Polynesian., 1844-06-22
latitude Of $50. 1t is well known to what an

ocean, and loaded with a fine, impalpable
mud. This must unquestionably be highly
deleterious to the coral polypes, ifnot suttici-
ent to utterly prevent their growth, as they
require the purest ocean water for their sue
ccssful development.
"But | am persuaded, after a careful exam
nation of the facts, that the absence of coral
on the other side of the continent, and in the
wide space between it and the low islands of
Polynesia, is to be attributed to the preva-
lence of cold currents, which proceeding
northward from the Polar regions are per-
ceptible the whole distance from Cape Horn
to Callao, and | presume much further to the
north, in a temperature of the ocean too low
for the existence of the coral animals, and
that in a similar low temperature we are to
seek for the cause of their absence at the
Cape Verde Islands. | have already allud-
ed to the greater heat on the southern part Of
our coast and the Bahamas, produced by the
vicinity of the Gulf Stream.
"a like temperature prevails along the
southern shore of Cuba, and the islands in its
vicinity, and though unable to speak positive
ly, from having no data, rs to the Bermudas,
| have no doubt from their proximity to the
Gull Stream, that they are washed by an
equally warm sea. Now let us glance for a
moment at the facts bearing on this question,
In regions situated in corresponding parallels
of latitude, where no coral formations exist.
At ' al paraiso, in lat. of $50 South, and thence
as far as the Goth parallel, in the month of
November, the surface temperature of the
ocean near the coast has been found to range
from 90 to 600; at Callao, in the lat. of12o,
from go to $50, and thence in a Northwest
erly direction to the Galapagos, to increase
gradually to GEO and 100. Among these
islands, at the same season, its average was
not above go, and at some of them it did not
exceed ego. But leaving these islands and
proceeding Southwest, we find it steadily
rising, till on the skirts of the Dangerous
Archipelago it is up to 100 and 100, nearly
200 higher than on the coast in the same par
allel. And here we enter upon the coral
formations. Among the Paumotus, the field
of their most lavish display, the temperature
varies from TO to $50; at Tahiti from TO to
800, and about the same at the large groups
to the West of it. At the Hawaiian Islands,
lying between 100 and go North latitude, it
is as high sometimes as 80.
In our own hemisphere, among the Anti
les, Bahamas, and along the southern coast
of Florida, | have found the temperature of
the water near the shore, at different seasons,
from 78o to $50, and in all these regions CO.
raj reefs abound.
cat the Cape Verde Islands, and in the
neighborhood Of trinidad, Martin Vas, and
Fernando Noronha, it falls to $50 md 10;
and these islands, as was before remarked,
are entirely destitute Of coral formations. 1t
is not unlikely that there are cold currents
from the Antarctic along the East as we'll as
the West coast of South America, which
combine with the fresh water of its large riv-
ers, in preventing such formations upon a
certain portion OF it, but this l have at pre-
sent no means of determining, being without
any data as to the temperature North of $50
on that side. 1t appears to me, that such
condolences as the facts here submitted
prove to exist, between certain temperatures
of the ocean and the absence or presence of
coral reefs, can scarcely be considered by
any rejecting mind, as merely casual; and
that there are strong grounds for believing
that we have here a clue to the real cause of
the singular absence of recent coral forma-
tons in certain regions corresponding in eve
ry thing save temperature to those where
they are most proiusely scattered"
The observations upon the growth of coral
are novel, and have already attracted much
attention, but to whom the merit of first no.
ting belongs, is a matter of controversy. Mr..
{. was the first to lay them before the pub
lie, but Mr.. James Dana, the gcologist of
the Exploring Expedition, claims for himself
the honor of first broaching the theory, and
charges Mr.. G. with having borrowed his
facts from him. Those who may feel an in
terest in the dispute, will find the facts on
either side fully stated in vol. 45, of the Am.