MINERALOGY. 



metallic substances. This class contains eighteen 

 genera, characterised by the different metals. Class 

 IV. Unmetallic, combustible sulistances. 



In proceeding to notice the labours of professor 

 Mohs, we come to an era in the history of minera- 

 logical science. This eminent philosopher, no less 

 distinguished as a cultivator of the mathematics than 

 of mineralogy, published at Dresden, in 1822, his 

 Grundriss tier Mineralogie, a work replete with new 

 and philosophical views of our science. His first 

 object is to fix the exact limits of mineralogy, and to 

 exclude from it a variety of foreign matter belonging 

 to other sciences, which had before rendered it a 

 heterogeneous mass of information, incapable of 

 derivation from constant principles by any regular 

 process of reasoning. He then proceeds to develope 

 the science under the following heads : 1. termino- 

 logy ; 2. theory of the system ; 3. nomenclature ; 4. 

 characteristic ; 5. physiography. Under the first of 

 these he explains those properties of minerals which 

 manifest no change, either in the properties them- 

 selves, or in the substances which possess them 

 during their observation or examination, and which 

 properties alone form the object of consideration 

 in mineralogy, viewed as a pure science. They 

 had before been treated of under the denomination 

 of external or physical characters, though, from 

 the stress which had been laid upon chemical 

 characters, the greater part of them had been but 

 very imperfectly determined ; and this part of the 

 subject is called terminology, because, besides the 

 general investigation of those properties, it embraces 

 also the explanations of the expressions which, for 

 the sake of precision, are used in a determinate and 

 peculiar sense. Decomposed and imperfectly formed 

 minerals, or those which are destitute of several of 

 die properties peculiar to these bodies, are not re- 

 garded as suitable objects for the consideration of 

 the science ; in which respect they are treated like 

 mutilated, defective, or monstrous plants or animals 

 in botany and zoology. And in order to study the 

 productions of the mineral kingdom in their purest 

 state, Mohs takes notice of those properties which 

 belong to minerals occurring in single individuals, 

 separately from those which belong to several 

 individuals of the same quality, formed in a common 

 space, one being the support of, or at least contiguous 

 to, the other, of the former of which only does he 

 make use in the determination of the species, while 

 he pays no attention to the properties of minerals 

 composed of individuals belonging to different species 

 (mixed minerals), these last falling within the province 

 of geology. This is a distinction of the highest im- 

 portance and utility, in rendering all the departments 

 of mineralogy mutually consistent, though one which 

 had been almost wholly disregarded by all his prede- 

 cessors. According to this system, the individual of 

 the mineral kingdom, or the simple mineral, is the sole 

 object of mineralogy, and the natural properties of 

 the Simple mineral are the only ones to which, in this 

 science, we ought to direct our attention. It will be 

 obvious, therefore, that all information thus derived 

 must be of one kind, and consequently its aggregate 

 conformable to the logical idea of a science. Mohs 

 has particularly distinguished himself in treating of 

 that part of terminology which relates to the regular 

 forms of minerals. The fundamental forms, from 

 which he derives all the occurring forms among 

 minerals, are but four in number, viz., the scalene 

 four-sided pyramid, the isosceles four-sided pyramid, 

 the rhombohedron, and the hexahedron ; and the geo- 

 metrical constructions by which he illustrates the 

 simple forms capable of appearing in the individuals 

 of one and the same species, or which may produce 

 combinations with one another, entitle him to the first 



rank as a crystallographer. The natural-historical 

 properties of compound minerals are treated of in 

 the most precise manner, the previous neglect of 

 which had involved the science in numerous impor- 

 tant errors. But one of the greatest improvements 

 under this head was the establishment of an accurate 

 scale for the degrees of hardness. This was effected 

 by choosing a certain number of suitable minerals, 

 of' which every preceding one is scratched by that 

 which follows it, while the former does not scratch 

 the latter; and the degrees of hardness are expressed 

 by mean's of numbers prefixed to the different indi- 

 viduals of the scale. Thus 



1 expresses the hardness of talc ; 



gypsum ; 



calcareous spar ; 

 fluor spar ; 

 apatite ; 

 feldspar; 

 qunrtz ; 

 topaz ; 

 corundum ; 



diamond. 



The second general head under which mineralogy 

 is developed, according to Mohs, is the theory of the 

 system, which contains the reasoning or philosophical 

 part of the science. It determines the idea of the 

 species ; fixes the principle of classification ; and 

 upon the idea of the species it founds, according to 

 this principle, the ideas of the genus, the order, and 

 the class ; and lastly, by applying all these ideas to 

 nature, the outline of the system thus constructed is 

 furnished with its contents, in conformity to our 

 knowledge of the productions of nature, as obtained 

 from immediate inspection. The idea of the species 

 is here, for the first time, scientifically obtained, and 

 is founded upon all the series of natural properties 

 without the introduction of any considerations foreign 

 to natural history, which had proved the source of 

 the contamination that the science had before suffered 

 from heterogeneous principles. The principle of 

 classification consists in the resemblance of natural 

 properties, since in every science the classification 

 must rest upon such relations as are objects of the 

 science. On the different degrees of resemblance 

 are founded the higher ideas of the theory of the 

 system. An assemblage of species connected by the 

 highest degree of natural-historical resemblance is 

 termed a genus; an assemblage of similar genera an 

 order ; of similar orders a class ; and the collection 

 of these ideas conformably to the degree of their 

 generality, and applied to the productions of the 

 mineral kingdom, constitutes the mineral system. 

 The mineral system is therefore the systematic exhi- 

 bition of the natural resemblance as observable in 

 the mineral kingdom, or of the connexion established 

 by nature among its products by means of this re- 

 semblance. For this reason it is called the natural 

 system, because, in fact, it expresses nature in this 

 very remarkable relation. 



The third idea of the science, as developed by 

 Mohs, is its nomenclature, which relates to the con- 

 nexion of its unities with certain words, through 

 which the ideas and representations may be so ex- 

 pressed as to be conveniently applied in writing and 

 speaking. Nothing is better calculated to furnish us 

 with an idea of the situation in which mineralogy had 

 before been placed, than the consideration of its for- 

 mer nomenclature, and of the method employed in 

 giving new names. Those were regarded as the best 

 which had no signification, as is obvious from the fre- 

 quency with which designations were adopted derived 

 "from colours, persons, localities, and other accidental 

 circumstances ; and, as respects those names which 

 referred to the connexion of the different minerals in 

 regard to their resemblance, these were still more 

 objectionable, since the connexion expressed by them 



