Vol. VIII, No. 9.] | The Origin of Meteorites. 319 
[N.S.] 
cept that the expansion of the garnets on liquefaction tended 
oO produce brecciation of the rock, such brecciation being a 
common feature of chondritic meteorites. Other writers have 
noticed such metallic rims to chondrules, without explaining 
their occurrence.! As a result of the reaction given above, 
O, (or CO) must have been formed. It is important to notice 
that both these gases are well known in meteorites. 
If the chondritic meteorites represent the garnetiferous or 
infra-plutonic zone of the primitive body, 
¢tia non-chondritic meteorites, which 
are otherwise very similar to the chondritic ones, should repre- 
sent the plutonic zone lying immediately above the infra- 
plutonic zone. In oe same way the siderites or iron meteorites 
Achondrites. 
oe a varia primitive body, and the siderolites, which 
mixtures of metallic nickel-iron and 
of various silicates, shoe represent the passage zone between 
the infra-plutonic zone and the metallic core. The chondritic 
meteorites also contain a considerable amount of primary 
onan ee el-iron formed on the breaking down of the 
original garnets), and it is evident that 
we should expect the amount of nickel-iron in the crust of this 
primitive body to decrease with distance from the centre. The 
non-chondritic meteorites, therefore, if they represent the 
plutonic zone, should contain less nickel-iron than the chondri- 
tic meteorites, which represent the infra-plutonic zone. This 
is, in general, the case.’ 
The theory appears, therefore, to be justified by the facts. 
Biased ion aac Let us now see if the iron meteorites offer 
baebite any evidence of these supposed reductions 
of pressure. Siderites frequently contain 
carbon, Vom in the form of graphite, but occasionally as 
diamond, as in the Cafion Diablo meteorite. In Moissan’s 
wane the ‘ < Blectric Furnace,’ page 96, there is given a figure 
of a portion of this meteorite in which the central fragment of 
diamond is surrounded by a black sheath consisting of carbon 
and iron carbide. Assuming this iron carbide to have the 
composition of cementite® (Fe,C), found in artificial iron and 
steel, I find that under the greatest pressure a system of iron 
and carbon would exist as iron and diamond. A small reduc- 
e.g. H. L. Bowman an dHLE asks, , Min. ‘Beep: XV, D, in Fig. 3 
of Plate TX (1910). (The cheudukanet aerolite te). 
Fletcher: ‘ An Introduction to on web td wre yang Sages 
page 38; also the classification of meteo ove pp. 447, , of 
se * Die Meteoriten in Sasaatipel,* 1897. 
ilar to cohenite (Fe, Ni)3C, a well-known meteoritic mineral. 
Moi senile’ s value (7°07) for the "density of artificial cementite has been 
taken, the published values for natural Gabienite being very variable ; 

