Permian. { ------------------- + | | { | | | (1) _Bakewellia._ { | | | (2) _Productus._ { | I | I | (3) _Palæoniscus._ { + | +------------------------ { 11. DEVONIAN | L | L | 10. CARBONIFEROUS. { | | | { | L | L | (1) _Goniatites._ { | | | (2) _Lepidodendron._ { | L | I | (3) _Calamites._ { ------------------- + | +------------------------ P { | U | U | 11. DEVONIAN. R { | | | I { | S | S | _Pterichthys._ M -{ | | +------------------------ A { 12. SILURIAN | T | T | 12. SILURIAN. R { | | | Y { | R | R | (1) _Strophomena._ { | | | (2) _Lingula._ { | A | A | (3) _Pentamerus._ { | | | (4) _Calymene._ { ------------------- + T | T +------------------------ { | | | 13. CAMBRIAN. { | I | I | { 13. CAMBRIAN | | | _Oldhamia._ { | O | O +------------------------ { ------------------- + | | 14. LAURENTIAN. { 14. LAURENTIAN | N | N | { | | | _Eozoon._ --------------------+--------+--------+------------------------ Had the levelling power of water never met with an antagonistic force, there can be no doubt that the last remains of the dry land, supposing it could ever have risen above the ocean, must long since have been swept into the sea. But while water has been constantly tending to reduce the irregularities of the earth’s surface to one dull level, the expansive force of subterranean heat has been no less unceasingly active in restoring the unevenness of the external crust by the ejection or protrusion of new masses of stone (porphyry, trachyte, basalt, lava, &c.), and by the consequent disturbance, in a variety of ways, of the stratified rocks. [Illustration: AQUEOUS STRATA DISTURBED BY IGNEOUS FORMATIONS. B C D, aqueous strata, originally horizontal, raised by protrusion of A, granitic rock. ]