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Published online by Cambridge University Press: 06 July 2012
The mapping of sub-drift topography is an important problem in this country and one which, under suitable circumstances, lends itself readily to solution by the method of gravitational survey with the Eötvös Torsion Balance. It has been pointed out in previous papers that structures such as anticlines, synelines, faults, and dykes may be determined by a linear traverse with the balance transverse to the strike; but in the case of buried topographic features a network of observations with subsequent plotting of the gradients and isogams, i.e. lines of equal gravity, is necessary to determine even approximately the shape and dimensions of rock-masses underlying a thick covering of drift.
page 141 note * “The Use of the Torsion Balance in the Investigation of Geological Structure in South-West Persia,” Summary of Progress for 1926. Mem. Geol. Surv., 1927, pp. 173 et seq. “A Gravitational Survey over the Swynnerton Dyke, Yarnfield, Staffs,” Summary of Progress for 1927, pt. ii, Mem. Geol. Surv., 1928, p. 8.
page 144 note * Summary of Progress for 1926, Mem. Geol. Surv., 1927, p. 191.
page 145 note * 1 E. = 1 Eötvös unit = 1 × 10−9 c.g.s. unit.
page 146 note * “A Gravitational Survey over the Swynnerton Dyke, Yarnfield, Staffs,” Summary of Progress for 1927, pt. ii, Mem. Geol. Surv., 1928, p 3.
page 146 note † Schweydar, W., “Die topographische Korrektion bei Schweremessungen mittels einer Toraionswage; zweite Mitteilung,” Zeitsch. f. Geophysik, vol. iii, pt. 1, 1927, pp. 17–23Google Scholar.
page 147 note * Shaw, H., and Lancaster-Jones, E., “The Theory and Practical Employment of the Eötvös Torsion Balance,” Mining Mag., vol. xxxvi, No. 6, 1927, pp. 339–340Google Scholar.
page 149 note * This expression has been derived by several authors. It is the result of
page 149 note † Mekel, J. A. A., Theorie van het tektanisch-gravimetrisch onderzoek, Delft, 1928, pp. 28–32.
page 153 note * Add to the expression XII. the quantity 
obtained from the general formula for a rectangular block (see Shaw, and Lancaster-Jones, , Proc. Phys. Soc. Lond., vol. xxxv, pt. 3, 1923Google Scholar).
