21 G D. Waldie— O;^ tie Muddy Water of tie Hngli. [No. 4, 



Another obvious-looking plan was to dry a measured portion of the 

 water and add its solid constituents to an equal quantity of water, so as to 

 double the total amount. But there were practical difficulties in this 

 process, in the changes the constituents would undergo by evaporation ; it 

 was, however, done thus : a portion of filtered water from the Calcutta 

 hydrants was concentrated by evaporation over the water-bath to one-fifth of 

 its volume ; after this carbonic acid gas was passed through the concentrat- 

 ed liquor in order to redissolve the carbonates of lime and magnesia which 

 had separated. One volume of this concentrated water was now mixed with 

 four volumes of muddy river water, so as to make up the original quantity. 

 This mixture, on being allowed to stand, settled well and the water could be 

 filtered easily. In all cases a similar bottle of the muddy water, unmixed 

 with anything, was placed beside these mixed waters for comparison. 



In all the above experiments the waters were allowed to stand 24 or 

 48 hours to settle. This was a point I had calculated on, as the object was 

 not to clarif}^ the waters as rapidly as possible, but to imitate the settling 

 and clearing of other natural waters or of the Hugli water itself during 

 the dry season, by assimilating its composition so far as regards soluble salts 

 to that of those. 



III. — I have examined the tables given in Bischoff's Chemical Geolo- 

 gy* of the composition of various river waters for anything to be found 

 bearing on this subject, and the author's remarks connected with rivers. 

 The varieties of composition are obvious, and a few rivers are to be found 

 containing but a small quantity of saline constituents and particularly of 

 earthy salts in their waters. In a few cases the composition is given at 

 different localities or at different periods of the year, but generally there 

 is not enough of information to connect these facts with the subject under 

 consideration. Two analyses of the Khine water at Basle and at Stras- 

 burg shew fully 14 parts of Carbonate of Lime and Magnesia in 100,000 : 

 again at Bonn in March, 1852, there are fully 10 parts ; in March, 1857, 

 only 4|- parts ; but in the former case the river was verj^ low and of the 

 usual clearness, in the latter it was much swollen and very turbid. Bischoff 

 has a chapter on mechanical deposits from water, in which he notices various 

 particulars respecting rivers. Of torrents which issue from glaciers, he says, 

 all of them roll along in a turbid grey milky or dark stream according to 

 the nature of the pulverized rock. Generally speaking, in rivers, the quan- 

 tity of suspended matter increases with the height of the water, and the sub- 

 stances dissolved diminish. The suspended matter consists generally of 

 claj^, but in limestone districts it may consist partly or chiefl}'' of carbonate 

 of lime itself. Of course even water containing a considerable quantity of 

 soluble salts of lime may be muddy, but if the mud consist of clay, the mud 

 * Cavendish Society's Trans., 1851. 



