564 R. T. CHAMBERLIN 
can produce it, but as they approach the surface much of the hydrogen 
and water vapor escapes and pyroxene minerals crystallize instead 
of these hydrous micas. 
All of these facts and deductions lead to the general conclusion 
that our surface waters have been derived from the interior of the 
earth, and oppose the idea that to explain the presence of hydrogen, 
or water, in magmas and rocks, we have merely to appeal to the pene- 
tration of surface waters. The meteoric waters are limited to their 
superficial place and function, both in the evolution of magmas and 
in vulcanism; an ultimate source is found for these waters; and a 
steady supply of water and gases is furnished to the earth to offset the 
loss of vapor into space, and thus contributes to the globe one of the 
factors necessary to a long period of habitability for hving organisms. 
VOLCANIC GASES 
The gases which escape from fumarolic vents are in many respects 
similar to those obtained by heating igneous rocks im vacuo, but with 
the addition of oxygen and vapors of chlorides, fluorides, boric acid, 
and other high-temperature volatilizations. Though nitrogen is much 
more conspicuous in the analyses of volcanic gases than in those 
from rocks, this is doubtless due, in the main, to a mixture with atmos- 
pheric air. However, the greater heat of the volcano would also 
favor a higher proportion of nitrogen, as shown by my experiment. 
Much of the oxygen also is probably from the air. But an analysis 
of gas escaping from a stream of lava flowing on the sea bottom at 
Santorin gave Fouqué: oxygen, 21.11 per cent.; nitrogen, 21:90 
per cent.; and hydrogen, 56.70 per cent." This would suggest that 
the dissociation of water also contributes free oxygen. 
Fouqué’s studies at Santorin confirm the law of variation in com- 
position of volcanic gases, first established by Sainte-Claire Deville,’ 
namely, that the nature of the gas evolved depends upon the phase of 
volcanic activity. Hydrochloric acid, with free chlorine and fluorine, 
is given off only from the hottest fumaroles where the heat is sufficient 
to liberate these gases from chlorides and fluorides. At less active 
vents, sulphur dioxide is the most noticeable of the corrosive gases, 
while the cooler fumaroles exhale chiefly hydrogen sulphide, carbon 
« Fouqué, Santorin et ses éruptions, p. 230. 
2 Sainte-Claire Deville, Ann. de chim. et phys., 52 (1858), p. 60. 
