SUN AND CLIMATIC VARIATION 45 



winds blow according as the air reaching them and carried to 

 lower levels is dry or moist ; and, finally, the distance from 

 the sea, and the variable temperature in its vicinity depending 

 on whether it is in open communication with warm equatorial 

 water or the cold oceans of polar regions. 



We have seen how, in the course of geological periods, mighty 

 mountain chains were formed and then gradually levelled ; 

 their gradual elevation to great heights little by little cools 

 the climate at their base, whilst around them the reciprocal 

 effects of continents on islands, and land masses on seas, change 

 incessantly. So that not only have there everywhere been 

 slow yet ceaseless modifications in the general nature of 

 meteorological phenomena, but all that was accomplished by 

 the agency of the sun's energy on the earth has also undergone 

 consecutive changes of aspect. 



The study of plant and animal fossils by palaeontologists 

 would seem to support all that has been said above as to 

 climatic changes. To-day there are animals and plants peculiar 

 to cold countries, and others to temperate and hot countries. 

 Conifers, birches, and analogous trees constitute the stock 

 type of vegetation found on high mountains and more or less 

 polar regions ; annuals and caducous trees abound in temperate 

 regions ; tree-ferns, cycads, palms, monocotyledons with large 

 flowers, spices, such as the cinnamon, the clove, etc., at once 

 evoke the idea of tropical countries, just as coral reefs and 

 the greater shell-fish immediately suggest tropical seas. It is 

 generally held to-day that, in warm climates only, can such 

 creatures nourish as crocodiles among the greater reptiles, birds 

 such as parrots, and mammals such as the elephant, rhinoceros, 

 hyena, panther, lion, tiger, and monkey. We judge the climate 

 of a region by the presence among its fossils of the remains of 

 plants or animals analogous to whose habitat is known to-day. 

 The method is far from unimpeachable, and the misadventure 

 which befell even Cuvier should be enough to warn us 

 to proceed in this direction with the greatest caution. The 

 elephant was regarded by Cuvier as belonging to a warm 

 climate ; so that the discovery of the bodies of mammoths 

 with flesh and hair still preserved, in the Siberian ice, seemed to 

 him to prove that this country once enjoyed a tropical climate. 

 To explain the presence of elephants buried in the ice he did 

 not hesitate to assume that, owing to some miraculous 



