Manod and the Moelwyns

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Abstract
On the north and west of the great mass of Harlech Grit which forms the centre of the Merioneth anticlinal, the Lingula and Tremadoc strata dip under the mountains of the Moelwyns and Manods, and are there overlain hy the Arenig ashes and slates. The beds exposed on the southern slopes of these mountains have therefore the same general stratigraphical age as those cropping out on the northern slopes of Cader Idris and on the western aspect of Arenig and the Arans. The general relations of the rock-masses of this difficult district have been admirably elucidated by the officers of the Geological Survey, and the results of their work published in Sir A. Kamsay's invaluable memoir on the Geology of North Wales. In the present paper, which is the result of observations carried on interruptedly for several years, our objects are :— To offer conclusive evidence as to the intrusive nature of the great crystalline mass known as the Syenite of Tan-y-grisiau. To correct what seems to us an inaccuracy of some importance in the correlation of beds in different parts of the range, as interpreted in the map and memoir of the Geological Survey. To trace with greater completeness the position and constancy of the beds of slate in the Arenig series ; a subject of considerable local and practical importance, when we remember that those who are engaged in slate-quarrying have so far had to rely mainly on their personal and unaided observation. In order to make the

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