CLASSIFICATION OF THINGS 119 (3) Immovables require special formalities of alienation or hypothecation.^ (4) Special rules apply to the alienation of the immovable property of minors.^ (5) The process of execution upon immovables differs from the process of execution upon movables.* The above distinctions, though a useful guide, are not invariably conclusive. A thing may, for instance, be treated as immovable for some purposes but not for all. Thus a mortgage of land, like a sale or other alienation, requires to be solemnly executed and registered if it is to bind third parties, and so far resembles immovable property ; ^ but is, nevertheless, as we have just seen, in other respects classed with movables. CHAPTER III HOW OWNERSHIP IS ACQUIRED In this chapter we shall deal with the acquisition and Modes of extinction of ownership in corporeal things ; and princi- tfo'^f paUy with the legal modes of acquisition of ownership, corporeal i.e. the processes which, in law, make a thing mine. The "^^^' modes of acquiring and losing ownership of incorporeal things will be considered in connexion with the various incorporeal things of which we shall speak hereafter. The modes of acquisition of corporeal things, i.e. of single things {rerum singularum) — for with acquisition per universitatem we are not here concerned — are principally the following : viz. (1) occupation ; (2) accession ; (3) tra- dition or delivery ; (4) prescription. We shall speak of these in order. Since the Dutch Law of modes of acquisition closely follows the Roman Law, we shall credit the reader with a knowledge of the first title of the second book of Justinian's Institutes ; and limit ourselves ^ Op. cit., cap. xix, sees. 3 and 4. ^ Op. cit., eap. xviii, sec. 1. ^ Op. cit., cap. XX, sec. 7 ; Van der Linden, Verhandeling over de JuAicieele Practijcq, book iii, chap, vi ; Nathan, Common Law of South
Africa, vol. iv, pp. 2208 fi. * Voet, 1. 8. 27.