66 
JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
the latter stages of their history by the action of vegetable and 
animal life, and their products. When once a soil has been 
brought under cultivation, the continual ploughing, digging, 
hoeing, stirring, and other operations of the gardener—all com¬ 
prehended under the term “ tillage ”—assist most powerfully the 
weathering influences, and cause cultivated soils to become finer 
and more permeable, and consequently in that respect better and 
better. 
The purposes of tillage are twofold. First, it improves the 
texture of the soil in the mere mechanical sense; or, in other 
words, it stirs and loosens the soil so that the roots of plants 
may readily pass through it. Air and water are allowed to enter 
freely, and water is enabled to pass easily through the mass, 
while at the same time it ensures that the soil shall retain a 
sufficient amount of moisture for plant-life. 
Secondly, tillage alters the position and condition of the soil 
particles, facilitating the chemical changes in these particles 
through the action of atmospheric agencies. Helping also the 
microscopic organisms in their work of nitrifying the organic 
matters contained in the soil. 
The weight of soil on an acre of land is so enormous that 
small proportions of plant-food present in it may amount to 
very considerable quantities when reckoned up to the acre at any 
given depth. Table I. illustrates the weight of different de¬ 
scriptions of soil, cut to 9 inches deep, when perfectly dry and 
free from stones. 
TABLE I. — Weight of 
Sandy soil 
Arable loamy soil 
Pasture soil ... 
Forest soil 
Peaty soil 
Acre of Soil, cut to 9 
Free from Stones. 
inches deep, Dry and 
Pounds. 
... 3,500,000 
... 3,000,000 
... 2,250,000 
... 1,500,000 
... 1 , 000,000 
These illustrations show that an acre of sandy soil will weigh 
8,500,000 lbs.; an ordinary arable loamy soil 8,000,000 lbs.; 
a pasture soil when dried and the visible roots removed will 
weigh about 2,250,000 lbs.; a forest soil that contains an 
abundance of decaying vegetable matter will weigh but 
1,500,000 lbs. per acre; while an acre of peaty soil cut to 
9 inches deep, in consequence of its light and spongy character, 
