18.5.5.] HAMILTON TERTIARIES OF HESSE CASSEL. 13? 



beds either with those of Mayence to the south, or with those of 

 Magdeburg and Westeregehi to the north, or rather N.E. 



Dr. F. Sandberger, in his work ah-eady quoted on the geological 

 position of the Mayence tertiary basin, has identified the AYeinheim 

 tertiaries with the Limburg beds of Belgium ; and more particularly 

 has he identified the Weinheim sands with the Middle Limburg beds, 

 and the overlying Cyrena-marls with the Upper Limburg. Then, 

 adopting Philippi's view respecting the age of the Cassel beds, — viz. 

 that they belong to the Subapennine formation. Dr. Sandberger 

 places them considerably above the Weinheim beds. And with 

 regard to the formations of Northern Germany, he considers the 

 sands of ^Magdeburg and Westeregehi as of the same age as the Wein- 

 lieim sands ; and the overlying Septaria-clay of Celle, Berlin, and 

 Mecklenburg, as of the same age as the Cyrena-marls of the Mayence 

 basin (he. cit. p. 79). 



Prof. Bey rich, in his last work on the fossils of the tertiaiy forma- 

 tions of the North of Germany, published in the Journal of the 

 German Geological Society*, states that in his opinion the oldest 

 North German tertiary formation, viz. that of the sands of Weste- 

 regehi and Alagdeburg, belongs to the Lethen formation of Belgium, 

 which is placed by Sir C. Lyell as the lowest member of the Middle 

 Limburg series f, although Prof. Bey rich considers it as the lower 

 Tongrian system, which properly belongs to the Lower Limburg 

 series. The next youngest formation in North Germany, according 

 to Prof. Beyrich, is the Septaria-clay of Brandenburg, Berlin, &c., 

 which he identifies with the Belgian formations of Boom, Baesele, 

 and other places south of Antwerp. These form, according to 

 Dumont's classification, a part of the System of Riipelmonde [Systeme 

 Rupelien), constituting the Upper Limburg beds of Sir C. Lyell. 

 Prof. Beyrich also observes that it is as yet uncertain whether there 

 exist in Northern Germany any beds exactly corresponding with 

 those which Dumont has placed between the Riipelmonde and the 

 Lethen beds, — in other words, with the Middle Limburg beds : this 

 he considers an important point, inasmuch as this is the Belgian 

 deposit which has the greatest analogy with the Mayence basin. 



Having thus given the views of the German geologists who have 

 principally occupied themselves with this question, I proceed to 

 make a few observations on this question of relative age. 



It is a somewhat remarkable circumstance, that the marine depo- 

 sits in the three localities above alluded to have such a small hori- 

 zontal and even vertical development, apparently belonging in each 

 case to such a short geological period ; and it has struck me as in the 

 highest degree improbable that these three formations, situated at no 

 considerable distance from each other, showing no evidence of super- 

 position, and containing a certain number of organic remains in 

 common, should be referred to three different periods. Beginning 

 with the most southern formation, we have the Weinheim beds re- 

 ferred to the Middle Limburg ; the next nearest beds, of Cassel, are 



* Zeitschrift der Deutschen Geol. Gesellschaft, vol. v. p. 277. 

 t Quart. Journ. Geol. Soc. vol. viii. p. 307. 



