Chemical element (85.6 °F), respectively. Melting and boiling points, typically expressed in degrees Celsius at a pressure of one atmosphere, are commonly used in characterizing the various elements. While known for most elements, either or both of these measurements is still undetermined for some of the radioactive elements available in only tiny quantities. Since helium remains a liquid even at absolute zero at atmospheric pressure, it has only a boiling point, and not a melting point, in conventional presentations. The density at selected standard temperature and pressure (STP) is frequently used in characterizing the elements. Density is often expressed in grams per
Lowest bridging point Lowest bridging point The lowest bridging point is the location on a river which is crossed by a bridge at its closest point to the sea. Historically - that is, before the development of engineering technology that allowed the construction of tunnels and high-level road bridges - the lowest bridging point of a river was frequently the point at which an important town or city grew up, and particularly where trade and commerce took place. The place could be served by roads on either side of the river, allowing access from a wide hinterland; had river transport available upstream; and