10 PHYSICAL GHOGRAPHY OF THE SEA. 
of mud and sand, which so many rivers continually carry along 
with them into the sea. Thus at the mouths of the Nile, of the 
Ganges, and of the Mississippi, large alluvial plains have been 
deposited, which now form some of the most fruitful portions of 
the globe. The whole Delta of Egypt, Bengal, and Louisiana, 
have thus gradually emerged from the waters. 
The volcanic powers, which once caused the highest mountain 
chains to rise from the glowing bosom of the earth, are still 
uninterruptedly active in changing its surface, and are gradually 
displacing the present boundaries of sea and land, upheaving 
some parts and causing others to subside. 
On the coast of Sweden, it has been ascertained that iron 
rings fixed to rocks which formerly served for the fastening ot 
boats are at present much too high. Flat cliffs on which, ac- 
cording to ancient documents, seals used to be clubbed while 
enjeying the warm sunbeam, are now quite out of the reach of 
these amphibious animals. In the years 1731, 1752, and 1755, 
marks were hewn in some conspicuous rocks, which after the 
lapse of half a century were found to have risen about two feet 
higher above the level of the sea. This phenomenon is confined 
to part of the coast, so that it is clearly the result of a local and 
slowly progressive upheaving. 
Whilst a great part of Scandinavia is thus slowly but steadily 
rising, the shores of Chili have been found to rise convulsively 
under the influence of mighty volcanic shocks. Thus after the 
great earthquake of 1822, the whole coast, for the length of a 
hundred miles, was found to be three or four feet higher than 
before, and a further elevation was observed after the earthquake 
of Feb. 21st, 1835. 
While to the north of Wolstenholme Sound, Kane remarked 
signs of elevation, a converse depression was observed as he 
proceeded southwards along the coast of Greenland, Esquimaux 
huts being seen washed by the sea. The axis of oscillation 
must be somewhere about 77° N. lat. 
At Keeling Island, in the Indian Ocean, Mr. Darwin found 
evidence of subsidence. On every side of the lagoon, in which 
the water is as tranquil as in the most sheltered lake, old cocoa- 
nut-trees were undermined and falling. The foundation-posts 
of a store-house on the beach, which the inhabitants had said 
stood seven years before just above high-water mark, were now 
