_B._ From many, and such as to almost all men are known and familiar. If two hard bodies, flat and smooth, be joined together in a common superficies parallel to the horizontal plane, you cannot without great force pull them asunder, if you apply your force perpendicularly to the common superficies: but if you place that common superficies erect to the horizon, they will fall asunder with their own weight. From whence I argue thus: since their contiguity, in what posture soever, is the same, and that they cannot be pulled asunder by a perpendicular force without letting in the ambient air in an instant, which is impossible; or almost in an instant, which is difficult: and on the other side, when the common superficies is erect, the weight of the same hard bodies is able to break the contiguity, and let in the air successively; it is manifest that the difficulty of separation proceeds from this, that neither air nor any other body can be moved to any, how small soever, distance in an instant; but may easily be moved (the hardness at the sides once mastered) successively. So that the cause of this difficulty of separation is this, that they cannot be parted except the air or other matter can enter and fill the space made by their diremption. And if they were infinitely hard, not at all. And hence also you may understand the cause why any hard body, when it is suddenly broken, is heard to crack; which is the swift motion of the air to fill the space between. Another experiment, and commonly known, is of a barrel of liquor, whose tap-hole is very little, and the bung so stopped as to admit no air; for then the liquor will not run: but if the tap-hole be large it will, because the air pressed by a heavier body will pierce through it into the barrel. The like reason holds of a gardener’s watering-pot, when the holes in the bottom are not too great. A third experiment is this: turn a thin brass kettle the bottom upwards, and lay it flat upon the water. It will sink till the water rise within to a certain height, but no higher: yet let the bottom be perforated, and the kettle will be full and sink, and the air rise again through the water without. But if a bell were so laid on, it would be filled and sink, though it were not perforated, because the weight is greater than the weight of the same bulk of water. _A._ By these experiments, without any more, I am convinced, that there is not actually in nature any vacuum; but I am not sure but that there may be made some little place empty, and this from two experiments, one whereof is Toricellius’ experiment, which is this: take a cylinder of glass, hollow throughout, but close at the end, in form of a sack. _B._ How long? _A._ As long as you will, so it be more than twenty-nine inches. _B._ And how broad?