Note 127 — Chapter I · SPECULATIVE PHILOSOPHY IN GREECE, BEFORE AND IN THE TIME OF SOKRATES.

Karsten, De Emp. Philosoph. p. 480.

Emp. Fr. v. 307 — τό τ’ ἐν μήνιγξιν ἐεργμένον ὠγύγιον πῦρ — πῦρ δ’ ἔξω διαθρῶσκον, &c.

Empedokles illustrates this influx and efflux of air in respiration by the klepsydra, a vessel with one high and narrow neck, but with a broad bottom pierced with many small holes. When the neck was kept closed by the finger or otherwise, the vessel might be plunged into water, but no water would ascend into it through the holes in the bottom, because of the resistance of the air within. As soon as the neck was freed from pressure, and the air within allowed to escape, the water would immediately rush up through the holes in the bottom.

This illustration is interesting. It shows that Empedokles was distinctly aware of the pressure of the air as countervailing the ascending movement of the water, and the removal of that pressure as allowing such movement. Vers. 286:—

οὐδέ τ’ ἐς ἄγγος δ’ ὄμβρος ἐσέρχεται, ἀλλά μιν εἴργει ἀέρος ὄγκος ἔσωθε πεσὼν ἐπὶ τρήματα πυκνά, &c.

This dealing with the klepsydra seems to have been a favourite amusement with children.