Monday, August 31, 2015

Wall Thickness of the Chambers of the Knives — בית החליפות


SUMMARY Using the standard Talmudic ratios of wall thickness to height it is possible to calculate a minimum wall thickness for the Chambers of the Knives.


The Chambers of the Knives were enclosed by walls on all four sides. Of these, the thicknesses of the western, eastern, and outermost walls are known, while the thickness of the wall dividing each chamber from the interior of the Antechamber is not stated.

Bava Basra 1:1 discusses the construction of a wall, 4 amos high, to divide two properties and lists the minimum thicknesses needed for a number of different building materials in order to construct a stable wall. For hewn stone (which was the type of wall used in the Temple), the minimum thickness is 5 tefachim, and Rashi (to 3a s.v. למימרא דבגזית) writes that the ratio of thickness to height follows a linear progression, such that a wall twice as high (8 amos) would need to be twice as thick (10 tefachim).
Walls following the standard ratio of thickness to height

If everything is expressed in terms of tefachim, the ratio is 5:24 (4 amos high x 6 tefachim per amah) which can be reduced to 1:4.8. All we need now is the height of the chamber's wall, which can be deduced from the Mishnah (Middos 4:6) and turns out to be 85 amos, or 510 tefachim. Doing the math results in a wall thickness of 17.7 amos.

The problem with this result is that there were other walls in the Sanctuary Building (such as the eastern wall of the Antechamber) which were just as tall and not nearly this thick. Does this mean that these other walls were unstable since they were too thin? The Gemara (Bava Basra 3a-b) addresses this issue by distinguishing between a free-standing wall and a supporting wall. A free-standing wall uses the ratio given above of 1:4.8, but a supporting wall (which is defined as a wall which supports a ceiling/roof) can be much taller since it is stabilized by the weight of the structure above it. The benchmark example given in the Gemara is the wall which divided the Holy from the Holy of Holies in the First Temple. This wall measured 6 tefachim thick and stood 30 amos high for a ratio of 6:180, which reduces to 1:30.

The dividing wall of the Chamber of the Knives was a supporting wall (since it went all the way up to the roof of the Antechamber), and according to the new ratio would have to be at least 2.8 amos thick.
[This again assumes, as per Rashi above, that there is a linear relationship between wall thickness and height.]
Comparison of the Amah Traksin wall and the wall
of the Chamber of the Knives

The Amah Traksin
Based on this relationship of thickness to height, a wall which was one amah thick could not be built any higher than 30 amos. This is why, in the Second Temple, curtains were hung between the Holy and Holy of Holies in place of a wall, since the ceiling height in the Second Temple was 40 amos instead of 30 amos. Such a wall would had to have been 1.3 amos thick, but the builders were not allowed to increase the thickness of the wall since this would have taken away space from either the Holy or Holy of Holies.

Courtyard Walls
A question arises about the thickness of the Courtyard walls. Since they are free-standing walls, they should follow the ratio of 1:4.8 which means that their height of 40 amos would require a thickness of 8.3 amos. The thickness of the walls is not mentioned in the Mishnah and so, in theory, they can be as thick as needed, the only problem is that, according to at least one opinion, the walls were only 5 amos thick. I hope to address this issue in the next post.

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