Shabbos Domains
מסכת שבת דף ק' ע"ב:
איתמר ספינה רב הונא אמר מוציאין הימנה זיז כל שהוא וממלא רב חסדא ורבה בר רב הונא אמרי עושה מקום ארבעה וממלא רב הונא אמר מוציא הימנה זיז כל שהוא וממלא קסבר כרמלית מארעא משחינן ואוירא מקום פטור הוא ובדין הוא דזיז נמי לא ליבעי אלא כי היכי דליהוי ליה היכרא רב חסדא ורבה בר רב הונא אמרי עושה מקום ארבעה וממלא קסברי כרמלית משפת מיא משחינן מיא ארעא סמיכתא אי לא עביד מקום ארבעה קא מטלטל מכרמלית לרשות היחיד.
It was stated: A ship, Rav Huna said: They extend a ledge from it, no matter how small, and he fills [a bucket with the water]. Rav Chisda and Rabbah bar Rav Huna said: He makes an enclosure of four [tefachim], and fills [the bucket from that enclosure]. Rav Huna said: They extend a ledge from it, no matter how small, and he fills [a bucket with the water] - he maintains that [the ten tefachim] of a karmelis is measured from the floor [of the body of water], and the air [above those ten tefachim] is a makom patur. And strictly speaking, one should not even need a ledge, but it is to serve as a reminder [of the prohibition to carry from a karmelis to a reshus hayachid. Rav Chisda and Rabbah bar Rav Huna say: He makes an enclosure of four [tefachim], and fills [the bucket from that enclosure] - they maintain that the karmelis is measured from the water's surface, [as if] the water is like solid ground, so if one does not make an enclosure of four [tefachim], he is carrying from a karmelis to a reshus hayachid.
The following material is excerpted from The Contemporary Eruv:Eruvin in Modern Metropolitan Areas by Rabbi Yosef Gavriel Bechhofer; it is reprinted here with permission. The passages here are a translation of Tur (Orach Chaim #345):
There are four domains that pertain to Shabbos: Reshus ha'yachid, reshus ha'rabbim, carmelis and makom patur.
A reshus ha'yachid is an area enclosed by walls that are at least ten tefachim high. The size of the area must be at least four by four tefachim. A reshus ha'yachid may, however, extend several miles in each direction, if its perimeter was [originally] enclosed for the purpose of habitation and its doors are closed at night. An animal pen or corral, even a trench that is ten tefachim deep and four by four tefachim in area at its bottom, or a mound that is ten tefachim high and four by four tefachim in area at its top, are all reshuyos ha'yachid.
Both the tops of, and the nooks in, the walls surrounding a reshus ha'yachid are part of that reshus ha'yachid.
The airspace of a reshus ha'yachid is part of that reshus ha'yachid.
Even a movable object such as a box, a beehive or portable closet, is a reshus ha'yachid if it is ten tefachim high and four by four tefachim in area.
A reshus ha'rabbim is a street or marketplace that is: a) at least sixteen amos wide by sixteen amos long; b) that runs in an uninterrupted line from one gate of the city to another gate of the city; and, c) that six hundred thousand people traverse.
Any object present in a reshus ha'rabbim that is not three tefachim high is considered part of the surface of the reshus ha'rabbim. This is true even if the object is one that people avoid stepping upon, such as thorns or excrement. If the object is between three and nine tefachim in height and four by four tefachim in area, it is a carmelis. If it is less than four by four tefachim, then it is a makom patur. If the object is between nine and ten tefachim high and people make use of its top to shoulder their loads, then it is part of the reshus ha'rabbim - even if it is less than four by four tefachim in area.
An object in a reshus ha'rabbim that is ten or more tefachim high and four by four tefachim in area is a reshus ha'yachid. If the object is less than four by four tefachim, it is a makom patur - even if it is large enough that a four by four surface could be hewed in it somewhere beneath the height of ten tefachim.
A hole in a reshus ha'rabbim that is shallower than three tefachim is part of the reshus ha'rabbim. If the hole is between three and ten tefachim in depth and is also four by four tefachim in area, it is a carmelis. If it is less than four by four tefachim, then it is a makom patur.
The airspace above a reshus ha'rabbim is only part of the reshus ha'rabbim up to the height of ten tefachim. The airspace above ten tefachim is a makom patur.
A hole in a wall that abuts a reshus ha'rabbim is not included in the reshus ha'rabbim. Its definition depends on its dimensions. If it is four by four tefachim in area and ten tefachim high, it is a reshus ha'yachid. If it is four by four tefachim in area but not ten tefachim high, it is a carmelis. If the hole is smaller in area than four by four tefachim, but more than three tefachim above the ground, it is a makom patur.
A carmelis is a place that is not intended to serve as a thoroughfare for masses. Examples of carmelis include a lake [or sea], an area encompassing many cultivated fields, areas [in front of stores that line a reshus ha'rabbim] designated for storekeepers to sit in, areas [designated for peddlers to hang their wares] between pillars that interrupt a reshus ha'rabbim, the raised platforms surrounding those pillars [designated for peddlers to sit upon], and streets that come off a reshus ha'rabbim at an angle. [This category] includes streets surrounded by three walls that do not possess a post or beam on the fourth side [to set them off from the adjacent reshus ha'rabbim]. [Other categories of carmelis] include a reshus ha'rabbim that has been roofed over, an area completely enclosed by walls that are not ten tefachim high, mounds that are four by four tefachim in area, but not ten tefachim high, and trenches that are four by four tefachim in area but not ten tefachim deep.
A house that is: a) four by four tefachim in area; b) shorter than ten tefachim in height internally; but, c) higher then ten tefachim externally because of the additional height of its roof, is a carmelis within its roof and under its ceiling, but a reshus ha'yachid atop its roof. If, however, in some part of the house there is a depression that is at least four by four tefachim in area, from which there are ten tefachim to the ceiling, then the entire inside of the house is a reshus ha'yachid.
A roof that extends beyond the walls of the house underneath it - so that the walls of the house are not visible to someone standing on that roof - is a carmelis - even if the roof is very high and broad. If, however, an opening [that is at least four by four tefachim in size (Beis Yosef adds this parameter on the basis of the ruling of the Rosh)] opens from the house below onto the roof, then the roof is a reshus ha'yachid. Similarly, a platform four by four tefachim in area that juts out from the wall of a house is a carmelis unless an opening from the house leads to it.
A hole in a wall that abuts a carmelis is not included in the carmelis.
The airspace of a carmelis only extends ten tefachim above its surface. The airspace higher than ten tefachim is a makom patur. In the case of an object floating on the waters of a lake or river, the first ten tefachim above the water are still a carmelis; the airspace above that is a makom patur. [Beis Yosef explains why the Tur brings this specific example. There is a disagreement in Shabbos 100b whether the ten tefachim of the carmelis begin from the bed of the lake or river or from the water’s surface. Tur meant to clarify that we follow the opinion of Rav Chisda and Rabba bar Rav Huna that the measurement begins from the water’s surface.]
A well within a carmelis is a carmelis - even if it is one hundred amos deep - unless the well is four by four tefachim in area [in which case it is a reshus ha'yachid]. (The comment within the brackets is made by Beis Yosef, who notes that while we have already seen that a trench in a reshus ha'rabbim that is less than four by four tefachim in area is considered a makom patur; when, however, that same type of trench is within a carmelis, it acquires the more stringent parameter of the surrounding carmelis. This phenomenon reflects the principle of “matza min es mino” [literally: “a kind finds its kindred kind”], i.e., the similarity between carmelis and makom patur is so great that the surrounding carmelis assimilates the makom patur.
A makom patur is either: a) an object that is not four by four tefachim in area, yet is higher than three tefachim above the ground (even as high as the sky); or, b) a trench that is not four by four tefachim in area, but is deeper than three tefachim beneath the ground. Similarly, if walls higher than three tefachim above the ground enclose an area that is less than four by four tefachim in size, even if that area is very long [and narrow], it is a makom patur. (Bayis Chadash [“Bach”] notes that in light of the Tur’s previous ruling it seems that these parameters of makom patur only apply to an object or trench in a reshus ha'rabbim, while in a carmelis we would apply the principle of “matza min es mino.” As the Bach himself notes, others disagree and draw a distinction between trenches - that are assimilated into the surrounding carmelis; and outcroppings and objects - that are not.