CENTRAL HEAT OF THE EARTH. 421 



for example, are found in their fossil state in all latitudes, 

 and even in the centre of the frozen regions of Siberia. 



In the primitive world, these northern regions enjoyed 

 then, in winter, a temperature at least equal to that 

 which is experienced in the present day under the paral- 

 lels where the great palms commence to appear : at 

 Tobolsk, the inhabitants enjoyed the climate of Alicante 

 or Algiers ! 



We shall deduce new proofs of this mysterious result 

 from an attentive examiiicition of the size of plants. 



There exist, in the present day, willow grass or marshy 

 rushes, ferns, and lycopodes, in Europe as well as in the 

 tropical regions ; but they are not met with in large di- 

 mensions, except in warm countries. Thus, to compare 

 together the dimensions of the same plants is, in reality, 

 to compare, in respect to temperature, the regions where 

 they are produced. Well, place beside the fossil plants 

 of our coal mines, I will not say the analogous plants of 

 Europe, but those which grow in the countries of South 

 America, and which are most celebrated for the richness 

 of their vegetation, and you will find the former to be of 

 incomparably greater dimensions than the latter. 



The fossil flora of France, England, Germany, and 

 Scandinavia offer, for example, ferns ninety feet high, 

 the stalks being six feet in diameter, or eighteen feet in 

 circumference. 



The lycopodes which, in the present day, whether in 

 cold or temperate climates, are creeping-plants rising 

 hardly to the height of a decimetre above the soil ; which 

 even at the equator, under the most favourable circum- 

 stances, do not attain a height of more than one metre, 

 had in Europe, in the primitive world, an altitude of 

 twenty-five metres. 



