Test for measuring the permeability of ground in sections of boreholes. An inflatable tube (‘packer’) is lowered down a borehole and expanded so that the sections above and below are isolated. Alternatively, two packers may be used to isolate a certain section. Water is pumped into the section under investigation and leakage can be measured. The rate at which water is absorbed per metre length of hole is measured in units of lugeon, named after the French geologist Maurice Lugeon (1870–1953). One lugeon is approximately equal to 1.0 × 10⁻⁵ cm/s permeability.