The city shall be divided into six (6) districts, known as Districts 1, 2, 3, 4, 5 and 6. The City Council shall, as often as deemed reasonable, determine as nearly as practicable the population of the respective districts and shall, by ordinance, revise the boundaries of any or all of said districts to maintain a substantial equality of population in each. Within sixty (60) days after the adoption of this Charter, the City Council shall by ordinance designate the original district limits.