Dear Rabbi Kornfeld,
Is there any physical/chemical/biological basis for the "foul air" found in some (deeper, narrow) pits.
If not, what is this thing we call "foul air"?
Gemar tov,
Yehuda Wiesen, Newton, Massachusetts
Here is how we described it the Background to the Daf (50b):
21a) [line 19] HEVLO - its air that is hard to breathe (i.e., the limited space inside the Bor creates a situation where the somewhat rarified air of the pit, combined with the dust that rises due to a person or animal's fall (see Shabbos 95a), makes it hard to breathe inside the pit)
The panic-driven shortness of breath of the person or animal that fell probably intensifies the effect of the limited space. In any case, I assume that the Amora'im were describing a physically calculable phenomenom, rather than a metaphysical one.
The main point of Rav is that the one who dug the pit "put" a hole in the street that was not there before, but did not "put" the sides of the pit there. They were always where there are.
Gemar Chasimah Tovah,
Mordecai Kornfeld
In our discussion of the meaning of "foul air" there were two additional factors that we brought in:
1) The fact that the diaphragm of a person or animal has only so much power by which to push carbon dioxide laden air out and pull in fresh air. We were not sure of the distance but felt that the use of a snorkeling tube is a good example of this limitation. Could this be the difference between the 9th and 10th tefach?
2) In "korbanos" in the morning davening the term all is hevel is used to describe both man and beast in a limiting sense of existence.
Does this fit in with your concept as well?
Yehudah Wiesen
1) Maybe. It's still hard to imagine that Ten Tefachim (about 40 inches at most) would create a measurable difficulty. Keep in mind, also, that the laws of Bor do not take into account how high above sea-level the Bor is dug (i.e. a Bor on top of Everest has the same laws as one in the Dead Sea Valley.
2) Hevel of Megilas Koheles and of Korbanos means nothingness. Anything that cannot be touched physically, but is nevertheless a physical, and sometimes visible, phenomenon (such as vapor), is referred to by Chazal as Hevel.
-Mordecai
How would this explanation reconcile with the fact that The Gemara states that a keli can also break from hevel? Thanx!!
The Gemara says that "new pots" only, can crack from the Hevel of a pit. As Tosfos (5b) points out, this implies that many, if not most, Kelim are not affected at all by Hevel -- which is indeed consistent with what we wrote.
As for the affect Hevel does have on new Kelim, it would seem that the sudden change in air pressure can contribute to the damage of new, and highly sensitive, pots. This is also included in the category of "Hevel" (for the reasons we mentioned in our previous correspondence).
It is interesting to note that the YERUSHALMI (5:7, cited by the Rashba here) explains that the effect of the pit on the Kelim is "Hitrifu" because of the air in the pit. From Bava Basra 19b, it would seem that "Hitrifu" means "they spoiled." How can Kelim spoil? From Tosfos in Bava Basra 20a, it seems that the Kli can become permanently unusable if its contents become spoiled and wormy ("Hitrif"). The Yerushalmi then means that the Hevel can affect the contents of the Kli (e.g. it can cause the figs inside of it to spoil, since they are living objects, and can be sensitive to the Hevel we noted), and thereby "spoil" the Kli as well.
M. Kornfeld