t 
418 i 
earth parts with more heat than the air, so as to 
become lower than the air. In light substances 
in. contact with the earth, it is often from 15° to 
20°. Hence 10 grains of wool, on a grass plot, 
in a night, gave 16 grains of dew,—9 on a gravel 
walk,—and 8 on mould. MHoar-frost is frozen 
dew. Grass is often but 30° when the air is 
39°, and hence early freezing. 
“The disputes,” says the writer in the 10th 
volume of the Journal of Agriculture, “which 
have arisen regarding the merits of different 
cultivated grasses, have partly arisen from 
forgetting that a grass, valuable on account 
of its produce in one part of Britain, may, 
in another part, and consequently under a 
different climate, be found less profitable ; 
and further, the power of becoming accli- 
mated may be different in different species or 
varieties. ‘The distribution of the cultivated 
grasses,’ says Schouw, ‘is determined not merely 
by climate, but depends on the civilization, in- 
dustry, and traffic of the people, and often on 
historical events.’ The truth of these remarks 
cannot be denied, but the first (climate, viz.) 
places impassable boundaries to the influence of 
the others. The same author remarks, ‘The 
grains which extend furthest north in Europe, 
are barley and oats. These which, in the milder 
climates, are not used for bread, afford to the in- 
habitants of the northern parts of Norway and 
Sweden, and of a part of Siberia and Scotland, 
their chief vegetable nourishment.’ In Norway, 
at Attengard, near N. lat. 70°, barley succeeds 
sometimes in the valleys, the snow line there is 
3,600 feet; in N. lat. 65°, oats ripen. In Swe- 
den, early barley reaches almost to the bounda- 
ries of the pine woods in N. lat. 69°, where the 
sun never sinks below the horizon from the lat- 
ter part of May to the end of July. Oats, to the 
north of N. lat. 66°, very seldom ripen ; the snow 
line here is 4,800 feet. ‘In the course of the 
month of May,’ remarks Dr. Richardson, ‘ ground 
was prepared at Cumberland House, and, toward 
the end of it, barley sown, to be reaped again in 
August, after an interval of about 90 days, whose 
mean temperature may be stated at 67°°8 Fahr. 
This place borders on the isothermal line of 32° 
F. According to Humboldt, barley, to be culti- 
vated to advantage, requires, during 90 days, a 
temperature of from 47°3 F. to 48°2 F. Al- 
though the mean annual temperature of any 
place may be far below that at which seeds can 
germinate, still grain will come to maturity if 
the mean of the vegetating season reach a cer- 
tain degree. Oats seldom ripen farther north 
than lat. 66°, the annual mean temperature 
being 33° F., that of the summer being 57°°8 F., 
while barley reaches to N. lat. 69°, where the 
annual mean is only 27° F., that of the summer 
being 54°°8. Professor Playfair proposed to date 
the vegetating season from 20th March to 20th 
October, and supposed that it is on the nature of 
that season that the quantity of the crop princi- 
—— ~~ 
TEMPERATURE. 
pally depends. He assumed 40° F. to be the 
lowest temperature at which corn will vegetate, 
and considered 56° F. as the mean temperature 
of a good vegetating season. The limit at which 
corn will not ripen he stated to be about 48° F. 
In the following table Professor Playfair’s method 
has been adopted; and by the vegetating season 
is meant the period from 20th March to 20th 
October in each year. 
sumed as fair criteria of the productiveness of 
the seasons, and are placed in comparison with 
the mean temperature of each year, the mean ° 
temperature of the vegetating season, and the 
total fall of rain. The fiars are those of Aber- 
deenshire as given in the Aberdeen almanack. 
Mean of | Annual 
Excess of Rain in| Oatmeal 
Years, | veg. sea- |mean tem-|veg. season 
inches.] per boll. 
son. perature. | above 40°. 
s. d 
1829 50°94 46°-62 10°94 28°:66 13 6 
1830 51 +24 46 ‘81 11 -24 30 +60 16 8 
1831 53 49 48 14 13 -49 29 °16 14 10 
1832 51 98 47 +83 11 -98 21 07 12 0 
1833 52 05 47 ‘13 12 -05 22 -04 11 10 
1834 53 °22 49 +18 13 +22 12 :28 14 6 
1835 51 -50 46 °96 11 ‘50 14 ‘94 13 6 
1836 50 ‘92 46 -14 10 :92 24 -69 18 0 
1837 48 67 45 °35 8 67 20 :29 15 6 
1838 48 -58 44 +25 8 58 34 °40 21 6 
Annual mean temperature at Aberdeen, from observations 
during the last sixteen years, = 47°°22. 
“ Professor Playfair says, ‘ Whether the quan- 
tity of the crop may be expected to be propor- 
tional to the excess of the mean temperature of 
the vegetating season, above 40° F’., may deserve 
to be more accurately considered. There is every 
reason, however, to think that the variations of the 
crop, at least corn, will be greater than in propor- 
tion to the variations of temperature. By doubling 
the deficiency of the heat, we do a great deal 
more than double the deficiency of the crop, so 
that the latter varies in a higher ratio than the 
former. The limit at which corn will not ripen 
may perhaps be stated at 48°.’ A writer in the 
Aberdeen Journal of January 18th, 1837, re- 
marks, ‘I have observed that if May, June, and 
July had an average of 54°5 per diem, grain 
would fill and ripen notwithstanding an autumn 
as wet as that of 1829. In that year grain did 
ripen, while in the present year (1836) the aver- 
age heat for the three months being 43°29 F. 
only, the staple crops (barley and oats) in this 
district (Huntly) have ripened so imperfectly as 
in most cases to be unfit for seed, and deficient 
in weight compared with any crop since 1821.’ 
In making such comparisons, it would be neces- 
sary to take into account the comparative tem- 
peratures of shorter periods of time. It is of 
importance to note the daily range of tempera- 
ture, as this forms a prominent feature in the 
nature of the seasons. The study of the relation 
between climate and the productiveness of the 
different crops, is deserving of much attention. 
The difference between the nature of any two 
The fiars prices are as- | 
