490 
GEOGRAPHY. 
BOOK V, 
almost daily in the middle of summer ; and, in the same place, 
in the middle of December, the smi not setting for eighteen 
hours together, Krusenstern observed that the thermometer 
never rose higher than 52^; while, on the contrary. Von 
Buch remarked it as high as 79.4° in Lapland under the 
parallel of 70°. In 60° S. lat., which nearly answers to the 
position of St. Peter sburgh in the northern hemisphere, Cook 
and Forster found the temperature at midsummer not higher 
than 36° ; and icicles were continually forming on their ship. 
Even in the extreme points of Lapland, in 70° N. lat., the 
pines attain the height of sixty feet ; while at the Straits of 
Magellan and in Station Island, near New Year's Harbour, 
in latitude 55° S., nothing like a tree is found, except scrubby 
birches and Wintereae. 
Viewing the distribution of plants with respect to longitude, 
we find that, while the great forms of vegetation are wholly 
controlled by circumstances attendant upon the parallels of 
latitude, there are wide differences, of a secondary nature, 
which correspond in some with the parallels of longitude ; 
and that particular genera and species do not extend beyond 
the limits of particular districts, to which they give peculiar 
features. Thus, in North America, on the east of the Rocky 
Mountains, azaleas, rhododendrons, magnolias, vacciniums, 
actasas, and oaks, form the principal features of the landscape ; 
while, on the western side of the dividing ridge, these genera 
almost entirely disappear, and no longer constitute a striking 
characteristic of the vegetation. The genera of Proteaceae 
and the Ericeae, at the Cape of Good Hope, are replaced in 
New Holland by different genera of Proteaceae, and by Epa- 
crideae ; while neither the one nor the other exist on the con- 
tinent of South America, with the exception of some Rhopalas. 
The natural order of Bromeliaceae is exclusively confined to 
America : Calathea, a genus of Marantaceae, is only found on 
the same continent : cinnamon, cloves, and nutmegs are con- 
fined to the Indian Archipelago ; and hundreds of other in- 
stances are to be named of similar exclusive stations. Whether 
these differences depend upon geological causes, or arise from 
some other circumstances, is entirely unknown. 
Such are the most striking facts connected with the dis- 
