630 ^ OLIVER C. EARRING TON 



which exists in quantity amounting to several tons. Such 

 diamonds have been produced by Moissan by heating to a high 

 temperature iron saturated with carbon and allowing it 'to cool 

 under pressure. This is exactly the process through which the 

 substance of an iron meteorite would pass if formed according 

 to the above hypothesis. The other meteorite known to contain 

 diamonds, Nowo-Urej, is also one which would have formed not 

 far from the metallic center of such a globe, as it contains large 

 metallic veins and by some is classed among the iron-stone 

 meteorites. 



The hypothesis outlined above may ask the special attention 

 of the geologist, on account of the suggestions it may offer 

 regarding the history of the earth. If it be true that meteorites 

 are fragments of a broken-up globe, it is not unlikely that they 

 show to us, to some extent, the constitution of our own globe. 

 Uniformity of cosmic matter has been indicated by all studies 

 of meteorites, as well as by all spectroscopic inquiries into the 

 chemistry of space. Uniformity of cosmic history seems there- 

 fore probable also. 



I have shown in the studies previously referred to that 

 meteorites chiefly differ in composition from the crustal terres- 

 trial rocks with which we are familiar in havino" an excess of iron, 

 nickel, and magnesium, and in being practically without free 

 silica, oxygen, and water. Assuming that the earth, however, 

 has passed through a history like that of the globe above 

 hypothesized, the absence of iron, nickel, and magnesium^ from 

 its crust is explained by the conclusion that they have been car- 

 ried within its interior by their density. They are therefore 

 removed from our observation, except as occasional outflows such 

 as that known in Greenland bring them to view. It is well known 

 that the density of the earth as a whole requires that its interior 

 contain matter of higher specific gravity than that with which we 

 are familiar upon its crust, and it has often been suggested that 



'Magnesium is here referred to not as the element, wliicli is relatively light, but 

 as the essential constituent of chrysolite, which is of high specific gravity and forms 

 some of the heaviest terrestrial eruptive rocks. 



