XVI 
THE VOYAGE OF H.M.S. CHALLENGER. 
hy Sir William Thomson in 1870 was a still further improvement, and, indeed, since the 
commencement of submarine telegraphy, the process of taking deep-sea soundings has been 
rapiilly perfected. ^lany submarine telegraph ships, surveying vessels, and even private 
vnchts, have now been fitted with the most improved apparatus for sounding ; so that, 
when it is desired to know the depth only, this can be ascertained expeditiously and 
with great accuracy. 
During the past thirty years the ocean has been sounded in all directions, and we 
have in consequence a very correct notion of the general form and relief of all the great 
ocean btisins and enclosed seas. Not only in a knowledge of the bathymetry of the 
iKcan, but in an acquaintance with all the other conditions of the deep sea, there has 
been a rapid and important development, thanks to the investigations of the Challenger 
Expedition, as well as the previous and subsequent expeditions of this and other 
countries. 
This Report being limited to a consideration of the sedimentary deposits of the deep 
sea, it seems desirable to indicate the views that have at difierent times been held with 
reference to marine sedimentation. 
Herodotus' discussed the formation of alluvium at the entrance of the Nile, and 
the relations subsisting between land and sea, but on these it is unnecessary to dwell. 
Plato,* in the myth of Atlantis, supposes a great extent of land situated in the 
external sea to have disappeared in one day and one night beneath the water of 
the ocean. Since that time, he adds, the Atlantic Sea has ceased to be navigable ; its 
waters have become muddy and charged with clay derived from the engulfed land.® 
Skylax of Coryanda,^ in speaking of the sea which bathes the west of Europe, 
limits his remarks to saying : — “ Beyond the Pillars of Hercules there are many 
Carthagenian commercial stations, much muddy water, high tides, and open seas.”® 
Aristotle* Inis no new views with regard to the great external ocean, which, he 
states, in accordance with the ideas generally admitted in his time, is muddy and 
little agitated by the wind.s. 
Polybius' points out that in the Sea of Azov the rivers bring down considerable 
quantities of sediment. He estimates the time it will take for this fiuviatilc alluvium 
to fill up, not only the Sea of Azov, but also the Euxinus or Black Sea. The ideas 
of Polybius, from a geological point of view, are most reasonable, but the rate of 
encroachment h{us been much slower tluin he supposed during the 2000 years which 
sr-panite us from tlie time when he wrote. The modifications in these seas have' 
not Ijccn ver)' appreciable. 
StralK)* says: Running water works profound modifications on the surface of the 
• 4 s.i -.108 11.C. * Bom 42ft n.c. * Plato, Tima:ufl, c. 5, 6, and CritioiS, c. 3, 8. 
* Flonriahwl in the middle of the fourth centurj' B.C. * Skylax, Periplus, 1. " 384-322 u.c. 
2t>4-122 B.C • Born alx)ut CO B.c. 
