172 SURVEY OF THE SNOWDON REGION CHAP, v 



deposit of the Old Red Sandstone. These upper purple beds will 

 interest you, not that there is anything in purple and (their common 

 associates) greenish beds ; they are found of all ages. The upper 

 purple beds in Ireland, the position of which is undoubted, often 

 remind one of the Cambrians of Bray Head and other places. 



It seems to me, before anything be written or published, it will be 

 needful for you and self to go over some of the main sections and points. 

 This you will be the better able to do after your present examinations. 



I have not the maps with me ; indeed I am writing away from 

 the Museum, and therefore cannot point out more distinctly where I 

 would wish you to look. There are some capital cases of smashing 

 on the coast from granitic intrusions beyond (southward of) the range 

 of the rocks holding the Parys mountain mines really good things ; 

 so is the whole coast. I believe I have walked or boated the 

 whole in Anglesey. I should like a run with you in Anglesey, and, 

 please the small porcines, we will have one, whether the lower rocks 

 be Tertiaries turned topsy-turvy or superfine elders. I am called 

 to attend to other things. Yours sincerely, 



H. T. DE LA BECHE. 



It will be obvious from this letter that the Director- 

 General had recognised conglomerates at the base of 

 the Cambrian series of Anglesey, that he wished to 

 keep an open mind as to the relations and age of the 

 rocks underlying these conglomerates (which he seems 

 to have been inclined to class as pre-Cambrian), and 

 that he had observed the presence of trappean or 

 volcanic intercalations among the older Palaeozoic 

 formations of the island. It was unfortunate that on 

 all these points, where he was undoubtedly right, his 

 able lieutenant came to differ from him. Selwyn, 

 indeed, clearly detected the unconformability of the 

 lowest Cambrian strata upon an older series of schists. 

 But on the maps as finally published Ramsay's views 

 prevailed. No pre-Cambrian rocks were there shown. 

 The crystalline schists were classed as * altered Cam- 

 brian/ and the existence of volcanic breccias and other 

 proofs of volcanic action were not recognised. 1 



1 See a discussion of this subject in Presidential Address to Geological 

 Society, Quart. Journ. Geol. Soc. vol. xlvii. p. 81, 1891. 



