Sea Walls — Eruvin 87a

Sea Walls — Eruvin 87a


תלמוד בבלי מסכת עירובין דף פז/א
בימה של טבריא הואיל ויש לה אוגנים


רש"י עירובין דף פז/א
אוגנים - שפה גבוה דהויא כמחיצות סביב לה, דאיכא קצת הכירא דהיתר, דהא כרמלית מדרבנן היא, גזרה משום הוצאה מרשות היחיד לרשות הרבים, הואיל ויש לה קצת היתר, ואף על גב דאכתי כרמלית היא דהא קרפף יותר מבית סאתים שלא הוקף לדירה הוא, מיהו בתקנתא פורתא כי הא סגי:

From The Contemporary Eruv:
In the last decade of the seventeenth century, we find the Chacham Tzvi (§5 and §37) addressing the possibility that natural walls, such as the canals surrounding The Hague in Holland, or even the cliffs surrounding the entire British isle, might constitute an eruv. While he rejected the latter possibility, he did accept the former possibility.

An issue concerning the use of lake/seashores or river/canal banks, raised by the Rama (Orach Chaim 363:29), is that even where the shores or banks are sufficiently steep to form a halachic wall when the eruv is first put into effect, they may later be obliterated by a build-up of sediment. There was also concern that the river may freeze. Where, however, the wall above the highest tide is sufficient to meet the minimum standards, neither of these two concerns would impede upon the incorporation of the banks in an eruv (Mishna Berura 363:121). The Tikvas Zecharia (pp. 14-22) maintains - and musters significant evidence to support his position - that the concern over build-up of sediment is only a problem when parts of the shore or bank comprising the halachic wall are at or near the water line. Where, however, the entire portion of the shore or bank comprising the halachic wall is safely above the water line, the concern is not relevant and need not be taken into account. This is the prevalent view - see Mishna Berura, ibid. and Nesivos Shabbos 15:10 and note 25. The Mishna Berura also notes that most sources raise the concern of sediment only when discussing seashores, not riverbanks. In discussing riverbanks, however, they are concerned only with freezing. A great river such as the Mississippi, however, may be more similar in these respects to a sea (although the Tikvas Zecharia, p. 56, does not entertain that possibility). (There were Poskim who permitted one side of an eruv to consist of a seashore or riverbank, if the other three were bona fide walls or tzuros ha'pesach - see No’am, ibid., pp. 214-217, and Nesivos Shabbos, ibid.) We should note that the eruv in Manhattan did include banks and shores that were not of sufficient halachic height above the waterline, and that other rationales were necessary to allow leniency there. See No’am, ibid., pp. 213-217. See also Hilchos Eruvin by Rabbi Elimelech Lange (Yerushalayim, 1972) 3:8-12.