The influence of Alexandria in the 3rd and 2nd centuries BC Mathematicians and inventors[165]

Is it to increase their prestige that the first Ptolemites set themselves up as protectors of the sciences, techniques and arts? Ptolemy I created the Library of Alexandria — more of a personal collection than a true institution. The Library is then completed by the Museum, either by Ptolemy I himself, or by his successor Ptolemy II Philadelph, who reigned from 285 to 246 BC. The Library is dedicated to the acquisition[166] and conserva­tion of books, whereas the Museum was what one would call today a research institute. The director of the Library and the members of the Museum are supported by the Ptolemites and in general, the financing of the two institutions is entirely assured by the state. It is believed that the Museum and the royal Library — the latter thought to have contained 500,000 rolls of papyrus[167] — were housed in the same building, in the interior of the royal palace grounds. A library annex, open to the public, was set up outside the palace grounds in a temple called the Serapeum.

Scholars from the entire Hellenistic world flocked to Alexandria, either to live there, or to study or make extended stays. This is why one can confidently use the term school

of Alexandria to describe the vast intellectual movement associated with it.

First there was mathematics. The foundations had been laid by the Greeks during the classical period, and the easterners, Babylonians and Egyptians, were equally known for their mastery of geometry. In about 300 BC Euclid set forth the foundations of our modern geometry, and through his students the mathematical school of Alexandria becomes a reference for Antiquity. Geometry underpins and enables many lines of thought and activity; we will see this later in the context of Archimedes of Syracuse. Geometry enabled Eratosthene of Cyrene, director of the Library during the era of Ptolemy III Evergete (who reigned from 246 to 221 BC), to determine the circumference of the earth with remarkable precision.[168] Eratosthene deduced this circumference from measurement of the height of the sun at noon at Alexandria when the sun is at its zenith at Syene (Aswan) — a city which is near the Tropic of Cancer — taking into account the measured distance between Alexandria and Aswan.

The new element here, compared to Greek science, is that the applied sciences are for the honor of Alexandria, even if their function is often only to “please our senses in charming our eyes and ears.”[169] Ctesibios of Alexandria (around 270 BC) and Philon of Byzantium (around 200 BC) invented “marvelous machines” — water clocks, pumps, automata, diverse mechanical devices. The invention of the hydraulic organ is credited to Ctesibios. The invention of the hydraulic screw (called cochlea (snail) by greco — roman historians, with reference to the snail’s spiral shell) as a mechanism for lifting water, is attributed by ancient authors to Archimedes at the time of his sojourn at Alexandria. During the Hellenistic period it is these Archimedes screws (Figure 5.3) which make it possible to create the famous hanging gardens of Babylon.[170] Other lift­ing devices, always muscle-powered,[171] appear during this period: the waterwheel and the bucket chain, or saqqya (Figure 5.4). Strabo, at the beginning of the roman occupation, notes the use of the lifting waterwheel in Egypt, a device that will be widespread in Asia during the roman period.