Heliopolis (ancient Egypt) from him the true length of the year and month, upon which he formed his octaeterid, or period of 8 years or 99 months. Ptolemy II had Manetho, the chief priest of Heliopolis, collect his history of the ancient kings of Egypt from its archives. The later Ptolemies probably took little interest in their "father" Ra, and Alexandria had eclipsed the learning of Heliopolis; thus with the withdrawal of royal favour Heliopolis quickly dwindled, and the students of native lore deserted it for other temples supported by a wealthy population of pious citizens. By the 1st century BC, in fact,
Irrigation works in ancient Sri Lanka to 367 BC. It is said that he had three tanks built, namely "Abhaya weva", "Gamini weva", and "Jaya weva", yet, presently, only one tank named "Basawakkulama weva" can be identified. After King Pandukabhaya, King Parakramabahu I had many tanks built, with one large tank called "Parakrama samudraya" still providing water for agriculture. It can be said that many rulers of Sri Lanka contributed to the development and construction of tanks all over the "Raja Rata" (Northern part of the country). Irrigation works in ancient Sri Lanka The irrigation works in ancient Sri Lanka, the earliest dating from about 300