September 2, 1898.] 



SCIENCE. 



285 



and the American Eepublic in particular, 

 ■whether in our own ej^es or in the eyes of 

 other nations and later times, they will 

 come to the conclusion that more glory, 

 honor and love are to be won by national 

 justice, sincerity, patience in failure and 

 generosity in success than by national im- 

 patience, combativeness and successful self- 

 seeking — and glorj', honor and love more 

 by as much as the virtues and ideals of 

 civilized man excel those of barbarous men. 



A HALF-CENTURY OF EVOLUTION, WITH SPE- 

 CIAL REFERENCE TO THE EFFECTS OF GEO- 

 LOGICAL CHANGES ON ANIMAL LIFE* {II.). 



THE APPALACHIAN REVOLUTION AND ITS 

 BIOLOGICAL BESDLTS. 



Unless we except the great changes in 

 physical geographjj^ which took place at the 

 end of the Tertiary period, when the moun- 

 tain chains of each continent assumed the 

 proportions we now see, the Appalachian 

 revolution, or the mountain-building and 

 continent-making at the close of the Pale- 

 ozoic age, was the most extensive and bio- 

 logicallj' notable event in geological history. 

 In its effect on life, whether indirect or di- 

 rect, it was of vastly greater significance 

 than any period since, for contemporaneous 

 with and as a consequence of this revolu- 

 tion was the incoming of the new types of 

 higher or terrestrial vertebrates. Through 

 the researches, now so familiar, in the field 

 and study of the two Rogerses, of Dana 

 and of Hall, we know that all through the 

 Paleozoic era at least some 30,000 to 40,000 

 feet of shoal water sediments, both marine 

 and fresh-water, derived from the erosion 

 of neighboring lands, were accumulated in 

 a geosynclinal trough over the present site 

 of the range extending from near the mouth 

 of the St. Lawrence to northern Georgia. 



* Address of the Vice-President before Section F — 

 Zoology — of the American Association for the Ad- 

 vancement of Science, August, 1898 ; continued 

 from Science, August 27th. 



At the end of the era ensued a series of 

 movements of the earth's crust resulting 

 from the weight of this vast accumulation, 

 which in a geologically brief period sank in, 

 dislocated and crushed the sides of the 

 trough, and folded the strata into great 

 close parallel folds, besides inducing more 

 or less metamorphism. These folds rising 

 from a plateau formed mountain ranges 

 perhaps as high as the Sierra Nevada or 

 Andean Cordillera of the present day. The 

 plateau emerged above the surface of the 

 Paleozoic ocean, and was carved and eroded 

 into mountain peaks, separated by valleys 

 of erosion, the rivers of the Appalachian 

 drainage-system cutting their channels 

 across the mountain ranges. 



But this process of mountain-building 

 and erosion was not confined to the end of 

 the Paleozoic era. Willis * has shown that 

 there were several successive cycles of de- 

 nudation, covering a period extending from 

 the end of the Paleozoic era to the present 

 time. And it is the fact of these successive 

 cycles of denudation both on the Atlantic 

 and Pacific slopes of our continent that is 

 of high significance to the zoologist from 

 the obvious bearings of these revolutions 

 on the production of variations. Indeed, 

 it is these phenomena which have sug- 

 gested the subject of this address. 



We can imagine that this great plateau, 

 in the beginning of the Mesozoic era, with 

 its lofty mountain ranges and peaks rising 

 from the shores of the Atlantic, presented 

 different climatic zones, from tropical low- 

 lands, with their vast swamps, to temperate 

 uplands, stretching up perhaps to alpine 

 summits, with possibly glaciers of limited 

 extent filling the upper parts of the 

 mountain valleys. New Zealand at the 

 present day has a subtropical belt of tree 

 ferns, while the mountains bear glaciers on 

 their summits ; and in Mexico, only about 



* National Geographic Magazine, 1889, Vol. I. , pp. 

 291-300. 



