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1)

(a) Rav Huna forbids carrying in a small boat which is tapered to a point at its bottom - because walls that come to a point, are not considered Mechitzos, and the boat is therefore a Karmelis.

(b) Carrying in such a boat is permitted however, if the angle of the walls is not sufficiently acute to reach four Tefachim wide within three Tefachim from the floor, or if the bottom of the boat is filled in with thin willow twigs and canes, provided, in the latter case, the walls extend ten Tefachim beyond that point.

(a) 'Gud Acheis Mechitzasah' - means 'extend its wall downwards' - meaning that we extend whatever wall there is, or even just the edges of the (ninety-degree) ledge of four by four Tefachim, down to the ground, and consider it as if there was a wall there.

(b) Rebbi Yossi b'Rebbi Yehudah rules - that if someone stuck a cane with a basket perched on its top into the ground of the Reshus ha'Rabim, one would be Chayav for throwing something into the basket.

(c) Even if the Rabbanan disagree with Rebbi Yossi b'Rebbi Yehudah in the above Din - they do however, concede that in the case of a plank of four Tefachim on top by three at its base, which is stuck in the street, one is Chayav for throwing on to its top, because of 'Gud Acheis Mechitzasah'.

(d) The cane is different - because, due to the 'T'-shape of the pole with the basket, the kid-goats are able to squeeze past where the wall theoretically descends, so we cannot apply there 'Gud Acheis' ...

(a) The concept of '*Gedayim Bok'in Bah*' does *not* apply to fish in the water, since they are not visible. Consequently, '*Gud Acheis Mechitzasah*' *does*.

(b) Otherwise, how could we permit a 'Mechitzah Teluyah' in the water more than on dry land? After all, the fish are able to swim underneath the suspended wall?

4)

(a) The Gemara tried to explain that our Mishnah (which permits carrying from one ship to another when they are tied together) is coming to permit carrying from one ship to the other even via a third ship, which is wedged between them but not tied to them; the Chidush then being that we do not worry about the possibility that the third ship might float away, and they will continue carrying directly from the one ship to the other (from one Reshus ha'Yachid to another via a Karmelis), which is forbidden.

(b) The problem with this answer is that the Mishnah says 'mi'Zu le'Zu', implying that there are only *two* ships, and not *three*.

(c) The Gemara therefore establishes our Mishnah by two ships belonging to two people, who made an Eiruv. However, the Eiruv is valid only as long as the two ships are tied together, and our Mishnah is teaching us that the moment they become untied, the Eiruv becomes nullified, and carrying from one to the other is prohibited.

(d) That is only the case, however, as long as the ships remain untied. Should the Mechitzah be re-built, even on Shabbos, the Eiruv is re-instated, and it will be permitted to carry from one to the other once more.

(a) A Mechitzah that is put up on Shabbos does have the Din of a Mechitzah.

(b) If the Mechitzah was erected be'Shogeg or be'Ones, then it is a Mechitzah in every regard; but if it was erected on purpose, then it only has the Din of a Mechitzah le'Chumra - i.e. for someone who throws into it from a Reshus ha'Yachid, but not le'Kula - i.e. to give it a Din of a Reshus ha'Yachid, and to permit carrying inside that area.

(c) Shogegin refers to someone who performed a Melachah be'Shigegas Shabbos or be'Shigegas Melachos, whereas Muta'in refers to someone who is a Misasek - meaning that he meant to tie something that is permitted, but inadvertently, he tied a forbidden object (such as a Mechitzah.

(a) It is only if the rope will hold firm, that the tying is effective, but not if the two ships will easily come apart.

(b) Shmuel establishes the Mishnah in Ohalos ('Kashrah be'Davar ha'Ma'amidah, Mevi Tum'ah') - by a metal chain ('Davar ha'Ma'amidah' - something with which one usually ties it). The reason that he does so, is because the Mishnah rules that the chain renders both the ship and the vessels Tamei. Now if it was speaking about an ordinary rope, it would not render the ship more than a Rishon le'Tum'ah, in which case, the vessels would remain Tahor; whereas if it is speaking about a *metal chain*, where one end is Ma'ahil over a corpse, and the other end is tied to the ship, then ship itself, which touched metal, adopts the same Tum'ah as the metal - i.e. an Avi Avos ha'Tum'ah (because of the principle 'Cherev, Harei Hu ke'Chalal'), and the ship in turn, will render the vessels which it touches, Avos ha'Tum'ah.

(c) On the other hand, he establishes *our* Mishnah, which is speaking about Shabbos, and not Tum'ah, by an ordinary rope, which serves its purpose of tying the two ships together - irrespective of whether it is made of metal or of other materials.