i855 REVISION OF SOUTH WALES 231 



persistent zone they formed in North Wales. Hence 

 at last, and after much objection on De la Beche's 

 part, who, as we have seen, was weary of these re- 

 peated re-examinations of Wales, Ramsay obtained his 

 chief's authority in 1855 to send Aveline into South 

 Wales for the purpose of inserting the more glaring 

 omissions on the maps and improving the representa- 

 tion of the associated igneous rocks. How keen was 

 the interest that Ramsay took in this work is shown 

 by the voluminous correspondence which he carried 

 on with his colleague in Wales. For weeks together 

 every second or third day he would write to Aveline 

 when at work in North Wales, commenting on the 

 last report received from him, and suggesting localities 

 for re-examination or points to be kept in view. Two 

 of these letters may be cited as examples. 



LONDON, 1 2 th April 1855. 



MY DEAR TALBOT I have Sir Henry's consent for 

 you to have a turn in Pembrokeshire when you have 

 done with the Wenlock line. The business will be 

 first to do the Cambrian line, and secondly to walk 

 across each bit of trap in the country, tap it and 

 note down whether it is hornblendic or felspathic, 

 melted or felspathic ash. Except errors stare you in 

 the face, don't bother about them ; but of that more. 

 This job is urgent now, because Sir Henry has decided 

 to change the colouring, and to colour all greenstones 

 green, and all felspathic traps and granites shades of 

 red. I am glad of it, for it gives us a good oppor- 

 tunity of improving the Pembrokeshire maps, and with 

 Sir H.'s determination about the colouring, there is no 

 escape from the necessity of looking at it. I suspect, 

 indeed I know, there will be mapping to do in the 



