The Pneumatics

it will remain, raised upward according to the part HB, and suspended downward according to BC. But if the outer orifice of the siphon be below the straight line FG, as at K, the water flows, because the part in KB, being heavier than that in BH, prevails and draws it; and it flows until the orifice K is positioned in a direct line with the surface of the water, and then, for the same reason, it will flow no longer. If, however, the outer orifice of the siphon be below K, as at L, it flows until the surface of the water reaches the orifice A. Therefore, if we wish to draw off all the water that is in the vessel, we shall lower the siphon so that the orifice A touches the bottom of the vessel, being distant from it only as much as may seem sufficient for the flow of water. Now some have assigned this cause, which we have mentioned, for the siphon, saying that the longer leg, because it contains more water, draws the shorter. But that a cause of this kind is false, and that he who believes it is greatly mistaken if he should attempt to draw water from a lower place, we shall thus demonstrate. For let a siphon be constructed having the inner leg both longer and narrow, and the outer leg wider and much shorter in length, so that it contains more water than the longer leg; and let it be thus filled with water. Then let its longer leg be immersed in a vessel of water, or even into some well. If, therefore, we permit the outer leg to flow, as it contains more water than the inner, it ought to draw water from the longer leg, which in turn would also draw that which is in the well; and when it has begun to flow, it would draw it all off, or flow perpetually, because the outer liquid is greater in quantity than that contained in the inner leg. Yet this is not seen to occur. Therefore, the stated cause is not true. Let us, then, examine the natural cause. For since every continuous liquid, when at rest, assumes a spherical surface having the same center as the earth; and when not at rest, it flows until, as has been said, in a single spherical surface