RELATION OF BIOLOGY TO GEOLOGICAL INVESTIGATION. 287 



Condensed scale of the fossiUferoua rocha, No. ', 1890 — Continued. 



Danian 



Senonian 



Turouiau . . . 

 Cenomanian. 



Ganlt 



Neocomian . . 



( Iretaceous 



l'ortlandian 



Oxfordian , , 



Bathouiau 



Lias, or Scbwarzcu Jura. 



Jurassic 



Rba-tic 



Keuper 



Muschelkalk 

 Bunter 



Triassic 



Mesozoio, 



Permian, or Dias. 



Goal Measures 



Millstone Grit 



Carboniferous Limestone 



:1c, 



arboniferous . 



Upper Devonian : \ 



Middle Devonian Devonian 



Lower Devonian ' 



Paleozoic. 



Upper Silurian 

 Lower Silurian. 



Silurian. 



Upper Cambrian 



Lower Cambrian \ 



Jo. 



nibrian 



It was the intention of the founders of this scale, as it is and has 

 been of all other geologists, that it should represent the whole of geo- 

 logical time from the beginning of life upon the earth until the begin- 

 ning of the epoch of human history,* and that its divisions in the order 

 in which they are named in the tables should represent consecutive 

 portions of that time. It is necessarily assumed that each of these 

 time divisions was represented by sedimentary deposits wherever dur- 

 ing its continuance bodies-of water existed upon the earth, and where 

 they did not exist the passage of time was not recorded at all, or that 

 it was not so recorded as to be understood without reference to the 

 aqueous record as represented by the scale. That is, it is necessarily 

 assumed that although during every epoch of geological time there 

 were portions of the earth's surface upon which no sedimentary de- 

 posits were made because they were then above water level, there were 

 during every epoch large portions of it beneath waters which were 

 constantly depositing sediments. Thus, contemporaneously with such 

 breaks in sedimentation within certain regions as have just been men- 



* Tbis statement may be taken as a definition of tbe term geological time, in tbe 

 use of which term no direct reference is made txxsiderial time. 



