HOVEY, THE FOYER METEORITES 19 
been found: hydrogen, carbon dioxide, carbon monoxide, nitrogen and 
marsh gas (light carburetted hydrogen). 
‘Troilite is common in meteorites and constitutes brass- or bronze- 
yellow nodules, plates and rods which are to be seen in nearly every 
section, particularly of siderites. ‘The mineral is usually considered to 
be the simple sulphide of iron, FeS, but its exact chemical composition 
and crystalline structure are still matters of investigation and dispute. 
Canyon Diablo and Willamette contain, or contained, much  troilite 
in the shape of rods, and the fusion and dissipation of this mineral during 
the aérial flight of the masses gave rise to some of the holes which pene- 
trate them, and the same statement is true of many other meteorites. 
Pyrrhotite, the magnetic sulphide of iron, Fe,, S,, occurs in stone 
meteorites and chiefly in the form of grains. Daubréelite is likewise 
a sulphide of iron, but it differs from those just mentioned through con- 
taining much chromium, giving the chemical formula FeS, Cr, $,. ‘The 
mineral is peculiar to siderites and siderolites and has never been found 
in the stone meteorites or in the earth’s crust. It occurs in Canyon 
Diablo, where it may be seen surrounding nodules of troilite as a black 
shell with metallic luster. 
Oldhamite, a sulphide of calcium, CaS; tridymite, a form of silica, 
SiO,; chromite, an oxide of iron and chromium, FeCr, O,; magnetite, 
the magnetic oxide of iron, Fe, O,; osbornite, another sulphide or 
oxysulphide of calcium, and lawrencite a chloride of iron, Fe Cl,, occur 
sparingly in some meteorites. Lawrencite manifests itself rather dis- 
agreeably through alteration to the ferric chloride, which oozes out of 
the masses of iron and stands in acrid yellow drops on the surface or runs 
in streaks to the bottom. Glass like the volcanic glass of terrestrial 
rocks seems never to be absent from the interior of stone meteorites, 
but from the nature of the case it is not found in iron meteorites. 
Surface Characteristics. 
The surface of a newly-fallen meteorite always consists of a thin 
veneer or crust which differs in marked degree from the interior of the 
mass. In the case of the siderites, this seems to be a polish due to melt- 
ing and friction, together with partial oxidation. Some iron meteorites 
which are known to haye lain long in the ground likewise show a crust 
which is somewhat similar in appearance, but it is due to slow oxidation 
