the Limits of the Jurassic and Cretaceous Periods. 333 



necessary to put prominently forward some special points of 

 view. 



The first to which I call attention relates to what is designated 

 in geology under the name of normal. The earliest works which 

 threw a great light upon the classification of strata were prin- 

 cipally produced in England and the north of France. In the 

 eyes of many naturalists the results obtained in the Anglo- 

 French basin constitute normal geology, or the normal succes- 

 sion of the stages. The geology of other countries, where not 

 strictly identical with this, only forms apparent exceptions which 

 must be reduced to a signification in accordance with this nor- 

 mal state. To these naturalists the classification of the strata 

 in the Anglo-French basin is the Sacred Ark, and the interpre- 

 tation of facts observed outside of it should have for its object 

 to make them fall within the frame of the picture. In this we 

 easily recognize the tendency of a celebrated school, the chief 

 representative of which, under this point of ' view, was the 

 learned and lamented D'Archiac. 



But why should the geologies of other countries not be 

 equally normal?, and why should they not have an equal right 

 to fix the great divisions in the palseontological history of the 

 globe ? We may here refer to an excellent note by our learned 

 colleague M. P. Merian*, who, with his accustomed uner- 

 ring scientific tact in placing his finger upon errors of me- 

 thod, has been so often able to give excellent advice to those 

 geologists who have consulted him. In this note M. Merian 

 shows that if it had chanced that the first development of 

 geology had taken place in other countries, the bases of the 

 classification of formations would have been in part different. 

 There is no reason whatever why a Table constructed under 

 these conditions should be less normal than that of the Anglo- 

 French basin. In the case before us, in particular, we may 

 say with certainty that if the first classifiers had commenced 

 by the investigation of all that belt of land which is inclu- 

 ded between Galicia and the Mediterranean, passing through the 

 Tyrol and the south-east of France, not one of them would 

 have looked for the limits of one of the great periods in the 

 neighbourhood of the Tithonian stage. The circumstance that 

 the boundaries are very strongly marked in the Anglo-French 

 basin does not imply of necessity that they are equally so in 

 this other zone. These two orders of facts are not necessarily 

 connected. 



The second point of view upon which it is necessary to say 

 a few words is with regard to the more or less complete inde- 

 * Ueber die Grenze zwischen Jura- und Kreide- Formation. Basel, 1868. 8vo. 



