INORGANIC GEOLOGICAL DYNAMICS. 54:3 



heavenly motions : they could not advance in the study of the 

 Mechanics of the heavens, till they had learned the Mechanics of ter- 

 restrial bodies. And thus they were, in such speculations, at a stand 

 for nearly a century, from the time of Kepler to the time of Newton, 

 while the science of Mechanics was formed by Galileo and his succes- 

 sors. Till that task was executed, all the attempts to assign the causes 

 of cosmical phenomena were fanciful guesses and vague assertions ; 

 after that was done, they became demonstrations. The science of 

 Dynamics enabled philosophers to pass securely and completely from 

 Phenomenal Astronomy to Physical Astronomy. 



In like manner, in order that we may advance from Phenomenal 

 Geology to Physical Geology, we need a science of Geological Dyna- 

 mics ; that is, a science which shall investigate and determine the 

 laws and consequences of the known causes of changes such as those 

 which Geology considers : and which shall do this, not in an occa- 

 sional, imperfect, and unconnected manner, but by systematic, com- 

 plete, and conclusive methods ; shall, in short, be a Science, and not 

 a promiscuous assemblage of desultory essays. 



The necessity of such a study, as a distinct branch, of geology, is 

 perhaps hardly yet formally recognized, although the researches which 

 belong to it have, of late years, assumed a much more methodical and 

 scientific character than they before possessed. Mr. Lyell's work 

 (Principles of Geology], in particular, has eminently contributed to 

 place Geological Dynamics in its proper prominent position. Of the 

 four books of his Treatise, the second and third are upon this di- 

 vision of the subject; the second book treating of aqueous and 

 igneous causes of change, and the third, of changes in the organic 

 world. 



There is no difficulty in separating this auxiliary geological science 

 from theoretical Geology itself, in which we apply our principles to 

 the explanation of the actual facts of the earth's surface. The former, 

 if perfected, would be a demonstrative science dealing with general 

 cases; the latter is an setiological view having reference to special 

 facts ; the one attempts to determine what always must be under 

 given conditions ; the other is satisfied with knowing what is and has 

 been, and why it has been ; the first study has a strong resemblance 

 to Mechanics, the other to philosophical Archaeology. 



Since this portion of science is still so new, it is scarcely possible to 

 H'ive any historical account of its progress, or any complete survey of 

 its shape and component parts. I can only attempt a few notices ; 



