Algce a Colouring Matter in Salt Marshes. 183 



which we observe a scum of the same colour. Water thus 

 coloured is very dense (25 to 26 degrees of Baume), and is just 

 at the point of depositing crystallized marine salt ; but this 

 phenomenon is by no means so common as it is believed to be, 

 and, to use the expression of the salt-makers, it only occurs in 

 old water. Very often the tables crystallize without our per- 

 ceiving in the water any trace of red matter. Thousands of 

 quintals of salt have been collected this year in the salt-works 

 of Bagnas de Villeneuve, and at that of Peccais, and scarcely 

 any coloured salt has been met with. The red colour of salt- 

 marshes had been attributed to the presence of a small bran- 

 chiopode the Aitemia salina ; but M. Dumal has visited several 

 salt-works where that crustaceous animal existed in innumer- 

 able quantities, and where the water, nevertheless, remained 

 limpid and colourless. The Artemia salina observed in these 

 waters was not at all red ; the young individuals had a greyish 

 colour, and those more advanced in age a rose tint, approach- 

 ing the colour of rust. When the water is concentrated by 

 evaporation, the crustaceous animal acquires a red colour, but 

 the water itself is not at all tinged. We cannot attribute the 

 red colour of the water of salt-works to the dead remains of 

 the Artemia sahna ; for, at the salt-works of Bagnas and of 

 Peccais, MM. Dunal and Legrand observed a considerable 

 quantity of the dead animals half decomposed, which had a 

 milky appearance. 



Not being able to assign the presence of the Artemia salina as 

 the cause of the coloration of the water, M. Dunal began to inves- 

 tigate the phenomena with attention. On taking some water from 

 the upper part of a pool, which seemed filled with a liquid of a 

 beautiful rose colour, or rose tinged with a violet reflection, M. 

 Dunal only obtained a colourless liquid ; but, when he plunged 

 his vessel to the bottom, he brought up some coloured matter. 

 This substance, when submitted to the microscope, presented 

 to M. Dunal numerous spherical globules, which were extremely 

 small and hyaline, and seemed to be a true Protococcns, to which 

 he has given the name of Salinus. This small j)laiit is develop- 

 ed at the bottom of the water, and its beautiful rose or violet 

 colour is reflected through the whole of the licjuid which covers 

 it. In other reservoirs where he did not find the Frotococcus 



