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The Greek inheritance
The Roman empire
     Donations of Alexandria
     Atmospheric devices
     Hero's dioptra
     A Roman port
     City of Arius
     Eclipsed by an old rival

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The Donations of Alexandria: 34 BC

A great crowd gathers in a stadium in Alexandria. All eyes are on two tiers of thrones. On the upper level sit Antony and his wife Cleopatra, robed as the Egyptian goddess Isis. On four lower thrones are their own three children together with Cleopatra's eldest son, Caesarion, the child of Julius Caesar.

In the ensuing ceremony, later known as the Donations of Alexandria, Antony distributes the kingdoms of the eastern Mediterranean to his new family.


Antony declares Cleopatra to be the Queen of Kings and Caesarion the King of Kings, jointly ruling over Egypt and Cyprus and joint overlords of the kingdoms of the other children. To Alexander, his own elder son, aged six, he gives the territories east of the Euphrates; to Alexander's twin sister, Cleopatra, he gives Libya and Tunisia; and to his younger son, Ptolemy Philadelphus, aged two and appearing in Macedonian costume, he gives Syria and much of Anatolia.

It is a gorgeous occasion, but one which will need to be explained on the battlefield.


Greek atmospheric devices: 1st century AD

Hero, a mathematician in Alexandria in about AD 75, enjoys inventing mechanical gadgets, which he describes in his work Pneumatica. Whether he has the technology to make them we do not know, but his scientific principles are correct.

One such gadget is a primitive version of a steam turbine. Hero says steam should be directed into a hollow globe with outlets through nozzles on opposite sides of the circumference. The nozzles are directed round the rim of the globe. As the steam rushes out, like sparks from a catherine wheel, the globe spins.


Hero makes another significant use of atmospheric pressure in a magic altar, putting to work the expansion and contraction of air. A fire heats the air in a container, causing it to expand and force water up a tube into a bucket. The increased weight of the bucket opens the doors of an altar. When the fire is extinguished, the air contracts, the water in the bucket is sucked out and the doors close.

Any temple managing to work this trick is certain to attract more pilgrims, and more money, than its rivals.


Hero's dioptra: 1st century AD

One of the surviving books of Hero of Alexandria, entitled On the Dioptra, describes a sophisticated technique which he has developed for the surveying of land. Plotting the relative position of features in a landscape, essential for any accurate map, is a more complex task than simply measuring distances.

It is necessary to discover accurate angles in both the horizontal and vertical planes. To make this possible a surveying instrument must somehow maintain both planes consistently in different places, so as to take readings of the deviation in each plane between one location and another.


This is what Hero achieves with the instrument mentioned in his title, the dioptra - meaning, approximately, the 'spyhole' through which the surveyor looks when pinpointing the target in order to read the angles.

Hero adapts, for this new and dificult task, an instrument long used by Greek astronomers (such as Hipparchus) for measuring the angle of stars in the sky. It is evident from his description that the dioptra differs from the modern theodolite in only two important respects. It lacks the added convenience of two inventions not available to Hero - the compass and the telescope.


A Roman port: 1st - 4th century AD

During the Roman empire Alexandria retains its commercial importance, for it is the port through which the grain of Egypt passes on its way to the granaries of Italy. With the decline of Greek influence, the city loses something of its intellectual edge - though the encyclopedic efforts of Ptolemy in the 2nd century AD will exert a long and profound influence, and an important step in algebra is taken in Alexandria at much the same time.

A disaster in AD 215 demonstrates that the inhabitants have also retained an independent spirit. The emperor Caracalla, visiting Alexandria, becomes the butt of some disrespectful satires. His response is to order a widespread massacre of the citizens.


The city of Arius: AD 323

In the 4th century Alexandria plays a prominent role in an entirely new context, that of Christian dogma. The preeminence of the city in the eastern Mediterranean makes it an important early centre of Christianity long before Constantine bestows official approval on the religion. What the Christians of Alexandria believe is a matter of significance.

In 323 a priest, Arius, is dismissed from his post in one of the city's churches for holding heretical views on the Trinity. In Alexandria itself orthodoxy soon prevails again. But the Alexandrian heresy echoes round Europe and north Africa for the next two centuries.


Eclipsed by an old rival: 7th century AD

Alexandria suffers a double blow in the 7th century. First it falls victim to the final struggle between the Persian and Byzantine empires, being captured by the Persians in 616. Then, after a siege lasting more than a year, it is taken without bloodshed in 642 by the Arabs in their first great wave of expansion.

The Arab commander establishes a garrison town on the Nile. This gradually develops into the city of Cairo, which from the 10th century overshadows Alexandria. The new city is on the opposite bank from the old site of Memphis, the capital of the first Egyptian dynasties. The centre of political power in Egypt returns, after the Alexandrian centuries, to its original home.


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