File:The Quarterly journal of the Geological Society of London (1891) (14781304972).jpg

Identifier: quarterlyjournal47189geol (find matches)
Title: The Quarterly journal of the Geological Society of London
Year: 1845 (1840s)
Authors: Geological Society of London
Subjects: Geology
Publisher: London (etc.)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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f of their origin even under the microscope. Therock of Bowdlers Chair appears, in part at least, to be an unques-tionable rhyolite-tuff, and as the adjacent felsites seem closely toresemble those of Caradoc, it may, I think, be assumed that theCaradoc and Hope Eowdler masses form part and parcel of onegreat series of lavas and tuffs, which, judging from their thickness,must once have been continuous over a wide area. Eefore attempting to examine these rocks, I was aware thatProf. Blake * and Dr. Callaway t had alluded to the presence ofrhyolites among them, but since their writings contained no de-tailed description which afforded evidence that these rocks weretrue rhyolites, further investigation seemed desirable. In the * On the Monian and Basal Cambrian Eocks of Shropshire, Quart. Journ.Geol. Soc. \o\. xlvi. (1890) p. 386. t On the Unconformities between the Keck Systems underlying the Cam-brian Quartzite in Shropshire, p. 1*20 of this volume. Quart.Journ.Geol.Soc.Vol.XLVn.Fl.lIK.
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X 45 . / /a Frank Rubiey del F.HMcKa-el lith 1,2,3,4,8,7. MEi^PHYRES OF CARADOC HILL . 6 PERLITIC FELSITE ABOVE CARADOC COPPICE Mirit-ern. Bros iwvp MELAPHTRES AND FEL8ITES OF CARADOC. 543 foregoing paper I have, therefore, endeavoured to supply some ofthe proof which seemed, hitherto, to be wanting. VI. SurrLEMENTARY NOTR. When this paper was read I was not aware that Prof. Lapworthhad been devoting his attention to the eruptive rocks of Caradocand its neighbourhood. In the discussion which followed, SirArchibald Gcikic alluded to the detailed map which Prof. Lapworthhad constructed and of the existence of which I was unfortu-nately ignorant. On writing to Prof. Lapworth he most generously gave me a largeamount of valuable information relating to his work and forwardedhis unpublished map to mo for inspection. The latter is, unques-tionably, a very careful and detailed piece of surveying : a mapwhich, when published, will be the most important exponent of thegeology of this district w

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