$20 Cursory Remarks on 
If we compare the foregoing analysis with 
those, which mineralogists have given us of 
limestones, we shall find, that the chief differ- 
ence (in a chemical point of view) between 
Rotten-stone and certain varieties of limestone, 
exists in the larger proportion of alumine, 
which the former of these substances contains, 
and its comparative, or, in some instances, its 
total want of the carbonate of lime. The 
particular varieties of limestone now alluded 
to are thosé, which Mr. Kirwan has denomi- 
nated argilliferous marlites, on account of 
their holding a large proportion of argill 
(alumine) in their composition. (v. E. Min. 
v. 1. p. 99.)—Some of -these stones, though 
lysis, never exceeded 1,5;—hence the proportion of 
“ inflammable matter” may be stated as varying from 5,5. 
to 7,5. At the time of making my experiments on Rot- 
ten-stone, the principal object in view was to ascertain the 
predominating earth in its composition, and not determin- 
ing the nature of the inflammable matter, it was placed with 
the loss ;—there can be little doubt, however, of its being 
carbon. Silex was found in all the specimens examined. 
Carbonate of Lime only in the harder varieties, and not 
constantly in those. Two or three specimens analysed, in 
‘all external respects similar to No. 5, were without it. 
Oxide of Iron was only present in the harderRotten-stones.— 
The actual constituents, therefore, of genuine or perfect 
Rotten-stone (that is, Rotten-stone in which the disinte- 
gration of the original substance is complete) may be 
stated to be alumine, silex and inflammable matter (carbon? ) 
