18 Precious stones too, and gems, and all other things found on the seashore, become immediately by natural law the property of the finder:
19 and by the same law the young of animals of which you are the owner become your property also.
20 Moreover, soil which a river has added to your land by alluvion becomes yours by the law of nations. Alluvion is an imperceptible addition; and that which is added so gradually that you cannot perceive the exact increase from one moment of time to another is added by alluvion.
21 If, however, the violence of the stream sweeps away a parcel of your land and carries it down to the land of your neighbour it clearly remains yours; though of course if in the process of time it becomes firmly attached to your neighbour's land, they are deemed from that time to have become part and parcel thereof.
22 When an island rises in the sea, though this rarely happens, it belongs to the first occupant; for, until occupied, it is held to belong to no one. If, however (as often occurs), an island rises in a river, and it lies in the middle of the stream, it belongs in common to the landowners on either bank, in proportion to the extent of their riparian interest; but if it lies nearer to one bank than to the other, it belongs to the landowners on that bank only. If a river divides into two channels, and by uniting again these channels transform a man's land into an island, the ownership of that land is in no way altered:
23 but if a river entirely leaves its old channel, and begins to run in a new one, the old channel belongs to the landowners on either side of it in proportion to the extent of their riparian interest, while the new one acquires the same legal character as the river itself, and becomes public. But if after a while the river returns to its old channel, the new channel again becomes the property of those who possess the land along its banks.
24 It is otherwise if one's land is wholly flooded, for a flood does not permanently alter the nature of the land, and consequently if the water goes back the soil clearly belongs to its previous owner.
25 When a man makes a new object out of materials belonging to another, the question usually arises, to which of them, by natural reason, does this new object belong—to the man who made it, or to the owner of the materials? For instance, one man may make wine, or oil, or corn, out of another man's grapes, olives, or sheaves; or a vessel out of his gold, silver, or bronze; or mead of his wine and honey; or a plaster or eyesalve out of his drugs; or cloth out of his wool; or a ship, a chest, or a chair out of his timber. After many controversies between the Sabinians and Proculians, the law has now been settled as follows, in accordance with the view of those who followed a middle course between the opinions of the two schools. If the new object can be reduced to the materials out of which it was made, it belongs to the owner of the materials; if not, it belongs to the person who made it. For instance, a vessel can be melted down, and so reduced to the rude material—bronze, silver, or gold—of which it is made: but it is impossible to reconvert wine into grapes, oil into olives, or corn into sheaves, or even mead into the wine and honey out of which it was compounded. But if a man makes a new object out of materials which belong partly to him and partly to another—for instance, mead of his own wine and another's honey, or a plaster or eyesalve of drugs which are not all his own, or cloth of wool which belongs only in part to him—in this case there can be no doubt that the new object belongs to its creator, for he has contributed not only part of the material, but the labour by which it was made.
26 If, however, a man weaves into his own cloth another man's purple, the latter, though the more valuable, becomes part of the cloth by accession; but its former owner can maintain an action of theft against the purloiner, and also a condiction, or action for reparative damages, whether it was he who made the cloth, or some one else; for although the destruction of property is a bar to a real action for its recovery, it is no bar to a condiction against the thief and certain other possessors.
27 If materials belonging to two persons are mixed by consent—for instance, if they mix their wines, or melt together their gold or their silver—the result of the mixture belongs to them in common. And the law is the same if the materials are of different kinds, and their mixture consequently results in a new object, as where mead is made by mixing wine and honey, or electrum by mixing gold and silver; for even here it is not doubted that the new object belongs in common to the owners of the materials. And if it is by accident, and not by the intention of the owners, that materials have become mixed, the law is the same, whether they were of the same or of different kinds.