220 CONTEIBUTIONS TO MICRO-MINERALOGY. 



less lost in the mass so formed. Indeed, in the situation last 

 mentioned, lamination of an indistinct character may take the 

 place of fibres ; or both the laminated and fibrous arrangement 

 may be replaced by a structure exhibiting little arrangement 

 of parts. In any case, however, this deviation from the 

 normal structural character of enamel is limited to the ter- 

 minal edge of the tissue. The development of dentine and 

 cement will form the subject of a future communication. 



Contributions to Micro-Mineralogy. By Samuel Highley, 

 F.G.S., F.C.S., &c. 



Introduction. 



In 1847, not finding any classification of Minerals whereby to 

 arrange my collection, that satisfied my mind, I laid the 

 scheme of a Mineral-System founded on the chemical crys- 

 tallographic and physical characters according to their re- 

 lative value, and which I conceived threw the species into 

 more natural groups than any of the Systems 1 was tlien 

 acquainted with, all being either too chemical or too physical 

 in their arrangements to meet the requirements of a Natural 

 History method, where all the characters must receive their 

 due share of consideration. 



My scheme was based upon the isomorphous relations of 

 the electro-negative to the electio-positive elements, and ap- 

 proached more the since-published Systems of Nordenskiold,* 

 (which I did not become acquainted with till 1851, when that 

 author visited the Great Exhibition), Danaj and Rose.| 

 This I showed at the time to several eminent chemists and 

 naturalists, who advised me to publish it as a Synopsis, 

 which I determined on and announced (and which I trust will 

 be produced ere long) ; but the more I advanced the more I 

 became assured that a searching analytical inquiry must be 

 instituted in various departments of Mineralogical Science 

 before anything approaching a philosophical or logical dis- 

 tribution of inorganic bodies could be hoped for. Among 

 other things, heterogeneous masses of mineral matter, mine- 

 ralized plants and animals, &c., have, foi^ convenience, been 

 classed as true species under the mineralizing constituent. 



* Ueb&r Das Atomistisch-Chemische Mineral System, (fee, von Nils Nor- 

 denskiold, Hehinr/fors, 1849. 



t System — Chemical Classification, edition of 1850. 



X D&s Krystallo-ClieiniBche Mineral Svstem, von Gustav Eoso, Leipzig, 

 1852. 



