On the proportionality of mass and weight

Abstract

In a previous paper* the writer has described some experiments carried out under the direction of Prof. 0. W. Richardson on the gravitational acceleration of substances rich in hydrogen. It was pointed out that the nuclei of all elements are probably built up of hydrogen and helium nuclei, and that the substances on which gravitational experiments have been performed might in nearly all cases be considered as consisting almost entirely oi the latter. By use of the pendulum method the gravitational accelerations of ammonium fluoride and paraffin wax were compared with that of brass. According to the suggestions put forward in the paper referred to, these two substances would contain 24 per cent, and 15 per cent, of hydrogen respectively, whereas brass would consist almost entirely of helium. A small effect, amounting to about one part in 70,000, which made substances rich in hydrogen appear to have an acceleration greater than the normal value was obtained. This was attributed to experimental error, but further tests appeared desirable. The experiments have recently been repeated using an Eotvos torsion balance. This instrument, which compares for different substance the ratio of the force due to the earth’s rotation and that due to its attraction, is capable of an accuracy far greater than that obtainable with the pendulum.