308 Prof. DecandolJe on a new Animal which dyed 



putrid smell, and during the night the whole disappears, to re- 

 appear again the next day. 



When the lake is agitated by high winds the phenomenon 

 disappears, and presents itself again when a calm returns. 



Several species of fish, such as the perch and the pike, pro- 

 bably from having eaten of this matter, had their outline, and 

 even their flesh, tinged red as if they had been fed upon mad- 

 der, but without experiencing any inconvenience. Several small 

 fish, however, (as Dr Engelhart and M. Treschel both mention) 

 which came to the surface to breath and to catch flies, died with 

 convulsions in passing through this matter, an effect which is as- 

 cribed by some to their having swallowed a portion of it, and 

 by others to the putrid air which existed at the surface. 



MM. Engelhart and Treschel, to whom we owe these in- 

 teresting details, first directed the attention of naturalists to this 

 subject, and, in consequence of this, several bottles, filled with 

 the different substances, were forwarded to Geneva. These 

 substances were examined by Professor Decandolle in so far as 

 they were connected with natural history, and by MM. Col- 

 ladon-Martin, and Macaire Princep, in their chemical rela- 

 tions. 



When the bottles were opened a»t the end of twenty-four 

 hours, they exhaled an extremely fetid odour. When the 

 contents were poured out, there appeared two substances very 

 distinct, viz. a red and very minute matter of a brownish-red 

 colour, and another in irregular plates of a dirty green colour. 



By filtering the mass there was obtained a great quantity of 

 the reddish- brown substance. When placed in water this sub- 

 stance swam on its surface ; but if it was obtained without fil- 

 tration, and if it was mixed with water, the fluid presented 

 three zones, an upper one which contained the substance almost 

 pure, a middle one which was water, and an under one which 

 was a mass of different fragments and mud which had been 

 mixed with the brown matter. 



On the first day, the water which separated these two zones 

 was perfectly clear and colourless ; but at the end of two or 

 three days it had a rose lilac colour, and afterwards a very bril- 

 liant red lilac. This colour begins always on the upper part. 

 It continues to descend in the liquid ; and it is evident that it 



