« 
1816.} Humloldt’s, &c. Plants of South America. 881 
Mean Temperature, Differ. in 
Mean) ie eat 
Places, | Lat. N, | ann. Coldest| Hottest) of these 
temp. Winter/Spring 
Philadel.| 39° 56’ | 12-79 # Le 11-79}, 24°09 | 13°49)4 0°49) 25.09] 24-60 
Pekin ..| 39 54 {12-7 | —3-1 | 13°5 | 28:1 124 |— 41 291 33°2 
Summ.|Autump month, | month. | months. . 
Nantes ..| 47 13 | 12°6 | +4°6| 12°5 | 204 13"1 |+ 3°9 21:4 175 
Reme ..! 41. 53 | !5°8 | +7°T| 143 | 24:0 TL |+°56 25:0 19°4 
Paris....| 48 50 |10°8 | +34) 9:8 | 18°8 107 |+ 2°2 19-7 175 
Quebec..) 46 47 | 5:4 | —9°9 | 3°8 | 20:0 78 |—10'7 23°0 33°T 
Upsala... 59 51 | 5°55 |—3°9) 4:1 | 157 60 |— 43 16:6 20°9 
In North America, as far as latitude 48°, the summers are four 
centigrade degrees hotter than in the corresponding latitude in 
Europe; hence the reason why magnolias and other equinoxial 
plants appear so far north in America. In treating of the geogra- 
phical distribution of plants, it is of consequence to distinguish 
between the mean annual temperature and the mean temperature 
of summer. 
| Diff. between the 
temp. of the 
Mean annual temp. in) Latitudes, | Mean equator and Ratio of the 
each Continent, A. America.| heat of ‘mean annual 
| £. Europe, |summer.} Mean |Temp, ofjsummer temp. 
annual |summer, 
temp 
15° AP86T LEZ? | URSP POST Pia 
(Rome, 15°S°.) | E43 || 23:0) 125°) 457)" beo155 
10° | Adee) Dig WS 5-7 ed | 
(Paris, 10°8°.) E492 | 18°0 | 17°5 95 Be. Bs 
5° | A 48 Sb Mh S2rS 8 | Ns ee, 
(Stockholm, 5°7°)| E60 | 15°] | 22:5 | 12:4 V3 
oe PPE * Ss fh —- 
6° A 54 P20) Bb 15°5 pas 4 
(North Lapl.) | E682 | 115 | 275 | 15 1: 115 
LLL I 
From Barton’s observations it appears, that America is warmer 
to the west of the Aleghany mountains than to the east of them; 
hence certain plants are found four degrees further north in Loui- 
siana and on the Ohio, than on the borders of the Atlantic. Hum- 
boldt supposes that this difference does not extend farther north 
than latitude 42°. Beyond Lake Superior and at Hudson’s Bay it 
is said that the earth is perpetually frozen at the depth of three feet 
from the surface, which prevents the inhabitants from digging 
wells. The same thing happens in Siberia in the latitude of 62° 
on the banks of the river Lena; while in Lapland at the tempe- 
