4 i 6 HIS TOR Y OF SCIENCE. 



classification of minerals ha jiever attained to the same perfection as 

 those of animals and vegetables. They exhibit every shade of grada- 

 tion in almost all of their properties, and, unlike animals and plants, the 

 species are connected by none of those relations of affinity or descent 

 to which the much-sough t-for natural systems would in reality be the 

 clue. The system of classification of minerals proposed by Linnaeus was 

 much inferior to those of the same author in the two other kingdoms of 

 nature. Werner used the external character of minerals for the deter- 

 mination of his species, and he endeavoured to assign certain strata- 

 graphical relations among certain divisions. It has since been found 

 impossible to rely upon physical properties alone, and indeed these have 

 been made subordinate to distinctions founded on crystalline form and 

 chemical composition. The Abbe HAUY (i 745 1822) will be remem- 

 bered as the first to methodize crystallography, or the study of the 

 crystalline forms of minerals. Haiiy discovered a beautiful simplicity, 

 symmetry, and constancy concealed beneath, apparently irregularity 

 and complexity in crystals. Measurements of the angles of crystals by 

 instruments in some cases reveal differences inappreciable by the un- 

 assisted eye, and these differences are known to be related to diffe- 

 rences of chemical composition. 



