. Deep borehole surveys and problems. Boring. CORE ORIENTATION 59 grip, preventing sliding. In action the lowering tool holds trigger h out. At the core and after sufficient time has elapsed and the needle has come to rest, the lowering tool on being withdrawn releases the trigger h, throwing the catch g, allowing/to ascend and lift the card off its bearing, pressing it against the glass lid c. The core is now wrenched off and lifted to bank and on unscrewing lid h the orientation of the core is read. The weaknesses of the apparatus are the same as those of Vivian's apparatus; chiefly insuffic
. Deep borehole surveys and problems. Boring. CORE ORIENTATION 59 grip, preventing sliding. In action the lowering tool holds trigger h out. At the core and after sufficient time has elapsed and the needle has come to rest, the lowering tool on being withdrawn releases the trigger h, throwing the catch g, allowing/to ascend and lift the card off its bearing, pressing it against the glass lid c. The core is now wrenched off and lifted to bank and on unscrewing lid h the orientation of the core is read. The weaknesses of the apparatus are the same as those of Vivian's apparatus; chiefly insufficient protection against water pressures which is more necessary here, since there are more moving parts. The drawbacks of space demands in the core and trouble in the measuring method have not been removed any more than in Vivian's method. Again there is the liability of premature dis- turbance of the needle due to shocks as in wrenching off the core. There appear to be as little data in professional literature respecting its actual employ- ment as in the case of Vivian's apparatus. Wolff's Apparatus.—This device was invented in 1889,^ and marked the introduction of a new feature. In this method the apparatus was lowered ^^° over a stub of core in the hole and a mold taken. Clockwork was used. ////////// r // y///. 32.—Wolf's core- cast device. to clamp a magnetic needle after a predetermined time. The core was then removed and orientated from the clamped needle attached to it. Figure 32 shows Dr. Wolff's method for fixing the compass in a mold or cast, the latter being a plastic material. The apparatus consists of a two-part tube A1A2, with a lead filling B, which serves to guide and hold tight the lower plastic mass giving the imprint of the 1 See German Patent, 47, 221, Oct. 27, 1888; also Osterr. Z. Berg-Huttenw., Nos. 41-43, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration an
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