1)

(a)Rebbi Yossi says that straw which one has specifically in mind not to move away is like Stam earth and is Batel; and earth which he specifically has in mind not to move away, is like Stam straw, which is not Batel (in other words, Stam earth is Batel, but Stam straw is not). In that case, why should the Mishnah in Ohalos go like Rebbi Yossi, and not our Mishnah?

(b)Consequently, Rav Asi learns that Stam Tana in Eruvin is Rebbi Yossi, in which case our Tana will conform with the Mishnah in Ohalos, both of which go like Rebbi Yossi.

(c)Rav Huna Brei de'Rav Yehoshua differentiates between Tum'ah and Shabbos - Tum'ah requires permanent Bitul, and unless we know that the owner was Mevatel, it is not Batel; whereas Shabbos, anything that is Muktzeh (such as earth, or even a purse) the owner will be Mevatel there, even though it is only for one day (straw etc., is not Muktzeh, since it is fit to feed his animals).

(d)The Mishnah in Ohalos, answers Rav Ashi, is speaking about a house, which does not stand to be filled in with straw or with anything else. Consequently, the Tana contends that Stam is not Batel; whereas in our Mishnah, which speaks about a ditch, which does stand to be filled in, the Tana maintains that Stam it is not Batel.

2)

(a)A ledge of even a Mashehu which runs along the length of the ditch which is exactly four Tefachim wide will suffice to combine the two courtyards (since the ditch is no longer four Tefachim wide).

3)

(a)A plank that combines two protruding ledges from the upper floor of two adjacent houses will not be effective - either if one of the houses protrudes into the street more than the other one (since the plank is placed diagonally, and not at ninety degrees); or if one of the ledges is more than three Tefachim higher that the other.

4)

(a)The residents of the two courtyards will be forced to stop feeding their animals from the hay-stack - as soon as the hay decreases to a height of less than ten Tefachim to a length of more than Amos.

(b)We not worried that this may happen without them realizing it - because we are talking about a lot of hay, and it is unlikely that the animals will devour so much straw in the course of one day.

(c)For the reason mentioned in the previous question, Rav Huna forbade the residents to take straw in boxes to feed their animals. He may however, have forbidden them to do so because, since the straw was designated for the Mechitzah, he considered it Muktzeh. (See Rosh, Si'man 6, who queries both of Rashi's explanations, and establishes our Sugya by Erev Shabbos).

5)

(a)One is ...

1. ... permitted to place one's animal on top of growing grass on Shabbos - because, due to the fact that the Isur of detaching grass on Shabbos is d'Oraysa, the Jew is unlikely to pluck it for his animal; whereas ...

2. ... not however permitted, to place one's animal on top of a detached pile of hay. Here, since the Isur of feeding one's animal involves no more than Muktzeh, we suspect that the owner may be tempted to pick up some straw in order to feed his animal.

(b)Rav Huna permits him to feed his animal by standing in front of his animal at a slight distance from the straw, thereby coaxing it to walk to the pile of straw and eat.

(c)The Beraisa permits them to take straw in boxes from the haystack which is in the barn - because the fact that the barn has walls makes it easier to realize when the hay-stack in the middle has reached a level of less than ten Tefachim (and this will apply even to Rashi's second explanation of Muktzeh - in 4c - because as long as the wall is higher than ten Tefachim, the straw is not really Muktzeh, because it is not needed for the Mechitzah).

6)

(a)If the hay in the barn dropped to a level of less than ten Tefachim for a distance of more than ten Amos - then they are only permitted to make a combined Eruv, but not independent ones.

(b)To reconcile our Beraisa, which implies that, as long as the straw is ten Tefachim high, the hay-stack is considered a Mechitzah, on those who hold (above 72a) that a case such as this (see Tosfos DH 'Shema Minah'), the walls must reach the ceiling in order for them to qualify as Mechitzos - Abaye establishes the Beraisa by walls that are a fraction under thirteen Tefachim high, in which case the ten Tefachim walls will indeed be considered as if they reached the ceiling, because of 'Levud'.

(c)Rav Huna, who forbids the owners to take hay from the hay-stack to feed their animals, establishes the Beraisa (which expressly permits them to take hay on Yom-Tov from a barn which divides between two Techumei Shabbos) when the walls are exactly ten Tefachim high - in which case a hay-stack of anything more than seven Tefachim will constitute a Mechitzah (because of 'Levud').

(d)When the Beraisa says 'Nisma'et ha'Teven me'Asarah' - it means to say mi'Toras Asarah' (and if a Mechitzah reaches within three Tefachim of where it is supposed to, the seven plus hay-stack is considered as if it was ten Tefachim, and reached the ceiling).

7)

(a)When the Beraisa says 'Nisma'et ha'Teven me'Asarah Tefachim, Sheneihem Asurin', who said that the straw diminished to less than Tefachim on Shabbos? Maybe that had happened already on Friday, and the 'new' residents forbid because they failed to make an Eruv then.

(b)According to the Gemara's second explanation - both Bitul Reshus and locking the door are necessary, because, since he is used to carrying in the Chatzer, we are afraid that he will continue to do so. In fact, this applies to every Mevatel Reshus (i.e. that the one who is Mevatel his Reshus must lock his door). Note: This Chumra is restricted to the first Shabbos only - Tosfos DH 've'Iba'is Eima'. In addition, it does not mean that he cannot use the door, but that, when it is not in use, he must keep it locked - Rosh Siman 7.

(c)'Hu Asur, va'Chavero Mutar' speaks even if his friend was then Mevatel his Reshus back to him - to teach us 'Ein Mevatlin ve'Chozrin u'Mevatlin'.

(d)The Chidush of 'v'Chen Ata Omer b'Guv shel Teven she'Bein Shnei Techumei Shabbos' - is that even according to Rebbi Akiva, who holds that Techumin d'Oraysa, the residents on both sides of the Techum are permitted to take from the straw in the middle, and we are not worried that they might mistakenly take from each other's straw, which is an Isur d'Oraysa; whereas Eruv Chatzeros is only an Isur de'Rabbanan - even according to Rebbi Akiva.

8)

(a)Someone places his own food (for a Shituf Mavo'os) in one of the Chatzeros on behalf of his co-residents, says - 'Harei Zu l'Chol B'nei Mavoy.

(b)One's small children (or possibly even grown-up children who are still eating at their father's table - see Tosfos DH 'u'Mezakeh'), and one's non-Jewish slave are not eligible to act as agents to place the Shituf on behalf of the Mavoy.

(c)The Sheli'ach must lift the barrel with the food one Teach from the ground - in order to be acquire it on their behalf.

9)

(a)The Sabi de'Pumbedisa - were Rav Yehudah and the Talmidim of his Yeshiva. Besides the previous Halachah, they also said - that the person who recites Kidush is obligated to drink a cheekful of wine in order to fulfill one's obligation.

(b)The Heter of making a fire on Shabbos for a woman who gave birth - does extend to other sick people as well, since we learnt in the name of Shmuel that if someone who let blood is feeling cold, it is permitted to light a fire for him ...

(c)... even in the middle of summer.

10)

(a)Shmuel defines an unspecified Asheirah as one - whose fruit they specifically designated for their celebrations during their idolatrous festivities.