"MANUAL OF GEOLOGY" 



tracting, cooling globe. Others had spoken of geology 

 as a history; but he appears to have been the first to 

 write a manual of geology in English based on this idea. 

 ' In history,' he commented, ' the phases of every age are 

 deeply rooted in the preceding, and intimately dependent 

 on the whole past. There is a literal unfolding of events 

 as time moves on, and this is eminently true of geology/ 

 Hence he began his geology with the beginnings, and 

 followed the course of the history of the earth onward. 



" Again, to Dana the means of measuring the sequence 

 of events was the succession of fossils. ' Geology is not 

 simply the science of rocks, for rocks are but incidents in 

 the earth's history, and may or may not have been the 

 same in distant places. It has its more exalted end, 

 even the study of the progress of life from its earliest 

 dawn to the appearance of man ; and instead of saying 

 that fossils are of use to determine rocks, we should 

 rather say that the rocks are of use for the display of the 

 succession of fossils. Both statements are correct; but 

 the latter is the fundamental truth in the science.' It 

 was this idea which dominated in his classification of 

 geological formations. 



" American geologists are all aware that it is from the 

 use of Dana's system that the habit of speaking of geo- 

 logical Periods and Epochs has been acquired. Other 

 manuals speak of formations, systems, and stages, of 

 series and groups ; rocks being classified as if they were 

 distinguished by some qualities of their own. It is from 

 Dana that we have learned to classify geological forma- 

 tions in relation to the stages of progress in the building 

 of the continents and its local structural features, and to 

 regard rocks as not simply aggregates of mineral matter, 

 but as geological formations bearing a definite relation- 

 ship to the progress in the history of the earth, and hence 

 as belonging to, and to be defined as of a particular period 

 or epoch. In the first edition of his Manual, in 1862, the 

 author wrote : 



' It has been the author's aim to present for study, not 

 a series of rocks with their dead fossils, but the successive 

 phases in the history of the earth, its continents, seas, 

 climates, life, and the various operations of progress.' * 



* Manual of Geology : treating of the principles of the science with spe- 



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