1 874 REVISION OF WELSH GEOLOGY 329 



succeeded Sedgwick as Woodwardian Professor at 

 Cambridge, and also with Mr. R. Etheridge, and Mr. 

 D. Homfray of Portmadoc, he traversed a good deal 

 of ground in the district of Cader Idris, Aran Mowd- 

 dwy, and Portmadoc. Rain and wind buffeted the 

 party a good deal, but the Director-General declared 

 that every day hardened his old legs more and more, 

 and by the end he cared little for the fatigue. In an 

 account of his doings (qth August) he wrote to me that 

 the necessity for a second edition of my North Wales 

 is now urgent, and I am seriously at work making out 

 a new line of division, that between the base of the 

 Llandeilos and the top of the Tremadocs, or, en grand, 

 between the Lingula Flag series and the Llandeilos. 

 I have accurately traced twenty miles of it, and have 

 for the first time (yesterday) got perplexed. We have 

 been at work for about eighteen days. 



Some further information is given in a letter to his 

 brother William, written from Portmadoc during a 

 subsequent excursion. (i3th September 1874): I 

 am busy revising a deal of country and realising all 

 the discoveries that have turned up since Selwyn and 

 I were here more than twenty-five years ago. It 

 involves the tracing of one new geological line that no 

 one suspected long ago, and which I surmised must 

 exist ever since Sir Roderick and I were in the north 

 of Scotland some fifteen years ago. 



The progress of his work and the nature of some 

 of his engagements during the year 1875 are told in 

 the following letters : 



^oth January 1875. 



MY DEAR GEIKIE I highly approve of your vindi 

 cation of De la Beche [in proof-sheets of the Life of 



