MUECHISON — ON THE NEW TERM DYAS. 
7 
in ' Siluria,' 2nd edition, particularly at p. 342. Near the northern 
extremity of the Thiiringerwald, for example, and especially in the 
environs of Eisenach, an enormous thickness of the Rothliegende, 
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 
Bunter Schiefer " of the German geologists. The same ascending 
order is seen around the copper-mining tract near Eeichelsdorf, as well 
as in numerous sections on the banks of the Fulda, 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 Germany, 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 stmta ; subsequently, when Mr. Rupert Jones (1857) was 
my companion, we saw other sections clearly exliibiting this upward transition 
which I hare described. Since then, Professor Ramsay, when at Eisenach, con- 
vinced himself of the accui-acy 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. 
