352 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
or an assemblage of blocks, deeply and unequally hollowed out, with 
folded ranges welded to solid arch stones, and on the summits of 
these folded ranges wreaths of islands outlining arabesques. 
In conclusion, after having seen what is at present occurring in 
the sea, and having shown by comparison how this study of the 
present sea yields information on the story of the ancient seas, we 
are led to ask ourselves whether this same story will go on indefi- 
nitely, whether the seas will continue to be displaced on the surface 
of the globe. 
I do not think the seas can ever be lacking on the earth, at least 
not until the day when the earth becomes only an extinct and frozen 
globe. It does not seem to me, in fact, that the loss in water could 
be very great at the surface. Granting that to a certain depth there 
surely do not exist empty cavities in which this water could be 
engulfed, it can disappear only through chemical reaction by yielding 
its oxygen to the oxidation of rocks, while the hydrogen escapes 
into the heights of the atmosphere. Such a reaction as that certainly 
does take place. The land exhales hydrogen, and toward a height 
of 70 to 80 kilometers this hydrogen takes the place of nitrogen. 
But this is a much restricted phenomenon compared with the immense 
volume of the seas which, if spread all over the earth, would form a 
mantle of water 3 kilometers thick, and which even now cover three- 
quarters of the land. The oxidations, to be effectual, must become 
more and more limited by the fact that the region of the crust where 
they act could not exceed 60 kilometers. On the contrary, it is even 
very possible that volcanism and certain thermal springs may furnish 
at the surface some new water, fresh, never having seen the light. 
I believe, then, in conclusion, that the total volume of the seas, which 
must, no doubt, have been diminishing since the beginning of geologic 
time, at the same time that their salinity was increasing and as 
their average temperature has been reduced, might diminish still 
more. You will see the same phenomena continued, but they will 
without doubt be retarded more and more in such a way that the 
cooling of the sun, which will lead to the death of the earth, will 
probably have had time to be completed before these seas have 
disappeared. 
