问答题 翻译：Other instruments used in gravity work are the torsion balance and the pendulum.These instruments, however, have been practically replaced by the gravimeter.

问答题 翻译：The permeability of a porous medium may be determined from samples extracted from the formation or by in-place testing.

问答题 翻译：The main function of a rotary rig is to drill a hole, or as it is known in the industry, to make hole.