The Structure and Distribution of Coral Reefs | Page 6

of the scientific staff. When,
in 1839, the expedition arrived at Sydney, a newspaper paragraph was
found which gave the American naturalist the first intimation of
Darwin's new theory of the origin of atolls and barrier-reefs. Writing in
1872, Dana describes the effect produced on his mind by reading this
passage:--"The paragraph threw a flood of light over the subject, and
called forth feelings of peculiar satisfaction, and of gratefulness to Mr.
Darwin, which still come up afresh whenever the subject of coral
islands is mentioned. The Gambier Islands in the Paumotus, which
gave him the key to the theory, I had not seen; but on reaching the
Feejees, six months later, in 1840, I found there similar facts on a still
grander scale and of a more diversified character, so that I was
afterward enabled to speak of his theory as established with more
positiveness than he himself, in his philosophic caution, had been ready
to adopt. His work on coral-reefs appeared in 1842, when my report on
the subject was already in manuscript. It showed that the conclusions
on other points, which we had independently reached, were for the
most part the same. The principal points of difference relate to the
reason for the absence of corals from some coasts, and the evidence
therefrom as to changes of level, and the distribution of the oceanic
regions of elevation and subsidence--topics which a wide range of
travel over the Pacific brought directly and constantly to my attention."

Among the Reports of the United States Exploring Expedition, two
important works from the pen of Professor Dana made their
appearance;--one on "Zoophytes," which treats at length on "Corals and
Coral-Animals," and the other on "Coral-Reefs and Islands." In 1872,
Dana prepared a work of a more popular character in which some of the
chief results of his studies are described; it bore the title of "Corals and
Coral-Islands." Of this work, new and enlarged editions appeared in
1874 and 1890 in America, while two editions were published in this
country in 1872 and 1875. In all these works their author, while
maintaining an independent judgment on certain matters of detail,
warmly defends the views of Darwin on all points essential to the
theory.
Another able exponent and illustrator of the theory of coral-reefs was
found in Professor J.B. Jukes, who accompanied H.M.S. "Fly", as
naturalist, during the survey of the Great Barrier-Reef--in the years
1842 to 1846. Jukes, who was a man of great acuteness as well as
independence of mind, concludes his account of the great Australian
reefs with the following words:--"After seeing much of the Great
Barrier-Reefs, and reflecting much upon them, and trying if it were
possible by any means to evade the conclusions to which Mr. Darwin
has come, I cannot help adding that his hypothesis is perfectly
satisfactory to my mind, and rises beyond a mere hypothesis into the
true theory of coral-reefs."
As the result of the clear exposition of the subject by Darwin, Lyell,
Dana, and Jukes, the theory of coral-reefs had, by the middle of the
present century, commanded the almost universal assent of both
biologists and geologists. In 1859 Baron von Richthofen brought
forward new facts in its support, by showing that the existence of the
thick masses of dolomitic limestone in the Tyrol could be best
accounted for if they were regarded as of coralline origin and as being
formed during a period of long continued subsidence. The same views
were maintained by Professor Mojsisovics in his "Dolomit-riffe von
Sudtirol und Venetien," which appeared in 1879.
The first serious note of dissent to the generally accepted theory was
heard in 1863, when a distinguished German naturalist, Dr. Karl
Semper, declared that his study of the Pelew Islands showed that
uninterrupted subsidence could not have been going on in that region.

Dr. Semper's objections were very carefully considered by Mr. Darwin,
and a reply to them appeared in the second and revised edition of his
"Coral-Reefs," which was published in 1874. With characteristic
frankness and freedom from prejudice, Darwin admitted that the facts
brought forward by Dr. Semper proved that in certain specified cases,
subsidence could not have played the chief part in originating the
peculiar forms of the coral-islands. But while making this admission,
he firmly maintained that exceptional cases, like those described in the
Pelew Islands, were not sufficient to invalidate the theory of subsidence
as applied to the widely spread atolls, encircling reefs, and barrier-reefs
of the Pacific and Indian Oceans. It is worthy of note that to the end of
his life Darwin maintained a friendly correspondence with Semper
concerning the points on which they were at issue.
After the appearance of Semper's work, Dr. J.J. Rein published an
account of the Bermudas, in which he opposed the interpretation of