i875 GEOLOGY OF WALES 333 



above which in N. Wales comes the Caradoc series, 

 of which the old-fashioned Llandeilos of Murchison 

 may with propriety be considered a part. From the 

 Tremadocs into the Arenig beds there pass about ten 

 or eleven species ; from the Arenigs into the ordinary 

 Llandeilo and Caradoc beds eight species. I hear 

 that you have equivalents of the Arenigs in the S. 

 of Scotland, somewhere towards the Cambrian country. 

 Can you give me any idea of their real relations to any 

 overlying Silurian strata, and underlying strata, if any ? 

 . . . I have some evidence that the Arenigs of 

 Caernarvonshire have overlapped all below, and lie 

 direct on the Cambrians. It is in my Geology of N. 

 Wales, but I think these Arenigs are there called 

 Llandeilos. 



* i ^th September. I scarcely think I have had 

 enough of rest in the entire way. I am getting on with 

 my new edition in spite of too much correspondence, and 

 I have now got all the data except a scrap. The great 

 Arenig and Lower Llandeilo line is done and run out 

 to sea at both ends. I think I would almost rather 

 write a new book than a new edition. Dovetailing is 

 often so troublesome. I think (or hope) that I shall 

 soon get to the last half, which may need but little 

 alteration, except a few words here and there. As it 

 turns out, a good deal of my book will be almost re- 

 written. It will be a great improvement on the last 

 edition: In the Welsh section, the trappy inter- 

 stratifications are, of course, accidents, and sometimes, 

 as at Criccieth, they are absent. 



' 2$rd December. I am so head and ears at present 

 in the River Dee (Wales) that I think I have got water 

 on the brain. It is the most curious bit of physical 

 history of any river I have yet tackled. It will make 



