Various, Notes and Queries, Vol. V, Number 117…
“ If a pendulum be placed at one of the poles of the earth, it is obvious, that while it swings in one plane, the revolution of the earth beneath it will cause it to appear to describe a complete circle in twenty-four hours. This position is simple enough, but it is true also in any latitude, excepting near the equator. For there is no doubt, that, as gravity acts on the pendulum, only in the line which joins the point of suspension and the centre of the earth (thereby merely drawing the "bobs" towards that line) it can have no effect on the plane of oscillation ”
