THE COMPILATION OF EARTH HISTORY 5 



Observational geology versus speculative philosophy. There 

 appears to be a more or less prevalent notion that the views which 

 are held by scientists in one generation are abandoned by those 

 of the next ; and this is apt to lead to the belief that little is really 

 known and that much is largely guessed. Some ground there 

 undoubtedly is for such skepticism, though much of it may be 

 accounted for by a general failure among scientists, as well as 

 others, to clearly differentiate that which is essentially speculative 

 from what is based broadly upon observed facts. Even with 

 extended observation, the possibility of explaining the facts in 

 more than one way is not excluded ; but the line is nevertheless 

 a broad one which separates this entire field of observation from 

 what is essentially speculative philosophy. To illustrate : the 

 mechanics of the action which goes on within volcanic craters is 

 now fairly well understood as a result of many and extended 

 observations, and it is little likely that future generations of 

 geologists will discredit the main conclusions which have been 

 reached. The cause of the rise of the lava to the earth's surface 

 is, on the other hand, much less clearly demonstrated, and the 

 views which are held express rather the differing opinions than 

 any clear deductions from observation. Again, and similarly, the 

 physical history of the great continental glaciers of the so-called 

 " ice age " is far more thoroughly known than that of any existing 

 glacier of the same type; but the cause of the climatic changes 

 which brought on the glaciation is still largely a matter for specu- 

 lation. 



In the present work, the attempt will be, so far as possible, to 

 give an exposition of geologic processes and the earth features 

 which result from them, with hints only at those ultimate causes 

 which lie hidden in the background. 



The scientific attitude and temper. The student of science 

 should make it his aim, not only clearly to separate in his studies 

 the proximate from the ultimate causes of observed phenomena, 

 but he should keep his mind always open for reaching individual 

 conclusions. No doctrines should be accepted finally upon faith 

 merely, but subject rather to his own reasoning processes. This 

 should not be interpreted to mean that concerning matters of 

 which he knows little or nothing he should not pay respect to the 

 recognized authorities; but his acceptance of any theory should 



