MUECHISON — ON THE NEW TERM DTAS. 



7 



in ' Siluria,' 2nd edition, particularly at p. 842. Near the northern 

 extremity of the Thiiringerwald, for example, and especially in the 

 environs of Eisenach, an enormous thickness of the Bothliegende, 

 in itself exhibiting at least two great and distinct parts, is surmounted 

 by the Zechstein, thus being even so far tripartite, whilst the Zech- 

 stein is seen to pass upwards to the east of the town, by nodular 

 limestones, into greenish and red sandy marl and shale, the " Lower 

 Banter Schiefer " of the Grerman geologists. The same ascending 

 order is seen around the copper-miniug tract near Eeichelsdorf, as well 

 as in numerous sections on the banks of the Pulda, between Eotheburg 

 and Altmorschen, where the Zechstein crops out as a calcareous band 

 in the middle of escarpments of red, white, and green sandstone.* 



But in showing that in many parts of Germany, as well as in 

 England, the Zechstein has a natural, conformable, and unbroken 

 cover of red rock, I never proposed to abstract from the Trias any 

 portion of the Bunter Sandstein or true base of the group, as re- 

 lated to the Muschelkalk by natural connection or by fossils. I 

 simply classed as Permian a peculiar thin red band (Bunter Schiefer), 

 into which I have in many localities traced an upward passage from 

 the Zechstein, and in which no triassic shell or plant has ever been 

 detected. 



On my own part, I long ago expressed my dislike to the term 

 Trias ; for, in common with many practical geologists who had sur- 

 veyed various countries where that group abounds, I knew that in 

 numerous tracts the deposits of this age are frequently not divisible 

 into three parts. In central Grermany, where the Muschelkalk forms 

 the central band of the group, with its subjacent Bunter Sandstein 

 and the overlying Keuper, the name was indeed well used by Al- 

 berti, who first proposed it ; but when the same group is followed to 

 the west, the lower of the three divisions, even in Germany, is seen 

 to expand into two bands, which are laid down as separate depo- 

 sits on the geological maps of Ludwig and other authors. In these 

 countries, therefore, the Trias of Alberti's tract has already become 

 a Tetras. In Britain it parts entirely with its central or calcareous 

 band, the Muschelkalk, and is no longer a Trias ; but, consisting 

 simply of Bunter Sandstein below, and Keuper above, it is therefore 

 a Dyas ; though here again the Geological Surveyors have divided 

 the group into four and even into five parts, as the group is laid 

 down upon the map — No. 62, ' Geographical Survey of Great Britain.' 



The order of succession in the Permian group all along the western 

 side of the Pennine chain or geographical axis of England proves 

 the impossibility of applying to it the word "Dyas;" for over wide 



* On two occasions (1853-4) Professor Morris accompanied me, and traced with 

 me these relations of the strata ; subsequently, when Mr. Rupert Jones (1857) was 

 my companion, we saw other sections clearly exliibiting this upward transition 

 which I have described. Since then, Professor Hamsay, when at Eisenach, con- 

 vinced himself of the accuracy of the fact that the Zechstein passes up conform- 

 ably into an overlying red cover. My note-books contains many additional 

 evidences, which I have not thought it necessary to repeat. 



