Correspondence — Mr. T. M. Hall. 583 



following might be provisionally adopted as the subdivisions of the 

 Silurians of the South of Scotland. 1, Hawick Eocks, the so-called 

 Bolton Eocks, of uncertain age. 2. Moffat Eocks (= Upper Llan- 

 deilo). 3. Girvan Limestone (=Caradoc Limestone). 4. Gala 

 Group, comprising the Abbotsford Flags, the Gala Grits, the Buck- 

 holm Sandstones, and the Greiston and Thornilee Slates (this group 

 is probably comparable with some of the beds which succeed the 

 Girvan Limestone, and also with the Coniston Flags and Grits). 5. 

 The Balmae Eocks (= Wenlock Shale). 6. The Ludlow Eocks of 

 the Pentland Hills. 



The author pointed out the resemblances which he thought might 

 be laid down between the above and the Silurians of the North of 

 England. He drew attention to the fact that the Wrae Limestone of 

 Peebleshire might very possibly be the equivalent of the Bala Lime- 

 stone of Wales, and the Coniston Limestone of Cumberland aud 

 Westmoreland ; and that this would considerably simplify the eluci- 

 dation of the Scotch Silurians. He showed, however, that much 

 work must yet be done before it would be possible to speak with 

 any certainty as to the correlation of these ancient deposits. 



coie-s-ESiPOisrnDiEiisrozE]. 



HALL'S MINERALOGIST'S DIRECTORY. 



SiE, — Owing to absence from h<3me, I have only just seen B. J. E.'s 

 letter in the Geological Magazine for September. 



Few tasks can be more difficult than the preparation for the first 

 time of a work which deals with so extensive an area as that of the 

 British Isles ; and whilst thanking B, J. E. for his notes on the 

 Cornish localities, I may repeat the assurance contained in my 

 preface that notices of omissions or errors, and any additional infor- 

 mation, whether publicly or privately sent to me, will be gladly 

 received for insertion in a future edition. The value of any such 

 communications will, however, be much enhanced if accompanied by 

 the name and address of the writer. 



B. J. E. takes exception to the names Towanite and Limnite, and 

 asks why I have used them instead of either Chaloopyrite or Copper 

 pyrites, and Limonite respectively. With regard to the first of these 

 minerals, I may say that the names Chaloopyrite and Copper pyrites 

 were both abandoned by me in order to avoid the use of the term 

 " pyrite " as applied to an ore of copper. It must be remembered 

 that the name Pyrite was originally given to one specific mineral, 

 the Sulphuret of Iron, from its property of striking fire with the 

 steel ; and as the corresponding ore of copper, from its comparative 

 softness, does not possess this quality, the appellation seemed to be a 

 decided misnomer. At the same time I do not justify the use of the 

 synonym Towanite,^ further than to say that in default of any better 

 name it appeared to be the least objectionable of the three. 



1 I think B. J. R. will find he is mistaken in supposing that " Towanite " was 

 ever employed hy Greg and Lettsom to represent a modification of chalcopyrite. 



