Vol. 58. | THE JASPERS OF SOUTH-EASTERN ANGLESEY. 495 
26. The Orteain and Assoctations of the JasPERS of SOUTH-EASTERN 
Aneesey. By Epwarp Grernty, Esq., F.G.S. (Read 
April 30th, 1902.) 
[Puarses XV & XVI.| 
ConrENTS. 
Page 
1 Gayla ilu 10a est BOE eect oes ARAREA Aone ae ache nen. a aan SuScargucccor a 220 
ies Meseni pion’ of Ghe ROCKS ea. ose teak solek censored. teeters orclecied vals 8 oe 425 
Hr Relations and Origin of the Jaspers\ J.0.2. 0. censsestenen 431 
PVe Neoiand) Nxternal Relations: ...s00.<...c0twesesese 40s rt Ae A 7 433 
UPS eOMNMM ys Beerge ci ieee si cis oa etis oe GioleeE) cremie imate ct smiles ar eeiee'e 436 
I. IyrRopvucrion, 
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. Iam 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, as to be in itself, I think, interesting to 
geologists who are investigating questions of metamorphism. 
II, Descrirerion oF THE Rocks. 
The principal associates of the jaspers are certain basic igneous 
rocks, limestones, and grits, the most important being the igneous 
rocks. Some fine shaly material, called elsewhere jaspery phy llite, 
will be described along with the Jaspers. 
Besides these, there are large quantities of a breccia which appears 
to be cataclastic, and also of various schistose rocks, the masses 
which retain original characters occupying comparatively small 
parts of the areas described, except in the Newborough district. 
