BakeWeU's Introduction to Geology, 3.59 



taining the remains of an herbivorous animal of the lizard 

 family, seventy feet in length. Our limits will not permit us 

 to dwell on chapter 13., which describes the Chalk Formation. 

 Chapter 14., On the Tertiary Formations, above the chalk 

 strata, is new. The existence and extent of the tertiary strata, 

 in Europe, were, till recently, imperfectly known. It is in 

 these strata that we first meet with the bones of large mam- 

 miferous quadrupeds, which belong to genera or species no 

 longer existing on the globe. In these strata we also find 

 the alternation of the remains of marine animals with beds 

 that contain exclusively the remains of land and fresh-water 

 animals, which indicate that a great portion of Europe has 

 alternately been covered by the sea, and by fresh-water lakes. 

 In England the tertiary formations are imperfectly deve- 

 loped; the extent which they cover, in this country, is 

 marked on the geological map that accompanies the present 

 volume ; under the map there is a small section of the vale of 

 Thames, which shows the arrangement of the tertiary beds, 

 over the chalk, in the vicinity of London. 



Chapters 1 5, 16., On Volcanoes and Volcanic Rocks; and on 

 the agency of subterranean fire in the formation of rocks and 

 strata. In these chapters we have a succinct account of volcanic 

 phenomena, and a comparison between ancient and recent 

 volcanoes. In a former state of our planet (Mr. Bakewell 

 observes) the internal fire must have been more intense than 

 since the records of authentic history ; this is shown by the 

 remains of ancient craters, which far exceed the magnitude 

 of any that are active at the present time ; and the craters 

 being formed by the eruption of volcanic matter, their size 

 bears evidence of the magnitude of their former operations. 

 The enormous craters, many leagues in extent, had, doubt- 

 less, an important office to perform in nature ; and it cannot, 

 our author observes, be unreasonable to infer that the earth 

 is the great laboratory, where the materials were prepared 

 that form its surface, and were thrown out either as melted 

 lava, or in aqueous solution, or in a gaseous state, &c. 

 Siliceous earth is found in hot springs ; and hence, he says, we 

 may infer that many siliceous rocks and veins were depo- 

 sited by subterranean waters at a high temperature. This 

 opinion, which was advanced by Mr. Bakewell in his second 

 edition in 1815, has recently been adopted by that eminent 

 geologist, M. A. Brongniart. The following chapters. On 

 Metallic Beds and Veins, and On Diluvial and Alluvial Depo- 

 sitions ; and chapter 19., On the Formation of Valleys, and on 

 Deluges and Denudations, are replete with interesting matter, 



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