438 ATOMIC CONSTITUTION, ETC., IN MINERALOGY. 



oxide of iron aud arsenic acid as laboratory or chemical products, but 

 certainly without value as regards the occurrence of iron-glance and 

 arsenic acid in their conditions as minerals — in relation to which the 

 following leading truth cannot be too strongly insisted on, viz. : that 

 chemical compounds and minerals are two and distinct ; frequently, at 

 least, if not always so. In the vast majority of cases, the products 

 obtained by the chemist from a given mineral are not in the same con- 

 dition as that in which they existed prior to their separation, and 

 hence are not, when properly considered, the same bodies. Allowing, 

 first of all, that bodies in combination preserve their atomic constitu- 

 tion unchanged, does it necessarily follow that they preserve their 

 actual physical conditions, or what we may call their normal state of 

 occurrence ? Carbonic acid, water, &c, if present as such in solid 

 bodies, must evidently be present in some physical condition altogether 

 unknown to us. Amongst simple bodies also, oxygen, chlorine, &c, 

 may be said to follow a similar law ; and hence we are not justified in 

 reasoning upon the nature of compound bodies from the nature of 

 their constituents when uncombined. But it may also be fairly in- 

 ferred, that compound bodies in combination do not always retain the 

 atomic constitution which they are assumed to possess in the simple 

 state ; and if so, the formulae by which we are accustomed to represent 

 these combinations may be absolutely false, and thus worse than value- 

 less, because leading to groupings of an artificial and arbitrary charac- 

 ter. When we place cinnabar in the same group with galena, or, on 

 account of the hexagonal crystallization, in a sub-group with millerite 

 and arsenical nickel (kupfer nickel), for example, we know that by 

 the test of the botanist and zoologist our collocation must be pro- 

 nounced a faulty one ; but we defend it on the plea that these minerals 

 are each and all simple binary combinations of a metal with sulphur 

 or with arsenic, exhibiting the general formula BS or BAs. But then 

 the question arises — can we be quite sure of this ? And so ultimately 

 we find ourselves obliged to confess that, after all, our knowledge is 

 limited to the fact (if fact it really be,) of the existence in these 

 minerals of equal atoms of base and electro-negative element. This, 

 however, does not necessarily exact for cinnabar the formula HgS. 

 The real formula may be Hg 2 S + HS 2 . It is true that this latter 

 compound HgS 2 has not yet been obtained in the laboratory, but 

 analagous compounds of silver and copper (metals considered by 

 Kiihn and other chemists to be closely related to mercury,) exist, and 

 whilst various recognized bodies still remain unisolated, the existence 

 of the compound in question cannot be considered entirely hypotheti- 

 cal. At the same time I would not be understood to deny that HgS 



