S62 
M. Humboldt 07i Isothermal Lines, and the 
pa!$ses to the N. of Bourdeaux, (lat. 45° 46', W. long. 0® 87',) 
near Pekin, (lat. 89° 54', E. long. 116° S7'.,) and Cape Foul- 
weather to the S. of the embouchure of the "Colombia, (lat. 
440 40', W. long. 104<^.) Its nodes are distant at least 162° 
of longitude. We have here pointed out only the empiri- 
cal laws, under which are ranged the general phenomena, 
and the variations of the temperature which embrace at once ^ 
vast extent of the globe. There are 'partial inflexions of the 
isothermal lines, which form, so to speak, particular systems 
modified by small local causes ; such as the strange inflexion of 
the thermometric curves on the shores of the Mediterranean, 
between Marseilles, Genoa, Lucca and Borne and those 
which determine the difference between the climate of the wes- 
tern coast and the interior of France. These last depend much 
less on the quantity of heat received by a part of the globe 
during the whole year, than upon the unequal distribution of 
heat between winter and summer. It will one day be useful 
to have upon particular charts the partial inflections of the iso- 
thermal lines, which are analogous to the hnes of soundings or 
of equal declivity. The employment of graphical representa- 
tions will throw much light upon phenomena, which are deeply 
interesting to agriculturist?. If, in place of geographical charts, 
we possessed only tables containing the co-ordinates of latitude, 
longitude, and altitude, a great number of curious facts rela«. 
tive to the configuration and the superficial inequalities of con- 
tinents would have remained forever unknown. 
We have already found, that towards the north, the isother- 
mal lines are neither parallel to the equator nor to one another ; 
and it is on account^ of the want of parallelism, that we have, 
in order to simplify such complicated phenomena, traced round 
the whole globe the curves of equal heat. The position of the 
line of 82° acts like the magnetic equator, whose inflexions in 
the South Sea modify the inclinations at great distances. We 
may even believe that, in the distribution of climates, the line 
of 82° determines the position of the curve of greatest heat. 
* 
Mean 
Mean 
Lat. 
Temp. 
Lat. 
Temp. 
* Bologna, 
44° 29' 
56°.3 
Marseiiiesj 
43° IV 
58°.8 
Genoa, 
44 f5 
6p.() 
Rome, 
41 53 
G0.4 
