on certain stony and metalline Substances, &c. igg 
have eluded the action of an acid, when the aggregation of 
the integrant parts of the stone was not destroyed by treat- 
ment with potash. As to the existence of alumina, I do not 
absolutely deny it ; yet I must observe, that the whole of the 
earth which seemed to have any resemblance, however small, 
to alumina, was at most 3 per cent, and there seems good 
reason to consider it as silica. Respecting the existence of lime 
in the stone of Ensisheim, I must appeal to Professor Bar- 
thold, whether, supposing lime a constituent part, sulphate 
of lime should not have been formed, as well as sulphate of 
magnesia, when sulphuric acid was generated by igniting the 
earths and pyrites. And, as to the proportion of alumina, in 
the same stone, I would ask, at least, whether it would have 
been so considerable, if the solutions formed by acids, after 
the treatment with potash, had been evaporated to the requisite 
dryness : not to observe, that no mention is made of any exami- 
nation of the properties of the earth called alumina. In the 
proportion of magnesia, I have the satisfaction to find my ana- 
lysis correspond very nearly with that of Professor Barthold; 
and, if what he considered alumina were supposed silica, the 
stone presented to the French Academy, the stone of Ensisheim, 
and the four I have examined, would agree very nearly in sili- 
ceous proportions. With respect to the nickel, I am confident 
it would have been found in all, had the metallic particles been 
separately examined. But, whatever be these variations, the 
mineralogical description of the French Academicians, of Mr. 
Barthold, and of the Count de Bournon, all exhibit a striking 
conformity of character, common to each of these stones ; and 
I doubt not but the similarity of component parts, especially of 
the malleable alloy, together with the near approach of the 
