82 The American Geologist. February, isss 
and the rounded, grassy Moel Eilio (2,382 feet). The next 
day we ascended Snowdon by its railway, rising from the 
lakes of Llanberis (400 feet above the sea) to the highest sum- 
mit of southern Britain, 3,570 feet above the sea. Around us, 
on all sides excepting northwestward, were the steep, mostly 
rugged and boldly serrate Welsh mountains, consisting of the 
very ancient Cambrian rocks. 
Moel Tryfan (or Tryfaen), the hill which for that day was 
my desired destination, lay in plain view at a distance of six 
miles westward, beyond a deep valley in which we saw the 
Cwellyn lake (about 500 feet above the sea) and the Snowdon 
Ranger inn, with its group of Scotch pines. Toward the drift 
sections displayed in the slate quarrying near the top of that 
hill, visited and much discussed by many geologists during 
the past sixty years, I walked down the stony path to the inn, 
past the lake, beneath the northern precipice of a spur of 
Mynydd Mawr, and up the drift-covered, smooth and pas- 
tured ascent of Moel Tryfan. Looking back, I saw a cloud 
bank enveloping the top of Snowdon and towering above to a 
great altitude, though elsewhere the air and sky were mostly 
clear. 
The area occupied by Moel Tryfan is about a mile in 
diameter. Its slopes, of moderate steepness, are almost wholly 
covered by till, with frequent or abundant boulders, beneath 
which, at the quarries, are extensive deposits of gravel and 
sand. At shallow depths the slate is reached and quarried; 
and at the summit a jagged mass of conglomerate juts up 
about 15 feet above the surrounding grassy pasture. The 
hight of this point is given on the Ordnance Survey map as 
1,399 ^s^t above the sea. The highest col dividing this hill 
from the neighboring mountains is on the southeast, at a dis- 
tance of about a mile, having an estimated altitude of about 
1,150 feet, whence the next mile eastward rises to the crest of 
Mynydd Mawr, at 2,290 feet. On the southwest and thence 
around to the north, all the country is much lower than our 
hill, and is a fine agricultural district, with the little seaport 
city of Carnarvon well seen four miles northwest. 
In 1831, Trimmer discovered fragmentary marine shells 
in the sand and gravel under the superficial boulders and till 
at the slate quarries near the top of Moel Tryfan; and by sub- 
