388 MR. E. WETIIERED ON THE DEVONIAI^ 



did SO chiefly on account of the valuable evidence they afford in 

 connexion with the cause of slaty cleavage. Probably on the whole 

 no group of limestones presents a greater range of characters. Not 

 only must their original nature have varied much, but the amount 

 of the changes due to chemical reactions and mechanical squeezing 

 has been very variable and great. He congratulated the Author on 

 having done so much to elucidate the structure of such interesting 

 rocks. 



Prof. BoNNEY expressed his sense of the great interest of the 

 Author's observations. Through the generosity of the latter he 

 had had the opportunity of examining some of these residues, 

 and could fully confirm several of the Author's conclusions. He 

 thought that the quartz crystals, which had often a nucleus of 

 silicate, must have been developed rather slowly in the rock. He con- 

 sidered that these investigations were of great value as illustrating 

 the history of mineral growth and development. 



Dr. Hicks said that the limestone at Hope's Nose, referred to by 

 the Author, had been much folded and broken ; and when examining 

 the section, during the visit of the Geologists' Association in 1884, 

 he pointed out the presence in it of a well-marked overthrust fault, 

 simulating an unconformity. 



He asked the Author whether the tubular structures, found in 

 parts of the limestone, were not allied to the so-called Serpuloe 

 described by Mr. Salter from the limestone in South Pembroke- 

 shire. 



Prof. Rupert Jones thought that Mr. Wethered would find an 

 analogous occurrence of carbon in limestone in Mr. Eulcher's account 

 of the Hirnant Limestone (Geol. Mag. for 1892, p. 114); and of the 

 quasi- tubules in Herr Kothplet/.'s description of fossil calciferous 

 Algae, published in the ' Zeitschrift der Deutsch. geol. Gesellsch.' for 

 1891, p. 295. He further suggested that minute parallel veins of 

 calcite in limestones occurred without stratal disturbance having 

 taken place, as for instance in a Cyrena-limeatonQ of the Hastings 

 Series. 



The President observed that the Society had been indebted to 

 the Author for work on the same lines on former occasions, and 

 would doubtless welcome this fresh instalment. 



With reference to the source of the carbonate of magnesia which 

 occurred in the dolomite crystals, he pointed out that sufficient of 

 the carbonate was present at the bottom of modern oceans to give 

 rise to such crystals. There was a large percentage of carbonate of 

 magnesia in the coral-sand from Bermuda. He referred to the pos- 

 sibility that carbonaceous material such as the Author had described 

 was of animal origin rather than vegetable. 



Prof. Hull, Dr. Hinde, and Mr. Etheridge also spoke. 



The Author, in reply, thanked the Fellows who had discussed 

 his paper, and especially Prof. Bonney, to whom he would always 

 be under an obligation for the encouragement given to him in the 

 past. 



In reply to Dr. Sorby, Mr. Wethered said that the Devonian 



