INTRODUCTION. 



their arbitrary and unnatural systems, as Dr. Townson has 

 observed, the Genera and Species are often confounded. 

 " Thus in the improved edition of Linnaeus, the characters 

 which constitute the Species in gypsum form Genera in the 

 carbonate of lime ; for the pulverulent, fibrous, spathous, 

 and compact kinds of gypsum form but so many Species, 

 whilst the pulverulent, fibrous, spathous, and compact kinds 

 of carbonate of lime form so many different Genera." 

 Now these very appearances, which constitute the arbitrary 

 Species and Genera of former authors, what would they be, 

 in the eyes of a philosopher or grammarian, except different 

 modifications, or modalities, of the same substance, and which 

 by a shorter term may be denominated Modes ? Hence the 

 term MODE, which is universally applicable and unobjection- 

 able, to distinguish such objects in mineralogy, is here ad- 

 mitted instead of Species f. 



To put the propriety of this new appellation to the test, 

 examples may be produced of what are called Species by the 

 most celebrated mineralogic writers. Wallerius, among the 

 species of garnet, first mentions that of an undetermined 

 figure, composed of granular particles j and his next species 

 is of an undetermined figure, but laminar. What are these 

 but different modifications, or modes, of the same stone? 

 His ripe asbestns, consisting of fibres which may be sepa- 

 rated, forms one species ; while that of which the fibres can- 

 not be separated constitutes another. What are these but 

 different modifications of the same substance ? In the last 

 edition of Linnaeus by Gmelin, the term modes (modi) has 

 been applied to various appearances of petrification : but 

 what are sometimes called Genera, and sometimes Species (as 

 already observed from Dr. Townson), are, in strict language, 

 mere modifications of matter. If we pass to one of the most 

 exact of the French mineralogists, we shall find the sapphire 

 arranged as the tenth species of the siliceous, and the topaz 



* Philosophy of Mineralogy, p. 173. 

 t E<8of implies modus, as well as species. 



