100 CHARLES DARWIN 



alongside each other, it is not easy to conceive ranks more 

 disproportionate in size. After the above facts, we are com- 

 pelled to conclude, against anterior probability, 8 that among 

 the mammalia there exists no close relation between the 

 bulk of the species, and the quantity of the vegetation, in 

 the countries which they inhabit. 



With regard to the number of large quadrupeds, there 

 certainly exists no quarter of the globe which will bear com- 

 parison with Southern Africa. After the different state- 

 ments which have been given, the extremely desert character 

 of that region will not be disputed. In the European divi- 

 sion of the world, we must look back to the tertiary epochs, 

 to find a condition of things among the mammalia, resem- 

 bling that now existing at the Cape of Good Hope. Those 

 tertiary epochs, which we are apt to consider as abounding 

 to an astonishing degree with large animals, because we 

 find the remains of many ages accumulated at certain spots, 

 could hardly boast of more large quadrupeds than Southern 

 Africa does at present. If we speculate on the condition 

 of the vegetation during these epochs, we are at least bound 

 so far to consider existing analogies, as not to urge as 

 absolutely necessary a luxuriant vegetation, when we see 

 a state of things so totally different at the Cape of Good 

 Hope. 



We know 9 that the extreme regions of North America, 

 many degrees beyond the limit where the ground at the depth 

 of a few feet remains perpetually congealed, are covered by 

 forests of large and tall trees. In a like manner, in Siberia, 

 we have woods of birch, fir, aspen, and larch, growing in a 

 latitude 10 (64) where the mean temperature of the air falls 

 below the freezing point, and where the earth is so com- 



8 If we suppose the case of the discovery of a skeleton of a Greenland 

 whale in a fossil state, not a single cetaceous animal being known to exist, 

 what naturalist would have ventured conjecture on the possibility of a 

 carcass so gigantic being supported on the minute Crustacea and mollusca 

 living in the frozen seas of the extreme North? 



9 See Zoological Remarks to Capt. Back's Expedition, by Dr. Richardson. 

 He says, "The subsoil north of latitude 56 is perpetually frozen, the thaw 

 on the coast not penetrating above three feet, and at Bear Lake, in lati- 

 tude 64, not more than twenty inches. The frozen substratum does not 

 of itself destroy vegetation, for forests flourish on the surface, at a distance 

 from the coast." 



10 See Humboldt, Fragments Asiatiques, p. 386 : Barton's Geography of 

 Plants: and Malte Brun. In the latter work it is said that the limit of 

 the growth of trees in Siberia may be drawn under the parallel of 70. 



