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POPULAR SCIENCE REVIEW. 
mologist will find, both on the shores and inland, many inter- 
esting birds and insects. 
To the shell-collector more especially, is this a locality of deep 
interest, for, about seven miles from Barmouth, in the direction 
of Harlech, there is a small tongue of land jutting into the sea, 
called Mochres, where shells of great rarity, both univalve and 
bivalve, are to be met with on the beach at low water, more 
particularly after tempestuous weather.* 
And now, what have we for the geologist and mineralogist ? 
Judging from the ecstasies of two learned professors from the 
metropolis, with whom we journeyed a few miles through this 
lovely district, as well as from our own observation, we should 
say that there are few parts of Britain which afford so many 
opportunities for the study of these subjects as do the hills and 
rocks of this neighbourhood. 
The following’ extracts concerning the geology of Cader 
Idris will convey to the reader some idea of the varied 
character of the strata in this district : — 
“ Geology. — It consists of silieious porphyry, quartz, and schorl, and is 
surrounded by slaty hills. Evidences of the volcanic character of the moun- 
tain are abundant. Numerous specimens of lava, pumice, and other volcanic 
products, have been discovered on the sides and base of the mountain. 
Columnar crystals of basalt are scattered in profusion about the summit and 
on some of the inferior cliffs, and particularly on one side, there are vast 
beds of porous stone, bearing evident marks of strong ignition and vitri- 
fication — some reduced to the state of slag, and others having the cellular 
appearance and lightness of pumice .” — Blacks Guide , p. 121. 
“ The slope of Cader, on the Talyllyn side, above Llynycae, is an igneous 
rock, principally composed of amygdaloidal green-stone, and under aro 
masses of felspathic trap and long lines of green-stone, interbedded with 
altered slate, forming the steep north cliff of the mountain, and overlooking 
the high valley between the cliff and Llynygader, which itself is formed 
almost entirely of felspathic ash and conglomerate, with interbedded lines 
of green-stone — the whole dipping under the igneous rocks of the cliffs. 
Lingular flags underlie these.” — Ramsay. 
* For the guidance of conchologists visiting this interesting locality, we 
may add that Mochres may be approached from two points, namely, from 
Llanduwe, a church and inn, situated rather over four miles on the road from 
Barmouth to Harlech, or from Llanbedr, a considerable village, three or four 
miles nearer to Harlech, on the same road. Although a little may be saved 
in the distance, by approaching it from the first-named place, yet, on account of 
the tedious walk across a dreary moor which must be traversed, as well as the 
difficulty sometimes experienced in crossing to Mochres from the mainland 
by this route, we strongly recommend the tourist to proceed along the 
beautiful coast-road to the village last-named (Llanbedr), which is close to 
the peninsula, and from which he may reach the shell-covered beach in a 
few minutes without any difficulty. 
