Ar/ricultural Meteorology. 
325 
puled from tlin number of hours during which the sun actually 
shinps in those several latitudes, the account would stand verydif- 
fcrenlly. 
Total July 
Sum of Me;in Tfmpi!riUure, 
Atmosplicric Sol:ir Honrs- out of from solar 
Temp, in Jii'.y. Heat. tin; 24. and atmospli. 
Toulouse. 654-1 13 x 14-75 -^21= 7-991 f247°-69 + G54-1 = 901-7 
Berlin . . 5G7-;5 20 x lG-1 -f 24 = 13-37 >x31<41 1-47 +'5G7-3 = 981-7 
Petersburg 530-1 25 x 18 -f 24 = 18-7jJ 1581-25 + 530-1 ^ 1111-3 
In the above tables the mean temperatures are extracted from 
Mahlmann's tables published in Kacmptz. The solar heat is de- 
duced from Daniell, Scoresby, and others; and, though entirely 
hypothetical, it is probably within the mark. 
Here there appears in a single month a difference of nearly 
200^ of the Centigrade in computing the degree of heat avail- 
able for vegetation at Petersburg above that of Toulouse, and 
more than 100^ in that of Berlin. 
The growth of maize is brought forward by M. Gasparin in 
support of his conclusions respecting solar heat. It ripens im- 
perfectly at Paris, but very well in Alsace. The mere difference 
of temperature is insufficient to account for the fact. This grain 
sown at Orange in the beginning of April is harvested there in 
September, after having received, as his instruments indicate, 
4108^ of heat. In Alsace it rijiens in October ; at Paris on the 
1st of November, with 4000°, as measured by the same instru- 
ments. M. Gasparin attributes the superiority of Alsace to its 
enjoyment of a brighter sky than at Paris. The thermometrical 
means are very similar ; Mahlmann's tables show them as fol- 
lows : — 
Mean Temperature, 
Spring. Summer. Autumn. 
o o o 
Paris . . . 10-3 18-1 U-i 
Strasburg . . 10 18- 1 10 
Indeed the difference is at first sight in favour of Paris; but 
the excess of solar heat derived from the greater number of bright 
days that shine upon Strasburg is to be taken into account ; the 
estimation, however, of two bases so shifting and variable in 
themselves is liable to considerable error. 
Although M. Gasparin does not explicitly demonstrate the 
truth of his theory, yet the facts he has advanced* may invite the 
*• In p. 126 of Mons.Gasparin's 2nd vol. (Section 'Sur la Formation des 
Nuages"),he remarks that a numerical expression for the nebulosity of 
climates would be important ; and in the chapter at p. 213 ('Repartition 
de la Luniiere,' &c.) this subject is again particularly alluded to. 
M. Gasparin remarks justly, that there are three ways of treating it 
practically : — 1. By 
