Geological Society of London. 101 
in the bay of Valparaiso, was far from being uniform, for a part of a 
fort not formerly visible from a certain spot has, subsequently to the 
earthquake, fallen within the line of vision. ‘The most unequivocal 
proof of a recent rise is drawn from the acorn-shells, Balanida, 
found adhering to the rock above the reach of the highest tides. 
These were observed by Mr. Darwin sixty miles south of Valpa- 
raiso, and at Quintero, a few miles to the north of it; but his friend 
Mr: Alison detected them on a projecting point of rock at Valpa- 
- yaiso itself. The attached shells were there seen at the height of 
fourteen feet above high-water mark, and were only exposed upon 
the removal of the dung of birds, by which they would have been 
concealed from ordinary observation. In Mr. Darwin’s paper you 
will find many other facts elucidating the rise of land at Valparaiso, 
and he has also treated of the general question of the elevation of the 
whole coast of the Pacific from Peru to Terra del Fuego. Beds of 
shells were traced by him at various heights above the sea, some a 
few yards, others five hundred or even thirteen hundred feet high, 
the shells being in a more advanced state of decomposition in pro- 
portion to their elevation. Mr. Darwin also shows that parallel ter- 
races such as those of Coquimbo, described by Captain Basil Hall 
and others, which rise to the height of three hundred feet and more, 
are of marine origin, being sometimes covered with sea-shells, and 
they indicate successive elevations. There are also grounds for be- 
lieving that the modern upheaval of land has proceeded not only by 
sudden starts during convulsions of the earth, but also by insensible 
degrees in the intervals between earthquakes, as is now admitted to 
be the case in parts of Norway and Sweden. 
This gradual and insensible rising is supposed to affect, not only 
the region of the Andes, but also the opposite or eastern coast of 
South America, where earthquakes are never experienced: for the ’ 
Pampas of Buenos Ayres bear marks of having risen to their pres- 
ent height during a comparatively modern period, while the coast 
line of the Pacific, or the region of earthquakes and volcanic erup- 
tions, has been the theater of more violent movements. 
It is curious to reflect that if in one portion of a large area of the 
earth’s surface a rise of land takes place at the rate of a few inches 
in a century, as around Stockholm, while in another portion of the 
same area land is uplifted about a yard during an equal period, there 
will be caused, if sufficient time be allowed, a group or chain of lofty 
mountains in one place, and in the other a low country like the Pam- 
pas of South America. 
