Hypaethros

Hypaethral is an ancient temple with no roof. (From the Latin hypaethrus, from Ancient Greek ὕπαιθρος hupaithros ὑπό hupo- "under" and αἰθήρ aither "sky, air".) It was described by the Roman architect Vitruvius in his treatise On Architecture written for the emperor Caesar Augustus probably about 15 BC. This term is in distinction from cleithral, which is covered with a roof. The Hypaethros or hypaethral opening is the term Vitruvius (iii. 2) used for the opening in the middle of the roof of temples, an example being found in Athens in the temple of Jupiter Olympius, which is octastyle. There was no example in Rome.

However, at the time Vitruvius wrote (c. 25 AD) the cella of this temple was unroofed, because the columns which had been provided to carry, at all events, part of the ceiling and roof had been taken away by Sulla in 80 BC. The decastyle temple of Apollo Didymaeus near Miletus was, according to Strabo (c. 50 BC), unroofed, on account of the vastness of its cella, in which precious groves of laurel bushes were planted.

Apart from these two examples, the references in various writers to an opening of some kind in the roofs of temples dedicated to particular deities, and the statement of Vitruvius, which was doubtless based on the writings of Greek authors, that in decastyle or large temples the centre was open to the sky and without a roof (medium autem sub diva est sine tecto), render the existence of the hypaethros probable in some cases; and therefore C. R. Cockerell's discovery in the temple at Aegina of two fragments of a coping-stone, in which there were sinkings on one side to receive the tiles and covering tiles, has been of great importance in the discussion of this subject. In the conjectural restoration of the opaion or opening in the roof shown in Cockerell's drawing, it has been made needlessly large, having an area of about one quarter of the superficial area of the cella between the columns, and since in the Pantheon at Rome the relative proportions of the central opening in the dome and the area of the rotunda are 1:22, and the light there is ample, in the clearer atmosphere of Greece it might have been less. The larger the opening, the more conspicuous would be the notch in the roof which is so greatly objected to; in this respect, Jacques Hittorf would seem to be nearer the truth when, in his conjectural restoration of Temple R at Selinus, he shows an opaion about half the relative size shown in Cockerell's of that at Aegina, the coping on the side elevation being much less noticeable.

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