| 摘要 |
Magnetic exploration apparatus which can be lowered into a drill hole, characterised in that the lower part 3 of this apparatus forms a cryostat filled with a cryogenic fluid and containing at least one cryogenic magnetometer 17, 18, 19, 20 mounted as a gradiometer so as to give data on the natural magnetisation of the rocks passed through by the drill hole. <IMAGE>
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