58 Cambrian 



to the top of the Bala beds or Caradoc sandstone of 

 Murchison. 



By way of healing differences and striking a just 

 middle boundary, Professor Phillips and Sir Charles 

 Lyell proposed that the term Cambrian should be used 

 as including all the strata from the known base of the 

 Longmynd, St. David's, and North Wales purple grits 

 and slates, through the Lingula flags up to the top of 

 the Tremadoc slates, a proposition which satisfied 

 neither of the claimants. 



This is not a book in which to enter into the details 

 of a controversy which has comparatively little interest 

 beyond the confines of the British Islands, and will by- 

 and-by be forgotten along with other minor debates, that 

 in their day were of equal or more importance ; but I 

 have thought it worth while to sketch out the questions 

 involved, that in the conflict of lecturers and writers of 

 memoirs and manuals, ordinary readers may know 

 something of the origin of the varieties of opinion im- 

 plied in the different nomenclatures. In the meanwhile 

 I shall use the old-fashioned nomenclature adopted by 

 the Geological Survey, as most convenient for me, see- 

 ing that if any one in reading this book should find it 

 needful to look at the maps and sections of that Survey, 

 and at most other maps as well, he will find the word 

 Cambrian restricted to those strata, that at St. David's, 

 and in Merionethshire lie below the base of the Mene- 

 vian beds. In this sense, then : 



THE CAMBRIAN ROCKS of Wales consist of the purple 

 grits and slates, that form the greater part of the group 

 of hills that lie east of Cardigan Bay between the 

 estuaries of the Mawddach and most of the country 

 S.S.W. of Ffestiniog. In that region their strati- 

 graphical relation to the overlying Lower Silurian 



