Sling some mud at this clock

If you're tired of conventional time-telling devices, how's this for you: a mud-powered clock.

Apparently you just plant some seeds in some mud you harvest from your garden, hook up a few wires, and within a short time, hey presto - you've got a working clock.

We have a feeling we must have learned the science behind how this thing works in primary school science class, but unfortunately, it escapes us now.

At $20, you can probably pick up a battery-powered alarm clock for less, but why be conventional?