Formation of Minerals. 345 
the general causes which have originated the different classes 
of metalliferous beds. I commence this problem by the study 
of the concretionary veins which approach most nearly to the 
existing formations, and the principles I have just explained 
have been the starting point of the researches I am about to 
submit to the academy (French Academy.) 
The concretionary repositories seemed to be formed 165 So- 
lution ; the mineral species we there find would then be the 
products of the humid method, derived from liquid deposits, 
and to acertain extent may be compared to geysers and ther- 
mal springs. Moreover, the principles most generally preva- 
lent, even at the present day, in these springs, are the car- 
bonic and hydro-sulphuric acids, the alkaline salts, and 
amongst others the carbonates and the sulphates; these, 
then, are the reagents I propose first to employ. But amongst 
the different influences which may modify in the subterranean 
canals the usual chemical reactions, we must undoubtedly 
reckon first pressure, and a temperature increasing indefi- 
nitely with the depth ; and I have endeavoured to realize this 
double experimental condition. It is very evident. that this 
creates numerous difficulties ; and we must not be surprised 
if the crystalline state of the products thus formed is some- 
times imperfect, and always microscopic. Besides, it is not 
the size of the crystals which results from such problems, it 
is the mere fact of their creation ; and in order to obtain more, 
all that is required is time, space, and rest, powerful means 
_ which belong to nature alone. 
The method I have pursued essentially consists in produc- 
_ ing all the chemical reactions in a liquid condition, and in 
glass tubes, hermetically sealed, heated from 100° to 350° C. 
I have almost solely employed solutions of carbonic and hydro- 
sulphuric gases, of bicarbonates and alkaline sulphurs, alone 
or mixed in variable proportions ; I have then, I repeat, as a 
starting point, the composition of mineral waters and their 
most energetic principles. By these means of procedure, I 
have artificially formed a great number of natural compounds. 
Each family of minerals generally group themselves around 
a@ common generating agent; so that we might then classify 
them thus in relation to the presumed composition of the 
