Explanation: [Ravina] holds that there is no Migrash in the corners. Rav Ashi holds just the contrary, that there is Migrash only in the corners, but not in the Techum (what is directly outside the Migrash.

Remark: Rashi said that Rav Ashi discusses a [square] city of 2,000 [Amos]. This is wrong. In every city, the Migrash in the corners is a quarter of the corners! (Maharshal deletes this from Tosfos, for Rashi himself says so in DH "Lishna Acharina.")

Observation: The calculation is not precise. If you cut a tablet 10 by 10 (Amos) lengthwise and widthwise (in the middle), it becomes four tablets five by five. If you make a square inside that [its sides] go along the diagonals of the four tablets, the inner square has area 50 square Amos, for it is half of the outer square, which has area 100;

If the diagonal of [a square] five by five were only like the calculation of an Amah and two fifths (for each Amah of the side, the diagonals are seven, and) the area of the inner square would be only 49 square Amos!

Also, [if so] the diagonal of inner square (which is the width of the outer square, i.e. 10) would be only [seven fifths the side of the inner square, i.e.] nine and four fifths Amos!

Conclusion: Rather, the diagonal is a little more than an Amah and two fifths (for each Amah of the side).

Opinion #1 (Ri): Only for two cities we give a Karfef to this and a Karfef to this according to Rabanan, just like according to R. Meir [Karfef is] only for a city, for he expounds a verse, also for Rabanan, two cities is precise;

However, we do not give two Karfifos for a city and a house. Only, if [the house] is within 70 Amos and a remainder of the city, it is appended to the city.

Similarly, if there is another house within 70 Amos and a remainder of that [first] house of one city, they can make shacks [to extend the Techum] as much as they want;

Source: It says above (21a) "you go [on Shabbos] from Barnish to the Beis ha'Keneses of Daniel, which was three Parsa'os..." Why do you rely on shacks? [R. Yirmeyah's grandson] showed him destroyed cities within 70 Amos and a remainder. (It was a question only because this was in Bavel, but all agree that shacks in Eretz Yisrael can extend the Techum, without limit.)

Support: Now it is fine in our Sugya (57b), that Rav Safra said to Rava that people of Aktisfun measure from the end of Ardeshir, even though the Diglas river separates them, and it is more than 141 and a third wide;

He mentioned 141 and a third Amos, which is two Karfifos, for he discusses two cities. It says that Rava showed to him part of the city wall in the river within 70 Amos and a remainder, for to join to a city, it must be within 70 Amos and a remainder.

Opinion #2: It seems that even for a house and a house without a city, we give one Karfef for both of them.

Source: If you would not say so, if a city has no wall, what joins [the houses] to be like one, if not that they are within 70 Amos and a remainder [of each other]? It is unreasonable to say that they must touch each other!

Implied question: According to this, Chiya bar Rav, who says that we give one Karfef for both of them, Rabanan were not precise when they said two cities. The same applies to two houses!

Answer: Since R. Meir mentioned one city, Rabanan mentioned two cities.

Implied question: A Beraisa in Sukah (3b) teaches that if a house is less than four by four Amos, we do not make it an Ibur between two cities. Why is the house needed? Even without it, we give a Karfef to a city!

Suggestion: Through the house, they can go further.

Rejection: If so, why did he mention two cities? He should have said "we do not make it an Ibur to a city"!

Answer #1 (Rashbam): The text there says "we do not make it an Ibur to a city."

Answer #2: He mentions two cities because then it is common to make shacks to go from one to the other when they are more than 4000 Amos apart, and one cannot go through an Eruv.

Pesak (R. Tam): The Halachah follows Rav Huna, who says that we give a Karfef to this one and a Karfef to this one.

Source #1: He was greater in Chachmah and Minyan (number of Talmidim) than Chiya bar Rav, who was much smaller than him, like is proven in Erchin (16b), for Rav Huna used to rebuke him.

Source #2: The Amora'im (Rabah, Abaye and Rava) who say that [the three cities that our Mishnah says are Meshulashim] are not truly Meshulashim (evenly spaced in a line. Rather, they are in a triangle) hold like Rav Huna, for according to Chiya bar Rav, they can be truly Meshulashim.

Support #3: Rav Safra said "the Diglas river separates them, and it is more than 141 and a third wide." This implies that if it were not wider, it would be fine. This is like Rav Huna.

Support #4: Even according to Chiya bar Rav, we answer that the Seifa of our Mishnah taught "70 Amos and a remainder for this, and 70 Amos and a remainder for this", like R. Meir, so it is a Machlokes v'Achar Kach Stam (after the argument, the Mishnah teaches one of the opinions Stam. In such a case, the Halachah follows the Stam.) If so, he holds that the Halachah follows R. Meir.

Question: Also according to Chiya bar Rav it is difficult. He establishes the Seifa (if there are 70 Amos and a remainder for this...) like R. Meir, and he does not require a middle [city to make them like one. Why does the very Seifa of three villages require one in the middle?]

Answer: He can establish the Seifa of three villages like Rabanan. It teaches that we can make many shacks one after the other, each within 70 Amos and a remainder of the previous, to make them all considered like one, just like here the middle [village] makes all three like one.

Explanation: "Between the outer ones" means between the outer ones and the middle, and there are 141 and a third on this side and 141 and a third on this side, like Rashi explained.

Question: Also initially, that we thought that they are truly Meshulashim (evenly spaced in a line), he can explain so, that it means between the outer ones and the middle, and it is not difficult for Rav Huna!

Answer: If they are truly Meshulashim, we cannot explain so, for if so, it should not have taught "between the two outer ones." Rather, it should have taught "if there is between this and this 141 and a third";

However, if they are not truly Meshulashim, we cannot teach "between this and this", since the middle one is not there between them.

Assertion: Also according to Chiya bar Rav, we must say that they are not truly Meshulashim. If they were truly Meshulashim, why does it say "between the two outer ones 141 and a third", and it includes the space on both sides [of the middle city, i.e. between it and the outer cities] together? It should have taught "if there is between this and this 70 Amos and a remainder"!

Consequence: If so, that Chiya bar Rav agrees to this conclusion, there is no proof from here that the Halachah follows Rav Huna [from the Amora'im who say that they are not truly Meshulashim. Since Chiya bar Rav agrees, this is not a proof].

Explanation #1: There, the people in the middle of the bow do not measure from the Yeser. We cannot say "fill" in this way, as if their houses in the bow were put in the Yeser, for if so they would lose in the other direction. If the Yeser was to the east, they would lose to the west;

Similarly, we do not say "fill" to view the middle [village] as if it stands between the outside ones, to measure from there 2000;

Only regarding the outer, he says that we fill, when people of this outer village come to go in the direction of the other outer one. We measure for each from the opening of [the wall of] the other;

Likewise, people at one end of the bow who want to go to the other end of the bow, [Abaye] said that we fill and measure 2000 for them from the other end of the bow, even if there are more than 4000 between the two ends, as long as there are not more than 2000 Amos between the Yeser and the bow, just like between the middle and the outer [village] here. We permit only up to 2000.

Explanation #2: There, we do not say "fill", since there are more than 2000. This is like Abaye taught elsewhere, that presumably Rava brei d'Rabah bar Rav Huna is correct, and when it is more than 2000 we do not say "fill", since there are more than 2000;

Here, we say "fill", since we establish that there are only 2000 between the middle and the outer.

Explanation #3: There, we do not say "fill", since the space in the Yeser cannot fit the people in the bow. The same applies here. If the middle [village] is bigger than the space between the two outer ones, we do not say "fill".