Note on the behaviour of the E?tv?s gravity balance in fluctuating gravitational fields

In this note attention is directed to the semi-diurnal variation of gravity at a point on the earth's surface, due to lunar attraction and recently measured by Loomis. It is shown that this temporal variation of g is much larger than the spatial differences measured by the E?tv?s gravity balance, but that it produces no effect on the balance. This constitutes an experimental proof of the power of the E?tv?s instrument to discriminate between space and time changes of terrestrial gravitation.