INTRODUCTION. 



As It is therefore granted on all hands, that chemistry alone 

 can decide what is called the species, and that it depends chiefly 

 on the MODE OF COMBINATION, is it not more logical and 

 philosophical to adopt the only term which can express its 

 real nature ? 



It is clear that Haiiy has abandoned his doctrine of species, 

 in which he had followed Dolomieu, who assumed the mole- 

 cule integrante of Delisle as the basis of a species*. Dolomieu 

 closes his elaborate essay on the subject with the following 

 strange definition of a species, in fact a mere ens rationis in 

 mineralogy. 



" The mineralogic species is a being distinct from all 

 others by a particular constitution, and which receives from 

 that constitution every thing which should characterise it. 

 This being exists in the integrant molecule, is physically re- 

 presented by the homogenous masses which have been sub- 

 mitted to the laws of regular aggregation, and it holds under 

 its dependence all the beings which have a similar constitu- 

 tion, even when faults of conformation set them at a distance 

 from the physical representation of the species, or when 

 superfluities and contaminations make it wear a foreign 

 livery." A very curious and original specimen of a defini- 

 tion ! 



Though Werner repeatedly allows that all mineralogical 

 arrangements must depend upon chemistry, as they can only 

 be formed on the quality and quantity, and mode of combi- 

 nation, of the constituent parts ; yet, with a not illaudable 

 predilection in favour of natural characters, he uses them 

 chiefly to decide the species; while the species is in fact 

 the most important and the most dependent upon chemical 



retire constamment les mmes principes, est une espece. II n'est pas necessaire 

 de savoir si elle a uoe molecule. Mais 1'analyse seule est insuffisante, il faut 

 encore avoir egard aux caracteres exterieurs, et aux proprie'te's physiques ; comme 

 pour le spatte calcaire et I'arragonite, le ruthil et 1'oisanite. Journ. de Ph. 

 Juillet, 1809. 



* See Tableau, p. ii. " J'ai prefers* V indication de la forme primitive a celle 

 de la molecule integranle," &c. 





