1889.] THE DISPLACEMENT OF BEACH-LINES. 35 



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

 on uninterruptedly from the remotest times. There has never 

 been any destruction of all the old life, never any complete new 

 creation. The new forms have developed themselves from the 

 old, through transition-stages and through millions of years. 

 If one knew all the beds that have formed themselves it would 

 become impossible to draw any line between geological forma- 

 tions. The one would imperceptibly pass into the other. 



The margin between the formations corresponds to great gaps 

 in the series of layers. In the period that separated the youngest 

 bed in an older, and the oldest bed of a later cycle, the continents of 

 the northern hemisphere lay so high that marine beds were not 

 formed in those parts of the crust of the earth which are accessible 

 for our investigations. Meanwhile the development of the various 

 forms of life proceeded in their usual course. But when the 

 land, after a long time, was again flooded the animal life of the 

 seas had become changed, and beds containing new fossils were 

 superimposed the old ones. And it is in accordance with the 

 animal remains in the marine beds that the formations are 

 established. Thus, the sudden alteration of fossils where a new 

 formation begins is not dependent on any catastrophe, but simply 

 upon shorter or longer interruption in the sedimentation in those 

 parts of the earth which we can investigate. There is no doubt 

 that the transition-layers between the formations are to be 

 found, but they lie hidden from our view at the bottom of the 

 sea. Only in a few especially folded ranges are those layers 

 upheaved, and thus capable of being investigated. Thus in the 

 Alps are found transition layers between Cretaceous and Ter- 

 tiary, between Permian and Trias etc. 1 



are of Jurassic and Cretaceous age, respectively. Since that date, the study 



facts of the same kind, showing that no classification of geological periods 

 can possibly be of worldwide application" (J. W. Judd, in Nature 1 March 

 1888, p. 426). Vide also Mqjsittowicz: Die Dolomitriflfe Sudtirols und 



