This rammed earth house project, located in Kobe, Japan, and built on the grounds of Kobe University, is one of the rare examples of rammed earth in the country. Japanese language web site.
[ Download a pdf of the project ]
If you live in an earthen structure, maybe you can power this mud clock with it.
The article Down and Dirty from the New York Times, discusses the growing populatiry of earthen floors. (subscription required)
Early one Saturday morning in January, Kevin Rowell dumped a bucket of dark mud on the floor of his big south-facing bedroom. It landed with a plop, spreading out and merging with a blanket of wet earth that already extended across much of the room. On his knees, Mr. Rowell took a trowel to the pile, nudging it this way and that until the mud was roughly level and about an inch and a half deep.