In arcifinious lands, where the bounds are formed by nature, any gradual change in the course of the river makes a change also in the boundaries of territory, and whatever accession is given by the river to one side, it will belong to the possessor of the land on that side. Because the respective nations are supposed originally to have taken possession of those lands, with an intention of making the MIDDLE of that river, as a natural boundary, the line of separation between them. Thus Tacitus in speaking of the Usipians and Tencterians, who border on the Cattians, says, "their territory lies on the banks of the Rhine, where that river, still flowing in one regular channel, forms a sufficient boundary." VIII. Decisions like those above can only take place in instances, where the river has not altered its channel. For a river, dividing territories, is not to be considered barely as so much water, but as water flowing in a PARTICULAR CHANNEL, and inclosed WITHIN CERTAIN BANKS. For which reason an addition, a decrease, or such a change of small portions, as leaves the ancient appearance, upon the whole, nearly the same, allows us to consider the river as still the same. But if the whole face of the river is changed, the case will be entirely altered. For as a river may be entirely destroyed by the erection of dams upon the higher parts of its stream, or by digging canals, which carry off its waters in another direction: so by the desertion of its old channel, and breaking out for itself another course, it will not continue to be same river it was before, but will be completely a new one. In the same manner if a river has been dried up, the middle of its channel will remain as the boundary between neighbouring states, who in taking possession of the neighbouring territory originally intended the middle of such a river to be the line of separation, and under all changes to preserve the same as a permanent limit. But in doubtful cases, the territories bordering upon a river ought to be considered as arcifinious, because nothing can be a more apt mark of distinction than those impassable bounds assigned by nature. It very seldom indeed happens, that the artificial or civil admeasurements of territory can be regulated by such natural bounds, as they are, in general, the effect of original acquisition, or have been ceded by treaty. IX. Although in doubtful cases, it has been said that the territories on each side of a river are determined by the middle of the channel; yet it may happen, and has happened, that the sole right to a river may belong to the territories on one side of it. Because that on the opposite side was of later occupancy, and subsequent to the possession of that river by the other power: or because this sole right may have been so settled by treaty.