MJ Thomas Wrote:
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_snip>

>Hello Jon,

>I see your point about the GG roof being limestone
>and the KC ceiling being granite.
>A difference I had not allowed for.
>I am not, as you've probably guessed, at all
>aquainted with structural engineering.
>However, this does not deter me from wondering:
>wouldn't the suitability of a block of limestone
>for a span of nearly 7 feet depend on the
>thickness of the block in relation to its length,
>i.e., the longer the span the thicker the block
>needs to be?

Sure does.... at least to a point since increasing thickness also means increasing weight. The ancient Egyptians appear to have thought there was a problem with limestone as long, unsupported roofing beams since they never used it for such. Probably learned that from underground quarrying of Tura limestone with the need for closely spaced support columns to prevent the roof from collapsing on them. They used Aswan granite and a sandstone from around Thebes (New Kingdom) for such because of the high hardnesses of these rocks and the need for less weighty blocks to span large enclosed spaces. In the case of the GG they are using the harder Tura limestone presumably because of its higher rock hardness, rather then the harder massive limestone from the Plateau which they used for apparent structural reason in the smaller core masonry blocks of the GP (i.e. base, corners of faces, etc.),

>The corbelling we see in Khufu's pyramid is indeed
>far from unique (see Meidum and Dahshur) but this
>does not, as far as I can see, mean that this
>corbelling was always done to span a passage more
>than 2 royal cubits wide (I'm taking the width of
>the GP's Descending and Ascending passages as my
>reference).

Probably has more to do with the volume of open space in the rooms.

>I see the Grand Gallery's corbelling as a nod by
>Khufu to his father, Sneferu.
>In other words, I see the GG and its corbelling as
>symbolic of something rather than as a practical
>solution to a practical problem - such as: how do
>you span a gap of 4 royal cubits using only
>limestone blocks?

Being symbolic does not preclude a structural and/or technological necessity for such.

Archae Solenhofen (solenhofen@hotmail.com)

>MJ