554 R. T. CHAMBERLIN 
absorption and retention, even if they were not originally present as 
occluded gases. The sources of the gases obtained from rocks are 
so complex that it is difficult to determine how much is to be assigned 
to each. Because of the penetration of surface waters containing 
carbonic acid in solution, throughout the accessible rocks of the earth’s 
exterior, it is likely that, in many cases, the bulk of the gas obtained 
by heating powders in vacuo has been derived from acquired water 
and carbonated compounds. But in fresh meteorites, which pre- 
sumably have not been subjected to action of this sort, occlusion is 
relatively more important. 
From the constitution of meteorites, some of the principles of 
early terrestrial evolution may, perhaps, be inferred, though the 
erowth of the earth was probably not quite analogous, in all respects, 
to the formation of the meteorites. Whether we take the meteoritic 
material to represent the heavier part of the original matter of the solar 
system, or the stellar system, as a whole, matters little in the geologic 
problem. If, in truth, the unoxidized, heterogeneously aggregated 
material of meteorites be typical of the original heavy material of 
the earth, it becomes evident that, in the case of our planet, other 
factors have been at work which are not operative in the bodies of 
which the meteorites are supposed to be fragments. ‘These visitors 
from space are characterized by such minerals as cohenite, (Fe, Ni, 
Co),C, lawrencite, FeCl,, oldhamite, CaS,, and schreibersite, (Fe, 
Ni, Co),P, which, next to nickel-iron, is the most widely distributed 
constituent of iron meteorites,t though of less importance in the stony 
specimens. Such compounds imply an absence of both free oxygen 
and water in notable quantities. Of like import is the absence of 
hydrated minerals, such as micas and amphiboles. Water and an 
oxygenated atmosphere appear to be the agents which are lacking 
in the bodies from which the meteorites were derived, but which have 
been the operative factors in working over the outer portion of the 
earth. 
But the original source of the earth’s atmosphere and hydrosphere 
is taken to be gas occluded, or absorbed, in the primitive meteoritic 
material. These original gases, escaping, furnished both atmosphere 
and hydrosphere when the earth became of sufficient size to retain 
« Farrington, Jour. of Geol., Vol. IX, pp. 405-7, 525, 526. 
