46 FORMATION OF THE EARTH 



cataclysm, a tropical climate had been instantaneously trans- 

 formed into a glacial one. Mammoths were simply hairy 

 elephants adapted to life in arctic countries, where they lived 

 together with the rhinoceros and other species of animals 

 whose representatives to-day are found only in tropical 

 climates. 



In fact, living organisms are exceedingly untrustworthy 

 guides to climate for two reasons : — 



1. Since they were produced successively only, the first 

 organisms achieved spread over the whole globe without 

 difficulty, with the result that the flora and fauna then 

 presented a homogeneity giving the impression of great 

 similarity in the conditions of existence, because we are accus- 

 tomed to see a close correlation between these conditions, 

 when they are diverse, and the presence of certain animal 

 and plant groups. This is the case, for instance, for the ferns, 

 horse-tails, club-mosses, conifers, and cycads which throughout 

 the Primary Period constituted the flora of continents that 

 possessed no flowering plants at that time. The same holds 

 true for the Trilobites, cartilaginous fish, and carapaced 

 Batrachians then dominating the fauna. 



2. The same fauna can both adapt itself to and resist climatic 

 conditions of the most varied kind. 



The tiger, for instance, is encountered in the high cold 

 plateaux of Tibet. Father Armand David also found monkeys 

 and parrots there, and M. Lefebvre, in his excellent book 

 Chaleur animate et bioenergetique, has described how he 

 succeeded in getting a Cercopithecus to live under snow. 1 

 Finally our domestic animals prove the extent to which an 

 animal organism can adapt itself to the most varied conditions 

 of existence. 



Moreover, glaciers have again and again left traces which 

 give us more precise information on the regions invaded by 

 extreme cold than living organisms have given about heat. 

 It is thus that the presence of glaciers during the Algonkian 

 epoch, at a time when the oldest gneisses had hardly been formed, 

 has been traced in Ontario, in the region between Lake Superior 

 and Temiscaming forest, and in Minnesota, Michigan, 

 Spitzbergen, and the Cape of Good Hope. It was the period 



1 XII, 407. 



