BAHIA BLANCA. [CHAP. v. 



conclude, against anterior probability,* that among the mam- 

 malia 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 cer- 

 tainly exists no quarter of the globe which will bear comparison 

 with Southern Africa. After the different statements which 

 have been given, the extremely desert character of that region 

 will not be disputed. In the European division of the world, 

 we must look back to the tertiary epochs, to find a condition of 

 things among the mammalia, resembling 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 accu- 

 mulated 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 those 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 knowf 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 iatitudej 

 (64), where the mean temperature of the air falls below the 

 freezing point, and where the earth is so completely frozen, that 



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

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

 what naturalist would have ventured conjecture on the possibility of a car- 

 cass so gigantic being supported on the minute Crustacea and mollusca living 

 in the frozen seas of the extreme North ? 



t See Zoological Remarks to Capt. Back's Expedition, by Dr. Richardson. 

 He says, " The subsoil north of latitude 50 is perpetually frozen, the thaw 

 ou the coast not penetrating above three feet, and at Bear Lake, in latitude 

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

 destroy vegetation, fur forests flourish on the surface, at a distance from the 

 coast." 



J See Humboldt, Fragment Asiatvques, 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. 



