And this Congruity (that I may here a little further explain it) is both a Tenaceous 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 AEther 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 AEther between these bodies can be the cause, since the AEther 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 dis-joyned by a shog.  To this I answer, That though