7 Freestone | Great Oolite Rock | 20 Upper Oolite 8 Blue Clay }| | 9 Yellow Clay }| | 10 Fuller's Earth }| | 21 Fuller's Earth and }| | Rock 11 Bastard ditto }| | and Sundries }| | 12 Freestone | Under Oolite | 22 Under Oolite 13 Sand | | 23 Sand | | 24 Marlstone 14 Marl Blue | Blue Marl | 25 Blue Marl 15 Blue Lias | Blue Lias | 26 Blue Lias 16 White Lias | White Lias | 27 White Lias 17 Marlstone, Indigo| | and Black Marls | | 18 Red Ground | Red Marl and Gypsum | 28 Red Marl 19 Millstone | Magnesian Limestone | 29 Redland Limestone | Soft Sandstone | 20 Pennant Street }| | 21 Grays }| Coal Districts | 30 Coal Measures 22 Cliff }| | 23 Coal }| | | Derbyshire Limestone | 31 Mountain Limestone | Red and Dunstone | 32 Red Rhab and Dunstone | Killas or Slate | 33 Killas | Granite, Sienite and | 34 Granite, Sienite and | Gneiss | Gneiss --------------------+-------------------------+-------------------------- The above table contains a very complete classification of the British Mesozoic rocks, one of the Tertiary strata which is less complete, and a preliminary division of the Palæozoic rocks into Permian (Redland Limestone), Carboniferous (Coal Measures and Mountain Limestone), Devonian (Red Rhab and Dunstone) and Lower Palæozoic (Killas). Since Smith's time the main work which has been done in classification is a fuller elucidation of the sequence of the Tertiary and Palæozoic Rocks, and this we may now consider. The Mesozoic rocks are developed in Britain under circumstances which render the application of the test of superposition comparatively simple, for the various subdivisions crop out on the surface over long distances, and the stratification is not greatly disturbed. With the Tertiary and Palæozoic Rocks it is otherwise, for some members of the former are found in isolated patches, whilst the latter have usually been much disturbed after their formation.