282 PROF. W. MORRIS DAVIS ON [Aug. 1909, 



technical style, that a body of ancient slates, felsites, and volcanic 

 ashes, greatly deformed in Palaeozoic time and greatly worn down 

 in successive cycles of Palaeozoic, Mesozoic and Tertiary erosion, was 

 reduced before the Glacial Period began to subdued mountain-form 

 with dome-like central summit, large rounded spurs, and smooth 

 waste-covered slopes, and with mature valleys drained by steady 

 flowing streams which branched delicately headwards, with steepening 

 slope, and which joined each other mouthwards in the accordant 

 fashion that so systematically characterizes the drainage of all 

 normally subdued mountain-masses. Also that this full-bodied mass 

 was transformed during the Glacial Period, chiefly by the glacial 

 excavation of valley-head cwms and by the glacial widening and 

 deepening of the valleys themselves, into a sharp central peak, 

 which gives forth acutely serrated ridges between wide amphi- 

 theatres : the serrated ridges changing into broad-spreading spurs 

 as they are followed outwards ; the wide amphitheatres, backed by 

 high rocky cliffs, opening by great rock-steps to irregularly 

 deepened trough-like valleys, with oversteepened, undissected sides, 

 sometimes smooth, sometimes of a peculiarly roughened slope; the 

 smaller lateral valleys hanging in strikingly discordant fashion 

 over the floors of the larger valleys : and the streams, far from 

 following graded courses in steady flow, frequently halting in lakes 

 or hastening in rapids and cascades. 



II. Excursions around Snowdon. 



My first excursion around Snowdon was made tor the most part 

 in company with the late Joseph Lomas, F.G.S., of Birkenhead, who 

 met me in the early morning of September 12th, 1907, when the 

 steamship Saxonia reached the landing-stage at Liverpool. We 

 started off at once, and by ferry, train and carriage, via Birkenhead, 

 Chester, and Bettws-y-Coed, reached the isolated hotel of Pen-y- 

 Gwryd, near the eastern base of Snowdon, in the afternoon. On 

 the four days following we walked around the mountain by the 

 valleys on the north-east, south-east, and south-west, ascended the 

 opposed slopes on the east (the western spur of Moel Siabod) and 

 west (the rounded summit of Mynydd Mawr) in order to secure 

 general views of the main mountain and its great cwms, entered 

 the cwms on the east (Cwm iJyli) and south (Cwm Llan) to gain a 

 closer view of their structure and form, and had a run over Moel 

 Trefan, a little farther west, to see its famous drift-cover bearing 

 northern erratics and sea-shells. After Mr. Lomas's return home, 

 I went up to the summit of Snowdon by the rack-railway from 

 Llanberis, and had an admirable review from above of much that 

 we had seen from below. Following this introduction to North 

 Wales, it was my good fortune, as a member of the excursion 

 conducted by Dr. Marr and Prof. Garwood, to see something of the 

 Lake District, and then during the Centenary celebration of 

 the Geological Society in London and the sectional adjournment to 



