ST5 
Distribution Heat over the Globe. 
ample still more striking of the union of very mild winters^ 
with cold and moist summers. Notwithstanding a difference of 
4° of latitude, the winters there are as mild as in Britain, while 
the mean temperature of the summers is three degrees less. 
This is the true maritime climate. The month of August, 
which on the same isothermal line, in the east of Europe (in 
(Hungary) has the temperature of 71°.6, reaches only 60°.8 at 
Dublin. The month of January, whose mean temperature at 
Milan, and in a great part of Lombardy, is only 35°.6, rises in 
Ireland to 5°. 4, and 7°.S. On the coasts of Glenarm, also (in 
north lat. 54° 56',) under the parallel of Konigsberg, the 
myrtle vegetates with the same strength as in Portugal f . It 
scarcely freezes there in winter, but the heat of summer is not 
capable of ripening the vine. 
These examples m’e sufficient to prove, that the isocheimal 
lines deviate much more than the isothermal lines from the ter- 
restrial parallels. In the system of European climates, the lati- 
tudes of two places that have the same annual temperature can- 
not differ more than from 4° to 5°, while two places whose mean 
winter temperature is the same, may differ more than 9° or 10 
in latitude. The farther we advance to the east, the mor^ ra- 
pidly do these differences increase. 
The lines of equal summer, or isotheral curves^ follow a di- 
rection exactly contrary to the isocheimal lines. We find the 
same summer temperature at Moscow, in the centre of Russia, 
and towards the mouth of the Loire, notwithstanding a differ- 
ence of of latitude. Such is the effect of the radiation of 
the earth oit a vast continent deprived of mountains. It is suf- 
ficiently remarkable, that the inflexions of the isothermal lines, 
and the division of lands and seas are such upon the globe, 
that every where in North America, in Europe, and in Eastern 
Asia, the mean temperature of the summers does not denote 
more than 36^ in the parallels of from 45® to 47®. The same 
causes which in Canada, and in the north of China, sink the 
curves of equal annual heat, where the isothermal lines (those of 
* Wahlenberg Flora Carpath. p. 90. 
+ Irish Transactions, tom. viii. p. 116, 203, 269. 
