On the Principles of Things.

...to be, from which even air existing under water, although in its own region, nevertheless strives to emerge higher: as is manifest in pitchers when they are turned over half-full, and in a bladder full of air that is submerged in water. But this motion is no different from the first, for water itself, when it is in a high place, endeavors to descend, and upon its descent, the air ascends so that it is not too greatly compressed. But in a bladder which is in a river, since the air is in the place of the water, it strives to ascend; therefore, one reason for the motion of elements to their proper place will suffice. However, that the water pushes the bladder upward and not that the air ascends [by its own power] is clear, since a bladder placed under the earth does not ascend.

But what is more worthy of inquiry is how water rises as much as it can descend while it is assisted by the motion of rarefaction The force created by a vacuum or the thinning of a substance, which "pulls" the liquid upward.; this very thing will be made clearer by an example. Let there be a vessel full of water, the top of which is E and the bottom F, in which there is a channel A B C. Let there be a line C D, equidistant from the horizon original: "finitore"; the boundary line or level. according to which a level original: "libella"; a tool used to determine a perfectly horizontal line. is drawn. Let the channel A B C be filled with water, and let the water be let out through C. I say that it will exhaust whatever water is above the line C D, but none of that which is below the line C D; instead, the channel will hang full, and the vessel will be seen to be full of water up to C D. Thus, an example declares this to be so. Perhaps someone might say these things ought to have been transferred to the treatment of water [specifically]: but it was not necessary, since whether the vessel be full of water, or wine, oil, or milk, it makes no difference. Therefore, the reasoning for this experiment must rather be rendered.

The water, therefore, which is above C D, since it is precisely original: "ad unguem"; literally 'to the fingernail,' an idiom for perfect accuracy. as much as that which ascends, is as much as that which is poured out from C, whether the channel be wider at C than at A, or narrower; because the entire channel is always perfectly full, the water which is poured out through C is lighter. The reason why the water in the part above C D is lighter than at C is because the water above C D desires to descend so that it may be lower than that which is in C, therefore it compresses the water and drives it into the channel. But that which is below C D does not desire to be in C, because C is higher than its place, and so it does not wish to ascend. But the water which flows out of C does not provide a cause for consideration, even though it is lower than the water contained in the vessel itself, because that attraction The siphoning effect. does not happen except by reason of continuity The physical principle that a liquid column will not break unless air enters.: continuity depends on the principle of rarefaction Meaning a vacuum would be created if the water column broke., which cannot exist once the water is already exiting the mouth of the channel C.

Finally, this entire contemplation is resolved by this argument: that water which must draw other water with it must be contained in a vessel, since without it, it cannot be pulled away; but it is helped by the arriving air so that the continuous body may reach equilibrium The balanced state of the fluid levels.. Therefore, when the opening C is lower, the water will reach it; but when it is higher, it will not descend: because that which is directly from a lower place, as in A, will be forced to ascend to C, which is directly across from D. If, however, the water...