THE REVOLUTIONS OF THE CRUST OF THE EARTH. 335 



change of climate of Switzerland ought to be attributed to the elevation 

 of the Alps. In 1841 he abandoned this idea to support that of the 

 rending of the Alps, and the ejection from the fissures formed of large 

 quantities of vapor, which in precipitating cooled the country. 



M. Kretntz was inclined to suppose a still greater elevation of the 

 Alps, as much as 20,000 feet. According to M. Lecocq, it is the unequal 

 distribution of heat at the surface of the globe, which on the one hand 

 favors the evaporation of the waters, and on the other the precipitation 

 of these vapors. M. de la Hive attributes to the evaporation of the 

 waters of the freshly-emerged continents, the formation of the more ex- ' 

 tended glaciers of some mountain chains. Mr. Frankland* proposed a 

 theory which rests upon the fact of the uuequal cooling of the ocean 

 and of continents. The sea, retaining the heat better, at a certain pe- 

 riod disengaged vapors, which were precipitated in the form of snow, 

 the fusion of which during the summer absorbed a large part of the 

 heat, so that the temperature of the continent was sensibly diminished. 

 M. Escher de la Linth thinks that thefeune (Fohn) warm wind from the 

 sea could not. blow at a period when as we suppose the Sahara was a 

 sea. Switzerland must have been then much colder.t Still other 

 hypotheses have been proposed, but not so much of the character of a 

 general and periodical cause. 



The variations of temperature which occurred during geological peri- 

 ods is most frequently explained by the presence or absence of the Gulf 

 Stream. We have in fact seen that the oceanic currents as well as the 

 aerial currents are variable in their direction and in their intensity. 

 It only remains to explain why the marine currents as well as the winds 

 are more intense in the austral than in the boreal hemisphere; why all 

 the most important currents, and the Gulf Stream itself, have their 

 starting-point in the three drifts of the Antarctic glacier, while the Arctic 

 currents are comparatively of little importance. We answer that it is the 

 unequal distribution of water and the unequal size of the two glaciers 

 which produce this variable intensity of the currents in general; but to 

 what can we attribute the disproportionate extension of the austral 

 glacier and the predominance of water in the corresponding hemisphere? 

 This explanation of the unequal temperature of the two hemispheres 

 and of the oscillation of climates in geological epochs is not sufficient, 

 for one might as well take the cause for the effect of the change of tem- 

 perature. 



Great progress, however, was made in the admission that the climatic 

 condition of the globe has not always been the same, and that the cold 

 which now prevails upon the austral hemisphere, formerly covered with 

 a stratum of ice a part of Europe and of Asia. It was a chamois-hunter, 

 of the valley of Bagne, named Perraudin, who suggested the idea to 

 Charpentier that the erratic blocks which incumbered the valleys might 



*Phil. Magaz., August, 1864. 



t Favre, Beoh. Gcolog., t. i, pp. 185-190. 



