370 MK. H. H. ARXOLD-BEMKOSE ON [Aug. I904, 



being less easy to work than the adjoining limestone, were left by 

 the workmen in quarrying, standing out like walls. There could 

 not be any doubt that these joints had been filled in from above. 

 In a quarry near Chipping Sodbury these infillings assumed 

 a columnar form, and consisted of sandstone with white quartz- 

 pebbles, probably the result of the denudation of the Triassic sand- 

 stones which once covered the district and were washed in and 

 finally consolidated. 



Mr. H. W. Mostckton complimented the Author on the beautiful 

 photographs of rock-faces shown upon the screen. He then referred 

 to the curious bands of hard calcareous sandstone which run through 

 the Kimeridge Clay at Ethie near Cromarty, and appear to be of 

 much the same nature as those described in the paper. The ' dike ' 

 at Ethie is harder than the shale, and stands well above it on the 

 shore. It is probably an infilled crack or fissure in the shale : for, 

 as the country-rock is (in that case) shale, the space occupied by 

 the ' dike ' cannot have been due to solution. The speaker thought 

 that the infilling had probablv come from above, although he could 

 quite understand that such a c dike ? might be formed by infilling 

 from below, somewhat on the principle of creep in coal-pits. He 

 did not think that the word ' dike ' should be confined to bands of 

 rock of igneous origin, for the word was a common one, and 

 in Scotland usually meant a wall. He thought that it was a good 

 term for the bands of rock in question. 1 



Prof. W. W. Watts asked whether the Author had considered 

 the possibility of the dykes being of Millstone-Grit age. He had 

 examined examples of Millstone-Grit in which the secondary 

 growth of quartz was precisely similar to that described in the 

 paper. Prof. Sollas's observations in Funafuti had shown that 

 the reef-limestone was seamed with deep fissures admitting sea- 

 water, and if the Carboniferous Limestone was formed under similar 

 circumstances, the oncoming Millstone-Grit would find the requisite 

 hollows for the formation of steep dykes such as those described by 

 the Author. The speaker had seen dykes of this nature, not only in 

 soluble rocks, but in quartzites like those of the Lickey Hills, and 

 in this case the dykes frequently contained Llandovery fossils. 



Mr. Teall referred to the dykes and veins of sandstone in the 

 Lewisian Gneiss of the North-Western Highlands, and pointed out 

 that they occurred at or near the junction of gneiss and Torridon 

 Sandstone. They were similar in petrological character to the 

 sandstone, and had no doubt been filled in from above. 



Mr. J. Allen Howe remarked that, a few miles north of 

 Snelston, near Brassington, large pipes and fissures existed in the 

 limestone, containing a mixture of sands and clays of Keuper, 

 Bunter, Mil] stone-Grit, and possibly of Glacial origin. He asked 

 the Author whether the dykes described in the paper were in 

 any way related to the above deposits, an occurrence which seemed 

 not unlikely, considering their proximity to Snelston. The sand in 



1 See, in confirmation of this, John Brand's 'Hist, of Newcastle' vol. ii. 

 (1789) p. 679, note d. 



