SC -

[margali]

I do remember reading about the desert practice of using stone pillars
to make ice with. The thermal difference being the method of icemaking.
The stone pillar gets warmed by the sunm after dark the heat of the
stone causes water to precipitate in shallow hollows in the top of the
pillar, which then freezes as the residual heat leaves and the ambient
temperatures drop to freezing. As any of our desert and mountain
dwellers can attest to, when the sun goes down, the temperature can drop
drastically when there is little to no cloud layer to hold in the heat.
Got to love manipulating radient energy!
margali.
Check out arthur c clarks ancient engineers or the book on ancient
technology that was used as the basis for the recent documentary on
ancient technology.