REPORT ON THE DEEP-SEA DEPOSITS. 
XVll 
land, and these changes are subordinate to the nature of the country through which 
streams and rivers pass. Torrents descending from mountains have a great erosive 
power, and the same is the case with rivers which flow over soft or sandy ground ; 
both spread out on the plains and transport to the sea immense quantities of 
alluvial matter. The sediment from rivers is not transported to great distances, 
for matters in suspension are arrested by the movements of the sea ; the bed of the 
ocean is not in consequence filled up so rapidly as one would think, but the places 
near the coasts are loaded with sandy materials, and it is here that the greatest 
modifications take place. He rejects the view that the sediment brought to the 
Black Sea by rivers could have bad any considerable effect in filling up that sea and 
causing it to overflow. Strabo likewise attributed an active part to the winds in 
all the changes taking place at the surface of the globe. To the combination of all these 
forces he attributes what has, since his time, been called the sculpturing of the continents.^ 
Seneca ^ says : In virtue especially of its persistence and continuity, water acts on the 
sobd bodies which constitute the land by dissolving and disintegrating them, and even 
transporting them, sometimes far from their place of origin. All rocks, even the 
hardest, are penetrated by water, which dissolves them at least partially. Seneca 
attributes the solvent action to the presence of a gas (spiritus) ; thermal springs 
possess the power of dissolving minerals in the highest degree. Among those which 
resist the least, he enumerates salt, sulphur, nitre, alum, bitumen, and lime. The 
matters dissolved by water are deposited again, and this precipitation is especially 
abundant when the waters are thermal and gaseous. He likewise explains the formation 
of calcareous tufas. He points out that the saline substances, held in solution by the 
aqueous element, may be absorbed by earthy layers, which in a way serve as a 
natural filter. What has just been said upon the chemical action of water shows 
that Seneca had clearly recognised those hydrothermic phenomena which play so 
important a role in geology. 
Seneca’s ideas regarding the mechanical action of water are not less just. The 
hardest rocks are not able to resist the repeated force exercised by a drop of water, 
and the erosive effects of water are most pronounced when the forces in play are 
those of rivers and the currents and waves of the sea, as may be observed in the 
beds of rivers and on bold coasts ; everywhere on the land, water is to be seen 
victoriously attacking and destroying rocks. Its chemical effects often precede the 
mechanical action ; this last finds its work half completed. Streams and rivers 
transport at all times, but especially during floods, clay, sand, and rocks picked up 
from the layers which they traverse. The erosive power of waves is, however, even 
1 See H. Fischer, Ueber einige Gegenstiinde der physischen Geographie bei Strab, als Beitrag zur Geschichte der 
alten Geographie, Wernigerode, 1879. 
^ Born a few years b.c. 
