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1)

(a) Pouring water into a Chatzer which has an Ukah is permitted, only because the water seeps into the ground and becomes absorbed - whereas in our case (pouring water into the river via a suspended Mechitzah), the water is poured directly into the river, which carries it outside the area underneath the walls of the ledge. That is why Rabah bar Rav Huna forbids it.

(b) In the second Lashon of Rabah bar Rav Huna - he draws no distinction between *drawing* water via the Mechitzah and *pouring it out*; both are permitted.

(a) Once the two ledges are more than four Tefachim apart, the lower one is restricted to using it via the air - and Rav holds that usage of the air alone does not prohibit the second owner from using his Reshus.

(b) It makes no difference how high the one ledge is from the other. When Rav makes a distinction between 'Semuchah' and 'Mufleges', he cannot be referring to the height - firstly because the word 'Mufleges' by definition means *horizontally* distant and not *vertically*; and secondly, because Rav said earlier 'Echad be'Shilshul ve'Echad bi'Zerikah, Sheneihem Asurim'.

(a) 'Yesh Gezel be'Shabbos' means that someone who 'steals' (i.e. uses someone else's Reshus - such as a ruin, which the owner hardly uses anyway), acquires it with regard to Hilchos Shabbos, and that *he* is permitted to use it, and *not* the owner; whereas 've'Churvah Machzir le'Ba'alav' - means that the same ruin reverts to the owner, and is not the property of the 'thief' (two statements which are contradictory).

(b) The Gemara answers that the Reisha means, not that there is 'Gezel', - - - but that there is a *Din* Gezel (i.e. an obligation to return it).

(c) Our Mishnah, which forbids the owner of the upper ledge to use his ledge, because the owner of the lower ledge uses it - speaks when the lower owner was a partner in the construction of the Mechitzah, which permits the use of the upper ledge.

(d) When the owner of the lower ledge makes Mechitzos - he demonstrates that he withdraws from the joint ownership of the upper one which he helped to build, thereby allowing the owner of the upper ledge to use his ledge undisturbed.

(a) The pit which is *outside* the Chatzer needs to be covered - to ensure that when he pours the water into the small remaining gap adjoining the Chatzer, he is pouring into a Makom Petur (and not the Reshus ha'Rabim); this is not necessary by a pit which is inside the Chatzer, which is anyway a Reshus ha'Yachid.

(b) The pit needs to hold specifically *two Sa'ah* of water - because that is the estimated amount of water that an average family uses on Shabbos.

(c) A 'Biv' is a drain or a ditch; a ditch of four Amos square is the estimated Shiur that will absorb two Sa'ah of water, and prevent it from flowing further.

(d) We are not concerned that the water might not sink into the ground fast enough, and will subsequently spill over the sides into the street - because, even if it does, he will not be Chayav, since his intention was for the water to sink into the ground, and not that it should flow any further.

(a) The Rabbanan say that, even if there is a one hundred-Amah long ditch in a courtyard or on a roof leading directly to the street - it is forbidden to pour directly into it. One may only pour into the courtyard or on to the roof, from where the water will flow automatically into the ditch.

(b) A Chatzer of less than four Amos which, together with the porch, totals four Amos - does not require an Ukah.

(c) If one of two raised stoeps with steps leading down into a common Chatzer that is less than four square Amos, made an Ukah, and the other did not - then the residents of the stoep who made the Eruv, are permitted to use the Chatzer, by pouring water or waste onto the stoep and allowing it to flow or drip into the Ukah; the other set of residents are not.

6)

(a) Rebbi Zeira explains that a Chatzer of four Amos does not require an Ukah - because the water gets absorbed in the ground anyway.

(b) The difference between Rabah and Rebbi Zeira's answers - is by a long but narrow ditch, which has the equivalent area to one of four by four Amos square (and will therefore absorb the water that is poured into it) but the owner will not bother to settle its dust, because it is not a usable tract of land.

(c) Rabah explains our Mishnah, which exempts a combined Chatzer and porch of four square Amos from an Ukah - when they combine to make a square of four by four.

(a) The author of the Beraisa, which explicitly requires a square of four by four Amos to exempt from an Ukah - is the Rabbanan, who do *not* permit pouring the water merely on the basis of the fact that the water will become absorbed; whereas the author of our Mishnah is Rebbi Eliezer ben Ya'akov, who *does*. (b) Rebbi Zeira infers from 'Chatzer she'Hi Pechusah me'Arba al Arba' - that if it has *the Shiur* of four Amos by four Amos, then irrespective of the shape, it will not require an Ukah (like Rebbi Eliezer ben Ya'akov). Otherwise, it should have said 'Chatzer she'Ein Bah Arba al Arba'.

(c) The Gemara concludes that the author of the entire Mishnah is Rebbi Eliezer ben Ya'akov, and that there are words missing. This is how the Mishnah ought to read: 'Chazter she'Hi Pechusah mi'Arba Amos, Ein Shofchin le'Tochah Mayim be'Shabbos; Ha Arba Amos, Shofchin, she'Rebbi Eliezer ben Ya'akov Omer, Biv ha'Kamur' ...

9)

(a) The Beraisa permits pouring water into the small pit during the rain season, even when there is no Ukah - because neither of the two reasons which cause the prohibition, apply: neither do we suspect that the owner will pour the water in the street, in order to keep his courtyard clean (since they are full of rain-water anyway); nor do we need to worry that others will suspect him of pouring water into the street (sdue to the fact that, on account of the rains, there is constantly water pouring out of his courtyard anyway, so people will attribute the water that is pouring out of his yard to them).

(b) The Chachamim forbid pouring sewage into the drain on the roof, where he also wants them to be absorbed - because even though the first of the above reasons does not apply there, the second one does.

(c) In the rain-season, says Rav Nachman, one is permitted to pour a Sa'ah into an Ukah that holds a Sa'ah; whereas in the dry season, he is not permitted to pour anything at all, because, if we permit him to pour *one* Sa'ah, he may come to pour in *two*.

(d) Abaye adds - that, seeing as in the rain season, there is nothing to worry about (as we explained in a), one may even pour a Kur (and even two), into an Ukah that only holds a Sa'ah.

(a) The Gemara rejects the suggestion that Rava establishes our Mishnah (which forbids the residents of the one raised stoep to use the Ukah of the other [despite the fact that they are sharing the same Chatzer]) even when they made an Eruv, because the two courtyards will now be pouring *four* Sa'ah into the pit, instead of *two* - because of the Beraisa, which permits pouring into the Ukah even if it was full on Erev Shabbos. So we see, that there is no limit on how much one may pour into an Ukah which can contain two Sa'ah.

(b) A Gistera is a broken earthenware vessel; a Bereichah is a pool of water, similar to a fish-pond and an Arivah, a small boat - all of which are used in our Sugya as an Ukah.

(c) If the residents of the second stoep did not make an Eruv, they are forbidden to use the Ukah - because we are afraid that they may bring sewage in vessels that they brought from the house to pour into the Ukah, and which they are forbidden to carry in the Chatzer.

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