86 



Under these several views the preceding cata- 

 logue was drawn up. But some preliminary ob- 

 servations respecting the adopted succession of 

 the families, or general titles, are necessary, to 

 prevent it from being imagined that this is the 

 order in which the several rocks actually occur in 

 nature. The minuter details requisite to illus- 

 trate this and many previous statements, must be 

 sought in systems of geology, if indeed they are 

 there to be found ; the most general sketch alone 

 must here be sufficient. 



With respect to the order of succession in the 

 primary class, the claim of granite to the first or 

 lowest place is unquestioned ; and has already 

 been discussed ; as has the unsteady and variable 

 position of serpentine ; but after the former, no 

 further certainty can be obtained as to the next 

 rock, or the first of the strata ; since they are all 

 occasionally found in contact with it. That place 

 has here been given to gneiss, chiefly because it 

 has been the custom so to do. 



The relative order among the stratified rocks 

 themselves is also inconstant ; but it is not impro- 



