VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. ^7 



These observations were made in a season, when the waters rose rather higher 

 than usual ; so that we may take 3 1 feet for the medium of the increase. 



The inundation is nearly at a stand for some days preceding the middle of 

 August, when it begins to run off; for though great quantities of rain fall in 

 the flat countries, during August and September, yet, by a partial cessation of 

 the rains in the mountains, there happens a deficiency in the supplies necessary 

 to keep up the inundation. The quantity of the daily decrease of the river is 

 nearly in the following proportion : during the latter half of August, and all 

 September, from 3 to 4 inches ; from September to the end of November it 

 Gradually lessens from 3 inches to an inch and a half; and from November to 

 the latter end of April, it is only half an inch per day at a medium. These pro- 

 portions must be understood to relate to such parts of the river as are removed 

 from the influence of the tides ; of which more will be said by and by. The 

 decrease of the inundation does not always keep pace with that of the river, by 

 reason of the height of the banks ; but after the beginning of October, when 

 the rain has nearly ceased, the remainder of the inundation goes off quickly by 

 evaporation, leaving the lands highly manured, and in a state fit to receive the 

 seed, after the simple operation of plowing. 



There is a circumstance attending the increase of the Ganges, little known or 

 attended to ; because few people have made experiments on the heights to which 

 the periodical flood rises in different places. The circumstance alluded to, is, the 

 difference of the quantity of the increase, as expressed in the foregoing tables, 

 in places more or less remote from the sea. It is a fact, confirmed by repeated 

 experiments, that from about the place where the tide commences, to the sea, 

 the height of the periodical increase diminishes gradually, till it totally disappears 

 at the point of confluence. Indeed, this is perfectly conformable to the known 

 laws of fluids : the ocean preserves the same level at all seasons, under similar 

 circumstances of tide, and necessarily influences the level of all the waters that 

 communicate with it, unless precipitated in the form of a cataract. Could we 

 suppose, for a moment, that the increased column of water, of 3 1 feet perpen- 

 dicular, was continued all the way to the sea, by some preternatural agency : 

 whenever that agency was removed, the head of the column would diffuse itself 

 over the ocean, and the remaining parts would follow, from as far back as the 

 influence of the ocean extended ; forming a slope, whose perpendicular height 

 would be 31 feet. This is the precise state in which we find it. At the point of 

 junction with the sea, the height is the same in both seasons at equal times of 

 the tides. At Luckipour there is a difference of about 6 feet between the 

 heights in the different seasons; at Dacca, and places adjacent, 14; and near 

 Custee, 31 feet. Here then is a regular slope; for the distances between 

 the places bear a proportion to the respective heights. This slope must add to 



