1S AMERICAN MUSEUM GUIDE LEAFLETS 
as graphite (cliftonite) and as hydrocarbons. Diamonds were first 
found in Canyon Diablo in 1891. They are extremely minute in size 
but recognizable crystals have been obtained. Graphite (cliftonite) 
occurs usually in nodules and only in siderites in particles that are large 
enough for easy examination. ‘The material is very fine. ‘The cliftonite 
form of graphite is considered by most authorities to be a pseudomorph 
after diamond. 
Hydrocarbons of several kinds have been found in meteorites. Ac- 
cording to Cohen’ they may be grouped into three classes: (1) compounds 
of carbon and hydrogen alone; (2) compounds of carbon, hydrogen and 
oxygen; (3) compounds of carbon, hydrogen and sulphur. None of 
the meteorites in the Foyer collection is known to contain any hydro- 
carbon, but the fact that any meteorite should contain such substances 
is of great scientific interest. It is pretty clear that they belong to the 
pre-terrestrial history of the masses; hence, since they are readily com- 
bustible or volatile, the meteorites that contain them cannot have been 
heated to high temperatures, at any rate, subsequent to the formation 
of the compounds. ‘This is an additional argument in support of the 
statement already made that the heating of meteorites during aérial 
flight is, in many instances at least, only superficial. Furthermore, the 
existence of hydrocarbon compounds in meteorites, where no life can 
have existed, shows that organisms are not absolutely necessary to the 
formation of such compounds in the earth’s crust. 
Cohenite, which is a carbide of iron, nickel and cobalt, is tin-white 
in color and looks like schreibersite. It is much rarer, however, and 
occurs in isolated crystals. The only terrestrial occurrence of cohenite 
is in the basaltic iron of Greenland. Moissanite, the natural carbide 
of aluminum corresponding to the artificial carborundum, has thus far 
been found only in Canyon Diablo, where it occurs in microscopic 
crystals. It is the latest discovery among the constituents of meteorites, 
having been found in 1905 by Henri Moissan. 
As far as investigations have been carried, heating develops the fact 
that meteorites contain gases condensed within them, either by occlusion 
in the same way that platinum and zine absorb hydrogen or by some 
form of chemical union. According to Cohen’ the following gases have 
' Meteoritenkunde, Heft I, p. 159. 
* Meteoritenkunde. Heft I, p. 169 
