N0ST0CHINEJ2. 271 



Leaving the limits of our own country, MM. Engelhardt and 

 Treschel have described a minute Al(jfa,which they have named 

 Oscillatoria ruhescens, and which tinges with a red colour 

 the lake of Morat, in Switzerland, assuming sometimes a 

 very beautiful arrangement, depending upon the motion of 

 the water in which it is immersed.* 



But it is not in fresh water merely that the productions of 

 tliis family are found; they likewise have been noticed to 

 occur in vast quantities in the sea, in different parts of the 

 world ; and it has been ascertained that the Red Sea owes its 

 name to the periodical dev elopement of a species of this 

 family, the Trichodesmium Ehrenbergii Montague. The 

 name of Ehrenberg has very properly been appended to 

 this species by Dr. Montague, that illustrious naturalist 

 being not merely the first to describe the species, but also 

 the first to discover and record the important and wonderful 

 fact that to a production in its individual parts so minute and 

 insignificant, the Red Sea owes its name and appearance. 

 This interesting discovery, however, of Ehrenberg was for 

 many years overlooked, the account of it having been pub- 

 lished in a work not devoted to natural history, but to 

 chemical science, " Annals of Poggendorf." The following 

 translation cannot fail to interest : — 



" During the year 1823," observes M. Ehrenberg, " I made 

 a stay of many months at Tor, upon the borders of the Red 

 Sea, close to Mount Sinai. On the 1 0th of December I there 

 saw the surprising phenomenon of the blood-red colouration 

 of all the bay which forms the port of that city. The high 

 sea, without the boundary of the corals, preserves its ordi- 

 nary colour. The short waves of a tranquil sea bring upon 

 the banks during the heat of the day a mucilaginous matter 

 of a blood-red colour, and deposit it upon the sand, in such a 

 manner as that In the course of a good half hour all the bay 

 with the receding tide is surrounded with a red border of many 



* Notice sur la matiere qui a colore en rouge le lac Morat, en 1 825, par 

 De CancloUe, dans les Memoires de la Societe de Physique et d'Histoire 

 Naturelle de Science, 1825, vol. ii. with fig. 



