Dutch Pendulum Observations in Submarines

Abstract

I MENTIONED in NATURE of December 1, 1923, p. 788, that Dr. F. A. Vening Meinesz, on board the Submarine K II of the Royal Dutch Navy, left Suez on October 31 to carry on his pendulum observations at sea with the Von Sterneck apparatus. In the Red Sea it was found that residence on board, where comfort is very scarce, was exceedingly trying because of the heat. The temperature of the sea-water was 31°C., but in the submerged vessel the thermometer went up to 37° C. Under the black cloth, which screens the apparatus from undesirable light-rays, an electric wolfram arc-lamp for the photographic registration further increased the heat. Accordingly the observer, who has to control the course of the observations, suffered from a temperature several degrees higher. The number of observations made in these unfavourable circumstances was four. On November 4, the sea being very smooth, Dr. Vening Meinesz tried to make an observation at the surface of the sea, but against all expectation the vertical accelerations proved to be so strong that no results could be obtained. The anomaly, i.e. the difference between the theoretical value—according to Helmerts' formula—and the actual value of the intensity of gravity deduced from the observations, had in the northern part of the Red Sea a positive, in the southern part a negative value.