“If these three holes be in a straight line, the water, when poured into the vessel, Α Β Γ Δ, will flow out through the tube, Λ Μ; but if the tube, Ν Ξ Ο Ρ, be turned in such a way as to displace the aperture, Σ, the flow will cease. It is only necessary, then, to so fix the wheel, Ν Ξ Ο Ρ, that, when made to revolve, the water shall flow.”
This ingenious system of cocks having several ways was reproduced in the sixteenth century by Jacques Besson, in his “Theatrum Instrumentorum et Machinarum.” Besson applied it to a cask provided with compartments, which gave at will different liquors through the same orifice. Some years later, Denis Papin proposed it for high-pressure steam engines. Further improved, it has become the modern long D valve.
CHAPTER II.
MIRACULOUS VESSELS OF THE GREEKS.
THE DICAIOMETER.
Heron, in his “Pneumatics,” describes a large number of wonderful vessels that were used by the ancients, and, among them, one called the “dicaiometer” (a correct measure), which allowed of the escape of but a definite quantity of the liquid that it contained.
