A great lake marks an underground soakage water level. A riverbed marks an underground seepage topography. The sea of water inside a continent is just as much a map of hills and dales of water as the land is a map of the hills and valleys of geography. The water is dynamic, it is flowing. The land surface is dynamic and rain fed; it is creeping soils. Together, groundwater and rivers are melting down the landscape as a living thing. Man dams the water and uses the power of the erosion melting down the land. When we went to Haystack Basin north of the Yellowstone Park, we found that all of the mountains surrounding it were audibly crumbling. Ultimately, the continent is all one thing: a falling body of rotten rock, ice, water, sand, boulders, and soils, self carved into valleys and mountains, always tumbling. And down below are the fault blocks, prisms of earth shell over the white hot core. And that also is eternally in motion, irrupting, earthquaking, lifting, falling, scraping, heating, cooling in waves through the ages. Man is very tiny, but if he listens he can hear the earth’s heartbeats. At hot springs the water mantle meets the hot earth shell. So the geyser basins of Yellowstone, California, New Zealand, and Iceland are a hot part of the great erosion system of groundwater. This brings us to the next group of experiments, the making of artificial geysers. Geysers as eroders show that the under earth is hot and is invaded by rainwater. In exceptional volcanic places the water is boiling hot. The Firehole River of the Yellowstone is carving down basins of solution faster than the regular geysers are building up siliceous sinter. Here is boiling-spring erosion by solution. It may be called the extreme thermal aspect of ordinary spring-water erosion. How does spring water erode? By bubbling up under the beds of rivers. The bubbling out of springs starts rivers, and flood rainfall starts soil gullies; land sculpture is the result. We introduce geyser experiments here because boiling springs make drama out of ordinary springs, just as active volcanoes make drama out of buried volcanoes. Ordinary springs and buried lavas intruding invisibly are much more important and extensive than geysers and volcanoes. Most people never think of a spring as one of millions bubbling up the beds of brooks and rivers and sea bottoms. Most people never think of volcanoes erupting--properly speaking, irrupting or inrupting--under Kansas or Brazil. Nobody denies those places are hot underground, but it all seems remote. Yet every spring is thermal if there is heat escaping through the rocks around it.