feet in depth. I removed from the water some specimens with
glasses, and carried them to a tent which I had near the sea.
I t was easy to perceive that the colouration was due to little
tufts, scarcely visible, often greenish, and sometimes of an
intense green, but for the most part of a deep r e d : the water
upon Avliich they floated was always colourless. This very
interesting phenomenon, sufficient to afford a reason for the
etymology of the name which this sea has received (an etymology
up to the present time always burled in complete
obscurity)— attracted all my attention, and I examined it at
leisure with aU the care of which I was capable. During
many days I observed also the colouring matter with the
microscope: the tufts were formed of little bundles of filaments
of an Oscillatoria; they Avere fusiform and elongated,
irregular, having rarely more than the diameter of a line,
and Avere contained in a sort of mucilaginous sheath; but
neither the filaments taken separately in each fleece, nor
the fleeces themselves resembled each other. When the
sun shines in the horizon, I observed, moreover, that these
last maintained themselves upon the surface of the Avater
in the glasses Avhich I had brought with me, and that
during the night, and Avhen I shook the vessel, they reached
the bottom. Some time afterAvards they remounted to the
surface.
“ The phenomenon of the Red Sea was not permanent, but
periodical. I observed it three other times, the 25 th and
30th of December, 1823, and the 5th of January, 1824.”
The same phenomenon of the colouration of the Red Sea,
although on a scale infinitely more surprising, has occurred
also more recently to other observers, especially to M. Evenor
Dupont, a very distinguished advocate of the Isle of Mauritius,
Avho also accurately determined, as did Ehrenherg
previously the cause of this colouration, although he had no
knoAvledge but that the discovery was entirely new to science,
and which he found to be an Alga, which Dr. Montagne
has ascertained to be identical with th a t described by the
Prussian naturalist.
The letter of M. Evenor Dupont is so very circumstantial
and satisfactory, and corroborative of Ehrenberg’s account,
that its Introduction cannot but be approved of. It is addressed
to his friend M. Isidore Geoffroy-Saint-Hilaire.
“ My dear Friend,
“ You demand of me certain details In reference to the
circumstances in which I gathered the Crgptogamic plant
which I sent you from the Red Sea, and Avhich you told me
appeared a ncAV species. They are as follow :—
“ The 8th Ju ly last (1843) I entered into the Red Sea
by the Strait of Babelmandel upon the steam-boat the At-
alanta, belonging to the Indian Company. I demanded of
the captain and the officers, who for a long time navigated in
these latitudes (parages) what Avas the origin of this ancient
name of the Red Sea ; if it was owing, as some have pretended,
to sands of tha t colour, or, according to others, to
rocks. None of these gentlemen could reply to me; they
nevei', they said, remarked any thing to justify this denomination.
I observed then for myself as Ave advanced ; whether
the ship approached by turns the Arabian coast or the African
coast, the red was in no part apparent. The horrid mountainous
barriers Avhich border the two banks were uniformly of
a blackish brown, except where in some places the appearance
of an extinct volcano had left long Avhite streams. The
sands were AA’hite, the reefs of coral Avere Avhite also ; the sea
of the most beautiful cærulean blue. I had given up the
hope of discovering my etymology.
“ On the 15th of Ju ly the burning sun of Arabia awoke
me suddenly by shining all at once, from the horizon w ithout
spot, and in all its splendour. I turned myself mechanically
toAvards the windoAV of the poop to seek a remnant of the
fresh air of the night before the ardour of the day had devoured
it. What Avas my surprise to behold the sea tinted
with red as far as the eye could reach ! Behind the ship,
upon the deck, and on all sides I saw the same phenomenon.
“ I interrogated the officers anew. The doctor pretended
that he had already observed this fact, which Avas, according
to him, produced by the fry of fish floating on the surface ; the