426 



The following Donations to the Society's Library were an- 

 nounced. 



Scheikundige Onderzoekingen, gedaan in het Laboratorium der 

 Utrechtsche Hoogesohool. St. 5. — By the Author. 



Natuurkundige Verhandelingen van de HoUandsche Maatschappij 

 der Wettenschappen te Haarlem. Deel. 2. — By the Society. 



The following Donations to the Museum were presented — 



Series of Specimens of the different Rock Formations. (150 speci- 

 mens.) — Presented by Lord Greenock. 



Specimens connected with Mr Shaw's paper on the Development 

 and Growth of the Sea-Trout of the Solway. — Presented by 

 Mr John Shaw. 



Monday, VJth April 1843. 



The Right Honourable Lord GREENOCK, Vice-President, 



in the Chair. 



The following Communications were read : — 



1. On the presence of Organic Matter in the purest Waters 

 from Terrestrial Sources. By Professor Connell. 



It must be well known to chemists, that when solution of acetate of 

 lead is added to the transparent and colourless water of springs, wells, 

 and rivers, a more or less dense white cloud is almost invariably pro- 

 duced. This reaction has been usually attributed to the presence of 

 inorganic salts, such as carbonates, sulphates, and muriates ; but it 

 will be found that, generally speaking, this precipitate is formed 

 even after the water has been boiled ; that it is usually dissolved by 

 the speedy addition of a drop or two either of acetic or of nitric acid, 

 without visible effervescence ; and that the agency of the water with 

 nitrate of silver is commonly too small to admit of its being caused 

 by any muriate. These facts exclude the idea that it is due in the 

 general case to carbonates, sulphates, phosphates, or muriates ; al- 

 though, of course, in those particular cases where the water has 

 enough of such constituents to affect acetate of lead, the reactions 

 will be modified accordingly. Thus, in some cases, where the first 

 action is as above stated, a deposition takes place after a certain in- 

 terval of sulphate of lead, no longer soluble in weak acids. 



