What is Hydraulic clock?
It is water clock also known as “clepsydra” in greek means water. Water is the only source of energy other than gravity which keeps this clock moving.According to my knowledge first hydraulic clock was build by Chinese scientist Yi Xing in 1088 C.E.
How it works?
It works on the concept of Hydraulics and often powered by Gravity. Its accuracy depends upon the inflow and outflow of water. Though it seems simple but to make it accurate is a mammoth task.
Is their any other alternatives ?
Yes they do, if you don’t want to use water as its power source you can use human power and gravity together to construct your own mechanical clock. Concept of this clock would remain same with only thing changed is that, now you need to pull up some mass for gravity to attract in a controlled manner. Moreover, you need to pull this mass up whenever it gets grounded by gravitational force.
What this mechanism called?
It is known as escapement which according to wikipedia is a device in mechanical powered clocks that transfers energy to the timekeeping element and allows the number of its oscillations to be counted.If you want you can Read More about escapement here.