Keywords: The Quarterly journal of the Geological Society of London (13205989604).jpg S6 <br> PROCEEDINGS OF THE GEOLOGICAL SOCIETY DcC 2 <br> any pressure arising within this bed On the upper side of the slab <br> a specimen of Spirifer disjunctus C E D has been tiattened by an ob- <br> lique pressure moving from B towards A On the lower side are two <br> Fig 15 <br> A <br> K <br> r/ <br> - <br> Ni ' <br> TT <br> <br> - <br> <br> <br> B <br> r <br> ˘ <br> ir <br> <br> <br> jr- <br> ~ r <br> lo <br> <br> r <br> - <br> - <br> r <br> a <br> ~- <br> - <br> <br> r <br> -4 <br> specimens of Orthis resvpinatus C F D pressed in a contrary direction <br> or from a towards b But in both cases the pressure is such as would <br> be produced by an expansion of the mass in the direction of the dip <br> of the cleavage Y Y Such an expansion would produce a pressure <br> on each surface equivalent to a force moving from the centre of the <br> bed in the direction of the lines Y Y It is here obvious that <br> there can be no difference in the distortion of the specimens which <br> come from the upper or the under side of a bed ; and it is impossible <br> to distinguish them The same proof of the expansion of the mass <br> along the planes of cleavage may be found in beds of every thick- <br> ness A bed of slate from Tintagel not the third of an inch thick <br> exhibits exactly the same phaenomena <br> The comparison of the two sides of the thin beds of shells which <br> separate the slate beds gives the same result the shells are pressed <br> in what appear opposite directions but which are in each case the <br> directions of a force pressing from the centre of the mass towards <br> each surface along the oblique planes of cleavage Fig 16 shows <br> Fig 16 <br> the section of two slabs of slate enclosing a thin bed full of shells of <br> the Spirifer giganteus from Tintagel one side of each shell is seen <br> in relief on the surface of the slabs the other being hid part of the <br> central bed has dropped away leaving a hollow space A B ah <br> represent the surface of the beds and Y Y the cleavage planes The <br> two surfaces are covered with shells C D of which those on the <br> upper surface are all pressed from B towards A and on the lower 36932815 113687 51125 Page 86 Text v 3 http //www biodiversitylibrary org/page/36932815 1847 Geological Society of London NameFound Orthis NameConfirmed Orthis EOLID 4333134 NameBankID 4270859 NameFound Spirifer disjunctus NameConfirmed Spirifer disjunctus NameFound Spirifer giganteus NameConfirmed Spirifer Martinia giganteus Caneva 1907 Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 3 1847 Geology Periodicals Smithsonian Libraries bhl page 36932815 dc identifier http //biodiversitylibrary org/page/36932815 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-17 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13205989604 2015-08-26 12 55 15 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1847 Photos uploaded from Flickr by FĂŚ using a script |