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X. On the Mineral Constituents of Meteorites. By Nevil Story-Maskelyne, M.A. , 
Professor of Mineralogy, Oxford, and Keeper of the Mineral Department, British 
Museum. Communicated by Professor H. J. Stephen Smith, F.B.S. 
Received October 9, 18G9, — Read January 13, 1870. 
I. The applications of the Microscope in the investigation of Meteorites. 
The mineralogical investigation of a meteoric stone presents difficulties very similar to 
those which have hitherto rendered the analyses and descriptions of many of the finer- 
grained terrestrial rocks unsatisfactory ; for a meteoric stone is in fact a fragment of a 
rock, though formed under conditions in some respects widely differing from those which 
have produced the rocks of our globe. 
The difficulties alluded to arise from the minute size and imperfectly developed crys- 
tallisation of the mineral constituents alike of the rock and the aerolite ; and they have 
in general baffled the efforts of the chemist on the one hand to effect their separate 
analyses, and of the crystallographer on the other hand to determine the forms of these 
constituents. The chemist indeed has endeavoured to overcome the difficulty by attempt- 
ing a chemical separation of the constituent minerals of these fine-grained mixtures into 
one group of such as are soluble and another group of those which are insoluble in acids, 
and then treating the numbers obtained from the analyses of these groups by the light 
of theoretical considerations founded on the formulae and properties of known minerals. 
This method is necessarily only an approximative one. Even granting that by its means 
we could divide a rock into two classes of ingredients, which we cannot in fact accurately 
do, there remains the question of how to separate from each other the mingled minerals 
in, for instance, its insoluble portion. 
But the great interest that attaches to whatever may throw light on the history of 
aerolitic rocks seemed to render it very desirable that some more reliable method should 
be sought for their investigation. With this end in view, and also with the purpose of 
basing on such an investigation a scientific classification of the now very extensive col- 
lection of aerolites in the British Museum, I some six years ago commenced a systematic 
examination of these bodies by the microscope. While the meteorites were being cut 
in order to show their polished surfaces, a small fragment of the portion detached was 
fastened by its flat side to a strip of glass and carefully worked down to the utmost 
tenuity. The transparent section thus formed was then examined in the microscope. 
The results to be obtained by the study of such sections may be divided into such as are 
structural, throwing light on the physical conditions under which the meteorite was 
formed, and such as are mineralogical and concern purely the particular minerals that 
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