1856.] Silt held in suspension by the Hooghly. 155 



It would thus appear that either there are very extraordinary 

 differences in the amount of silt and of lime in different years, or 

 that some errors exist somewhere. The fall of rain at Calcutta for 

 the whole year in 1842 was 76.14 inches, and from April 1854 to 

 March 1855, 65.89 inches only ; or 10.25 in. or 13.33 per cent, less ; 

 and this may partly, if not entirely, account for the deficiency ? 

 Another, and a probable source of error was that, in 1842 I did 

 not take up the water myself, but giving more pice to a good peon 

 than the boat hire would amount to, I sent him to obtain a bottle 

 full of water, strictly charging him to do so from the middle of the 

 river. But as usual where we fancy we employ a trustworthy native 

 it was not improbable that I might have been deceived, and I at first 

 supposed that the peon, to pocket the whole of the pice, just took 

 up water close to the shore by stepping into a boat at the ghaut ; 

 and this would account for the larger quantity of silt shewn, but 

 not at all for the very large quantity of carbonate of lime in 1842, 

 which as related in my former paper formed crusts on the side and 

 even stalactitic incrustations at the bottoms of the bottles ; so that 

 about this — to say nothing of the impossibility of any practical 

 chemist making any mistake as to carbonate of lime — there can be 

 no question. 



To clear up this doubt if possible, I took up on the 16th of No- 

 vember a bottle of water in mid channel opposite to the Governor 

 General's Ghat (half way between Chaundpaul Ghat and Fort 

 Point) and another bottle at not more than 20 yards from the shore. 

 This was about at half or three quarters flood. 



When examined for silt and carbonate of lime, the results were 

 found to be, for the same measure of water. 



Solid matter. Carbonate lime. 



In mid channel, 1.36 1.52 



At 20 yards from the shore, .... 0.75 2.00 



Hence we see, that the silt is less in shore, though the proportion 

 of lime is twenty-five per cent, more than in mid-stream. In 1842, 

 the table in my former paper gives for November, silt 2.12 and car- 

 bonate of lime 7.88, so that it is in this last constituent that the 

 great discrepancy exists, and we can only attribute it to the heavier 



x 2 



