Yol. 6^.~] THE TOADSTONES OF DERBYSHIRE. 241 



14. The Toadstones of Derbyshire : their Field-Relations and 

 Petrography. By Henry Howe Arnold-Bemrose, J.P., M.A., 



F.G.S. (Read April 17th, 1907.) 



[Plates XIX-XXII— Maps.] 



Contents. 



Page 



I. Introduction : 241 



1 1. The North- Western or Miller's-Dale Area 243 



III. The South-Eastern or Matlock Area, including Ashover 



and Crich 256 



IV: The South- Western or Tissington Area 266 



V. The Intrusive Dolerites or Sills 271 



VI. Summary and Conclusion 278 



I. Introduction. 



In June 1894 I read a paper before this Society, 8 On the 

 Microscopical Structure of the Carboniferous Dolerites & Tuffs 

 of Derbyshire' Quart. Journ. Geol. Soc. vol. 1, pp. 603-44 & 

 pis. xxiv-xxv. At that time I had made no attempt to establish 

 the relations in the field between the igneous rocks and the lime- 

 stones in which they occurred. During the interval which elapsed 

 between the acceptance of my paper by the Council of the Society 

 and the reading of it, I had the pleasure of taking Sir Archibald 

 Geikie over some typical parts of the district. He pointed out that 

 some of the toadstones were contemporaneous with the limestone, 

 others intrusive, and others represented the vents through which the 

 volcanic material was brought to the surface ; and that, in order to 

 arrive at the history of the toadstones, careful re -mapping of the 

 whole district would be necessary. 



In 1897, in his 'Ancient Volcanoes of Great Britain' vol. ii, 

 p. 12, Sir Archibald expressed the opinion that 



' the number of successive platforms on which igneous materials appear will 

 never be satisfactorily determined until the stratigraphy of the Derbyshire 

 Carboniferous Limestone is worked out in detail. When the successive members 

 of this great calcareous formation have been identified by lithological and 

 palaeontological characters over the whole district, it will be easy to allocate 

 each outcrop of toadstone to its true geological horizon.' 



Since November 1894, I have mapped the toadstones on the 

 6-inch Ordnance maps and in some places on the 25-inch maps ; 

 I have also examined many hundreds of new thin slices of rock, 

 made from specimens collected during the twelve years since my 

 first paper was read. 



Although I am unable to furnish a complete account of the 

 volcanic history of the county, I consider that it is more conducive 

 to the progress of geology to publish the results of my investigations 

 up to the present, than to keep them back until the different 

 members of the Mountain Limestone have been separated and 

 identified by lithological and palaeontological characters. 



Q.J.G. S. No. 251. s 



