146 Rev,. W. D. Couybeare on a Geological Map of [Feb. 



Porphyry is the prevalent rock ; the upper beds (as at Neustadt) 

 become conglomerated and approximate to the red sandstone. 



The coal measures occur at Lobegun, Wettin, Dolau, Brach- 

 wich, and C4iebicenstein ; they occur in the porphyry, sometimes 

 covering, sometimes covered by it (the map accompanying Freis- 

 leben represents them as generally beneath the porphyry) ; the 

 porphyry above and below the coal are distinguished by the more 

 granular structure of the former, which is associated with the 

 conglomerates ; the coal is stratified, but disposed in saddles, 

 troughs, Sec. and often swells into irregular masses. Where the 

 coal measures are thickest, and no porphyry is found beneath 

 them (as at Wettin), the coal sandstone prevails to the greatest 

 depth, and is often much like the greywacke. 



The red sandstone lies either upon the slate mountains of the 

 Hartz,* or upon the porphyry of llejield and the Petersbirge, and 

 forms a range of hills stretching through Mansfield between the 

 two points. J r 



With regard to the porphyry associated in these coal districts, 

 I have to add to the above account, that its relations with the 

 formations among which it occurs are very obscure. Humboldt 



* That is where the porphyry and coal are wanting, as appears from the remainder 

 of the sentence. See also the miip in Freisleben. 



t It appears from the statement of Freisleben, that the rothetodte of these hills 

 reposes upon the Wettin coalfield. His localities include all the rothetodte represented 

 by the map accompanying his work in that quarter ; so that the fact of the superposition 

 of the great mass of the rothetodte above that coal field cannot admit a doubt. It 

 appears, however, that a conglomerate resembling the rothetodte also occurs in some 

 places beneath these coal measures. On this account, Freisleben is inclined to rank this 

 field, not with the true coal formation, but with the carbonaceous beds subordinate to 

 the rothetodte. His inferences are, however, open to doubt, first, because, he says, he 

 hail never himself seen the iitfbrior conglomerate in situ, and reasoned from specimens 

 only ; and, secondly, because the occurrence of conglomerates of similar character above 

 and below the coal measures can never be admitted as a proof of identity of formation, 

 otherwise our own conglomerates of die old and the new red sandstone must be considered 

 as a single formation, and the carboniferous limestone and coal measures be treated as 

 subordinate to that formation — a conclusion which, in the mind of every instructed geo- 

 logist, will be fully equivalent to a reduclio ad absurdum. I, therefore, demur to the 

 statement that any part of these coal districts are really subordinate to the rothesandstein, 

 as one requiring further confirmation. Be this as it may, however, it will not prove that 

 the true coal formation {which, as ice hare seta, is distinct from these subordinate beds), 

 is similarly related. The whole evidence shows, as clearly as any evidence can do, that 

 the appearance of this rock is confined to the upper regions of the coal formation ; 

 and if it be not referable, as (following Auckland), I believe it to be, to the sandstone 

 series cf the succeeding geological rcra (with which I again assert, from personal exami- 

 nation, and not with our old red sandstone, it most closely agrees), it can only be consi- 

 dered as an upper member in the coal series. Humboldt inclines to consider the red 

 sandstone as associated with the coal series : La honille, he adds, paroit le p!ussouvent 

 au dessous du grts rouge, quelquefois il est placec evidemment ou dans cette roche ou dans 

 la porphyrir. He adds no other facts than those above alluded to ; and I, therefore, 

 adhere to the interpretation before given of the cases in which it is said to occur in the 

 red sr.ndstone. 



In concluding this note, I have to correct an error which has arisen from hasty trans- 

 cription in Mr. Weaver's account of the beds in the Lobegun colliery : he makes the 

 lowest stratum rothetodteliegende, whereas it stands in his original rothethonartigerlie- 

 gende ; not the rothetodte, but a red argillaceous stratum. The point is not very mate- 

 rial ; because Freisleben probably considered it as belonging to that formation ; but 

 questions of this kind can only be settled by minute accuracy. 



