an improved marsh case is disclosed . the marsh case contains and protects a geophone , which is inserted into the earth in the course of oil exploration . the marsh case provides an cap having an upper opening through which wires pass to the geophone and a lower internally threaded opening that attaches to the body of the case . the body of the case provides an upper externally threaded opening which attaches to the cap , and a lower internally threaded conical surface which allows a threaded cylindrical surface of a spike to be attached . the threads of the body are slightly tapered , thereby relieving some of the stress that would otherwise be applied to the threads . the rim of the upper external threaded opening of the body and an internal annular shoulder in the cap compress an o - ring , thereby making a water - tight seal . a quad ring seal is supported by a second internal shoulder in the cap , in a manner that firmly engages the geophone , allowing for compression of the quad ring seal in the event that the marsh case contracts due to temperature , thereby protecting the geophone from compression .