544 JOSEPH LE CONTE 
the earth’s crust; (2) by the formation or rejuvenation of great 
mountain ranges ; (3) by the formation of new constructional 
forms, and the inauguration of a new cycle of erosion forms ; 
(4) by great climatic oscillations ; (5) by wide migrations and 
minglings of faunas and floras, and fiercer struggle for life, and 
rapid changes of organic forms by wholesale destruction of old 
forms and evolution of new forms ; (6) by more rapid steps of 
evolution, but a partial obliteration of previous geographic 
diversity, and the inauguration of a new cycle of increasing 
diversity ; and (7) by the introduction of a new dominant type 
—man, who is now becoming more and more the great agent of 
change in the new era, especially in organic forms. 
There can be no doubt that we are now in the midst of a 
change more sweeping and rapid than has ever before taken 
place in the history of the earth, but which we imperfectly 
appreciate because we are in the midst of it, and therefore lose 
the perspective. Why then should we hesitate to recognize 
that the present is indeed one of the prime divisions of geologi- 
cal time? It is more: it is that which alone gives significance 
to all that precedes. 
JosErpH Le Conre. 
