r correcting Borelli's
estimate, calculated the quantity of cubic yards of lava in this current
at 140,000,000. Now, this would not equal in bulk one-fifth of the
sedimentary matter which is carried down in a single year by the Ganges,
past Ghazepoor, according to the estimate above explained; so that it
would require five grand eruptions of Etna to transfer a mass of lava
from the subterranean regions to the surface, equal in volume to the mud
carried down in one year to that place.

Captain R. Strachey, of the Bengal Engineers, has remarked to me, not
only that Ghazepoor, where Mr. Everest's observations were made, is 500
miles from the sea, but that the Ganges has not been joined there by its
most important feeders. These drain upon the whole 750 miles of the
Himalaya, and no more than 150 miles of that mountain-chain have sent
their contributions to the main trunk at Ghazepoor. Below that place,
the Ganges is joined by the Gogra, Gunduk, Khosee, and Teesta from the
north, to say nothing of the Sone flowing from the south, one of the
largest of the rivers which rise in the table-land of central India.
(See map, fig. 25, p. 275.) Moreover the remaining 600 miles of the
Himalaya comprise that eastern portion of the basin where the rains are
heaviest. (See above, p. 200.) The quantity of water therefore carried
down to the sea may probably be four or five times as much as that which
passes Ghazepoor.

The Brahmapootra, according to Major Wilcox,[374] in the month of
January, when it is near its minimum, discharges 150,000 cubic feet of
water per second at Gwalpara, not many miles above the head of its
delta. Taking the proportions observed at Ghazepoor at the different
seasons as a guide, the probable average discharge of the Brahmapootra
for the whole year may be estimated at about the same as that of the
Ganges. Assuming this; and secondly, in order to avoid the risk of
exaggeration, that the proportion of sediment in their waters is about a
third less than Mr. Everest's estimate, the mud borne down to the Bay of
Bengal in one year would equal 40,000 millions of cubic feet, or between
six and seven times as much as that brought down to Ghazepoor, according
to Mr. Everest's calculations in 1831, and ten times as much as that
conveyed annually by the Mississippi to the Gulf of Mexico.

Captain Strachey estimates the annually inundated portion of the delta
at 250 miles in length by 80 in breadth, making an area of 20,0