Paper, regarding an instrument to show the latitude at sea without seeing the horizon by Stephen Plank Planck describes an instrument he has invented which consists of tube containing a weight 'of near six feet long' which 'rests with the pointed end downwards in a brass socket which is fastened at the bottom of the tube, so that if the tube be made to decline from the vertical point, the weight will rest on that side the tube declines, this weight when it shifts from one side of the tube to the other it moves a rod, which said rod the observer is to hold slightly between his fingers thro a hole that is cut in the tube'. Subject: Navigation / Astronomy / Scientific apparatus and instruments Read to the Royal Society on 26 April 1733 1733