1855.] BEYRICH BROWN COAL. 551 



Mark Brandenburg. You take such a lively interest in the progress 

 of the knowledge of our North German tertiary formations, and have 

 so successfully laboured at the work yourself, that I would entreat 

 you to correct this error in your Quarterly Journal, in order to pre- 

 vent its adoption in your English literature, as well as to obviate the 

 propagation of an incorrect view in Germany. 



"You state, that in North Germany there are two distinct Brown- 

 coal formations : — 1. The oldest, which at Egeln, near Magdeburg, 

 is overlaid by the marine sands parallel with the Systeme Tovgrien 

 inferieur of Dumont. 2. A younger formation, which overlies the 

 Septaria-clay. Now, it must be observed, that neither Plettner 

 nor myself, nor any other German geologist, have ever stated that 

 the Septaria-clay was under the Brown Coal (viz. that of Mark Bran- 

 denburg), You will at once be convinced of this, if you refer to the 

 Journal of the German Geological Society, vol. iv. p. 453, and look 

 at the general view of the order of stratification which Plettner has 

 given as the result of his observations. The superposition of the 

 Septaria-clay over the Brown Coal was first clearly established by 

 borings in the neighbourhood of Sorzig near Kothen, of which I pub- 

 lished an account in my Appendix to ' Our knowledge of the Tertiary 

 formation in Mark Brandenburg,' in Karsten's Archives for 1847. 

 In no spot east of the Elbe has any marine, or indeed conchiferous 

 tertiary deposit been hitherto found either above or below the Brown- 

 coal deposits ; so that we are by no means justified in assuming in 

 North-Eastern Germany the existence of two distinct Brown-coal 

 formations, of such different periods as would be the case, if our 

 Brown Coal overlaid the Septaria-clay. For the present we must 

 believe that all the Brown Coals of North-Eastern Germany are older 

 than the oldest North German marine tertiary deposits." — [E. B.] 



This correction of Professor Beyrich's is a very important one. 

 On referring to Plettner' s above-mentioned memoir, I find that he 

 has there stated that the Septaria-clay is the youngest (jiingste) 

 formation in the Brown-coal fields of Mark Brandenburg, instead of 

 underlying the Brown Coal, as I had originally read the passage, not 

 having had an opportunity of visiting the country myself. The con- 

 sequences of this alteration in the order of stratification are most 

 important. There is a break in North-Eastern Germany and espe- 

 cially in Upper Silesia in that connected system of superposition of 

 strata which I had believed to exist from the Westeregeln beds up- 

 wards to those of the Vienna basin; and I am bound to admit, that 

 the possibility of the Marine tertiaries of Weinheim, Egeln, and 

 Hesse Cassel being Upper Eocene, rather than Lower Miocene, is 

 hereby considerably increased. We have still to look for that con- 

 tinued sequence of deposit which would, in my opinion, have proved 

 the connexion of the tertiaries of North Germany with the younger 

 deposits of the Vienna basin. The exertions of so many able geo- 

 logists who are now engaged in the investigation of these tertiary 

 beds, will, I trust, soon lead to a satisfactory conclusion. In the 

 meanwhile I have been unwilling to withhold from the Society the 



