Question: How does he bring a support from R. Yehudah? Rabanan argue with him!

Answer (Ri): They argue only about when it is 10 deep and 10 high. Rabanan hold that from Karmelis to Reshus ha'Yachid via Mekom Petur is forbidden, even though [one of the] Reshuyos is mid'Rabanan (mid'Oraisa, Karmelis is Mekom Petur), and R. Yehudah permits;

However, when it is 10 deep and not 10 high, to transfer from it to the sea, Rabanan do not argue with him.

Support: It says so in the Tosefta. If a boat on the sea is 10 tall and [the sea is] 10 deep, one may not transfer from it to the sea, and not from the sea into it. R. Yehudah says, if it is 10 deep and not 10 high...

R. Yehudah means as follows. Not only if it is 10 deep and 10 high, it is permitted to transfer absolutely, since he transfers via Mekom Petur;

Rather, also when it is not 10 tall, there is a solution to transfer, e.g. through Kocho, like the Gemara explains.

Question (Ri): Now, according to R. Yehudah, it is permitted to transfer through Mekom Petur regarding Reshuyos mid'Rabanan. Even Rabanan argue only when he does not do Hanachah in Mekom Petur;

In Eruvin (87b), it challenges Ze'iri, who forbids transferring from Karmelis to Reshus ha'Yachid through Mekom Petur. According to Ze'iri, the argument of R. Shimon ben Gamliel and Rabanan, who argue about this, is difficult! The Gemara answers this;

Now, the Tana'im here are unlike [Ze'iri]!

Answer: In any case, the Tana'im there, since we can establish them like him, we do so.

Implied question: This is difficult for the opinion above (100b) that we measure [the 10 Tefachim of Karmelis] from the [sea] floor!

Answer: Here we discuss when there is not a ledge of any size for a Heker (reminder).

Explanation #1 (Rashi): [These boats] are narrow below.

Question #1: Just like it is Batel from the law of Reshus ha'Yachid because it is not four [Tefachim] wide, it should be Batel from the law of Karmelis!

It says above (7a) that there is no Karmelis less than four, and Rabanan gave it the leniencies of Reshus ha'Yachid. If it is four wide, it is Karmelis. If not, it is Mekom Petur!

Question #2: What was the question "he should say Gud Achis!"? How does it help, that there are wide Mechitzos outside, since inside there is no space four by four, and it is not comfortable to use them, and the wall of the boat where it is narrow nullifies Gud Achis, just like dividing with a mat above (100a)?

Question #3: Why do we need that he filled it with sticks and thin willow branches? Even if he did not fill it, since he can fill it, it is Reshus ha'Yachid!

This is like it says in Eruvin (78a) regarding filling the entire [surface of a pillar] with pegs, [that this does not diminish the usable area], because if he wants, he could put something on it and use it!

Explanation #2 (R. Chananel): Beitzisa are small boats made to go in swamps. Because they go on Bitz'ei (marshes), they are called Beitzisa;

They have walls and the floor is made of planks, and there is a gap between planks, and water enters there. People sit in it, like in the water;

It is made like this so that even if it flips over, it will never sink.

Rav Huna said that since it is open, its law is like Karmelis, and one may carry in it only within four [Amos];

This was taught only when there is not between one plank and another a gap less than three. If there is not between one plank and another a gap less than three, it is like Lavud, and even though water enters, we are not concerned.

Assertion: It seems that the text does not say "there is not [a width of] four [Tefachim] within three [Tefachim of the bottom], and if he filled the entire interior with sticks and willow branches, one may carry in all of it."

Explanation: [He asks] why do you need all these [distinctions]? You should say Gud Achis Mechitzta! A Beraisa teaches that R. Yosi b'Ribi Yehudah says...

Inference: We view it as if the walls of the basket descend to the base of the stick. Also here, we view it as if the walls of the boat are bent and surround the planks, and it turns out that the planks are connected.

Implied question: According to the Havah Amina now that there is no distinction between a wall [over] water and other walls, and we are thinking also that Rabanan do not argue with R. Yosi b'Ribi Yehudah...

We should ask why the Mishnah (Eruvin 87b) says that if a balcony is above water, one may take draw water (through a hole in the balcony) from it only if he made a wall 10 Tefachim. Why is a 10 Tefachim wall needed? Even without a 10 Tefachim wall, [the balcony] should suffice, like regarding a basket!

Answer #1: [We do not ask, for] R. Yosi b'Ribi Yehudah considers only on top to be Reshus ha'Yachid, but not below. Gud Achis does not help for this.

Answer #2: Regarding a balcony, we require a wall 10 Tefachim to permit carrying, but [to obligate one who throws to there from Reshus ha'Rabim], we do not need a 10 Tefachim wall, like regarding a basket.

Explanation: Here, he asks as follows. We should say Gud Achis, just like R. Yosi b'Ribi Yehudah says Gud Achis when there is not a 10 Tefachim wall, to be Reshus ha'Yachid to be liable. Similarly, in a boat, which has a 10 Tefachim wall, we should say Gud Achis even to carry!

Explanation #1 (Rashi): [The narrow part of the beam] is three [Tefachim] above the ground.

Question: If it is very thin, like a stick, it is like a basket, and penetration of goats is Mevatel Gud Achis!

Explanation #2 (Ri): If the narrow part is three, i.e. the thickness of the narrow part is three [Tefachim]. Since the narrow part is three thick, and above it is four wide, Gud Achis applies.

Question: Why doesn't he rather resolve from the Mishnah in Eruvin (87b) that if a balcony is above water...? It is permitted through a wall above!

Answer (Ri): From the Mishnah, one might have thought that even other Mechitzos, which are not above water, a hanging Mechitzah permits. Therefore he brings from R. Tavla who explains the reason. It is a leniency that Chachamim gave for water.

Explanation #1: Now we are thinking that the two boats are of one person. Therefore, he asks that this is obvious;

When they are not tied, one may not transfer. This is a decree lest the item fall in the water, and he will transfer from Reshus ha'Yachid to Karmelis, and he will come to take it.

Implied question: Above, regarding two houses (97a), we do not decree lest he come to take it!

Answer: Here regarding boats, which are not fixed, there is more reason to decree lest it fall.

Explanation #1 (cont.): We conclude that [this clause permits] to make an Eruv and transfer. The Chidush is that an Eruv help for boats, even though they are not fixed there;

One might have thought that since in the future they will not be there, Eruv does not help. The Mishnah teaches that it helps.

Explanation #2 (Ri): Also from the beginning, we knew that we discuss boats of two people, and the Mishnah teaches that one may transfer from one to another through an Eruv;

Even so, it asks that this is obvious that Eruv helps, and this is why when they are not tied one may not transfer from one to another, because there an Eruv does not help;

We conclude that [the clause] is needed only [to permit] to make an Eruv and transfer, and even if they became separated, once they became tied again, like the Beraisa teaches...

Implied question: Why is this unlike one who made an Eruv through an opening, and it was sealed? Rav Huna and Rav Yehudah say (Eruvin 17a) that since Shabbos was permitted, [the entire Shabbos] is permitted!

Answer: Here is different. Since they were separated, it is as if Reshus ha'Rabim is between them;

If three houses made an Eruv, and the middle one fell, and became Reshus ha'Rabim, obviously we do not say that since it was permitted, it was permitted.

Implied question: It teaches that they return to the initial Heter even b'Mezid!

Answer #1: They did not totally return to the initial Heter to carry. Rather, they are Reshus ha'Yachid mid'Oraisa.

Question: Regarding boats, this is difficult. [Even] without become tied again, they are Reshus ha'Yachid mid'Oraisa!

Answer #2 (R. Tam): They returned to the initial Heter even b'Mezid. Rav Nachman teaches that b'Mezid it is a Mechitzah only to [obligate one who will] throw, but not to carry, i.e. when through the Mechitzah, it becomes Reshus ha'Yachid;

However, boats, which were already Reshus ha'Yachid, when they are tied, even b'Mezid one may transfer;

"Mats spread in Reshus ha'Yachid" discusses when there are mats separating between two Chatzeros, and they were rolled up. They are forbidden, for they are like one Chatzer, and they made two [separate] Eruvin;

If [the mats] were spread again, they return to their initial Heter, and these (this Chatzer) may carry here, and these may carry here (in their Chatzer).

Implied question: It says that every Mechitzah made on Shabbos is considered a Mechitzah!

Answer: This gives the reason why even if through the Mechitzah it became Reshus ha'Yachid, it is a Mechitzah for throwing or carrying, and all the more so this Mechitzah, which is only to permit an Eruv, like initially, is a Mechitzah;

The question against Rav Nachman is from the Seifa "any Mechitzah made on Shabbos..."

Implied question: In Eruvin (93b) it discusses a wall between two Chatzeros that fell, and one opinion there permits to carry up to the base of the wall!

Answer: Here is different. There, there was only one house in this Chatzer and one in this Chatzer. Here, there are many in each, we say that if [the mats] were rolled up, they are forbidden.

Question: This requires investigation in the Sugya of dwellers who come on Shabbos (Eruvin 17a). It says that since Shabbos was permitted, it is permitted.

Explanation #1 (Rashi): E.g. if one end was in Ohel ha'Mes.

Rejection #1: Why does it say "to teach unlike Shmuel"? What is the connection to Shmuel's law? There, it is because a sword is like a corpse, and not due to tying!

Rejection #2: Why does it teach "he tied it"? Even if the chain is resting on the boat without tying, it is Tamei!

Rejection #3: He should explicitly teach that a sword is like a corpse!

Rejection #4: The expression "bringing Tum'ah" does not apply in such a case!

Alternative text (Rashbam): The text does not say "it brings Tum'ah to it", rather, "it brings Tum'ah." This is a Mishnah in Ohalos (8:5);

The Reisha of this clause teaches "these do not bring [Tum'ah] and do not block - crops, a flying bird, an airborne Talis, and a boat floating on the water";

I.e. if a Mes is under one side (of any of these), and Taharos under the other side, it does not bring Tum'ah from this side to the other. They are not considered Ohalim, because they move constantly;

It teaches that if he tied it with something that holds it, it brings Tum'ah.

Shmuel explains that this is if he tied it with iron chains. Iron is not precise. Rather, he tied it tightly, so it does not move from its place;

When [the Gemara] wants to mention something strong, it mentions iron, e.g. an iron wall does not divide (Sotah 38b), Nichsei Tzon Barzel (Bava Kama 89a), because he has Achrayus for them (if she is widowed or divorced, she gets back their value at the time she brought them into the marriage), and they are hard like iron.

The text does not say 'regarding Tum'ah, it is written "b'Chalal Cherev" - a sword is like a corpse.' This is a mistake. Because he mentioned iron chains, [people] erred to say that the reason is because a sword is like a corpse.

Rather, the text says "this is only regarding Tum'ah. An Ohel must totally rest. However, the reason for Shabbos is due to one Reshus. A drawstring of a cloak suffices.