1885-86.] Edinburgh Naturalists' Field Club. 275 



made at Brussels ; but Dr Eau made another such research at Ulm 

 in 1755, and his results entirely disproved the suljihur theory, and 

 established the presence of organic bodies. It is also important to 

 note that instances have been recorded of red water resulting from 

 the fine dust emitted during volcanic activity ; and that, at sea, the 

 bleeding of large animals, such as Sharks and Sword-fish, may 

 cause red discoloration. De Saussure,^ in 1760, fovmd the cause 

 of the colour of red rivers to be sometimes pollen ; while in France, 

 in 1797, Girod Chantran found a pond filled with water of a car- 

 mine colour, which he attributed to the presence of a species of 

 Volvox (F. lacustris) — an infusor, which he has named, but not 

 described. 



During the nineteenth century, the investigation of this curious 

 subject was still prosecuted with zeal. Persoon, in 1801, examined 

 certain red mucilaginous specks observed on damp ground, and 

 found the cause to be a fungus, which he described as Thelephora 

 sanguinea, and which was later described by Fries as Plnjladeria 

 Crustacea, and still later, by Agardh, as an alga, Palmella cruenta. 



Andreossy, in Lower Egypt, and Ehrenberg, in the Astrakhan 

 Steppe, found a red-coloured " Salz-lage," — the colouring matter 

 being in the salt, and fading on drying. 



In 1815, the inhabitants of South Prussia were, like the ancient 

 classics, astonished by the presence of red, violet, and green patches 

 in the water of the lake of Lulotin ; and, in consequence of the 

 unusual occurrence, were not slow to predict misfortunes soon to 

 come. Klaproth- examined this water chemically, and found the 

 cause to be an albuminoid-like vegetable mucilage, peculiarly 

 tinged by an indigo dye, and attributable to the decomposition of 

 vegetables during harvest. The transition from green to violet 

 was caused by the presence of more or less oxygen. 



Scoresby,^ in 1820, noted the occurrence of green and blue stripes 

 in the sea around Greenland, and covering about one-fourth of its 

 surface. These he attributed to the presence of small animals 

 ( = small medusoid spherules, J- to § inch long), of which he calculated 

 64 to be in a cubic inch. 



About the same time, Captain Eoss was engaged in the study of 

 red snow, which he found very abundantly in the mountains of 

 Baffin's Bay. This colouring substance, which had been ascribed 

 to the ejectamenta of birds, was examined by Bauer, WoUaston, 

 Thenard, Brown, Hooker, Sprengel, Agardh, De CandoUe, Cladni, 

 and others ; and by all, save Cladni, it was declared to be of a 

 vegetable nature. The systematic position — whether algoid or 

 fungoid — of this new organism was uncertain, and various 



1 ' Voyage dans les Alpes.' 



2 'Beitrage z. chem. Kenntniss d. Min.,' vol. vi. p. 96. 

 ' ' Account of the Arctic Regions,' vol. 1. 



