When the Son flowed down its old channel joining the Ganges at Fatuha, the Ganges ran close past Arrah. Indeed, from a passage in the Mahábhárata, where the sojourn of the Pándavas in Ekachakra, now Arrah, is detailed, the Ganges is implied to have been not far of. When, however, the Son began flowing down its new channel, the natural result of the new force brought to bear on the waters of the Ganges at the junction would be to push the Ganges over to the north, thus gradually producing a large tract of newly formed land at the junction of the rivers. That the country now between the Ganges and Arrah was once the bed of the Ganges is sufficiently well established by the nature of its soil.
Contemporaneously with this pushing northwards of the Ganges at Arrah by the force of the Son there newly brought to bear on it, the withdrawal of the force from the Ganges at Fatuha would produce a reaction tending to send the Ganges southwards at that point, for the balance of forces which maintained the Ganges in its original course being destroyed by the withdrawal of the Son current (pushing northwards), the sum of the other forces, combined with the reflected force of the Son current from the north or opposite bank of the Ganges facing Dinapur, would cause the Ganges to work southwards. That the Ganges has worked a great space southwards all the way from Patna to Bakhtyarpur, i. e., on both sides of Fatuha as a central point, will be apparent from a glance at the map of the country; the greatest deflection being, as might be expected, just opposite Fatuha. I have not enough of facts to support my theory to the extent that would render it invincible to attacks, but the facts detailed exist beyond all question; and the theory I have propounded offers the simplest and most rational solution and explanation of the phenomena, at the same time fixing the limit of time at which the process of change commenced.
So far then as can now be ascertained, it appears that, through some unknown cause the Son abandoned its original bed and took its present course some little time before the Muhammadan conquest, and that contemporaneously with this change a large tract of newly formed land was thrown up between Arrah and the Ganges, while on the other hand a large portion of the south banks of the Ganges from Patna to Fatuha was cut away by the Ganges.
Accordingly, as Pâṭaliputra occupied the south banks of
