The priests there are said to be, for the most part, astronomers and philosophers. The former compute the days, not by the moon, but by the sun, introducing into the twelve months of thirty days each five days every year. But in order to complete the whole year, because there is (annually) an excess of a part of a day, they form a period from out of whole days and whole years, the supernumerary portions of which in that period, when collected together, amount to a day.[884] They ascribe to Mercury all knowledge of this kind. To Jupiter, whom they worship above all other deities, a virgin of the greatest beauty and of the most illustrious family (such persons the Greeks call pallades) is dedicated. She prostitutes herself with whom she pleases, until the time occurs for the natural purification of the body; she is afterwards married; but before her marriage, and after the period of prostitution, they mourn for her as for one dead. 47. Next after Thebes is the city Hermonthis, in which both Apollo and Jupiter are worshipped. They also keep an ox there (for worship). Next is the city of Crocodiles, the inhabitants of which worship this animal; then Aphroditopolis (the city of Venus),[885] and next to it, Latopolis, where Minerva is worshipped, and the (fish) Latus; next, the city of Eileithyia, and a temple. In the country on the other side of the river is Hieraconpolis (the city of hawks), where a hawk is worshipped; then Apollonopolis, the inhabitants of which are at war with crocodiles. 48. Syene is a city situated on the borders of Ethiopia and Egypt. Elephantina is an island in the Nile, at the distance of half a stadium in front of Syene; in this island is a city with a temple of Cnuphis, and a nilometer like that at Memphis. The nilometer is a well upon the banks of the Nile, constructed of close-fitting stones, on which are marked the greatest, least, and mean risings of the Nile; for the water in the well and in the river rises and subsides simultaneously. Upon the wall of the well are lines, which indicate the complete rise of the river, and other degrees of its rising. Those [CAS. 817] who examine these marks communicate the result to the public for their information. For it is known long before, by these marks, and by the time[886] elapsed from the commencement, what the future rise of the river will be, and notice is given of it. This information is of service to the husbandmen with reference to the distribution of the water; for the purpose also of attending to the embankments, canals, and other things of this kind. It is of use also to the governors, who fix the revenue; for the greater the rise of the river, the greater it is expected will be the revenue.