MAGAZINE OF SCIENCE AND AET. 
141 
portent fact that the population, in the strictest and 
narrowest souse of the term, is entirely dependent upon 
the produce of the surface of the soil—that it is, in fact, 
a pastoral and agricultural community, I think it will 
be admitted that there is not in the whole range of sub¬ 
jects bearing upon the occupation of the fiockowner, the 
agriculturist, and the horticulturist, a single one which 
is deserving of more careful study, or one from which, 
if properly understood and applied, greater or more 
beneficial results would be obtained. I have alluded 
to the climate, and it may he as well that I should 
state what, in my opinion, peculiarly characterizes it, 
Eut, in describing the climate of a country extending 
over 14 degrees of latitude and 10 of longitude, I must, 
of course, speak in very general terms. 
"With this limitation, 1 should, say that the climate 
of New South Wales was remarkable for its dryness, 
and consequent evaporative power, by which it acts 
upon the vegetation, not merely through, the foliage, 
which is rendered incapable of performing its functions, 
hut also by drying up the soil through which nutri¬ 
ment is conveved to the roots of the plants. And I 
may observe that, if this be the case at present, when 
so large a proportion of the country is covered with 
# timber, it vail prevail to a far greater extent when the 
denudation of tiic ground by the axe will diminish the 
quantity of rain, and allow the sun and air to act more 
powerfully than at present upon the exposed surface of 
the soil. It is, therefore, evidently, most desirable that 
attention should bo devoted to the investigation of the 
means of remedying an evil which, great as it is at pre¬ 
sent, is likely to be enhanced by the very steps which 
must be taken to render the country more productive, 
and I trust the time is not far distant when the Govern¬ 
ment, by making a proper use of the means at its dis¬ 
posal of acquiring information, will bo placed in pos¬ 
session of date sufficient to enable it to lay the foundation 
of a system of irrigation, by which only will it be 
'possible to apply even a partial remedy to the evil 
above alluded to. 
In the meantime, however, as the discussion of sub¬ 
jects of this kind canuot hut prove both interesting and 
useful, I propose in the present paper to describe the 
mode in which water applied to the surface of the soil 
acts upon the vegetation. I shall then give a brief 
sketch of the systems of irrigation as practised in dif¬ 
ferent countries, and of their results, both local and 
general; and I shall lastly discuss, specially and in 
detail, the advantages which would result to the indus¬ 
trial interests of the colony from the adoption of an 
extensive system of irrigation; the means by which the 
necessary supplies of water may be obtained; the cha¬ 
racter of the works which must be constructed to col¬ 
lect, convey, and distribute these supplies; and, lastly, 
the mode of proriding the funds which will be required 
to defray the cost of such works. 
1st. As to the mode in which water applied to the 
surface of the soil operates upon vegetation. 
Most plains derive their nourishment partly from the 
soil through the'intervention of their roots, partly from 
the atmosjdiere through the action of their leaves; the 
roots, however, perform the most important part in this 
combined system. It is through their action that the 
elementary substances are absorbed from the soil, which 
are afterwards combined in the plant, through the action 
of air and of light, into those forms which are distinc¬ 
tive of its existence as a species. These roots, however, 
are incapable of absorbing any solid substances. It has 
been proved by experiments that the finest powders, 
such as would require a most powerful microscope to 
define the particles of which they are composed, are, in 
a dry state, utterly incapable of maintaining the life of 
a plant, even though they should be composed of 
elements with which the plant has the closest affinity. 
Moisture, then, is necessary to vegetable life. The food 
upon which a plant is nourished must be supplied to it 
in a liquid form—I mean such food as is taken up by 
the roots. Water, then, applied to the surface of the 
soil, acts on vegetation by dissolving and presenting to 
■ the roots of plants those matters which are essential to 
their existence. 
Water, however, has a secondary action in modifying 
the effect of the atmosphere upon vegetation. In dry 
countries the presence of water w’ould neutralize to a 
certain extent the parching effect of the atmosphere, by 
altering its hygrometric state, and would .enable it to 
act its part in the chemistry of vegetation, which it 
could hardly otherwise perform effectively. 
In cold countries, again, water is applied to the 
meadows in winter, and it has been found by experi¬ 
ment that the temperature of that in contact with the 
grass is seldom below 40 degrees, while the surface is 
frozen ; and the effect of this irrigation is to preserve 
the tender roots and leaves of grass from the action of 
the frost. 
Such being the operation of water upon the produce 
of the soil, and such and so great the benefits derived 
from its application, it will not be a matter of surprise 
to us to find that mankind have not failed to avail 
themselves extensively of its agency. 
The great nations of antiquity, the Egyptians and 
Assyrians, with whom historv may be said to com¬ 
mence, occupied the fertile valleys of the Nile and the 
Euphratft, where the periodical overflowing of the 
livers gave', it may be, the first hint of the importance 
of water. History, and the still existing remains of 
the great works executed by these nations, for the pur¬ 
pose of extending and regulating the distribution of 
their natural supply, bear testimony to the value placed 
by them on this agent. 
* The state of these countries now% contrasting as it 
does so unfavourably with that which they exhibited 
some 25 centuries ago, may be imputed to a certain 
extent, at all events, to their neglect of the means 
which Nature has placed at their disposal, of which 
their ancestors availed themselves with, such skill and 
judgment. 
If we look around us in the present day and attempt 
to investigate the reasons which have induced the set¬ 
tlement of a dense population in any particular locality, 
we shall find, in an agricultural community, that popu¬ 
lation congregates in districts where, owing either to 
the richness of the soil, or the facilities offered for its 
cultivation, the means of subsistence .are easily pro¬ 
cured, and we shall also find that this will be most 
generally the case whore the means of irrigating the 
soil have been most extensively made available. 
Instances of this will occur to every one ; but I may 
particularize those districts in the North of Italy winch 
are watered br the Po and its affluents, and portions of 
the British territory in India, where population may 
bo said to follow the water ; for wherever the means of 
irrigation are provided, a dense population is sure to 
congregate in a few r years. 
The millions who inhabit the Chinese Empire could 
never be supported were it not for the care- bestowed by 
the Government and tbe inhabitants generally upon ail 
the works by which the cultivation of the soil is im¬ 
proved, and specially upon those which proride for the 
conveyance of water for irrigation, and other purposes. 
Any description of the means which have been and still 
are’employed in different countries, for tbe purpose of 
collecting*and distributing the water required for irri¬ 
gation, must in such a paper as this be confined to such 
an outline as may be sufficient to give an idea of their 
character. 1 hope, hereafter, to be able to go more 
fully into the details of particular schemes; at present, 
1 must speak in general terms. 
The principal sources from which supplies of water 
for the purpose of irrigation may be derived, are— 
1. Running streams. 
2. Reservoirs in which the drainage of the country 
is collected. 
3. Springs. 
4. "WellsI 
5. Sewerage or drainage from towns. 
The first and most effective source of supply will 
always be the rivers and streams, which have their 
