MODE III. BASALTItf. 5 



them, varied transitions between these different 

 kinds. 



" I think besides that, in the nomenclature of 

 mineralogy, it must be regarded as a principle, to 

 determine the kinds and species, from individuals 

 whose characters are the most striking ; and to 

 mark the transitions of doubtful and ill-defined 

 substances: for the principle established in bo- 

 tany, of considering as belonging to the same 

 species, individuals between which we observe 

 intermediate shades, cannot be admitted in mi- 

 neralogy, without reducing all known fossils to 

 one and a single species. Indeed there is none 

 that may not be departed from, to make the tour 

 of the whole chain of those which have already 

 been determined, by almost insensible shades; 

 and the more we shall study mineralogy, the 

 more this truth will become obvious, by the 

 number of varieties and shades that we shall 

 discover. 



" I therefore say, that when two fossils pre- 

 sent remarkable differences, we must not refrain 

 from distinguishing them, and giving them dif- 

 ferent names, under the pretext that we have 

 found intermediate varieties which seem to con- 

 nect them, by appearing to belong equally to 

 the one and the other; without which, I repeat, 

 that we shall no longer distinguish genera nor 



D 2 



