Abstract: A method and apparatus are disclosed for obtaining a core at in situ pressure of sedimentary deposits at the bottom of a well bore or body of water. The core barrel has a pressure chamber that is closed and opened by a ball valve actuated from the surface. When in position above the sedimentary deposits to be cored, a sample tube is extended from the pressure chamber into the sedimentary deposits to obtain a core. The sample tube is retracted into the pressure chamber and the valve closed to trap ambient pressure in the chamber. The sample tube and valve are operated from the surface.

Abstract: Disclosed is an apparatus for controlling sliding movement between two telescoping members of a jar or like apparatus for use in an oil well. The telescopic sliding movement between the two members is controlled by a hydraulic impedance device which is bypassed by a hydraulic fluid dump valve after a predetermined amount of telescopic movement between the two members. A dump valve opening means is releasably attached to the walls of one of the members and, after opening the dump valve mechanism, releases from the member wall to move with the telescoping member holding the dump valve mechanism in the open condition. Means is also disclosed for recocking the apparatus and for returning the opening means to its initial position such that the opening means is reattached to the wall of said one member.