42 Professor Bronn on sotne Geological and Physical 



perceptible in the hot zone, but little in the temperate, and most 

 of all in the cold zone, where it would operate most powerfully 

 in ^vinter and at night, so that a degree of diminution of the 

 mean temperature of the whole earth, distributed in the man- 

 ner indicated, must have made the winter at the edge of the 

 Polar zone several degrees colder. At all events, therefore, 

 since the period of the disappearance of the elephants, the 

 alterations in the temperature of the earth, taken altogether, 

 have been limited to the increase of the cold of the winter 

 and of the nights in higher latitudes, which had, as a conse- 

 quence, an increase of snow and ice towards the Pole and on 

 the mountains near it, and also an indirect action of this ice 

 on the temperature of the region, and especially on the 

 changeable nature of its summers. 



If, however, these alterations of temperature should not be 

 sufficient to explain the phenomena connected with the early 

 glaciers, the intervening local alterations of temperature ren- 

 dered possible by continental elevations and depressions, by ma- 

 rine and aerial currents, and by the local coolings of the crust of 

 the earth, and also, according to all the indications afforded, 

 the enormous length of the period of thousands of years which 

 elapsed during which similar local phenomena could affect all 

 parts of the temperate and cold zones, are more than enough to 

 account for them, when we reflect that these local phenomena 

 have even now the result, that in our hemisphere many such 

 places which are separated from each other by from 20° to 25° 

 of latitude, come under the same isothermal lines, and have a 

 similar mean temperature, while, on the other hand, there are 

 places lying in the same latitude which present a difference 

 of mean temperature of from 10° to 12° cent. (18° to 21°.6 F.), 

 nay, of even 17° cent. (30°.6 F.), and when further we re- 

 member, that even in the historical period, during the lapse 

 of from 200 to 300 years, Greenland (Gronland, formerly 

 Grunla?id) has been subjected to such mighty alterations, that 

 it has now become almost uninhabitable. What consequences 

 would be produced on the climate (supposing the heat 

 of the sun to remain the same) by a permanent increase of 

 the yearly fall of snow in Switzerland, caused by any geogra- 

 phical change I And if wc think of the fact that the quan^ 



