THE PAL^TIoLOGICAL SCIENCES. SOS 



conducted us to the boundaries of physical science, and gives us a 

 glimpse of the region beyond. In following the history of Life, we 

 found ourselves led to notice the perceptive and active faculties of 

 man ; it appeared that there was a ready passage from physiology to 

 psychology, from physics to metaphysics. In the class of sciences 

 now under notice, we are, at a different point, carried from the world 

 of matter to the world of thought and feeling, from things to men. 

 For, as we have already said, the science of the causes of change in- 

 cludes the productions of Man as well as of Nature. The history of 

 the earth, and the history of the earth's inhabitants, as collected from 

 phenomena, are governed by the same principles. Thus the portions 

 of knowledge which seek to travel back towards the origin, whether 

 of inert things or of the works of man, resemble each other. Both of 

 them treat of events as connected by the thread of time and causation. 

 In both we endeavor to learn accurately what the present is, and hence 

 what the past has been. Both are historical sciences in the same sense. 



It must be recollected that I am now speaking of history as setiolo- 

 gical ; as it investigates causes, and as it does this in a scientific, that 

 is, in a rigorous and systematic, manner. And I may observe here, 

 though I cannot now dwell on the subject, that all oetiological 

 sciences will consist of three portions ; the Description of the facts and 

 phenomena ; the general Theory of the causes of change appropriate 

 to the case ; and the Application of the theory to the facts. Thus, 

 taking Geology for our example, we must have, first Descriptive or 

 Phenomenal Geology ; next, the exposition of the general principles 

 by which such phenomena can be produced, which we may term 

 Geological Dynamics ; and, lastly, doctrines hence derived, as to what 

 have been the causes of the existing state of things, which we may call 

 Physical Geology. 



These three branches of geology may be found frequently or con- 

 stantly combined in the works of writers on the subject, and it may 

 not always be easy to discriminate exactly what belongs to each 

 subject. 4 But the analogy of this science with others, its present 



4 The "Wernerians, in distinguishing their study from Geology, and desig- 

 nating it as Geognosy, the knowledge of the earth, appear to have intended to 

 select Descriptive Geology for their peculiar field. In like manner, th 

 original aim of the Geological Society of London, which was formed (1807) 

 " with a view to record and multiply observations," recognized the possibility 

 of a Descriptive Geology separate from the other portions of the science. 



