1867.] with the supply of ivater to Calcutta. 139 



common use. These have been observed sometimes to increase the 

 quantity of organic matter in solution, but this is probably from 

 imperfect knowledge of the proper way to apply them, rather than 

 essential to their operation. 



This enquiry into the water of the Hooghly was commenced, as 

 formerly stated, without any reference to the water supply of Calcutta, 

 but simply as an investigation interesting in a scientific point of 

 view. For even in the single point of the organic matter there is 

 room for the expenditure of much labour and research. It is difficult 

 and not very promising, but persevering enquiry often brings much 

 of interest out of unpromising subjects. The high temperature of the 

 country increases the energy of chemical action, and the comparative 

 regularity of the seasons favours the simplicity of its operation ; and 

 thus a country like India affords a field well adapted for the study of 

 the influence of chemical changes on the phenomena of nature. Many 

 of these changes may not be very obvious to those unaccustomed to 

 study them, but they are not the less real on that account, and 

 not the less powerful in their operation on the world around us. 



16th September 1867. 



Since writing the above, the enquiry has been continued, with the 

 view of settling one or two points left in some degree of uncertainty. 

 These were the amount of organic matter in the river water during 

 the hot season and during the rains. The first of these was the point 

 on which the greatest doubt was felt by many as to the correctness 

 of the results given in my first paper, though little shared in by 

 myself : the second was the point on which my own opinion was 

 most undecided. The experimental results will be given in the tables, 

 and comments and explanations will follow, 



