258 
TOE GEOLOGIST. 
spokeji in a preceding number of The Geologist (vol. ii. p. 85). A 
first aual^'sis gave them "10 per cent, of magnetic substances (iron 
and iron-oxide) ; 1.70 of cliromo-irou, 5.70 of protosulphuret of iron, 
48 per cent, of silicates soluble in acids, and consisting principally of 
peridote ; 17 per cent, of silicates insoluble in acids, and consisting 
principally of feldspar and amphibolite." They then proceeded to 
analyse, with more care, that part of the aerolite which is insoluble in 
iiitric and hydrochloric acids ; and the result is as follows : — 
Berzelius, Rammelsberg, and other chemists who have occupied 
themselves with this sort of analysis, have already remarked that 
the composition of the silicates which are insoluble in acids does not 
coincide with that of any one known mineral. Thus, from the above 
analysis, it is impossible to write down any chemical formula, as the 
oxygen of the silica is not proportionate with that of the difi'erent 
bases. This circumstance shows that the insoluble residue is not 
composed of one silicate only, but of a mixture. Ilammelsbei'g has 
shown that the simultaneous existence of alumina and alcalies in such 
a case indicates the presence of feldspathic minerals. He found, as 
we have before noticed, that in some meteorites this residue coin- 
cided exactly with the composition of hornblende or augite, according 
as the alcalies were attributed to labradorite or to oligoclase. It is 
impossible, in the absence of distinctive crystalline forms, to prefer 
one of these hypotheses to the other ; each is equally good. 
Following M. Rammelsberg's method, MM. Chancel and Montessier 
conclude that the soluble portion of the silicates in the aerolite of 
Montrejeau represents labradorite, and the insoluble portion horn- 
blende ; or, if the soluble part he made to represent oligoclase, the 
insoluble portion becomes augite. Hence the mineralogical composi- 
tion of this remarkable aerolite may be thus represented : — 
Magnetic portion (iron and oxide of iron) . 10.04 
Chrome-iron 0.G7 
Proto-sulphuret of iron 5.72 
I'eridote 45.08 
Silica ......... 
Alumina 
Maguesia 
Lime 
Protoxide of iron 
Oxides of nickel and manganese . 
Soda 
Potash 
5G.G13 
G.G53 
19.447 
4.012 
9.212 
1.100 
2.128 
0.398 
99.563 
or. 
99.02 
