368 
IRRIGATION IN PALESTINE. 
The summers in Egypt, in Syria, and in Asia Minor, and 
even Rumelia, are almost rainless. In such climates, the 
necessity of irrigation is obvious, and the loss of the ancient 
means of furnishing it readily explains the diminished fertility 
of most of the countries in question.* The surface of Pales- 
Italy is partly explained by the fact that the superficial stratum of fine 
earth and vegetable mould is very extensively underlaid by beds of pebbles 
and gravel brought down by mountain torrents at a remote epoch. The 
water of the surface soil drains rapidly down into these loose beds, and 
passes off by subterranean channels to some unknown point of discharge; 
but this circumstance alone is not a sufficient solution. Is it not possible 
that the habits of vegetables, grown in countries where irrigation has been 
immemorially employed, have been so changed that they require water 
under conditions of soil and climate where their congeners, which have 
not been thus indulgently treated, do not ? 
There are some atmospheric phenomena in Northern Italy, which an 
American finds it hard to reconcile with what he has observed in the 
United States. To an American eye, for instance, the sky of Piedmont, 
Lombardy, and the northern coast of the Mediterranean, is always whitish 
and curdled, and it never has the intensity and fathomless depth of the 
blue of his native heavens. And yet the heat of the srnfis rays, as meas¬ 
ured by sensation, and, at the same time, the evaporation, are greater than 
they would be with the thermometer at the same point in America. I 
have frequently felt in Italy, with the mercury below 60° Fahrenheit, and 
with a mottled and almost opaque sky, a heat of solar irradiation which 
I can compare to nothing but the scorching sensation experienced in 
America at a temperature twenty degrees higher, during the intervals be¬ 
tween showers, or before a rain, when the clear blue of the sky seems 
infinite in depth and transparency. Such circumstances may create a 
necessity for irrigation where it would otherwise be superfluous, if not 
absolutely injurious. 
In speaking of the superior apparent clearness of the shy in America, I 
confine myself to the concave vault of the heavens, and do not mean to 
assert that terrestrial objects are generally visible at greater distances in 
the United States than in Italy. Indeed I am rather disposed to maintain 
the contrary ; for though I know that the lower strata of the atmosphere 
in Europe never equal in transparency the air near the earth in New 
Mexico, Peru, and Chili, yet I think the accidents of the coast line of the 
Riviera, as, for example, between Nice and La Spezia, and those of the in¬ 
comparable Alpine parorama seen from Turin, are distinguishable at greater 
distances than they would be in the United States. 
* In Egypt, evaporation and absorption by the earth are so rapid, that 
