1873. The Chief Kinds or Ways of Occupation.—(a) Animals.—Domestic animals (e.g., dogs, cats) may not be occupied, even though they have strayed from their owner; tamed animals (e.g., bees, pigeons, songbirds) may be occupied only when they have recovered their liberty; wild animals (e.g., birds, foxes, fishes, hares, etc., at large) may not be occupied, unless they are kept in a small enclosure from which they cannot escape.
(b) Land and Plants. These may be occupied only when they have no present owner.
(c) Treasure-trove.—This is a deposit of precious movables hidden away so long ago that it is impossible to discover the owner. According to natural law it may be occupied by the finder, but the civil law sometimes decides that the find must be divided with the owner of the place or with the government.
(d) Lost Property.—This embraces those movables which an owner has recently parted with, through accident or forgetfulness, without any intention of giving up his ownership of them, and which are now easily findable, although their owner is not known. The finder is obliged to make reasonable efforts to find the owner. If he neglects to make these efforts, proportionate to the worth of the found article, and is convinced that he might have found the owner, he is considered by some theologians to be a possessor in bad faith and bound to reserve the article for the owner or turn it over to the poor or to pious causes. Having made the effort unsuccessfully, according to natural law, he may use the article as his own. The prescriptions of civil law as to the time interval before he may begin to use the article must be observed.
(e) Abandoned Goods.—According to natural law one may occupy goods voluntarily relinquished by the owner (e.g., an old automobile left by the roadside), but the civil law sometimes awards certain classes of goods (e.g., immovables) to the State.
(f) Vacant Goods.—According to natural law the goods of one who died without heirs may be occupied; but under the civil law they usually devolve to the State, whether they be movables or immovables.
1874. Principles on Accession.—(a) According to natural law, if the two things united are separable, then each owner should be given his own property; but if the things are inseparable and one is more valuable, the owner of the more valuable part keeps all, but compensates the owner of the less valuable part; if the things are inseparable and of equal value, there is joint ownership.
(b) According to positive law, these natural principles are applied to various cases of accession, whether it be natural (as through growth of plants or deposit of land by rivers) or artificial (as through change made in a material by labor, or addition of one substance to another). These details are treated in books on law.
1875. Prescription.—Prescription laws (see 1798) are valid in conscience, since they are determinations about property rights made in the interest of the common welfare. But the following conditions are required for acquisition of property through prescription:
(a) the object of prescription must be a thing prescriptible according to natural and positive law. Thus, natural rights and public property may not be prescribed against;