DOMAIN VII. COMPOSITE. 



that it is theoretic, and constructed upon 

 geological ideas of the antiquity and forma- 

 tions of the several rocks ; which the suc- 

 cessive and general observations of future 

 ages may perhaps demonstrate to be only 

 local, or erroneous ; and which, even at 

 present, are very far from being univer- 

 sally admitted. Nay, if they proved to 

 be infallible, or uncontrovertible by any 

 future facts or arguments, still the plan of 

 arrangement would be improper for a truly 

 scientific work, the same substances being 

 repeated as primitive, transitive, and se- 

 condary, nay, sometimes of independent 

 formations; while, in any science, all that 

 is required is the knowledge of the object 

 collected into one strong point of view. 

 The denominations are also, as in the in- 

 stance of porphyries, so lax and vague, that 

 the very base and nature of the substance 

 are confounded, and no accurate know- 

 ledge can arise. In any science, on the 

 contrary, it is necessary that the objects 

 be classed, and most precisely defined, be- 

 fore even a plausible system can be con- 



B 2 



