ON THE MOVEMENTS OF THE EARTh's CRUST. 347 



have constantly had the same direction. And the same geologists have 

 justly insisted that this law is one of the most remarkable results of 

 geolooical investigations. 



The development of organic life, as we now know, has gone on unin- 

 terruptedly from the earliest times. There has certainly never been any 

 general destruction, never any completely new creation. The new has 

 developed from the old through transitional forms and in the course of 

 millions of years. If we kn*^w all the deposits which have been formed 

 it would be impossible to draw any boundaries between geological 

 formations. One would imperceptibly pass over into the other. The 

 boundaries between formations correspond with great gaps in the series 

 of beds. In the time which intervened between the youngest bed in an 

 older and the oldest in a younger cycle, the land in the northern hemi- 

 sphere lay so high that no marine deposits were formed in the parts of 

 the earth's crust which are accessible to our investigations. Neverthe- 

 less the development of living forms went on its even course. But 

 when, after a long time, the land was again submerged, the life in the 

 sea had changed, and beds with new fossils were deposited upon the 

 old ones. And it is from the animal remains of marine deposits that 

 the formations are determined. Hence, the sudden change of fossils 

 where a new formation commences is not due to any catastro])he, but 

 simply to a shorter or longer interruption in the formation of deposits 

 in the parts of the earth which we are able to examine. There is no 

 doubt that there are transition beds between formations, but they lie 

 concealed from us at the bottom of the sea. It is only in certain strongly 

 plicated chains that these beds are upheaved and can be examined. 

 Thus in the Alps there are transitional beds between the Cretaceous 

 and Tertiary, between the Permian and Trias, etc.* 



If we should attempt to establish geological formations by the aid of 

 the known remains of terrestrial animals and plants, the boundaries of 

 these would not coincide with tliose which are defined by marine ani- 

 mals.t Thus, to mention an example, the appearance of Dicotyledons 

 does not coincide with the boundary of any formation; but they first 

 appear with a number of forms in the Upper Cretaceous period (Ceno- 

 maniau). 



* " As long ago as 184G, Darwiu, iu his observations in South America, showed that 

 certain assemblages of fossils presented ableudiugof characterswhich are of Jurassic 

 and Cretaceous age, respectively. Since that date, the study of the fossil faunas of 

 South Africa, India, Australia, New Zealand, and the Western Territories of North 

 America has furnished an abundance of facts of the same kind, showing that no 

 classification of geological periods can possibly be of world-wide application." (J. 

 W. Judd, presidential address to the Geological Society, 1838, and Nature, March 1, 

 1888, p. 42G). See also Mojsisowics, Die DoJoniilriffe Siidtiroh inid Venetkns, Vienna, 

 1879, p. 36; and von Ilauer, Die Geologic, Vienna, 187'), p. .515. 



t "The growth of our kuowlege concerning the terrestrial faunas and lioras of an- 

 cient geological periods has constantly forced u])on the minds of uiany geologists the 

 necessity of a duplicate classification of geological periods, based on the study of 

 marine and terrestrial organisms respectively." (J. W. Judd, loc. cit. p. 427.) 



