Riverbanks, Horse's Necks and Really Long Articles

The Gemara in Bava Metzi'a 108a says:

Shmuel said: That one who took possession of [land on a] riverbank is an impudent person, but we certainly cannot remove him. But nowadays that the Persians write [in a title], "It [a field on a river] is acquired by you as far as the depth of the water reaching up to the horse's neck," we certainly remove him.

In other words, the land near the riverbank is never built upon nor fenced in, because the owner of adjacent property needs access to that area for loading and unloading from boats. This leaves open the opportunity for someone to come in, lay claim to that land and build on it. The halakhah disapproves of that action but cannot force the person off of the property. However, Persian (i.e. Babylonian) law changed at some point and included the stipulation that someone owning land near a riverbank also owns the adjacent riverbank and even into the river up to the depth of a horse's neck. Once that became the law, halakhah can allow forcing such a person off of the property.

Dr. Yaakov Elman researched this matter in Sasanian law books (the Sasanian dynasty ruled Babylonia from 224-651, i.e. the Amoraic period) and found a somewhat corresponding law. In Madayan i Hazar Dadistan, the "Book of a Thousand Decisions," an early seventh century compilation of earlier legal material, there is an indication that one can own a canal up to an ear's length. Dr. Elman suggests that it is referring to a horse's ear, and points out that a horse's ear ends at its neck, so that the Talmudic measure of a horse's neck and the Sasanian measure of an ear are one and the same. Dr. Elman then proceeds into a long discussion of Sasanian attitudes towards canal digging and taxation, and then uses it to explain the Talmudic passage above: Given what we now know of the economic and legal environment, why was Shmuel unwilling to remove an interloper from the riverbank? How did that change after the Sasanian tax reform?

This 55-page article reminded me, once again, how utterly boring academic study of the Talmud is.

(Full article here - PDF)
(See also this post)