Agricultural Meteorology. 
331 
Northern France and Germany 144'9; Italy, north of the 
Apennines, 101-2; Southern France and Italy 91 '2 days. 
The averafje fall in a rainy day in lingland is '2322 inches; 
in Western France "2122; Northern France -1847; Northern 
Italy • 3853 inches. 
The length and character of the intervals between the rains is 
another important ingredient in determining the climate and 
capabilities of a country. VMiere the rains, though light, are 
frequent, the sky is naturally cloudy; there will be little heat and 
little evaporation where rainy days are rare ; but where the quan- 
tity which falls on each day of rain is considerable, there the 
usual character of the atmosphere will be clear and bright, pro- 
moting rapid evaporation. At Paris the mean of the intervals 
between the rainy days for the whole year is 4 days ; at Orange 
4-6; at Niccolosi, in Sicily, 10 8 days. " A climate cannot be 
said to be a dry one because it has only a small amount in depth 
of inches of rain ; but if a country were to receive 3 3 inches of 
rain in one single day, in every month of the year, it would be a 
very dry one, for that water cannot have impregnated the soil, 
but will have run off into torrents from its surface, and the ter- 
restrial evaporation, increased by a bright sky, will soon cause 
the rest to disappear." 
Few points, indeed, are of more importance than the hygro- 
metrical condition of the soil and atmosphere, as influenced by 
these two opposite agents. An artificial permeability (effected 
by draining) of a naturally plastic and retentive earth may render 
it far less mischievously affected by an excess of wet than another 
description of earth less retentive, but where industry and skill 
have done nothing to promote the slow natural percolation to 
which it is abandoned. In the absence of other modes of relief, 
the excess of moisture can only be carried off by the tardy process 
of evaporation. This, in the neighbourhood of London, is more 
than equal to dispose of the wliole of the ram that falls in the 
course of the year. The average depth in inches is calculated 
by Mr. Daniell to be 22- 199, and the power of evaporation 
equal to 23'974; but of these quantities more than 12 inches 
(12*13) fall in the months of November, December, January, 
February, March, April, and May, while the corresponding 
evaporation during the same period amounts only to 9 '47 inches, 
leaving, even at the end of May, an excess of 2 -66 inches of 
moisture in the soil.* Putting aside the mechanical difficulties in 
the way of cultivation on land saturated with and retentive of 
* Mr. Josiah Parkes calculates that, of the whole annual rain, 424 P^r 
cent. (1 1 '3 out of 26 • 5 inches! filters through the soil, and that the annual 
evaporative force is only equal to the removal of 57*5 per cent, of the 
total rain that falls on any given extent of surface. " 
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