328 Geological Society. 
In regard to the discordance in the results at which these eminent 
conchologists have arrived, it may arise not only from the unequal: 
opportunities which they have enjoyed of examining the necessary 
data, but also, in part, to the different estimate which they have 
formed of the amount of variation necessary to constitute a distinct 
species. One example will sufficiently illustrate my meaning. Those 
naturalists who agree with M. Deshayes in referring all the living 
varieties of Lucina divaricata brought from different countries to 
one and the same species, will identify many more fossils with re- 
cent shells than those who agree with Dr. Beck in dividing the 
same recent individuals of Lucina divaricata into six or eight di- 
stinct species. Provided, however, each zoologist is consistent 
with himself, and provided the distinctive characters relied on as 
specific by each are commensurate one with another, no confusion 
will arise. 
In reviewing the proceedings of the Society during the last year, 
I find that the remaining memoirs, numerous as they are, may be 
all referred to one great class of subjects, for they either relate to 
changes now going on upon the surface of the earth as attested by 
man, or to geological proofs of similar changes since the rivers, lakes, 
and seas were inhabited by the existing species of testacea. Under 
these heads I shall be led to consider the effects of modern earth- 
quakes in upheaving and depressing the land; the gradual rising of 
land in one region and the lowering of its level in another; the rolling 
in of great waves of the sea upon the coast during earthquakes ; the 
transportation of rocks by floating ice; the signs of upraised beaches 
containing marine shells ; erratic blocks ; alluvial deposits of different 
ages; and other kindred topics on which a variety of new facts have 
been collected. 
The last year has been signalized in South America by one of 
those terrific convulsions which have so often desolated the western 
coast since the discovery of the new world. A brief notice of this 
catastrophe was sent me by Mr. Alison, written immediately after 
the event. He mentions that on the 20th of February, 1835, when 
Conception, Chillan, and other towns were thrown down in ruins, 
the sea first retired from the shores of the Bay of Conception, and 
then returning in a wave about twenty feet high, rolled over several 
of the towns, and completely destroyed whatever the earthquake 
had left uninjured. He also states that the coast of the bay was 
reported to have been heaved up, and that a rock off the landing~ 
place at the port of Taleahuano, which before the shock was nearly 
level with high water, stood afterwards three feet above that mark. 
Large fissures were made in the earth, and water burst from some 
of them. 
In these and other particulars Mr. Alison’s letter agrees with 
the more circumstantial account sent to the Royal Society by 
Mr. Caldcleugh, who was resident at Valparaiso, but who drew his 
information in great part from eye-witnesses. He mentions that a 
great number of the volcanos of the Chilian Andes were in a state 
of unusual activity during the shocks, and for some time preceding 
