Thirdly, That in all Parts of the Surface of the Earth, or rather in all Points equidistant from its Center, the Force of Gravity is nearly equal; so that the length of the Pendulum vibrating Seconds of Time, is found in all Parts of the World to be very near the same. 'Tis true at St. Helena, in the Latitude of 16 Degrees South, I found that the Pendulum of my Clock, which vibrated Seconds, needed to be made shorter than it had been in England, by a very sensible Space (but which at that time I neglected to observe accurately) before it would keep time; and since the like Observations have been made by the French Observers, near the Æquinoctial: Yet I dare not affirm, that in mine it proceeded from any other Cause, than the great Height of my Place of Observation above the Surface of the Sea, whereby the Gravity being diminished, the length of the Pendulum vibrating Seconds, is proportionably short'ned.
Fourthly , That Gravity does equally affect all Bodies , without regard either to their Matter , Bulk , or Figure ; so that the Impediment of the Medium being removed, the most compact and most loose, the greatest and smallest Bodies would descend the same Spaces in equal Times; the Truth thereof will appear from the Experiment I before-cited. In these two last Particulars, is shewn the great difference between Gravity and Magnetism , the one affecting only Iron , and that towards its Poles , the other all Bodies alike in every part. As a Corollary , from hence it will follow, that there is no such thing as positive Levity , those things that appear light, being only comparatively so; and whereas several things rise and swim in Fluids , 'tis because, Bulk for Bulk, they are not so heavy as those Fluids ; nor is there any Reason why Cork , for Instance, should be said to be light, because