176 
Italian Irrigation, 
the waters, but the numerous gratuitous grants which have been 
made during the lapse of five centuries have reduced greatly the 
income derivable from the canals." 
In Lombardy the actual income of the government canals has 
been so reduced by sales and grants, that it often does little 
more than pay the current expenses. The income of private 
canals is not readily ascertained, but it is believed that these 
have not generally yielded a large direct profit. 
Let us now take a hasty glance at the history of these works 
which have exercised such an influence on the fertility of the 
soil and the wealth of the people. 
W.— Tlie Climate and Natural Advantages. 
Northern Italy certainly possesses great natural advantages 
from her climate, rainfall, and range of temperature ; from the 
constanc}' of her supply of water in summer, from the manner in 
which the tributaries of the Po (but not that river itself) traverse 
her plain and intersect the line of her slope, from the generally 
porous nature of the soil, and from the services rendered by her 
splendid lakes. 
Of an annual rainfall of 37 inches, about 28^ inches come 
within the seven months fitted for irrigation, and in that period 
fall in about 71 days, the others being fine and generally clear. 
The mean temperature for Ma}-, June, July, and August is 
72^ Fahr., and 85° is the ordinary maximum in the shade ; but 
in the sun the mean is 92^, — an amount of heat which renders a 
supply of Avater almost indisjiensablc, but adds much to its effec- 
tiveness when procured, by raising its temperature. 
The soil, in its natural condition, was often poor, passing 
from an arid sand to a pestilential marsh resting on clay. The 
Lumellina district is a case in point, which now presents a 
remarkable contrast to the deplorable aspect it bore before it was 
irrigated and thereby rendered one of the most productive and 
populous regions in Europe. 
The main supply of water is drawn from the vast regions of the 
Alps, and being derived from snow is constantly furnished by 
the unvarying influence of the summer heat. As the more eastern 
rivers recede from tliis great storehouse, their streams become 
more capricious. 
m.— Lakes. 
Irrigation brings the famous Italian lakes before us in a 
commonplace point of view as groat tanks designed to receive 
and filter the water dashed down by the mountain-torrents, cold 
and charged with sediment. Yet, in travelling through this mag- 
