652. How high will atmospheric pressure raise water in the bore of a pump?
It will raise water to an elevation of thirty feet above its level.
653. Why will it raise water to an elevation of thirty-feet?
Because a column of water of thirty feet high, nearly balances the weight of a column of air of equal surface, extending to the whole height of the atmosphere. When, therefore, water is elevated to the height of thirty feet, the power of the pump is enfeebled, as the air and the water balance each other.
654. How is water raised to a greater elevation when it is required?
By mechanical contrivances, by which the water is forced to a greater elevation.
655. Why does water run through the bent tube called a syphon?
Because the atmospheric pressure upon the water on the outside of the syphon forces it into the tube as fast as the syphon empties itself through its longer arm.
656. Why does water run through the longer arm of the syphon?
Because the weight of the water in the longer arm of the syphon is greater than that in the shorter; therefore it runs out by its own gravity. And, as in running out, it creates a tendency towards a vacuum, the pressure of the outer air comes into operation, and forces the water through the tube.