*(Wikipedia): “William Penn (14 October 1644 – 30 July 1718) was an English writer and religious thinker belonging to the Religious Society of Friends (Quakers), and founder of the Province of Pennsylvania, a North American colony of England. He was an early advocate of democracy and religious freedom, notable for his good relations and successful treaties with the Lenape Native Americans. Under his direction, the city of Philadelphia was planned and developed. Philadelphia was planned out to be grid-like with its streets and be very easy to navigate, unlike London where Penn was from. The streets are named with numbers and tree names. He chose to use the names of trees for the cross streets because Pennsylvania means “Penn’s Woods”.”
“Mercury is a chemical element with the symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum(/haɪˈdrɑːrdʒərəm/ hy-DRAR-jər-əm). A heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is the halogenbromine, though metals such as caesium, gallium, and rubidium melt just above room temperature.
Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, though concerns about the element’s toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alternatives such as alcohol– or galinstan-filled glass thermometers and thermistor– or infrared-based electronic instruments. Likewise, mechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers.
Mercury remains in use in scientific research applications and in amalgam for dental restoration in some locales. It is also used in fluorescent lighting. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light, which then causes the phosphor in the tube to fluoresce, making visible light.
“Hg” is the modern chemical symbol for mercury. It comes from hydrargyrum, a romanized form of the ancient Greek word ὑδράργυρος (hydrargyros), which is a compound word meaning ‘water-silver’ (from ὑδρ- (hydr-), the root of ὕδωρ ‘water’, and ἄργυρος (argyros) ‘silver’) since it is liquid like water and shiny like silver. The element was named after the Roman god Mercury, known for his speed and mobility. It is associated with the planet Mercury; the astrological symbol for the planet is also one of the alchemical symbols for the metal. Mercury is the only metal for which the alchemical planetary name became the common name.”