(under the class definition) Process or apparatus comprising recovering valuable material in the fluid state from the earth and including (1) process steps involving the construction or use of a horizontal passage in which a human may work or (2) the structure of a horizontal passage in which a human may work.
(1) Note. Valuable material which is recovered from or through a tunnel is included under this definition even though the material may not be fluid in the native state (e.g., leached copper recovered in solution or coal gas formed by burning are included).
SEE OR SEARCH CLASS
166, Wells, appropriate subclasses for a process or apparatus for recovering fluids from the earth in which a tunnel is not involved, and particularly
