And this Congruity (that I may here a little further explain it) is both a Tenacious and an Attractive power; for the Congruity, in the Vibrative motions, may be the cause of all kind of attraction, not only Electrical, but Magnetical also, and therefore it may be also of Tenacity and Glutinousness. For, from a perfect congruity of the motions of two distant bodies, the intermediate fluid particles are separated and droven away from between them, and thereby those congruous bodies are, by the incompassing mediums, compell’d and forced neerer together; wherefore that attractiveness must needs be stronger, when, by an immediate contact, they are forc’d to be exactly the same: As I shew more at large in my _Theory_ of the _Magnet_. And this hints to me the reason of the suspension of the _Mercury_ many inches, nay many feet, above the usual station of 30 inches. For the parts of _Quick-Silver_, being so very similar and congruous to each other, if once united, will not easily suffer a divulsion: And the parts of water, that were any wayes _heterogeneous_, being by _exantlation_ or rarefaction exhausted, the remaining parts being also very similar, will not easily part neither. And the parts of the Glass being solid, are more difficultly disjoyn’d; and the water, being somewhat similar to both, is, as it were, a medium to unite both the _Glass_ and the _Mercury_ together. So that all three being united, and not very dissimilar, by means of this contact, if care be taken that the Tube in erecting be not shogged, the _Quicksilver_ will remain suspended, notwithstanding its contrary indeavour of Gravity, a great height above its ordinary Station; but if this immediate Contact be removed, either by a meer separation of them one from another by the force of a shog, whereby the other becomes imbodied between them, and licks up from the surface some agil parts, and so hurling them makes them air, or else by some small heterogeneous agil part of the Water, or Air, or Quicksilver, which appears like a bubble, and by its jumbling to and fro there is made way for the _heterogeneous Æther_ to obtrude it self between the Glass and either of the other Fluids, the Gravity of _Mercury precipitates_ it downward with very great violence; and if the Vessel that holds the restagnating _Mercury_ be convenient, the _Mercury_ will for a time _vibrate_ to and fro with very large _reciprocations_, and at last will remain kept up by the pressure of the external Air at the height of neer thirty inches. And whereas it may be objected, that it cannot be, that the meer imbodying of the _Æther_ between these bodies can be the cause, since the _Æther_ having a free passage alwayes, both through the Pores of the Glass, and through those of the Fluids, there is no reason why it should not make a separation at all times whilst it remains suspended, as when it is violently disjoyned by a shog. To this I answer, That though