1846 FIELD-WORK IN WALES 79 



Ramsay remained in London until the 25th April, 

 and passed the whole of the rest of the year in the 

 field, partly inspecting work already done, and partly 

 joining several of his colleagues in the tracing of fresh 

 lines and in the attack of new ground. The staff had 

 been recruited at the beginning of that month by the 

 addition of another palaeontologist in the person of J. 

 W. Salter, 1 who was to play a brilliant part in working 

 out the fossils of the Cambrian and Silurian forma- 

 tions of Britain, and who from time to time gave his 

 services to the working parties in the field. 



After a brief period of inspection with Bristow 

 around Yeovil, in Somerset, Ramsay turned his face 

 once more to North Wales, and remained there until 

 the middle of December. The problems which the 

 Survey was attacking in that region were of absorbing 

 interest. Besides the question of the relative bound- 

 aries of the Cambrian and Silurian systems, then 

 beginning to be agitated between Murchison and 

 Sedgwick, there was the marvellous display of 

 volcanic phenomena presented by the older Palaeo- 

 zoic rocks. Ramsay had already helped to map the 

 igneous masses north of Builth, in the Shelve and 

 Chirbury district, and among the Breidden Hills. 

 But it was a new experience to see volcanic sheets 

 developed on the magnificent scale which they pre- 

 sent in the noble range of mountains extending from 

 the ridge of Cader Idris northwards through the chain 

 of the Arans and the Arenigs. Selwyn was at work 

 from Dolgelli. Aveline was tracing the boundaries 

 of the Silurian series from Llanbrynmair eastwards to 



1 John William Salter, born 1820, died 1869 ; appointed to the Geological 

 Survey in 1 846, and for many years engaged both in the Museum and in the field 

 in determining fossils for the Survey. His knowledge of Palaeozoic forms of life 

 was unrivalled. He retired from the Survey in 1863. 



