In a treaty of peace between the Illyrians and Romans, the latter required that they should not pass beyond the Lissus with more than two frigates, and those unarmed. In the peace with Antiochus, he was bound not to sail within the capes of Calycadnius and Sarpedon, except with ships carrying tribute, ambassadors, or hostages. Now the instances alluded to do not prove the actual occupancy of the sea, or the right of navigation. For it may happen that both individuals and nations may grant as a matter of favour or compact, not only what they have a competent right to dispose of, but that which is the common right of all men as well as of themselves. When this happens, we may say as Ulpian did on a like occasion, where an estate had been sold with a reservation, that the purchaser should not fish for Tunny to the prejudice of the seller. He observed that the sea could not be rendered subject to a service, but still the purchaser and those who succeeded to his possession, were bound in honour to observe that part of the contract. VII. Whenever a river has changed its course, disputes have arisen between neighboring states to decide whether such an alteration creates any change in the adjoining territories, and to whom any addition of land occasioned by that change accrues. Disputes which must be settled according to the nature and manner of such acquisition. Writers, who have treated of the division of land, have described it as of a threefold nature: one kind they name DIVIDED and ASSIGNED land, which Frontinus the Lawyer calls LIMITED, because it is marked out by artificial boundaries. By land ASSIGNED, is meant that which has been appropriated to a whole community, comprehending a certain number of families; a hundred for instance: from whence it has derived that name. And those portions are called hundreds. There is another division called ARCIFINIUM, which is applied when the land is defended against an enemy by the natural boundaries of rivers or mountains. These lands Aggenus Urbicus calls OCCUPATORY, being such as have been occupied either by reason of their being vacant, or by the power of conquest. In the two first kinds of lands, because their extent and bounds are fixed and determined, though a river should change its course, it occasions no change of territory, and what is added by alluvion will belong to the former occupant.