562 Io I Gla A Oop IKI INS 
since that principle is dependent upon a marked difference between the 
capillarity of water and of steam, while at the critical point, the density 
of water-gas being the same as that of water, this force should be 
absent. The problem then becomes a question of equilibrium 
between the hydrostatic column of water and that of the lava, in which 
the pressure of the lava at a depth of 7,000 feet should be in the neigh- 
borhood of 2.7 times that of the water, though this preponderance 
steadily diminishes as the water-gas becomes condensed, with increas- 
ing depth, at a rate higher than lava. Whether under these conditions 
lava can absorb water-gas, is an open question. 
Water can only penetrate from 25,000 to 30,000 feet below the 
surface on account of the closure of all crevices by pressure. But on 
the assumption that the temperature gradient in the outer part of the 
earth’s crust is 1° C. for each too feet of descent (which is probably 
too high) the critical temperature will not be reached, except in the 
neighborhood of volcanic intrusions, until at a depth of about 36,000 
feet. Hence, over the greater part of the earth, water will remain in the 
liquid state as far down as fractures and fissures will allow it to seep, and 
no appeal can be made to the more rapid and potent gaseous diffusion 
to carry it beyond 30,000 feet. But because of their heat, lavas must 
originate at much greater depths below the surface, and hence far 
beyond the reach of surface waters, which can only come in contact 
with them, and only doubtfully then, in a very limited portion of the 
throat of the volcano. 
These considerations seem to indicate that, for the most part, the 
volcanic gases and vapors have not been supplied to the lavas by 
ground waters, but are original constituents of the magmas. Doubt- 
less at the beginning of an eruption, following a period of quiescence, 
much of the steam merely comes from such rain water as may have 
accumulated in the crater and upper part of the cone, but this does 
not account for the gaseous emanations from the lava itself, nor from 
those volcanoes, such as Stromboli, and the well-known Solfatara near 
Naples, which maintain a mild form of eruption for long periods. 
Such meteoric water could contribute to the volcanic gases little except 
some dissolved air, together with a trace of carbon dioxide, and 
perhaps hydrogen from chemical action. Such soluble salts as this 
water might dissolve from the crater walls were brought up from the 
