286 On the quantity of Silt held in suspension. [No. 3. 



dried to the consistence of a sun-burnt brick (a kaclia brick as it is 

 called) weighed 424 "grains, so that each cubic foot of water con- 

 tains 1.2988 cubic inches of solid matter • or in other terms, each 

 cubic foot of water holds T ^-$ (one thirteen hundred and thirty- 

 third) part of its bulk of silt in suspension on an average of the 

 year, opposite to Calcutta. 



In the months of March, April, May and June, in which the 

 largest amount of deposit is shewn, the average it will be seen is 

 much higher, being as follows. 



Cub. Ins. 



Average quantity of water, 25.50 oz. or 44.190. 



of silt, 24.77 grs. 



of carbonate of lime, 13.56 grs. 



of silt, in each cub. foot, 1678.92 grs. 

 being j^ part (one four hundred and thirty-sixth) of its bulk, of 

 which more than one half or f-f-f- is carbonate of lime ! 



This is far higher than the Eev. Mr. Everest's result for the four 

 months of the rains at Benares, of -g-ty in bulk,* but it is evident 

 that no parallel can be established between the waters of the great 

 Granges at Benares and those of an offset of it like the Hooghly, 

 flowing through a vast extent of alluvial soil ; depositing and re- 

 ceiving on its progress the detritus of both new and ancient allu- 

 vial soils, and of primitive and transition rocks from the country 

 on its western shores ; but the whole result now obtained here is a 

 highly curious one, and I think well worthy of being placed on re- 

 cord. 



I find that water taken on the 24th January, from the middle of 

 the river is turbid, but nothing more, and cannot hold much more 

 solid matter in suspension, than is shewn by our table. Upon 

 testing it by lime-water the large quantity of carbonic acid gas 

 which it holds in solution (and which indeed is seen rising from it 

 in bubbles when the bottle has been carried through the heat of 

 the sun) is immediately apparent,f as is also the lime by Oxalate 



* See Rev. Mr. Everest's paper ; Journal As. Soc. vol. I. p. 238 quoted by Sir 

 Charles Lyall also, in Principles of Geology, p. 269. 



t The absence of sulphates being first ascertained by Muriate of Barytes and 

 the carbonate redissolved by Muriatic acid. 



