<Ul> <Li> Quantities of liquid mercury ranging from 90 to 600 grams (3.2 to 21.2 oz) have been recovered from elite Maya tombs (100 - 700AD) or ritual caches at six sites . This mercury may have been used in bowls as mirrors for divinatory purposes . Five of these date to the Classic Period of Maya civilization (c. 250--900) but one example predated this . </Li> <Li> In Islamic Spain, it was used for filling decorative pools . Later, the American artist Alexander Calder built a mercury fountain for the Spanish Pavilion at the 1937 World Exhibition in Paris . The fountain is now on display at the Fundació Joan Miró in Barcelona . </Li> <Li> Mercury was used inside wobbler lures . Its heavy, liquid form made it useful since the lures made an attractive irregular movement when the mercury moved inside the plug . Such use was stopped due to environmental concerns, but illegal preparation of modern fishing plugs has occurred . </Li> <Li> The Fresnel lenses of old lighthouses used to float and rotate in a bath of mercury which acted like a bearing . </Li> <Li> Mercury sphygmomanometers (blood pressure meter), barometers, diffusion pumps, coulometers, and many other laboratory instruments . As an opaque liquid with a high density and a nearly linear thermal expansion, it is ideal for this role . </Li> <Li> As an electrically conductive liquid, it was used in mercury switches (including home mercury light switches installed prior to 1970), tilt switches used in old fire detectors, and tilt switches in some home thermostats . </Li> <Li> Owing to its acoustic properties, mercury was used as the propagation medium in delay line memory devices used in early digital computers of the mid-20th century . </Li> <Li> Experimental mercury vapor turbines were installed to increase the efficiency of fossil - fuel electrical power plants . The South Meadow power plant in Hartford, CT employed mercury as its working fluid, in a binary configuration with a secondary water circuit, for a number of years starting in the late 1920s in a drive to improve plant efficiency . Several other plants were built, including the Schiller Station in Portsmouth, NH, which went online in 1950 . The idea did not catch on industry - wide due to the weight and toxicity of mercury, as well as the advent of supercritical steam plants in later years . </Li> <Li> Similarly, liquid mercury was used as a coolant for some nuclear reactors; however, sodium is proposed for reactors cooled with liquid metal, because the high density of mercury requires much more energy to circulate as coolant . </Li> <Li> Mercury was a propellant for early ion engines in electric space propulsion systems . Advantages were mercury's high molecular weight, low ionization energy, low dual - ionization energy, high liquid density and liquid storability at room temperature . Disadvantages were concerns regarding environmental impact associated with ground testing and concerns about eventual cooling and condensation of some of the propellant on the spacecraft in long - duration operations . The first spaceflight to use electric propulsion was a mercury - fueled ion thruster developed by NASA Lewis and flown on the Space Electric Rocket Test "SERT - 1" spacecraft launched by NASA at its Wallops Flight Facility in 1964 . The SERT - 1 flight was followed up by the SERT - 2 flight in 1970 . Mercury and caesium were preferred propellants for ion engines until Hughes Research Laboratory performed studies finding xenon gas to be a suitable replacement . Xenon is now the preferred propellant for ion engines as it has a high molecular weight, little or no reactivity due to its noble gas nature, and has a high liquid density under mild cryogenic storage . </Li> </Ul> <Li> Quantities of liquid mercury ranging from 90 to 600 grams (3.2 to 21.2 oz) have been recovered from elite Maya tombs (100 - 700AD) or ritual caches at six sites . This mercury may have been used in bowls as mirrors for divinatory purposes . Five of these date to the Classic Period of Maya civilization (c. 250--900) but one example predated this . </Li> <Li> In Islamic Spain, it was used for filling decorative pools . Later, the American artist Alexander Calder built a mercury fountain for the Spanish Pavilion at the 1937 World Exhibition in Paris . The fountain is now on display at the Fundació Joan Miró in Barcelona . </Li> <Li> Mercury was used inside wobbler lures . Its heavy, liquid form made it useful since the lures made an attractive irregular movement when the mercury moved inside the plug . Such use was stopped due to environmental concerns, but illegal preparation of modern fishing plugs has occurred . </Li>

When was the element mercury discovered and by who