IRRIGATION IN EUROPE. 441 



the very borders of glaciers are freely irrigated ; in many parts of 

 N"orway water is applied to grass (partly as a protection against 

 frost) Loth by flooding and flowing, and on the Italian slope of 

 the Alps the meadows are irrigated at heights exceeding 6,000 

 feet. The smnmers in Northern Italy, though longer, are very 

 often not warmer than in the Northern United States ; and in 

 ordinary years, the summer rains ai'e as frequent and as abundant 

 in the former country as in the latter.* Yet in Piedmont and 



* The mean annual precipitation in Lombardy is thirty-six inches, of which 

 nearly two-thirds fall during the season of irrigation. The rainfall is about 

 the same in Piedmont, though the number of days in the year classed as 

 " rainy" is said to be but twenty-four in the former province while it is sev- 

 enty in the latter. — Baird Smith, Italian Irrigation, vol. i., p. 196. 



The necessity of irrigation in the great alluvial plain of Northern 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 sub- 

 terranean channels to some unknown point of discharge ; but this circum- 

 «stance alone is not a suflScient solution. Is it not possible that the habits of 

 vegetables, grown in countries where irrigation has been immemorially em- 

 ■ ployed, 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 ? It is a remarkable fact that during the season of irrigation, 

 when large tracts of surface are almost constantly saturated with water, there 

 is an extraordinary dryness in the atmosphere of Lombardy, the hygrometer 

 standing for days together a few degrees only above zero, while in winter the 

 instrument indicates extreme humidity of the air, approaching to total satura- 

 tion. — Baird Smith, Italian Irrigation, i., p. 189. 



There are some atmospheric phenomena in Northern Italy, which an Ameri- 

 can 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 sun's rays, as measured 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 mer- 

 cury 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 sensa- 

 tion experienced in America at a temperature twenty degrees higher, during 

 the intervals between 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 abso- 

 lutely injurious. 



In speaking of the superior apparent clearness of the sky in America, I cou- 

 19* 



