100 Geological Society of London. 
riod, but merely that these hills had been modified in shape in recent 
times, and that during that modification, alluviums of older date had 
been washed away, or the land shells which they may once have con- 
tained have decomposed and disappeared. In regard to the great 
numbers of these shells preserved throughout the bed at Gore Cliff, 
and in many other places even at greater depths, it will not seem 
surprising to those who have observed the number of dead land shells 
which are strewed over the surface of the chalk downs, or lie con- 
cealed in the green turf in numbers almost as countless as the blades 
of grass. If the slightest wash of water should pass over such a 
soil, it must float off myriads of these shells, and they would imme- 
diately be involved in that white cream-colored mud which descends 
from wasting hills of chalk after heavy rains. Land shells so buried 
may retain their color for indefinite periods, as is shown by the state 
of species in the loess of the Rhine, and even in tertiary strata of 
much higher antiquity. 
While a variety of geological monuments are annually discovered 
which attest modern alterations in the level of the land, it is impor- 
tant to remark that new testimony is also daily obtained of the rising 
and sinking of land in our own times. I discussed at some length, 
in my last anniversary address, the evidence for and against the up- 
heaval of the coast of Chili during the earthquake of 1822, a con- 
troverted point to which our attention has lately been again recalled. 
I may remark, however, that since we have ascertained the fact of 
a rise of three, five, and even ten feet in parts of the same country 
in 1835, so distinctly attested by Captain Fitzroy, all doubts enter- 
tained as to the permanent effects of a preceding convulsion are com- 
paratively of small interest. Don Mariano Rivero dissents from the 
opinion that a change of level occurred at Valparaiso in 1822, and 
Colonel Walpole, after seeing the ground and conversing with per- 
_sons who were on the spot in 1822, and who still reside there, also 
considers the statement of a rise to be inaccurate. On the other 
hand Mr. Caldcleugh, who was formerly sceptical on the same point, 
has now come round to the opinion of Mrs. Calcott, (Maria Gra- 
ham,) and believes that an elevation of land did take place. 
Mr. Darwin, whose opportunities of investigation both in Chili and 
other parts of South America have been so extensive, thinks it quite 
certain that the land was upheaved two or three feet during the 
earthquake of 1822, and he met with none of the inhabitants who 
doubted the change of level. He states that the rise of land, even 
