1825.] M, Berzelius's Hi/pothesis of the Atomic Theort/. 343 



atoms of oxygen combined with it. The oxides of copper, for 



instance, instead of the preceding signs, are indicated by Cu, 



and Cu ; the sign of sulphurous acid is S, that of sulphuric acid 



S, and so on ; and in the salts of copper Cu S, = oxidulous 



sulphate of copper, and Cu S-, sulphate of copper ; the little 

 figure placed above, like an algebraical exponent, indicating that 

 in the latter compound there are 2 atomsof sulphur or sulphuric 

 acid to 1 of base. 



The composition of atoms of the third order is denoted after 



the same manner ; for instance, Ca C- + Mg C* represents the 

 mineral called dolomite, which is composed of an atom of car- 

 bonate of lime, and an atom of carbonate of magnesia. The 



formula for alum is K S" +2 AL S^ + 48 Aq;'and indicates 

 its composition to be 1 atom of sulphate of potash + 2 atomsof 

 sulphate of alumina + 48 atoms of water (aqua). The small 

 exponential figure refers only to the initial sign immediately 

 preceding it ; but the coefficient applies to each element con- 

 tained between the sign + ; as, for instance, in the preceding 

 examples, the exponent ^ means that 3 atoms of sulphuric acid 

 combine with the atom of alumina to form the sulphate, and the 

 coefficient denotes that 2 atoms of that salt are taken. 



So far the symbols are tolerably simple and intelligible ; but 

 we frequently meet with such expressions as the following : — 



Al Si, siUcias aluminicus ; AP Si, siUcias bialuminicus ; Ca^ Si-, 



silicias calcicus ; Ca^ Si*, bisilicias calcicus ; Al S^, sulphas 



aluminicus ; Al S, sulphas trialuminicus ; Ca S'-, sulphas calci- 

 cus, &c. which require a little further explanation. 



In order to understand the meaning of these and similar for- 

 mulae, it is necessary to state some peculiarities in Berzelius's 

 views with respect to the composition of certain bases. 



If we refer to Thomson's or Phillips's table of the weights of 

 atoms, we shall find that lime, baryta, strontita, alumina, mag- 

 nesia, &c. as well as most of the protoxides of the common 

 metals, as lead, iron, tin, mercury, &c. &c. contain respectively 

 1 atom of base and 1 atom of oxygen. But Berzelius considers 

 them as containing 2, and some of them 3 atoms of oxygen, for 

 the following reason : — " If we take," he observes, " a compre- 

 hensive, general view of the compound bodies that have been 

 correctly analysed, we find that many of them, particularly the 

 oxides, contain decidedly more than two atoms, and that it most 

 frequently is the electro-negative element wliich enters in a 



