INTRODUCTION. 1X 
my cultivated land, which will likewise reduce the-- 
length of the time during which the growth of the 
plant is suspended, from the extreme dilution of its 
available food. 
‘The readiest way to attain this appears to me 
to be surface drains: not deep wide gaping chasms 
at long distances apart, but six inches deep to begin 
with, and an incline of one in fifteen, thirty feet 
apart on a surface of one in ten, wider apart on 
more level land, and closer on steeper. The capacity 
of the drains, besides, must to some extent be governed 
by their length: drains thirty feet apart, and one 
hundred feet long, will collect and deliver in the 
main the superfluous rainfall on 3,000 feet, but if the 
main should be 300 feet distant from the source, the ex- 
tent of surface will be9,000 feet, and the drain must have 
three times the capacity at the point of delivery, unless 
the incline is greater : thus the capacity of the drain 
should increase in direct proportion to its length, or the 
same object may be attained ky increasing the number, 
and reducing the distance between them. 
When I name thirty feet as the distance between 
the drains, it must be taken asa mere arbitrary assump- 
tion: the true principle is the permeability of the 
soil, and one tract may be as perfectly protected. 
from wash by drains one hundred feet apart, as 
another where thirty is the distance; indeed I have 
seen even steep land, that took in every drop of rain 
that fell, and that was in greater danger of being 
denuded of its surface soil in dry than in wet 
weather ; of course on such land it would be mere 
waste of labour to make drains. 
Whatever operation increases the permeability of 
the soil diminishes the necessity of drains. To break 
up and pulverize the soil before the decay of the 
roots is an operation that I cannot recommend, be- 
cause it would be a very costly one, and I have no 
data to prove it a remunerative one, but I have no 
doubt that if within the first year from planting 
an alavanga were driven a foot into the ground, 
one foot beyond the verge of the original hole, and 
the earth raised to the extent of the available lever- 
age, three or four repetitions of this operation round 
