"Erosion Machine” (1969): This piece uses water action to erode a series of “human rocks” in order to “model nature, its processes and effects for a future environment that may be entirely controlled or completely made by humans.
When this was installed in 1975, Carl says that the “Erosions" room was roughly 20 x 20 feet; and the “Environmental Changes” room was a bit smaller. Today, Carl says that could be installed in an array of configurations -- one option would be to use a commercial greenhouse as the “Environmental Changes” room.
The "nature machines" serve, as Carl Cheng writes, to "model nature, its processes and effects for a future environment that may be completely made by humans." Cheng's Erosion Machine is a microwave sized mechanism built from handmade and off-the-shelf materials. Cheng made "human rocks" that are fashioned through constant water erosion. Cheng's landmark 1975 exhibition, Erosions & Other Environmental Changes, held at Cal Tech's Baxter Art Gallery, included a selection of these nature machines in two exhibition areas - the "Erosions" room and the "Changes" room.