1867.] with the supply of water to Calcutta. 141 



One thing is to be noticed in connection with these, namely, that 

 the amount of saline contents is very decidedly smaller than it was in 

 the corresponding season of 1866. This may possibly have arisen 

 from the correct time of full flood not having been caught, but if so, 

 this must have happened on both occasions : and moreover the 

 quantity of saline matter at Ebb tide is also much smaller than in 

 1866. It appears to me more probable that the river water has 

 contained less saline matter this year. It would be difficult to give 

 an opinion as to the cause of this : besides, the observations were not 

 sufficiently numerous to draw conclusions from with certainty. 



The results of the examination of the river water of the rainy 

 season confirm those I have already given in Table III. of the first 

 paper and in Table V. of this. The absolute amount of organic 

 matter is somewhat less than in the waters of the hot season, but, in 

 proportion to the mineral constituents, very much greater. It is to be 

 observed that the waters which were simply settled, or even sand- 

 filtered, still contained clay : the water, clarified by a little sesqui- 

 chloride of iron, does not give the correct amount of saline matter, 

 therefore in the table this is omitted in these cases, but it was only 

 by such means that the water could be got clear and free from clay, 

 at the beginning of the rains, without delay. The two samples thus 

 clarified were evaporated next day after collection, the others after 

 greater delay. 



The waters were also examined for ammonia by the process given 

 in the first paper : the results are exhibited in the following table. 



Table XII. 



Shewing quantity of ammonia in 100,000 fl. grains water. 



Hot Season. 



Grains. 



River water of 13th May, Neap tide ...Ebb, .0350 



Flood, .0240 



20th May, Springtide ...Ebb, .0090 



Flood, .0155 



6th June, Spring tide Flood, .0190 



Average, 0205 



