44 REMARKS ON THE GEOGRAPHICAL 



simple. The presence of caloric, to whatever cause this 

 may be owing, is undoubtedly the chief excitement of energy 

 in the vital principle; which fact is demonstrated not only 

 by the myriads of organized beings which swarm within 

 the tropics, but also by the ingenious observations of Hum- 

 boldt and Latreille. These gentlemen have both shown 

 that the highest mountains in the warmest climes exhibit, 

 as we ascend towards their summits, all the various gra- 

 dations of organized matter which each hemisphere of the 

 whole globe presents as we proceed from the equator to 

 the pole. Still it must not be imagined that a horizontal 

 circle traced round the mountain, or the parallel of latitude 

 which encircles the hemisphere, are necessarily either of 

 them accurate isothermal lines. Experience indeed teaches 

 us the contrary, and fully confirms those inferences we 

 should have drawn from the consideration of the different 

 meteorological effects likely to arise from the variation of 

 the surface of the soil, and other similar causes. Vegetation, 

 for instance, which requires the absence of extreme cold 

 rather than the presence of extreme heat, is likely to ex- 

 tend itself in its tropical form towards the poles farther on 

 a dry continent than on a marshy or low one. Tropical 

 plants will therefore thrive better in Thibet and other in- 

 land parts of Northern Asia than they would do were we 

 to transport them to places of the same latitude in Ame- 

 rica. In this last country the extremes of heat and cold 

 are too widely asunder, and accordingly the vegetation of 

 Canada by no means corresponds either in its general cha- 

 racter or number of species with that of places in France 

 under the same latitude. 



Animals also are subject to the same sort of Hmitation 

 with plants : that is, they have to fear extreme cold rather 



