SCIENTIFIC SUMMARY. 
237 
A meteoric stone fell at Chassigny, near Langres, in October, 1815, and 
was described by Vauquelin. It has been lately re-examined by Mr. A. 
Damour, who was led to notice the similarity in its composition to one of 
the species of the mineral peridot. [Peridot, or chrysolite, is the name 
given to the paler and more transparent crystals of olivine.] His own 
analysis confirmed this supposition. The stone differs from the majority 
of meteorites by its pale yellow colour. It contains neither nickel nor 
iron in the metallic state ; and it is not magnetic, with the exception of a 
thin black crust covering it. This seems to indicate, that during its 
incandescence, the protoxide of iron which it contained became converted 
into black or magnetic oxide. On analysis, the substance of the stone 
furnished 35 per cent, of silica, 32 of magnesia, and 27 of protoxide of 
iron ; agreeing in composition with the ferruginous variety of peridot, 
called Hyalosiderite. [This mineral is found in a brown basaltic rock at 
the Kaiserstulil, in the Breisgau.] Several mineralogists have established 
two chief classes of meteoric stones : — 1. Those containing alumina, and 
which may be considered as belonging to the Felspar family. 2. Those 
containing no alumina, but more or less of magnesia, oxide of iron, 
lime, &c,, most probably in the form of pyroxene and magnesian silicates. 
Mr. Damour would place the Chassigny stone in the second of these 
classes. 
Effects of heat on Felspar. — M. des Cloizeaux has examined the molecular 
changes produced in certain minerals by the action of heat. By means of 
a polarizing microscope he could detect any alteration in the relative 
directions of their optic axes. Many crystals have the property called 
“ double refraction that is, they split up a ray of light passing through 
them into two parts. But there is one direction in each crystal, some- 
times two, as in felspar, in which there is no double refraction ; these 
directions are called the optic axes of the crystal. In a small plate of 
orthose (or common felspar, so often found in granite and other rocks), 
the optic axes separated the more, the higher the temperature was raised. 
On cooling again, they returned to their original condition ; showing, 
therefore, no permanent modification. He found, however, that if the 
substance were heated for thirty-six hours to a dull red, or for fifteen 
minutes to a white heat, a permanent change was effected. His experi- 
ments have led him to conclusions contrary to the hypothesis which admits 
the necessity of an excessive temperature to explain the formation of 
crystalline rocks where orthose and quartz predominate ; and he has 
found the same thing to hold with other varieties of felspar. On the 
other hand, several varieties of the same mineral show neither temporary 
nor permanent modification under the influence of heat ; and he infers 
that they have not been subjected in nature to the same influences as 
those previously referred to. 
Esmarkite was the name given by Erdmann to a mineral found at Brakke, 
in Norway. M. Pisani has shown, however, that the name has in reality 
been given to two species of Norwegian minerals which are distinct ; and he 
recommends, therefore, that the name be suppressed altogether. 
Mineral Wealth of Australia. — The Melbourne Argus has recently given 
a series of letters from a correspondent deputed to examine the mineral 
