Rocky Mountains. 429 



evident as all these crystalline rocks abound in organic re- 

 mains. 



In attempting an explanation of these appearances, can any 

 aid be derived from recourse to the suggestion that the mat- 

 ter of these crystalline beds and strata has been ejected from 

 beneath the crust of the earth in a state of chemical solution?-^- 

 These submarine eruptions may have been numerous, and 

 may have happened at different, and remote jjeriods; hence 

 the occurrence of rocks consisting of particles mechanically 

 aggregated, in alternation with those of chemical deposition. 

 Hence the existence of metallic ores overlying recent marine 

 sandstones and compact limestones, for these ores in a state 

 of solution, may have been thrown out in some of the latest 

 eruptions. 



This supposiuon mav derive some confirmation from the 

 well known fact that this region is still in a remarkable de- 

 gree, subject to subterranean concussions and earthquakes. 



Though this group of mountains has probably a nucleus of 

 primitive rocks running through its whole extent, yet these ap- 

 pear but rarely at the surface. We have seen such only in the 

 places already mentioned, and have been informed of others 

 in Washington county, near the sources of the St. Francis, 

 and about Lake Superior.f 



From the information we have been able to collect, we are 

 induced to believe that secondary rocks occupy the countrv 

 on both sides of Red river, from its sources to its confluence 

 with the Mississippi. If this be the case the primitive of the 

 Ozark Mountains, must be considered a small and insulated 

 mass. 



The inequalities of surface in this great secondary forma- 

 tion, are considerable. It has often been called the " basin 

 of the Mississippi," but with no great propriety, since it 

 might with perhaps equal accuracy be called the basin of the 

 St. Lawrence, the Saskatchawin, or Mackenzie's river. The 

 form of that part of it which contains the Mississippi river, 

 is, however, similar to that designated by geologists, a basin 

 shaped cavity. As far as our acquaintance extends, it is 

 bounded on all sides by a surface of greater elevation than 

 itself, but whether this surface is not sometimes secondary, 

 is doubtful. It is hazardous to infer the existence at a former 

 period, of an insulated inland sea, from any formation of se- 

 condary rocks, without being acquainted with its whole ex- 



* Bakewell. f Schoolcraft. 



