. Deep borehole surveys and problems. Boring. 158 DEEP BOREHOLE SURVEYS AND PROBLEMS f which actuates two drums on which a thin wire rope h to the head of the lower tube is wound. For closing the lenses up again spiral springs on the drums coil up the wire automatically. On the top end of each tube is a headpiece. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Haddock, M. H. (Marshall Henry). New York, McGraw-Hill

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Keywords: ., bookcentury1900, bookcollectionb, bookpublishernewyorkmcgrawhill