Rivers were used to turn watermills and the Romans even used geothermal water for heating. Until the middle of the 18th century renewable sources of energy were the only forms of energy available, but then, with the advent of the Industrial Revolution, fossil fuels began to be exploited.
The Sidereal Zodiac is the position of the sun referenced against the star background, as a measure of the flow of time. The framework for the star background is the constellations the sun passes in front of. This is the one astronomers use.
The Mobile zodiac signs are: Gemini, Virgo, Sagittarius, Pisces. They correspond to the end of the seasons. Gemini (May 21 - June 21), the end of spring, Virgo (August 24 - September 22) the end of summer, Sagittarius (November 23 - December 21) the end of fall, Pisces (February 20 - March 20) the end of winter.