_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 it swims on Water, any more than _Iron_, because it swims on _Mercury_.