class="tdr">183

CHAPTER XVIII. The Carboniferous system 192 CHAPTER XIX. The changes which occurred during the third continental period in Britain; and the foreign Permo-Carboniferous rocks 202 CHAPTER XX. The Permian system 209 CHAPTER XXI. The Triassic system 218 CHAPTER XXII. The Jurassic system 226 CHAPTER XXIII. The Cretaceous system 236 CHAPTER XXIV. The Eocene rocks 244 CHAPTER XXV. The Oligocene and Miocene periods 251 CHAPTER XXVI. The Pliocene beds 256 CHAPTER XXVII. The Pleistocene accumulations 260 CHAPTER XXVIII. The Steppe period 267 CHAPTER XXIX. The Forest period 275 CHAPTER XXX. Remarks on various questions 278

ADDENDA ET CORRIGENDA.

p. 38, line 15 from bottom: for 'joining' read 'jointing'

p. 208, line 6 from bottom: for 'Dr' read 'Messrs Medlicott and'

p. 214, line 15 from bottom: after 'Permo-Carboniferous Strata' insert 'through the Permian'

p. 217, last line of footnote: for 'Dr' read 'Messrs Medlicott and'

p. 217, insert a second footnote: 'For information concerning the Permian volcanic rocks see Sir A. Geikie's Ancient Volcanoes of Great Britain.'

p. 235, insert a footnote: 'A good account of the British Jurassic rocks will be found in Mr H. B. Woodward's Memoir on "The Jurassic Rocks of Britain." Mem. Geol. Survey, 1893—.'

p. 250, top line: for 'Gardiner' read 'Gardner'

[Trancriber's Note: Above corrections were made to the text.]

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CHAPTER I.

INTRODUCTION.

It is the aim of the Stratigraphical Geologist to record the events which have occurred during the existence of the earth in the order in which they have taken place. He tries to restore the physical geography of each period of the past, and in this way to write a connected history of the earth. His methods are in a general way similar to those of the ethnologist, the archæologist, and the historian, and he is confronted with difficulties resembling those which attend the researches of the students of human history. Foremost amongst these difficulties is that due to the imperfection of the geological record, but similar difficulty is felt by those who pursue the study of other uncertain sciences, and whilst this imperfection is very patent to the geologist, it is perhaps unduly exaggerated by those who have only a general knowledge of the principles and aims of geology.

The history of the earth, like other histories, is a connected one, in which one period is linked on to the next. This was not always supposed to be the case; the catastrophic geologist of bygone times believed that after each great geological period a convulsion of nature left the earth's crust as a tabula rasa on which a new set of records was engraved, having no connexion with those which had been destroyed. Careful study of the records of the rocks has proved that the conclusions of the catastrophists were erroneous, and that the events of one period produce their impression upon the history of the next. Every event which occurs, however