Yol. 55.] THE ASHBOTJENE AND BUXTON EAILWAY. 2,37 



EXPLANATION OE PLATES XVII & XVIII. 



Plate XVII. 



Figs. 1-3. Horizontal sections through Tissington, Highway Close Barn, and 

 Crake Low cuttings, on the scale of 40 yards to the inch. 



Plate XVIII. 



Figs. 1-6. Vertical sections of the beds above the thick ash, between Tissington 

 and Crake Low, on the scale of 12 feet to the inch. 



Discussion. 



Prof. Hull said that he had listened with interest to the paper, 

 knowing the district of Derbyshire to which it referred. He 

 reminded the Fellows that on the Geological Survey maps and 

 sections there were two outpourings of lava intercalated among 

 the Carboniferous Limestones — the upper lava being near the top 

 of the limestone-series. These had been originally traced by the 

 late Sir "Warington Smyth. He was not quite clear, from the 

 Author's account of the ash-beds, whether or not these represented 

 the uppermost of the two lava-flows mapped by the officers of the 

 Survey, or whether they were the products of a third and later 

 eruption. One of the finest examples of submarine volcanic energy 

 at the close of the Carboniferous Limestone period in the British 

 Isles was to be found in County Limerick, at Cahirconlish, where 

 no fewer than ten successive eruptions of lava and ash-beds were 

 interposed between the limestone and the overlying ' Yoredale ' 

 shale. These beds appeared to be representative of those described 

 by the Author. 



Prof. SoLLAs remarked that an examination of the specimens on 

 the table recalled the association of calcareous sands and volcanic 

 detritus now frequently presented by islands in the Pacific. He 

 had seen precisely similar ball-like lapilli in Oahu, where in some 

 cases they formed beds deceptively resembling lava-streams. Similar 

 basaltic glass, passing into palagonite, occurred in association with 

 detrital limestones in some of the islands of Torres Straits. In one 

 of the slides of limestone exhibited by the Author structures were 

 to be seen superficially resembling sponge-spicules. The speaker 

 also called attention to a series of contemporaneous basaltic rocks 

 associated with the Carboniferous Limestone of Limerick : these 

 had been studied in detail by Prof. Watts. 



Mr. Lamplugh commented on the strongly-marked difference 

 between the character of the Glacial Drift in the sections described 

 by the Author and that of the country a few miles farther south, 

 and on the importance of this difference as an indication of the 

 direction of ice-flow. He asked what other boulders besides local 

 rocks were found in this Drift. 



Mr. Strahan thought that the Author had made two important 

 points. In the first place, he had proved the contemporaneous age 

 of the igneous series by the existence of limestones containing ashy 

 material. Contemporaneous igneous rocks were now known in so 



