68 On Geological Climate. 



with the equatorial regions compared with the polar regions, as 

 with the first of these and the temperate regions. 



The facts which we have brought forward in our memoir on 

 Fossil Mastodons, seem to shew, that climates, in establishing 

 themselves, have preserved amongst themselves the same rela- 

 tions as at the present time ; and that life, at the surface of the 

 globe, has been disturbed only in a successive and gradual 

 manner.* 



The zone in which a particular plant or animal could live 

 must have been continually advancing from the pole to the 

 equator, and would arrive at its present invariable position so 

 much the more speedily in proportion as its position had been 

 near the poles. According to these facts, it would be possible 

 that these polar regions had enjoyed for a shorter time than the 

 equatorial regions, a temperature sufficiently elevated to enable 

 to live and prosper animals and vegetables whose analogies exist 

 only in the warmest regions of the earth. If, then, mastodons, 

 elephants, and rhinoceroses have formerly lived in the polar re- 

 gions, they could only do so because they found large plants 

 proper to nourish and support them ; and both animals and 

 plants could only live, from having the temperature and light 

 which the wants of their existence required. In fact, if light is 

 necessary to vegetables) it is not less so to animals. The latter 

 could change the places where they had just stationed them- 

 selves when the circumstances in regard to light were changed. 

 A similar advantage is not possessed by vegetables. 



Light undoubtedly produces sensible effects on vegetation ; 

 it favours it, and quickens it pretty generally ; but, whatever its 

 influence may be, it is much less considerable, and much less ab- 

 solute than that of temperature. To be convinced of this it ap- 

 pears to be sufficient to cast one's eyes on hot-houses. In fact, 

 the plants of climates where the light is more brilhant and more 

 intense flourish in the most foggy countries, and countries which 

 are in some measure deprived of the influence of direct light. 



It would, doubtless, be curious to study the action and influ- 

 ence of the luminous fluid on the plants of the different coun- 



• Memoire sur les Debris de Mastodontes decouverts en France ; inserted 

 in the Memoires de la Societe des Sciences de I.ille, vol. iv, vear 1829. 



