The Quarterly journal of the Geological Society of London (1898) (14592629319)

Identifier: quarterlyjourna541898geol (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

Text Appearing Before Image:

formsthat flank of Tinkers Hill, is the vesicular rock which I hadthe pleasure of pointing out to Prof. Green.^ My (sections 112 a& 283) show that the rock is vesicular and amygdaloidal. I cannotagree that this is a similar rock to the rock of Clutters Cave,though it is with great diffidence that I venture to differ from sohigh an authority as the late Prof. Green. My sections of theClutters Cave rock (7 a, 155, 160, 161 & 164) show much moreaugite, one of them (164) being quite a mosaic of that mineral,whereas the Tinkers Hill rock (291 a) has much more the appeaf-ance of an andesite than a basalt. My section 283 shows anextremely curious structure. It is very similar to another (180)which comes from a crag much farther south, but almost exactlyon the same strike. In both sections are oval and circular ringsof some isotropic mineral: inside the rings is chalcedony. The ^ Quart. Journ. Geol. Soc. vol. li (1895) p. 5.2 Op. cit. p. 4. Q. J. G. S. No. 215. 2 q ft^ tilo bo • i-H

Text Appearing After Image:

Vol. 54.) A VOLCANIC SERIES IN THE MALVERN HILLS. 561 origin of these rings appears to be very obscure, but it seems to methat they must arise from an originally vesicular structure in therock. If this be so, as they occur in an isotropic mineral on theedge of an andesitic mass, it would show that this may have beenthe original surface. Eastward of this is a narrow bed of felsite about 10 feet wide(292). ISText, a bed of andesite (293) 54 feet wide: this, in oneplace, has a most distinct dip of 45° to the west. My slide shows agood deal of decomposed felspar and of a dichroic mineral, probablyan altered augite. Then again comes abed of felsite (295), followed by andesite(296), and felsite again (297). In the last-mentioned slide isa curious doubled-up thread which polarizes yellow. The bedsalternate until no more exposures are visible. There is a small cragof brecciated dolerite close to the eastern boundary. Thiscorresponds apparently to the rock on the south-east of HangmansHill to

the quarterly journal of the geological society of london 1898 vesicular rocks book illustrations natural history geology high resolution images from internet archive united kingdom

1898

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