272 NOSTOCHINE^'. 



feet in depth. I i-emoved from the water some specimens with 

 glasses, and carried them to a tent which I had near the sea. 

 It Avas 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 red : the water 

 upon wliich 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 ety- 

 mology up to the present time always buried in complete 

 obscurity) — attracted all my attention, and I examined it at 

 leisure with all the care of which I was capable. During 

 many days I observed also the colouring matter Avith the 

 microscope : the tufts Avere formed of little bundles of fila- 

 ments 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 themseh^es 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 Avith me, and that 

 during the night, and Avhen I shook the vessel, they reached 

 the bottom. Some time afterwards they remounted to the 

 surface. 



" The plienomcnon of the Red Sea Avas not permanent, but 

 periodical. I observed it three other times, the 25th and 

 30th of December, 1823, and the 5th of January, 1824." 



The same plieuomenon of the colouration of tlie 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 Mau- 

 ritius, who also accurately determined, as did Ehrenberg 

 previously the cause of this colouration, although he had no 

 knowledge but that the discovery was entirely ncAV to sci- 

 ence, and which he found to be an Alr/a, Avhich Dr. INIontagne 

 has ascertained to be identical Avith that described by the 

 Prussian naturalist. 



The letter of M. Evenor Dupont is so very circumstantial 



