Geological Society, 571 



That this unconformity denotes two different oeras of deposition, 

 an inference supported by the difference in the organic remains ; and 

 Mr. Weaver further states, that he does not consider the occurrence 

 of a few coal plants in the WoUacomb sandstones (5) as at all inter- 

 fering with this inference. 



That the preceding data justify the conclusion, that the strata 

 from 1 to 6 belong to a system distinct from that which includes the 

 beds 7 and 8, the former constituting a peculiar transition group ; and 

 the latter belonging to the true coal measures of England, the old 

 red sandstone being alone wanting. 



In conclusion the author dwells upon the importance of attending 

 to mineral composition in surveying extensive systems of rocks ; but 

 he adds, that " the only safe guide in researcheb into the crust of the 

 earth, is to keep constantly united in view, relative position, organic 

 remains, and mineralogical characters ; and not to restrict our at- 

 tention to one of these distinctions when judging of geological form- 

 ations." 



January 17, — A paper by Dr. Bell, entitled "Geological Notes 

 to accompany Major Todd's Sketch of part of Mazunderan," was 

 first read. 



These notes were made during a journey from Teheran (lat. 35" 

 40' N., long. 50° 52' E.), eastward to Feeroozkooh, then northward 

 across the Elboorz mountains, and afterwards along the course of the 

 river Talar to the Caspian, and back to Teheran by the banks of the 

 river Heraz. The authors observations are given in the order in 

 which they were made during his journey, but the geological details 

 may be classed as follows : — 



1. Alluvium. — Teheran stands on a plain, consisting chiefly of the 

 debris of limestone and trap rocks. In the bed of a river at the 

 Caravanserai of Dalee Chaee, about 62 miles direct E. from Te- 

 heran, is a loose conglomerate composed of fragments of limestone 

 and trap, imbedded in dried mud. A similar deposit forms low hills 

 and valleys in several other places along the line of route, followed 

 by the author, as at the river Gazan Chaee, and on the summits of the 

 hills bordering the plain of Feeroozkooh. Below Pul-i-Seffeed, on 

 the Talar, is a conglomerate, formed of debris from the neighbour- 

 ing mountains, united by a calcareous cement. Further down the 

 river, it is finer, and stated to contain minute fragments of shells. 



Below Sheergah, the country, as far as the Caspian, is an alluvial, 

 muddy flat. This sea is stated to be fast filling up, and the disco- 

 loured water of the streams, which flow into it, may be traced for 

 five or six miles. Near the shore the water is so fresh that horses 

 drink it ; and Dr. Bell says, that the shells are chiefly freshwater. 

 Half imbedded in the banks of mud and sand are innumerable trunks 

 of large trees which have been drifted down by the rivers. A con- 

 glomerate similar to that at Dalee Chaee, was noticed at Karoo in 

 ascending the Herza ; also below the small stream Abi Noor, at the 

 foot of Demavend Peak. 



Lithographic Limestone. — A fine-grained limestone, used for litho- 

 graphy in Teheran, forms a high ridge north of the city, the beds 

 dipping to the north, and resting on serpentine, porphyritic claystone. 



