128 Mr. Waddle's Investigations connected [No. 2, 



looking rank vegetation, is very striking. I got in June last 

 year 20 grains organic in 100,000 ; but besides that I doubted the 

 correctness of the result, considering it perhaps over-estimated, the 

 difference of season must be taken into account.* Besides this is 

 a strongly saline marsh. The comparatively small quantity in the 

 canal water is also remarkable, and shews how difficult it is to 

 increase greatly the amount in the comparatively pure water of the 

 downward flowing stream.f 



And here it may be well to consider the amount of organic matter 

 which the river can receive from the sewerage of Calcutta. First, we 

 have to consider the amount of water carried by the Hooghly, for the 

 data for which I have to acknowledge my obligations to Mr. Leonard. 

 He estimates that at the lowest season, the river, through its tributary 

 affluents, receives only about 2,000 cubic feet per second, but 8 or 

 10,000 cubic feet more by percolation from its banks, or say from all 

 sources 10,000 cubic feet of water per second, equal to 864,000,000 

 cubic feet per day. Mr. Clark, in his report on the water supply, 

 proposes to distribute 6,000,000 gallons per day or even ultimately 

 12,000,000 gallons. Now let us take the highest of these quantities ; 

 at a rough estimate this is about 2,000,000 cubic feet, and its 

 proportion to the volume of the river water is as 2 to 864 or j\-^ part. 

 The greatest amount of organic matter I found in the filthiest ditch in 

 Calcutta at its worst in June was about 24 grains per gallon. Now sup- 

 posing all this large quantity of water was daily poured into the Hooghly 

 in the state of sewerage of this degree of concentration, it would be 

 only 7 i ¥ part of 24 grains of organic matter to each gallon of river 

 water or about .05 to .06 grain per gallon. Even supposing that 

 the amount of water carried by the river has been over-estimated, 

 and that it amounts to only one-half or one-fourth of the quantity 

 stated above, the proportion of organic matter added by the sewerage 

 would not exceed one-fourth of a grain per gallon at most, during 

 the hot season. 



* Dr. Parkes states that 12 to 40 or 50 grains per gallon is not uncommon. 

 It would be necessary to know how such results were obtained, before admit- 

 ting them. 



f Probably if the water of the canal, instead of having been collected at full 

 tide, had been taken when the river water was beginning to flow into the 

 canal, it would have contained more organic matter. An attempt indeed was 

 made to get such water two days before (18th February), but the proper time 

 was not hit. 



