156 



Silt held in suspension by the Hooghly. 



[No. 2, 



fall of rain, and thence perhaps the higher rise of the great Ganges 

 pouring in a larger quantity of calcareous matter.* 



We must therefore I think in fairness, and for the present, take a 

 mean hetween the surface water of 1842, and that taken at 3 

 fathoms depth in 1854-55 for about the mean quantity of silt held 

 in suspension by the Hooghly for a series of years ? though it seems 

 clear that nothing but water taken up at Nuddea where the Bha- 

 ghirutty, Jellinghee and Matabangah, the three off-shoots from the 

 great Ganges which form the river Hooghly, meet, and where the 

 influence of the tides is not felt, can give us the true quantity of silt 

 and carbonate of lime brought down ; and again that this must be 

 done for a series of years to obtain a really good average. t 



The means above proposed would be as follows : 



1842, Mean,... 



1854-55 at 3 fs. depth, Mean, . . . 



Mean of both series, 



Water. 



oz. 



25.| 



23.70 



49.03 



24.51 



£j-w 





-fc 3 00 



•+J -t-» 



U 



C3 cS 





g * 





^ a 



T3 at 



3 a 



53 <D 



W 



S 



6.04 



7.95 



6.G2 



1.32 



12.06 



9.27 



6.03 



4.63 



m A 1=1 

 O d 



13.99 

 7.34 



21.33 

 10.66 



Now with the same data then as in my former paper, i. e. 1.73296 

 inches to the cubic (apothecary's) ounce of water, the above average 

 quantity of water 24.51 oz. will be equal to 42.47385 cubic inches 

 which, to save decimals, we will call 42.48 cubic inches of water 

 containing 6.03 grs. of silt and 4.63 grs. of lime, which for a cubic 



* With which its waters are always charged, the lime depositing so fast when the 

 river lowers that it forms beds of kunkur, (impure limestone) which are often 

 serious obstructions to the navigation of the river. 



f The Indigo Planters are well aware of, and often suffer from the caprices of 

 the river in this matter of more or less silt (called by them Polar/, see Researches 

 Vol. XVIII. part II.) being deposited by the river on their inundated lands, where 

 it sometimes leaves them a rich bed of it for their next year's crop, and at another 

 barely enough to cover the old vegetation. We also see at the sections of the river 

 banks that the laminae of silt are of varying thicknesses. 



