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Published online by Cambridge University Press: 01 May 2009
Since the date of my communication to the Geological Society on the sections at and in the neighbourhood of Twt Hill, I have more than once visited the district, and have spent much time in working over the specimens which I have collected. The exact relation of these conglomerates to the granitoid rock on which they rest is a matter of great importance as bearing on theoretical questions relating to metamorphic changes in stratified rocks— questions at which for the last three or four years I have lost no opportunity of working. I should therefore, in all probability, have recurred to the subject, even if my attention had not been directed to it by my friend Dr. Roberts' communication and criticism of the above paper. In the latter, it may be remembered that we assigned the Twt Hill conglomerate to the granitoid series.
page 18 note 1 Written conjointly with Mr. Houghton, , Quart. Journ. Geol. Soc. vol. xxxv. p. 321.Google Scholar
page 18 note 2 See GEOL. MAG. Vol. VIII. Dec. II.
page 19 note 1 I have admitted this point, of which I was at first doubtful. See this MAGAZINE, VII. Dec. II. p. 300.
page 21 note 3 Further examination of specimens makes me doubtful if this is more than an accident owing to the state of the rocks; for I find some rotten fragments which may be felsite. Hence the section at Tan-y-maes (figured on p. 301, of Vol. VII. of this MAGAZINE) does not bear out the conclusion which from it seems more probable. I may also mention that I find from further examination that all the rock exposed in the bank under the cottage gardens is a spherulitic felsite.
page 21 note 2 Quart. Journ. Geol. Soc. vol. xxxv. p. 309.
page 21 note 3 Dec. II. Vol. VII. p. 298.
page 21 note 4 It will be prudent not to accept the “Drug beds” as an upper subdivision of the “Carnarvon series” till they have been further examined. Perhaps it may be found that the felsite has been at some of its old tricks in this district also.
