REPORT ON MINERALOGY. 
357 
iron, lead, tin, bismuth); 3. Oxides of Copper ; 4. Sulphates ol 
Copper;—and so on. 
Nothing could be more complete and symmetrical than such 
a system, if the object had been to arrange the products of the 
laboratory, or substances as definite and distinct as those. But 
it very soon appeared that the system contained in itself germs of 
inevitable confusion. Very many minerals are so complex and 
so imperfectly known as to their chemical composition, that it re¬ 
mained doubtful where they were to be placed; and the parts 
of the system which appeared to have equal claims to them 
were widely removed from each other. Nor did any approxi¬ 
mation of substances apparently of the same kind, or any analo¬ 
gies and rules with regard to the association of chemical for- 
mulae, come into view by means of this classification, and thus 
give it the air of a successful conjecture. 
The same may be said of the system of Brongniart, the suc¬ 
cessor of Haiiy, which proceeded on the chemical principles 
then (1806) generally recognised, and of that of Leonhard; in 
both of which there may be observed what was considered as 
a blemish in the first system of Berzelius,—a struggle between 
the “ scientific” or electro-chemical principle, and the ancient 
customary views which tended to place similar minerals together. 
Thus tellurium, like sulphur, is a mineralizing substance ; and 
hence there is no more reason, on the electro-positive princi¬ 
ple, for making a family for tellurium than for sulphur. Yet 
both Brongniart and Leonhard have made such a family, and 
have arranged the telluriurets in it, while the sulphurets stand 
each under its metal. This inconsistency is one of the marks 
of the unsatisfactory impressions produced by a rigid chemical 
system on such principles, and of the difficulty of adapting such 
a system to the mineral kingdom. 
When in the due course of time the examination of the che¬ 
mical difficulties of mineralogy had led to the doctrine of iso¬ 
morphism (1821), the untenable nature of Berzelius’s first sy¬ 
stem, and of all similar ones, became more obvious. With a 
candour and alacrity worthy of his elevated position in the world 
of science, Berzelius was himself one of the first to acknowledge 
the necessity of some change. In 1824 he published in the 
Transactions of the Academy of Sciences at Stockholm, a Me¬ 
moir “On the Alterations in the Chemical Mineral System 
which necessarily follow from the property exhibited by Xso- 
morphous bodies, of replacing each other in given proportions.” 
In this Memoir he gives a classification of mineral substances 
according to their electro -negative element; explaining that 
the fact that one isomorphous electro-positive element may take 
