272 NOSTOCHINE^E. 



feet in depth. I removed from the water some specimens with 

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

 It 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 red : the water 

 upon which 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 with the 

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

 ments of an Oscillatoria ; they were fusiform and elongated, 

 irregular, having rarely more than the diameter of a line, 

 and were 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 water 

 in the glasses which I had brought with me, and that 

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

 the bottom. Some time afterwards they remounted to the 

 surface. 



" The phenomenon of the Red Sea was 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 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 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 new to sci- 

 ence, and which he found to be an Alga, which Dr. Montagne 

 has ascertained to be identical with that described by the 

 Prussian naturalist. 



The letter of M. Evenor Dupont is so very circumstantial 



