INORGANIC GEOLOGICAL DYNAMICS. 603 



Although the study of the common operations of 

 water may give the geologist such an acquaintance 

 with the laws of his subject as may much aid his 

 judgment respecting the extent to which such effects 

 may proceed, a long course of observation and 

 thought must be requisite before such operations 

 can be analyzed into their fundamental principles, 

 and become the subjects of calculation, or of rigor- 

 ous reasoning in any manner which is as precise 

 and certain as calculation. Various portions of 

 hydraulics have an important bearing upon these 

 subjects, including some researches which have been 

 pursued with no small labour by engineers and 

 mathematicians; as the effects of currents and 

 waves, the laws of tides and of rivers, and many 

 similar problems. In truth, however, such subjects 

 have not hitherto been treated by mathematicians 

 with much success; and probably several genera- 

 tions must elapse before this portion of geological 

 dynamics can become an exact science. 



Sect. 3. Igneous Causes of Change. Motions of 

 the Earth's Surface. 



THE effects of volcanoes have long been noted as 

 important and striking features in the physical his- 

 tory of our globe ; and the probability of their con- 

 nexion with many geological phenomena, had not 

 escaped notice at an early period. But it was not 

 till more recent times, that the full import of 



