_B._ Truly I think it close enough to keep out straw and feathers, but not to keep out air, nor yet matter. For suppose they were not so exactly close but that there were round about a difference for a small hair to lie between; then will the pulling back of the cylinder of wood force so much air in, as in retiring it forces back, and that without any sensible difficulty. And the air will so much more swiftly enter as the passage is left more narrow. Or if they touch, and the contact be in some points and not in all, the air will enter as before, in case the force be augmented accordingly. Lastly, though they touch exactly, if either the leather yield, or the brass, which it may do, to the force of a strong screw, the air will again enter. Do you think it possible to make two superficies so exquisitely touch in all points as you suppose, or leather so hard as not to yield to the force of a screw? The body of leather will give passage both to air and water, as you will confess when you ride in rainy and windy weather. You may therefore be assured that in drawing out their wooden leather cylinder, they force in as much air as will fill the place it leaves, and that with as much swiftness as is answerable to the strength that drives it in. The effect therefore of their pumping is nothing else but a vehement wind, a very vehement wind, coming in on all sides of the cylinder at once into the hollow of the brass pipe, and into the hollow of the glass globe joined to it. _A._ I see the reason already of one of their wonders, which is, that the cylinder they pump with, if it be left to itself, after it is pulled back, will swiftly go up again. You will say the air comes out again with the same violence by reflection, and I believe it. _B._ This is argument enough that the place was not empty. For what can fetch or drive up the sucker, as they call it, if the place within were empty? For that there is any weight in the air to do it, I have already demonstrated to be impossible. Besides, you know, when they have sucked out, as they think, all the air from the glass globe, they can nevertheless both see through it what is done, and hear a sound from within when there is any made; which, if there were no other, but there are many other, is argument enough that the place is still full of air. _A._ What say you to the swelling of a bladder even to bursting, if it be a little blown when it is put into the receiver, for so they call the globe of glass?