280 TRANSACTIONS OF THE NORTHERN 



greater physical changes between one geological age and another, than 

 between the eighteenth and nineteenth centuries. 



Through the long lapse of past ages,alternate changes have occurred, 

 from ocean to dry land, and from land to ocean again. Geological 

 deposits are made only beneath water. When a portion of the earth's 

 surface is elevated to the condition of dry land it receives no deposits 

 — on the contrary, the face of continents are being continually denuded 

 and washed into the oceans. 



During the thousands of centuries that lands are above water the 

 modifying influence of changing conditions effects great changes in 

 living forms ; hence, when that land is, in time, again submerged be- 

 neath water it receives another deposit with quite distinct orders of 

 life, from the underlying older rocks that had been so long above water. 

 Here would appear an abrupt change in the geological record. Form- 

 erly such abrupt changes in the rocks were not understood, and were 

 unhesitatingly taken as evidence of a sudden destruction of living 

 forms, and the ushering in of a new era by a direct creation of new 

 forms. 



The hypothesis of a supernatural creation has sublimely covered 

 up a vast amount of human ignorance. But more extended research 

 tends to show that all such abrupt changes are but breaks in the geo- 

 logical record and have but a local extent. It is now well understood 

 that superincumbrance of position does not necessarily imply proxim- 

 ity of time. Various other conditions which time will not permit me 

 to set forth, cause abrupt changes in geological deposits. 



Our present forests are very distinct from the luxuriant flora of the 

 miocene age in the same latitudes. Of course the origin of our present 

 trees and plants was formerly accounted for on that convenient hypo- 

 thesis of a special creation. It was thought that the introduction of 

 an entirely new order of vegetable life, in a single geological age, 

 would admit no other solution. But, to that great American botanist, 

 Dr. Asa Gray, more than to any other man, belongs the credit of tracing 

 the origin of our present flora to high northern latitudes. Our present 

 plants, or their closely allied representatives, are found fossil in the ter- 

 tiary beds of high latitudes; and their lineal representatives are traced 

 even back to the cretacious. During the increased cold of the plio- 

 cene and post-pliocene, this northern vegetation was gradually pushed 

 southward; and succeeded to the more luxuriant flora of miocene 

 times which worked its way further to the south. Many of the lineal 

 representatives of that miocene flora are now found between the 

 tropics. 



Regarding the cause of the general change of climate during the 

 post-pliocene times, space will only permit me to say, it is mainly ac- 

 counted for, in the elevation of an excess of polar lands. This exces- 

 sive proportion of northern lands has made regions of perpetual ice, 

 where, in miocene times, rolled the waters of open seas warmed by cur- 

 rents from tropical regions. At the present time, the Antarctic conti- 



