Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. I have confined myself mostly, though not entirely, to American geology, especially in giving the distribution of the rocks and the physical geography of the different periods. In only one case have I made American geology subordinate, viz., in the J ura-trias period, and that only because of the meagerness of the record of this period in this country.