Page:Popular Science Monthly Volume 16.djvu/90

80 It will be observed that since the diagonal either of a square or of a parallelogram is longer than either of its sides, the resultant, A D, will have a greater intensity than gravity represented by A B. Now, suppose the point A' to be some point inside the earth's crust, and some



distance from the surface, and suppose also that it is a particle of water in a body of water imprisoned by surrounding rocks. This particle will be acted upon by a continual impulse to move in the direction A' F', with an intensity represented by A' D'. This will be true of every other water-particle in the imprisoned body of water.

If, now, in an hermetically sealed vessel of water a set-screw is turned and pressed upon the water inside until the resistance to it is equal to one pound, that one-pound pressure will be duplicated upon every other equal space of the vessel: and thus, if the end of the screw has one square inch of surface, every square inch of the inside of the vessel will feel a pressure of one pound. Exactly this will occur in the case of the water imprisoned in the rocks. The resultant of the two natural forces, centripetal and centrifugal, will be duplicated upon