1873.] D. W'Ad{Q—On tlie Muddy Water of the Thujli. 215 



so to change the character of the mud in the river water of the rains as to 

 enable it to settle with sufficient readiness, and in sucli a state as to render 

 the water capable of being filtered without dilHculty ? Will the difference 

 of quantity between tliat of the saline matter which exists in the water of the 

 rainy season and that, say, of December be sufficient ? Will the addition of 

 such small quantity of the same kind of saline matter that exists in the 

 river water to the water of the rainy season, so change its character that 

 these difficulties in settling and filtering will be removed ? Without delay 

 a few experiments were instituted and their results observed, and these 

 results shewed that the question was solved in the affirmative and the whole 

 difficult}^ cleared up. The Hugli water during the rains ■ contains too 

 much pure water in proportion to its saline constituents, or these natural 

 pi'ecipitants are present in too small quantity to precipitate the mud, as they 

 do in other localities which have no tropical rainfall to produce so great 

 dilution. And now my previous conviction as to the cause of the pecu- 

 liarity was at once confirmed and explained.* 



The first experiment was made by means which came at once to hand. 

 One quarter of a litre of muddy water from the river was mixed in a bottle 

 with an equal volume of water from a tank which, in the dry season, I had 

 found to contain a considerable quantity of saline constituents. Now, from 

 the rains, I knew that it must be considerably more diluted, nevertheless 

 not so diluted as the river water. In another bottle, for comparison, was 

 mixed an equal quantity of the river water with the same volume of distilled 

 water. It seemed natural to think that this mixture with distilled water 

 would settle most speedily, more particularly as the tank water contained 

 much glutinous vegetable matter ; nevertheless, notwithstanding this dis- 

 advantage, the mixture with the tank water settled best. It was not a very 

 good experiment, yet the result was quite distinct. 



Then solutions of sodium and of calcium chloride (common salt and 

 muriate of lime) were prepared of known strengths. The amount of saline 

 constituents in the river water during the rainy season was pretty well 

 known from former analyses, and these solutions were added in such quantity 

 as approximately to double the quantity of saline constituents in the water, 

 and thus bring it near the composition of the river water of December as 

 regards alkaline and earthy salts. This produced an improvement in the 

 settling, very slight in the case of common salt, very decided in that of 

 chloride of calcium (muriate of lime). This at once shewed, what was after- 

 wards abundantly confirmed, that lime salts were nmch more efficacious than 

 alkaline salts. I shall return to this part of the subject further on. 



* At the meeting of the Society on 4th August hist I iutiiuated tliat 1 luul discovered 

 ■what I believed to f)e the true explanation of the difhculty with the water. Vide Proceed- 

 ings for August, 1873. 

 27 



