Accession. In the law both of England and Scotland, property may be acquired by accession, and this accession may be either natural or artificial. The young of cattle and other animals, for example, belong to the person who is the owner of the mother, and the fruits and produce of the earth to the proprietor of the soil; and for the same reason, the gradual addition to lands on the bank of a river belongs to the proprietor of the land receiving the addition. These are instances of natural accession. Property, again, is said to be acquired by artificial accession, when it is the result of human industry; thus trees planted, or buildings erected, on the ground of another, belong to the owner of the ground itself, and not to the planter or builder.
In the United States, accession is the right to all which one's own property produces; the right to that which is united to it, naturally or artificially, by accretion. If the materials of one person are united by labour to the materials of another, so as to form a single article, the property in the joint product is, in the absence of any agreement, in the owner of the principal part of the materials by accession. If there be a sale, mortgage, or pledge of a chattel, carried into effect by delivery, and other materials are added afterwards by the labour of the vendor or mortgager, these pass by accession.