3870 French National Institute. 
--In mineralogy there has» also been a)similar case’iin’ that. 
of the arragonite,' where chemists have only found:a carbo- 
nate of lime, although its whch hardness, fracture, and 
erystallization ‘differ much from that of calcareous pet or 
eommon.-carbonated lime, 
A different example, but which also establishes a sort of 
opposition among the physical and chemical characters of 
the miinerals, has also presented itself this year. 
Jt is the ore of iron Known by the name of spathic iron *. 
It constantly has the’ same crystalline form: as carbonated 
lime, and indeed it often'contains avery considerable quan- 
tity of the latter substance. M. Haiiy had ranked it among 
the varieties of this species, considering the oxide of iron 
in it as merely accidentally arising out of the crystallization 
of the lime, nearly the same as it is with the sand in the 
singular cfystals‘of stone found in’the forest of Fontain- 
bleau: in fact, we have known for a long time past that 
the quantity of iron is very variable in it. ; 
But two young cheniists, Messrs. Drappier and Destos- 
tils, have discovered that the quantity of lime varies still 
raore considerably in spathic iron, that sometimes there is 
none at all in it; and that magnesia and the oxide of man- 
ganese are often in as variable quantities, according to the 
specimens. 
Here, therefore, there are very different combinations 
which present themselves under a form always the’same. 
These kinds of difficulties, these apparent oppositions be- 
tween two branches of one and the same science, or between 
two methods of regarding objects, must be referred to some 
imperfection in the principles of the one or other of the two 
methods, and merit all the attention of the friends of truth. 
Researches on the subject would probably terminate by the 
discovery of some new general fact, which conciliates every 
thing. 
The labours upon native platina, of which we have spoken 
in our two’ last reports, have been continued this year by dif- 
ferent chemists, and have led to some clear and satisfactory 
results. » to’ 
* See-Philosophical Magazine, vol. xxv. pages $1, 245, 911. 
ee”. M. Fourcroy 
’ 
