THE GASES IN ROCKS 555 
them. A self-regulating system was inaugurated. In the early 
stages of the hydrosphere, when growth by infalling planetesimals 
was rapid, much water was buried within the fragmental crust. This 
material, worked over by volcanic activity, brought to the surface 
and subjected to weathering and erosion, and buried beneath more 
material, has undergone assortment and alteration until the accessible 
rocks at the present time are very different from the meteoritic matter. 
Since the earth attained its growth and the infall of planetesimals 
slackened, much less water has penetrated to great depths below the 
surface. Post-Archean sedimentaries have not yet reached thicknesses 
sufficient to carry inclosed water down to the depths from which the 
lavas arise. Deep mines indicate that fractures and fissures do not 
convey water down to very great depths at the present time. If water 
does not penetrate so rapidly now, and hydration and carbonation 
are less effective, it is also probably true that subsiding vulcanism 
brings less gas to the surface. 
It is essentially a system of balance. At the same time that water 
is being buried with sediment, its elements, hydrogen and oxygen, the 
latter in the form of the oxides of carbon, are exhaled from the earth’s 
interior through volcanic outlets. But the system here suggested is 
very different from the postulated limited cycle of underground water 
which, following Daubrée’s famous experiment," has crept into geo- 
logic literature as the origin of volcanic vapors and the modus operandi 
of vulcanism. Instead of surface waters following cracks and fissures 
down to the hot lavas there to be absorbed, the water already is present, 
and is a part of the rocks and magmas in the interior, whether actually 
combined as water, or as its elements held in solution, or chemically 
united in other compounds. ‘These gaseous elements form an integral 
part in the magmas, having been vital factors in their development 
from the primitive planetary matter. That this process of reworking 
has gone on to considerable depths, if we are to start with typical 
material, is evidenced by the fact that the deep-seated plutonic rocks 
are characterized by micas and other hydrous minerals, while mineral 
species of the meteoritic type are absent.? 
« Daubrée, Etudes synthétiques de géologie expérimentale, Tome 1, pp. 236-46. 
2 This statement should perhaps be qualified. The basalt at Ovifak, Greenland, 
contains iron strongly resembling the meteoric meta!, in which the minerals cohenite, 
