping from a 
certain capital the surest heaviest income. 
Agriculture may be taught or studied in three different ways : as a trade 
or mechanically, as an art, and as ascience. Mechanically considered, agri- 
culture does not differ from other trades, and consists in the imitation of 
practice, and the exercise of. judgment. As an art it takes a wider range, 
and follows fixed rules and precepts, which are the result of long-continued 
observations upon nature. So long as these rules are founded upon nature, 
they are of value ; but in most cases they spring from isolated observations, 
are not in accordance with first principles, and are unworthy of confidence. 
The insufficiency of such rules, without distinction of cause and effect, is 
never more apparent than in the case of an agriculturist who has followed 
them with advantage in one district, and who, when he moves to another 
of different character, finds they but mislead and deceive him. 
Science, on the contrary, fixes no positive rules, but developes the prin- 
ciples to be followed in every variety of case that may arise, teaches us to 
dive to the bottom of nature’s springs for the foundation stones of a rational 
theory, and is in fact itself the only true basis on which a system of agri- 
culture can be erected. Theory alone, however, can never make an agri- 
culturist, but only when hand in hand with practice. 
Lo Lire 
A. The Soil. 
The surface of the earth, the grand workshop of the vegetable kingdom, 
produces everywhere, when left to itself, those plants to the growth of which 
the soil and climate are congenial. The original elements of the soil, silex 
or sand, clay, lime, and iron, now one now the other preponderating, con- 
stitute, as it were, the vessel in which is prepared the food necessary for 
the growth of plants and in which it is offered to their roots. 
These elements impart certain qualities to the soil, according as they pre- 
ponderate, one producing a light, dry soil, with but little power of retaining 
moisture; another, a close, moist soil, having strong affinity for water, and 
retaining it for a great length of time. A certain medium between the two 
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