Joint A crack, which in limestone forms at an angle to a bedding plane. A series of joints often intersect each other in a four-sided pattern. Limestone A rock consisting chiefly of calcium carbonate, usually an accumulation of organic remains such as shells. Marble Limestone crystallized by metamorphism. Metamorphose To change into a different form, such as changing sedimentary rock (limestone) into a metamorphic rock (marble). Moonmilk A rare form of hydromagnesite or calcium carbonate which is semisolid. Phreatic zone The region, below the water table, in which rock is saturated with water. Popcorn Nodules of mineral deposits formed in such a way as to resemble popcorn. Rimstone A calcite deposit around the edge of a pool of water. Sedimentary rock Formed from deposits of sediments or from fragments of other minerals. Shale A sedimentary rock formed from deposits of clay or silt. Solution The process by which a substance is chemically combined with a liquid. Also, the state of being chemically so combined. Soda straw A small, hollow stalactite inside which drops of water descend. Speleogen A cave feature produced by solution of base rock. Speleologist One who makes a scientific study of caves. Speleology The scientific study of caves in all their aspects. Speleothem A cave feature produced by deposition of mineral. Spelunker One who explores caves as a sportsman or amateur speleologist. Stalactite A calcite speleothem which grows downward, icicle-fashion, as a result of deposition by dripping water. Stalagmite A calcite speleothem which grows upward from a cave floor as a result of deposition by dripping water. Vadose zone The region lying between the surface of the earth and the water table. Water which seeps or flows through this region under the pull of gravity is called vadose water. Water table The meeting place of the phreatic and vadose zones. Below it, the rock is saturated with water; above it, water under the pull of gravity is continuously flowing downward. SUGGESTED READING Davidson, E. J., “History of the Discovery of the Marble Halls of Oregon.” _Oregon Historical Quarterly_, Vol. 23, pp. 274-276 (1922). Folsom, Franklin, _Exploring American Caves_. New York, Crown Publishers, Inc., 1956. Halliday, William R., _Adventure Is Underground_. New York, Harper and Brothers, Publishers, 1959. Mohr, Charles E., and Howard N. Sloane, _Celebrated American Caves_. New Jersey, Rutgers University Press, 1955. Wells, Francis G., Preliminary geological map of southwest Oregon. U.S.G.S. Mineral Investigation Map, MF 38, 1955. _RULES AND REGULATIONS_ (_Briefed_)