The property of rivers, by the laws of most nations, and by the natural turn of our thought, Is attributed to the proprietors of their banks, excepting such vast rivers as the Rhine or the Danube, which seem too large to the imagination to follow as an accession the property of the neighbouring fields. Yet even these rivers are considered as the property of that nation, thro’ whose dominions they run; the idea of a nation being of a suitable bulk to correspond with them, and bear them such a relation in the fancy.
The accessions, which are made to lands bordering upon rivers, follow the land, say the civilians, provided it be made by what they call alluvion, that is, Insensibly and Imperceptibly; which are circumstances that mightily assist the imagination in the conjunction. Where there Is any considerable portion torn at once from one bank, and joined to another, it becomes not his property, whose land it falls on, till it unite with the land, and till the trees or plants have spread their roots into both. Before that, the imagination does not sufficiently join them.
There are other cases, which somewhat resemble this of accession, but which, at the bottom, are considerably different, and merit our attention. Of this kind Is the conjunction of the properties of different persons, after such a manner as not to admit of separation. The question is, to whom the united mass must belong.
Where this conjunction is of such a nature as to admit of division, but not of separation, the decision is natural and easy. The whole mass must be supposed to be common betwixt the proprietors of the several parts, and afterwards must be divided according to the proportions of these parts. But here I cannot forbear taking notice of a remarkable subtilty of the Roman law, in distinguishing betwixt confusion and commixtion. Confusion is an union of two bodies, such as different liquors, where the parts become entirely undistinguishable. Commixtion is the blending of two bodies, such as two bushels of corn, where the parts remain separate in an obvious and visible manner. As in the latter case the imagination discovers not so entire an union as in the former, but is able to trace and preserve a distinct idea of the property of each; this is the reason, why the civil law, tho’ it established an entire community in the case of confusion, and after that a proportional division, yet in the case of commixtion, supposes each of the proprietors to maintain a distinct right; however necessity may at last force them to submit to the same division.