1)

(a)(Rebbi Chiya's version of) the Beraisa that so amused Rebbi Yossi b'Rebbi Chanina stated that fish-nets (in the form of a wall of reeds) placed between two Techumei Shabbos of two cities (whose borders met in the water) were not sufficient to divide the water between the two cities, and that consequently, no-one from either city was permitted to draw water from the river (because the water from each one's Techum mixed with the water of the other), unless they put up a metal wall.

(b)Rebbi Yossi b'Rebbi Chanina's amusement cannot have been due to ...

1. ... the fact that the Beraisa followed the opinion of Rebbi Yochanan ben Nuri (who holds Cheftzei Hefker Konin Shevisah), whilst he held like the Rabbanan. Is it because Rebbi Yossi b'Rebbi Chanina holds like the Rabbanan, that Rebbi Chiya is obligated to do likewise?

2. ... another Beraisa, which gives the water of a flowing river or of a fountain the Techum of whoever collects it - because maybe that speaks about water that is still (e.g. the water in a lake), but not water in a river - that is moving.

3. ... the fact that Rebbi Chiya required a metal wall (in other words, he laughed because, just as a wall made of fish-nets was futile because it allowed the water to pass, so would a metal wall be futile - for the same reason) because maybe what the Beraisa was saying was that even a metal wall would be ineffective.

(c)Rebbi Yossi b'Rebbi Chanina laughed - because all this is not necessary. Chazal were lenient by water, and permitted even a suspended Mechitzah (which does not even reach the water), as if it was a proper one.

2)

(a)The Chachamim in our Mishnah, who say that someone who slept during Bein Hashemashos has only four Amos - mean four Amos in all directions (a total of eight Amos square); whereas Rebbi Yehudah, who says 'le'Eizeh Ru'ach she'Yirtzeh, Yelech' - only gives him four Amos, either in the one direction, or two Amos in each direction from the point where he is standing.

(b)Although the Rabbanan permit him to walk eight Amos, he is permitted to carry only four.

(c)According to Rebbi Yehudah, the extra Amah the Torah gives to each person -to enable him to take an object from below his feet and place it above his head.

(d)According to Rebbi Meir - the four Amos are large ones (i.e. slightly more than four ordinary Amos, since one needs more than an Amah to stretch), whereas according to Rebbi Yehudah, the four Amos are exact.

3)

(a)The four Amos of which we are speaking - could mean four Amos measured by each individual's arm-length, or it could mean the fixed Amah that was used in the Beis ha'Mikdash (and which consisted of six average Tefachim).

(b)If we were to learn like the first explanation - then a giant would have more space to carry than an ordinary person (a leniency which the Torah is unlikely to have given him. A small person would have less, which would not present a problem, because that would entail a Chumra.

(c)Even if we were to learn that everyone's four Amos consisted of their own arm-length, the fact that the Mishnah in Kelim does not include this case in the list of 'ha'Kol Le'fi Mah she'Hu Adam' would not bother us - because that rule is not absolute in this case: because, in any event, an ordinary-size person with small arms, will have four regular-size Amos (like the four Amos in the Beis ha'Mikdash), and not those measured by his own arm-length).

4)

(a)By comparing the case of the three men, where the middle man's Techum partially overlaps the Techumin of the outer ones, to three courtyards, where the outer two open into the Reshus ha'Rabim, and which made an Eruv with the courtyard in the middle, but not with each other - Rebbi Shimon was asking the Chachamim why it was that they argued with him in the latter case, where they forbade all three courtyards to carry in each other's courtyard (even in the courtyard with whom they had made an Eruv - unless all three combined with an Eruv), they agreed with him in the former (that each of the outer two were permitted to carry in the middle one's two Amos and vice-versa.

(b)The Chachamim replied - that they agreed with him in the former case, because there were only three individual people involved, sufficiently few to expect them to be careful (th at the two outer ones would not carry from one to the other); whereas in the latter case, which deals with three groups of people, they issued a decree, forbidding even the members of the courtyards who had made an Eruv with each other, to make use of it, just in case some of the residents would forget and come to carry from one of the outer courtyards to the other.

(c)The fact that the two outer courtyards combined to make an Eruv with the middle one, will not help to make the three Chatzeros into one, says Rav Yehudah - because it speaks when it was the middle courtyard which placed the Eruv into the two outer ones (and not vice-versa, as we thought at first).

(d)Rav Sheshes concedes that, had the outer two courtyards placed their Eruv in the middle one in one room, then all three would be considered as one courtyard, so that they would all be permitted to carry in all the courtyards. However, the Mishnah speaks when they placed their Eruv (even) in the middle courtyard, but in two rooms (one courtyard in one, and the other, in the other).

5)

(a)Beis Hillel holds that an Eruv placed in two vessels in one room is valid - because it was placed in the same room, but if it was divided and placed in two different rooms, they may well agree that the Eruv is Pasul, like Rav Sheshes.

6)

(a)If the members of the middle courtyard placed their Eruv in the two outer ones, asks Rav Acha B'rei de'Rav Ivya on Rav Yehudah, then, the moment they made an Eruv with one of the outer courtyards, they merge as if they were one courtyard. In that case, when the same courtyard went on to make an Eruv with the second outer courtyard, why are they not also the Sheluchim of the courtyard with whom they merged, in which case the two outer courtyards should now have merge too - to be able to carry in each other's domain (as if they had made their own Eruv).

(b)Not so, says Rav Ashi. Because from the fact that the two outer courtyards made an Eruv with the middle one and not with each other, it is clear that each outer courtyard does not want the middle one, to act as its Sheli'ach in that regard.

(c)Rav Acha B'rei de'Rav Ivya also has a problem with Rav Sheshes - since the two outer courtyards placed their Eruv in the middle one, according to him, it should be considered as if they were all living in the middle courtyard, and since the two pouter courtyards placed their Eruvin in two different rooms, they clearly did not make an Eruv with each other. Consequently, they should all be forbidden to carry anywhere in the courtyard, even in the middle section - like five people, four of whom made an Eruv, when the fifth failed to participate, in which case the one who failed to participate forbids the other four to carry in the entire courtyard.

(d)In the case of the five residents of the courtyard, the reason that the one forbids all the others, is because he too, resides in the courtyard; whereas, in our case, the two residents of the two outer courtyards do not really reside in the middle one. There, they will only combine to permit carrying from one courtyard to the other, but not to forbid doing so.

7)

(a)According to Rav, the Rabbanan hold that, wherever they placed the Eruv - the outer courtyards (who made an Eruv with the middle one) are permitted to carry in the middle courtyard, but not the middle one with the outer ones, since each of the outer courtyards draws the middle one to it, and its residents cannot be residents in two courtyards which did not make an Eruv with each other (i.e. each courtyard prevents the middle one from carrying in the other one).

8)

(a)In fact, even Shmuel agrees with the previous statement, forbidding the middle courtyard to carry in the two outer ones. The Rabbanan however, forbid even the two outer courtyards to carry in the middle one.

(b)Everyone agrees that when all three courtyards make an Eruv together, they are combine to become one courtyard, and all three may carry throughout.

(c)According to Shmuel, 'Hi Muteres Imahen' - refers, not to the middle one being permitted to carry in the outer courtyards, but to its being permitted to carry together with them in the middle courtyard.

(d)When Shmuel said 'Af Zu Divrei Rebbi Shimon' - he meant that even Rebbi Shimon, who is more lenient than the Chachamim, agrees with them here, that one has to be strict.

9)

(a)The Beraisa proves Shmuel right on both scores - both with regard to his opinion in Rebbi Shimon, where the Tana only refers to the members of the two outer courtyards being permitted to carry in their courtyards, but not the members of the middle one; and with regard to his opinion in the Chachamim, where he forbids members of all three courtyards to carry, unless they made an Eruv combining all three courtyards.