TRANSACTIONS OF SECTION M. 657 
for very large extensions of land, the quantity of water that can be impounded 
in an artificial lake is always comparatively small. 
Canals.—So, when large quantities are required, the water is obtained from 
rivers, fed, generally, by some natural lake, like the rivers Ticino, Adda, 
Oglio, Mincio, or by some glacier which, melting in the summer season, acts 
practically like a lake of frozen water; in this condition are the rivers Tanaro, 
Po, Dora, Orco, Adige, and many others. 
The engineering works consist of a submergible dam of very substantial 
masonry, built across the river, and capable of raising the level of the water to 
that of the country to be irrigated ; of some controlling sluices at the canal head ; 
and of a main canal, with lateral distributing ditches, provided at their intake 
with some apparatus for measuring the water to be delivered. Generally, the 
“Cipeletti Weir’ or some such over-fall weir is used. No mechanical meters 
are adopted, except for very small deliveries. 
The price of this canal water varies from 20 to 45 francs per hectare per year 
(8s. to 1, per acre). 
Many of these irrigation canals date back from the Middle Ages. For 
instance, the ‘ Naviglio Grande’ was built in the twelfth century, and is used 
also for inland navigation—in fact, it is a feature of these canals called 
‘Navigli’ to serve both for irrigation and navigation purposes. The 
‘ Naviglio Grande’ is about 50 miles long, and has a capacity of 55 cubic metres 
(2,275 cubic feet) per second; and in order of date come the ‘ Muzza’ with 
60 cubic metres, the ‘Cremona’ with 30 cubic metres, and scores of smaller ones. 
Of the canals of modern times—that is, built during the last fifty years—the 
most interesting, also from the point of view of the engineering features, are 
the ‘Cavour’ canal with 110 cubic metres discharge (3,850 cubic feet) per 
second, the ‘ Villoresi’ with 44 cubic metres (1,500 cubic feet), the ‘Marzano’ 
with 30 cubic metres (1,050 cubic feet), the ‘ Veronese’ with 15 cubic metres 
(510 cubic feet), and the ‘Tagliamento’ with 17°5 cubic metres (600 cubic feet) 
per second. They are really models, both from the engineering point of view and 
the perfection of their administration; so much so, that many engineers come 
_ from all parts of the world to study them. 
* The largest and longest of all is the ‘Cavour’ canal, with a discharge 
capacity of 110 cubic metres (3,850 cubic feet) per second, and a development of 
fully 1,000 miles, including its branches. It was built in 1855-65 by a private 
company that failed, and was taken over by the State. 
This canal, the most important in Europe, was the means of transforming an 
almost barren region of 250,000 acres of sand and gravel—useful only for growing 
timber and bushes—into the most fertile rice-fields and meadow-land of Italy, 
where the best Parmesan and Gorgonzola cheeses are produced. A still larger 
canal is about to be undertaken, the ‘ Emiliano’ canal, with a capacity of 300 
cubic metres (10,500 cubic feet) per second, 120 miles long, and estimated to cost 
12,000,000/. 
Results of Irrigation.—The author described, with the help of lantern slides, 
the most salient engineering features of some of these canals, i.e., their head- 
works—one of them at the ‘Ombrone’ inlet is capable of receiving 600 cubic 
metres (21,000 cubic feet) per second—and the numerous aqueducts and syphons 
over and under existing canals or rivers; pointing out that the irrigation canals 
of Italy carry the life-blood of the national agriculture. He described also how 
the water is applied to the crops, the ‘rotations’ or periods of irrigation used 
according to the nature of the land, its permeability, and the crops to be raised ; 
concluding with the results obtained by irrigation, which are most satisfactory 
from the agricultural point of view, as the rent of the fields is more than 
doubled or trebled by irrigation. From the financial point of view of the 
Canal Administration, however, with very rare exceptions, the results are not 
so satisfactory, and in fact are generally disappointing. It is not sufficient to 
build a canal carrying a large volume of water, it is necessary to sell this water— 
that is, find the farmers ready to use it—and provide to pay for the original cost 
of the canal and its ordinary expenses. But in order to use the water, it is 
necessary for the farmers first to prepare their own distributing ditches, then 
to level their fields properly, and learn how to apply the water to the land at 
the moment, and in the proportion most convenient ; to decide which crops are’ 
1914. r= 
