Ohalos, Chapter 15, Mishnah 3. This mishnah continues the chapter's discussion of objects that are spread out over a tumah and the question of whether they function as an ohel. Here the objects are barrels, arranged in rows in the open air, and the Mishnah teaches us both how tumah travels around them and when the barrels do become a genuine ohel.
The Mishnah presents the barrels in two possible positions. Either "shehein yoshvos al shuleihen," they are resting on their bases, so that the mouth of each barrel faces upward, or "mutos al tzideihen," they are lying on their sides, so that the mouth of each barrel faces sideways. In both arrangements the barrels are "ba'avir," out in the open air and not inside a house.
A further detail: "venogos zo bazo befoseiach tefach." The barrels touch one another, and at the point where they meet there is a full open handbreadth. This is in contrast to a case of boards that meet only at a corner, where the point of contact does not amount to a poseiach tefach. The Tiferes Yisroel points out that in the first ruling of our mishnah this detail actually carries no practical weight, since there we are dealing with barrels that do not form an ohel at all. The Mishnah mentions it now because it will become decisive in the later part of the mishnah.
Tumah Beneath One of the Barrels
The case: "Tumah tachas achas meihen," impurity is situated below one barrel of the group. What follows? "Tumah boka'as ve'olah": the tumah pierces upward in a straight column all the way to the heavens, and "boka'as veyoredes": it pierces downward until it reaches the bottom of the earth. Sideways movement toward the neighboring barrels does not occur.
Why not? Because there is no handbreadth of space beneath the barrels. The Mishnah does not state this explicitly, but it does not have to: once we are told that the barrels are sitting on the ground, whether upright or on their sides, it is self understood that no open tefach exists beneath them. Without a tefach of space there is no ohel, and where there is no ohel the tumah simply travels straight up and straight down.
The Difference Between Upright Barrels and Barrels on Their Sides
The Bartenura teaches that although both arrangements share the ruling that no ohel is formed, the practical halachos are not identical, and the difference concerns the keilim stored inside the barrels.
Begin with those barrels reclining on their sides, whose openings point horizontally. Tumah situated below one of them travels down and travels up, yet the contents of that barrel stay tahor. Barrels of this sort are earthenware, and a keli cheres has this property: contact with tumah on its exterior does not carry inside, so what it holds is shielded. The tumah therefore climbs until it meets the barrel's underside, skirts around the vessel, and resumes its ascent beyond it. Neither the keilim within nor anything positioned to the flank of the tumah is affected.
Consider next the barrels that stand on their bases, their openings facing the sky. In such a case, the Bartenura holds, tumah below the barrel does affect the keilim it contains. Trace the route the tumah takes: it ascends from underneath, bypasses the body of the vessel, and resumes its climb above the barrel's rim and beyond. The airspace directly over the barrel is thus tamei. Now, what separates that tamei air from the air inside the vessel? Nothing whatsoever, since the opening gapes upward. No hefsek stands between the two. The tumah consequently drops back down into the barrel and makes its interior tamei.
Once the interior airspace of the barrel is tamei, everything in the barrel is tamei, even keilim sitting off to one side and not in the direct vertical path of the tumah. Anyone who has learned perek Keveres will recognize this pattern of reasoning from the mishnayos there.
When Do the Barrels Not Form an Ohel?
The Mishnah now turns to the second half of its teaching. Until now we have said that even barrels stacked in rows, one on top of another, form no ohel, since the bottom barrel rests on the floor and there is no open tefach beneath it. To this the Mishnah asks: "Bameh devarim amurim," under what circumstances is this so?
The Mishnah replies: "bithoros," when the barrels are tahor. According to the mefarshim, the word here means barrels of a kind that can never become mekabel tumah, vessels with no capacity to receive tumah in the first place. The Bartenura leaves this unstated in our mishnah, having already clarified it in an earlier place, and a good number of other rishonim read the term the same way.
"Aval im hayu tmei'os": should the barrels be tamei, that is, of a type susceptible to tumah, then even with the bottom row planted on the floor, the barrels above them do take on the din of an ohel. "O": or else, if they happen to be "gevohos min ha'aretz befoseiach tefach," lifted a handbreadth off the ground for whatever reason, the gap underneath makes them an ohel. Under either of these circumstances, "tumah tachas achas meihen, tachas kulam tamei": tumah lying below any single barrel makes everything below all of them tamei, since they all join together into one ohel.
A Barrel That Cannot Receive Tumah
These closing words of the Mishnah need explaining. First: how can a barrel not be fit to receive tumah? It is a keli cheres, made precisely to hold things inside, the classic example of a vessel that is mekabel tumah.
The resolution is that barrels were not all manufactured with one function in mind. Some served as swimming floats: the learner would grasp such a barrel, work his legs, and slowly acquire the skill, until at some point the barrel was removed and he swam unaided. A barrel of that design was never intended as a container for anything, so it does not become tamei. A second, more prosaic suggestion: the barrel was left incomplete, never having been fired in the kiln that would have brought it to its finished state. By either route we arrive at a barrel with no capacity to receive tumah.
Why the Lower Barrels Sometimes Do Not Count
A barrel with no susceptibility to tumah, whichever of the mefarshim's several explanations we adopt, forms no barrier separating the barrel above it from the floor. The barrel resting on top is considered attached to those below, and those below are attached to the earth, leaving no gap whatsoever underneath the pile. Compare the halachah of marble slabs: the slabs on the bottom are not counted as an independent object but as if the ground had risen higher. Our stack is likewise regarded as a single elongated barrel. The mechanics of this, and what qualifies as such an attachment, occupy the rishonim at length; we will take the rule as given.
Where the barrels on the bottom are susceptible to tumah, though, they provide no link to the barrel above. Each is an object standing on its own, and there is no longer one unbroken barrel stretching upward off the floor. The barrel on top therefore functions as a covering spread above those below it. Think of clothing or planks piled in layers: the lower layers count, halachically speaking, as though they were air, because the item above is independent of the item below. An ohel is thereby created underneath.
So in rows of piled barrels whose lower members are susceptible to tumah, those lower barrels are not attached to the one above and are ignored entirely; the measurement runs downward from the uppermost barrel, a tefach is found, and there is an ohel. Certainly the same conclusion follows where the barrels were elevated a handbreadth above the floor from the start, since the gap beneath them constitutes an ohel by itself, and this applies even to barrels that are tahor, the open space being present in any case.
Given an ohel with tumah underneath it, the halachah is "tumah tachas achas meihen, tachas kulam tamei." What lies below one barrel spreads to the space below every one of them. Here the detail noted at the beginning proves decisive: these barrels are not like boards meeting merely at a corner, for they abut one another with a full tefach by tefach of open space where they meet, and the whole array consequently fuses into a single ohel. Nothing more is required for the tumah to pass from one end of the rows to the far end.
Reviewing the Mishnah
We have rows of barrels in the open air, either standing with their mouths open upward or lying on their sides, touching one another with a poseiach tefach at the points of contact, so that were they an ohel they would be a single ohel. But since they rest on the ground, there is no ohel beneath them, and tumah found there behaves as it does wherever there is no ohel: it does not spread sideways but breaks through upward and downward.
With a barrel lying on its side, tumah beneath it descends and renders tamei whatever lies below, and rises past the barrel and continues upward. Picture the tumah rising to the underside of the barrel, passing around it, and going on upward from the other side. The keilim inside remain tahor. The outer surface of the barrel becomes tamei, but that does not affect the contents, which is the rule of a keli cheres.
When the barrel stands on its base, tumah below it ascends, moves past the vessel, and makes the air above its uncovered opening tamei. From that air it comes back down into the barrel, so that everything held inside turns tamei, even objects that do not sit in the tumah's straight vertical path.
All of this holds only "bithoros," with barrels that are not fit to receive tumah, where the stack is treated as effectively one vessel connected to the ground, on the model of the marble slabs. But if the lower barrels can receive tumah, they cannot be ignored and cannot be treated as empty space; they are a distinct entity, like garments piled one on another, and the upper barrels become a roof over them. Between the upper barrels and the floor there is a tefach, and these lower barrels do not remove it. The same applies if the upper barrels are suspended a tefach above the ground for any reason. In such cases the whole arrangement becomes a single ohel, and tumah anywhere beneath it spreads from one end to the other.