. Early geophysical papers of the Society of Exploration Geophysicists. Petroleum; Prospecting. 34 N. N. ZIRBEL tion was reached in about 7 hours instead of many days. At higher tempera- tures still less time was required. During this baking process the total rota- tion was often 180° or more. It was also found that if a wire from which the time drift had been removed by baking were strained beyond the elastic limit by a longitudinal stress, then the time drift again appeared and could. Fig. 1. be removed only by further baking. The same result followed when the brass cylinder attached to the
. Early geophysical papers of the Society of Exploration Geophysicists. Petroleum; Prospecting. 34 N. N. ZIRBEL tion was reached in about 7 hours instead of many days. At higher tempera- tures still less time was required. During this baking process the total rota- tion was often 180° or more. It was also found that if a wire from which the time drift had been removed by baking were strained beyond the elastic limit by a longitudinal stress, then the time drift again appeared and could. Fig. 1. be removed only by further baking. The same result followed when the brass cylinder attached to the lower end of the wire was twisted through about half a revolution and held in this twisted position for several hours. The time drift is thus quite easily removed. There remains, however, the change in equilibrium position with the temperature of the wire, as shown in Fig. 1. The next problem is then to study the effect of heat treatment on this temperature coefficient, which in Fig. 1 is — mm per °C. Fig. 2 shows. 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 Society of Exploration Geophysicists. Tulsa
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