XXIV PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



opinion, also thrown cut by Mr. Smithson, that siHca acted as an 

 acid, he called the combinations of sihca and of most of the bases, 

 siliciates. Silicium being, as you are aware, (in the form of its oxide,) 

 the most abundant of all the metals known on the surface of our 

 planet, siUca constituting from 64 to 75 per cent, of granites, whence 

 so many other rocks have been derived, and about 55 per cent, of 

 greenstones, the importance of the labours of Berzelius to geology in 

 establishing the true character of sihca will be at once appreciated. 



In the work of 1814, above mentioned, he further explained his 

 views respecting silica, and pointed out the mode of calculating 

 mineral formulee. He gave 49*64 as the atomic weight for sihca 

 (that now used is 51-96), for alumina 467 (still employed) ; and he 

 also gave numbers nearly the same as now used for magnesia, lime, 

 baryta, soda and potash. In his classification of minerals he di- 

 vided them into — 



I. Bodies formed according to the laws of composition prevailing 

 in inorganic nature, i. e. combinations of two elements, or combina- 

 tions of such combinations, or binary combinations. 



II. Bodies formed according to the laws of organic nature, i. e. 

 combinations of three or more elements, or combinations of these, or 

 ternary and quaternary combinations. 



The elements were divided into three classes: 1. oxygen; 2. me- 

 talloids, or simple combustibles the metallic character of which is 

 not established; and, 3. metals. Each of the simple elements was 

 considered to form the basis of a mineralogical family, consisting of 

 itself and of all its combinations with bodies acting in an electro-ne- 

 gative manner towards it, i. e. occupying, with a few exceptions, a 

 higher place in the series of elements which he gave. These families 

 were then divided into orders, as sulphurets, carburets, arseniets, tel- 

 lurets, oxides, sulphates, muriates, carbonates, arseniates, siliciates, 

 &c., and specimens of such a system are given for silver, iron, &c. 

 In an appendix to this memoir Berzelius gave an account of the 

 method of determining the atomic weight of the elements, as also 

 a table of them with their signs and numbers, and a second table 

 of their combinations with oxygen. 



In another memoir, published in 1815, he defended his system 

 from objections that had been raised against it ; gave a further ex- 

 planation of his views of the constitution of minerals ; criticised 

 some other systems — those of Brunner, Werner, Hausmann, Kar- 

 sten, Hauy, and others; and presented a complete view of his owii 

 classification, with the names of the species and their chemical 

 symbols. 



In his annual report to the Swedish Academy for 1822, Ber- 

 zelius criticised Mohs' system, published in 1820, and noticed Mit- 

 scherhch's discovery that some compounds are dimorphous, and 

 hence that Hauy's principle of similar primary forms implying simi- 

 lar composition could not be true. He also then noticed Mitscher- 

 lich's doctrine of isomorphism, as the most important discovery in 

 chemistry since that of chemical proportions, and as likely to change 

 the whole aspect of mineralogy. It may be here observed respecting 



