QUANTITY OF WATER APPLIED. 
377 
Mediterranean basin by a quantity bearing no inconsiderable 
proportion to the area naturally covered by water within it. 
As near as can be ascertained, the amount of water applied 
to irrigated lands is scarcely anywhere less than the total pre¬ 
cipitation during the season of vegetable growth, and in gen-. 
eral it much exceeds that quantity. In grass grounds and in 
field culture it ranges from 27 or 28 to 60 inches, while in 
smaller crops, tilled by hand labor, it is sometimes carried as 
high as 300 inches.* The rice grounds and the marcite of 
* Niel, Agriculture des Mats Sardes , p. 237. Lombardini’s compu¬ 
tation just given allows eighty-one cubic metres per day to the hectare, 
which, supposing the season of irrigation to be one hundred days, is equal 
to a precipitation of thirty-two inches. But in Lombardy, water is applied 
to most crops during a longer period than one hundred days; and in the 
marcite it flows over the ground even in winter. 
According to Boussingault (Economie Rurale , ii, p. 246) grass grounds 
ought to receive, in Germany, twenty-one centimetres of water per week, 
and with less than half that quantity it is not advisable to incur the expense 
of supplying it. The ground is irrigated twenty-five or thirty times, and 
if the full quantity of twenty-one centimetres is applied, it receives about 
two hundred inches of water, or six times the total amount of precipitation. 
Puvis, quoted by Boussingault, after much research comes to the conclu¬ 
sion that a proper quantity is twenty centimetres applied twenty-five or 
thirty times, which corresponds with the estimate just stated. Puvis 
adds— a nd, as our author thinks, with reason—that this amount might be 
doubled without disadvantage. 
Boussingault observes that rain water is vastly more fertilizing than the 
water of irrigating canals, and therefore the supply of the latter must be 
greater. This is explained partly by the different character of the sub¬ 
stances held in solution or suspension by the waters of the earth and of the 
sky, partly by the higher temperature of the latter, and, possibly, partly 
also by the mode of application—the rain being finely divided in its fall or 
by striking plants on the ground, river water flowing in a continuous sheet. 
The temperature of the water is thought even more important than its 
composition. The sources which irrigate the marcite of Lombardy— 
meadows so fertile that less than an acre furnishes grass for a cow the 
whole year—are very warm. The ground watered by them never freezes, 
and a first crop, for soiling, is cut from it in January or February. The 
Canal Cavour, just now commenced—which is to take its supply from the 
Po at Chivasso, fourteen or fifteen mile3 below Turin—will furnish water 
of much higher fertilizing power than that derived from the Dora Baltea 
