Mr. J. Lucas on the Origin of Clay- Ironstone. 231 



by narrow gorges and fissures. These marls, the stratification of 

 which is much disturbed, are loaded with sulphur. In the principal 

 gorge there are several lateral fissures, forming caverns, communi- 

 cating with the interior by deep cracks ; these caverns are com- 

 pletely lined with crystals of sulphur and other volcanic minerals, 

 and are rendered inaccessible by the large body of hot stifling 

 vapours constantly emitted through them. The temperature of 

 this vapour, where it can be reached, is about 100° E. ; but the floor of 

 the caverns is too hot to stand on, even near the entrance. The 

 author is of opinion that the rocks in this gorge might be profitably 

 worked for sulphur. Similar phenomena occur in several other 

 places within about a mile of the ravine described ; and the author 

 was informed that this was the case also several miles further to 

 the east. 



The author adverted to other signs of volcanic action to the west 

 of these solfataras, and especially to the structure of the Acropolis 

 of ancient Corinth, and inferred that lines of volcanic action parallel 

 to the spurs of the Alps of which Etna and Vesuvius and Santorin 

 are the modern vents, ranged far to the north at no distant period. 



3. " On the Origin of Clay-Ironstone." By J. Lucas, Esq., 

 E.G.S. 



The author commenced by giving a general view of the varieties, 

 chemical composition, and mode of occurrence of Clay-ironstone, and 

 suggested that the formation of all the bedded varieties may be ex=- 

 plained by the supposition that they originated in peaty or nonr. 

 peaty lagoons on the alluvial flats of the deltas of the Carboniferous 

 formations, which would present semiterrestrial conditions — that is 

 to say, a surface exposed to the air, but subject to be covered by 

 floods. Carbonic acid (formed in the lagoons from decomposing 

 vegetable matter) meeting with protoxide of iron in solution, would 

 unite with it to form carbonate of iron, which, with the mud of 

 the lagoon, would produce Clay-ironstone. Thus, in the author's 

 opinion, the beds of Clay-ironstone, like Coal-beds, mark terrestrial 

 horizons. The author supported his views by reference to various 

 sections, and also cited the occurrence of what he regarded as an 

 analogous phenomenon on a small scale in some mud obtained from 

 the shore between Redcar and Saltburn. 



4. i ' Note in vindication of Leptophloeum rhombicum and Lepido- 

 dendron gaspianum." By Principal Dawson, LL.D., E.H.S., E.G.S. 



This note accompanied some photographs of the remains of plants 

 referred to, and was in opposition to the identification of these re- 

 mains with the Lepidodendron nothwn, linger, as proposed by Mr. 

 Carruthers in his Appendix to Mr. Daintree's paper on the Geology 

 of Queensland. The author maintained that his Lepidodendron 

 gaspianum is distinct from Unger's species, although nearly allied 

 to it, and that his Leptophloeum rhombicum differs from both gene- 

 rically and specifically. He tabulated as follows the characters of 

 his two species ; — 



