Considerations connected with the Glacier Theory. 45 



horizontal strata have been deposited, have also afforded 

 proofs of boundaries. When, however, we become more ac- 

 curately acquainted with such concealed portions of the inte- 

 rior of the earth, or with the more remote parts of the sur- 

 face, these local blanks will more and more disappear, and 

 others will occur where previously only uninterruptedly gradu- 

 ating series of strata were known.* Supposing that geology 

 had been developed in another portion of the earth than cen- 

 tral Europe, entirely different divisions into periods would 

 have been the result, and with just as much incorrectness in 

 relation to the whole. There is still, however, no doubt the 

 distinction, that in the first period of the deposition of the nep- 

 tunian rocks, the temperature was higher, and was therefore 

 more uniform over the whole surface of the globe, so that the 

 living beings on the earth and the remains derived from them 

 might have a uniform character ; and that at that time also 

 the continents, probably less elevated and extensive, might 

 have presented a less interrupted continuity than at present 

 of the strata formed under the water. 



In my Lethda Geognostica^ I have already given a list of 

 such species of organisms as are common to different periods, 

 and I shall not return to it now, as here I have more to'do 

 with the strata of rocks than with the species of petrifactions. 

 While I willingly admit that, by a more minute examination, 

 many of these species may be divided into two, or may turn 

 out to be incorrectly determined ; yet still the number of such 

 common species has since been much increased, notwithstand- 

 ing that much more careful determinations are now made, 

 and De Verneuil and D'Archiac have prepared more exten- 

 sive lists. 



I. Regarding the boundaries between the present time and 

 the molasse period, it is known that there are tertiary deposits 

 which have 0.95, 0.90, 0.80, 0.50, 0.020 of their fossil species 

 that are common to the living creation, and though some 

 intermediate links are still awanting, yet these will yet be 

 found. Efere, therefore, we can hardly assume any real limit. 



* Constant Frevost likewise expresses the same opinion. 



