The Origin and Associations of the Jaspers of South-eastern Anglesey

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Abstract
I. Introduction. One of the most singular and striking rocks in that region of Anglesey which lies to the south-east of the principal mass of Carboniferous rocks, is a bright red jasper. Though never in masses of large size, it is widely distributed, occurring in three distinct areas, which may be called the Newborough, the Pentraeth, and the Beaumaris areas. The character, mode of occurrence, and associations of this jasper throw much light on its origin; they are so remarkable, and present such singular analogies with those of groups of rocks which have lately been described in different parts of the world, as to be, I think, matter of general interest, as well as important to workers among the older rocks of Britain. The object, therefore, of this paper is to describe the rocks and their relations in the districts where they have escaped the effects of the movements that have modified most of the region. Their geological age, and, in particular, their relations to the crystalline schists of the region, cannot, in my opinion, be regarded as settled, some of the evidence being conflicting. But as questions of the greatest interest regarding metamorphism are involved, I propose, in the fourth part of this paper, to set forth this evidence as briefly as is consistent with clearness. I am the less unwilling to do so, because the problem is so closely allied in its nature to those that are still under discussion at the margins of several other metamorphic areas

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