_The quantities of water which issue from orifices of different areas are very nearly proportional to the size of the orifice_, provided the level remains constant, and this is true irrespective of the form of the opening which may be round, square, or any other shape. _Escape of liquids through short tubes._—We often place in an orifice, to increase the flow, a short tube (called an adjutage) either cylindrical or conical. If the vein pass through the tube without adhering to it, the flow is not modified; if the vein adhere (the liquid wetting the interior walls) the contracted part is dilated, and the flow is increased. In the last case, and with a cylindrical adjutage, its length not being more than four times its diameter, the flow is augmented about one-third. Conical pipes, converging towards the exterior, increase the flow still more than the preceding, the flow and velocity of the vein varying with the angle. _Escape of liquids through long tubes._—When a liquid passes through a long straight tube, the flow soon diminishes greatly in velocity, because of the friction which takes place between the liquid particles and the walls. If there be any bends or curves in the tube, it is still further diminished by the same cause. The discharge is then much less than it would be from an orifice in a thin wall, and therefore the tube is generally inclined; the liquid then passes down this inclined plane, or it is forced through by pressure, applied at the opposite end. _Direction of the jet from lateral orifices._—From the principle of the equal transmission of pressure, water issues from an orifice _in the side of a vessel_ with the same velocity as from an aperture in the bottom of a vessel at the same depth. MEASUREMENT OF WATER PRESSURE. _In reference to the table on the next page_, it may be well to say that it has two uses; by it when the “_head_” is known the _pressure_ can be ascertained to a fraction, thus, _Ex. 1_, If the head is 140 feet, then the pressure is 60·64 pounds per square inch. Again, _Ex. 2_, If the pressure is 15·16 per square inch, then the head is 35 feet. [Illustration: INSIDE. (_See Page 115._) OUTSIDE.] PRESSURE OF WATER. The pressure of water in pounds per square inch for every foot in height to 300 feet; and then by intervals, to 1000 feet head· By this table, from the pounds pressure per square inch, the feet head is readily obtained; and _vice versa_.