VI PREFACE. 



avowal of our scientific friends, that we have in this 

 particular exceeded their expectations. 



A prospectus of this work, so new in its nature, and 

 necessarily capable of many improvements as it goes on, 

 seemed to us better omitted. We had rather perform 

 more instead of less than might have been promised. 



Of the many systems proposed by the learned, not 

 one has been fully established. We have presumed 

 to form one in a general way, for the present pur- 

 pose of arranging the plates and letter-press, feeling 

 the greater confidence in the chance of its permanence, 

 as we have endeavoured to make it conformable to 

 nature. We have made combustible genera, among 

 which are included Calor or matter of heat, the dif- 

 ferent Airs, Alkalies and their compounds, as ne- 

 cessary to be known to every mineralogist, although 

 some are perhaps not strictly minerals. These, 

 with the Earths and Metals, make the three Grand- 

 Divisions or Classes under which we arrange the 

 whole into Orders, Genera, and Species, — the Genera 

 chiefly from their specific gravity. For further particu- 

 lars, we refer to the Observations on the System. 



