Ἰστέον δέ, ὅτι ὁ μὲν Ἀριστοτέλης αἴτιον λέγει τῆς εἰς ὕδωρ μεταβολῆς τὴν ψύξιν μόνον· Θεόφραστος δὲ οὐ μόνον τὴν ψύξιν αἰτίαν φησὶ τῆς τοῦ ὕδατος γενέσεως, ἀλλὰ καὶ τὴν πίλησιν. ἰδοὺ γὰρ ἐν Αἰθιοπίᾳ μὴ οὔσης ψύξεως ὅμως ὑετὸς κατάγεται διὰ τὴν πίλησιν· φησὶ γὰρ ὄρη εἶναι ἐκεῖσε ὑψηλότατα, εἰς ἃ τὰ νέφη προσπταίουσι, καὶ εἶθ’ οὕτως καταρρήγνυται διὰ τὴν γινομένην πίλησιν. ἀλλὰ μὴν καὶ ἐπὶ τῶν λεβήτων ὑγρότης, φησίν, ἀντικαταρρεῖ, ἔτι δὲ καὶ ἐπὶ τῶν θόλων τῶν λουτρῶν μὴ παρούσης ψύξεως, διὰ τὴν πίλησιν δηλονότι τούτου γινομένου.
(Olympiodorus, In Aristotelis Meteorologica 1.9 346b30 (CAG t.12.2 p.80.30-81.1 Stüve)
One should know that Aristotle says that the cause of the change to water is the cooling only; but Theophrastus says that not only cooling is the cause of the coming-to-be of the water, but also compression. For consider; there is no cooling in Ethiopia, but nevertheless rain falls because of compression. For he says that there are very high mountains there, against which the clouds strike, and then in this way rain bursts out because of the compression that takes place. Moreover, in the case of cauldrons too moisture, he says, runs down again, and also in the case of the domed rooms in baths, where there is no cooling, this clearly coming about because of the compression. (tr. William W. Fortenbaugh, Pamela M. Huby and/or Robert W. Sharples)
