346 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1908. 



adjacent seas. There is no evidence of anj^ Pleistocene glaciation on 

 the mainland of Australia, except on the highest summit of the 

 Australian Alps; and though Mount Kosciusko, which is now 7,256 

 feet above sea level, in a region with a 60-inch rainfall, had once a 

 few small glaciers, there is no evidence in Australia generally of a 

 colder Pleistocene climate. In fact the early Pleistocene or Pliocene 

 fauna of central Australia indicates the extension then of the tropical 

 fauna of northern Australia into the temperate regions of the Conti- 

 nent. Neither the flora nor fauna of the Pleistocene deposits of 

 Victoria indicates a colder climate than that of the present time. 



The glaciations themselves, moreover, though often very extensive, 

 appear to have been always local.. Thus those of the Pleistocene in 

 the Northern Hemisphere were grouped around a series of centers, 

 which are not always in particularly high latitudes. In North 

 America there appear to have been three glacial centers, that of the 

 Canadian Eocky Mountains in latitude 55° to 60° ; that of eastern 

 Canada in latitude 50° to 55°, and with its southern edge extending 

 to latitude 42° N. ; and that of Greenland of which the center is from 

 70° to 75° N. 



In Europe the glaciation of the British Isles extended as far 

 south as latitude 52° ; that of Scandinavia, from a center between 

 latitude 60° and 65° N., overrode the country as far south as northern 

 Germany in latitude 53° N. ; and the other centers farther south 

 developed where high mountains, such as the Alps, occurred near 

 warm seas. 



Causes of Climatic Variations. 



If it be accepted that former climatic changes involve less extreme 

 changes of temperature than have been generally assumed, and that 

 we are not called on to explain former tropical forests in the arctic 

 lands, or fossil coral reefs in the arctic seas, or occasional universal 

 refrigerations of the earth, then the problem of climatic variations is 

 greatly simplified. 



THE elevation THEORY. 



Several explanations, attractive from their simplicity, may then be 

 at once dismissed. The theory of the migrations of the poles into 

 temperate regions, although supported by Oldham and Penck for the 

 Upper Paleozoic glaciation, is contradicted by the evidence of pale- 

 ontology; and the explanations it would give of world-wide changes 

 are not required. The once popular theoiy that ice caps have been 

 produced by the greater elevation of the land may be abandoned, 

 as opposed to meteorological principles, and as implying a reversal 

 of the facts, glaciations having so often accompanied periods of 

 greater submergence of the land, and milder climates having coin- 



