Ivory point

{
  "id": "MLC-T-MET-006733",
  "term": "Ivory point",
  "field": "Meteorology and atmospheric science",
  "definition": "A fixed reference mark, typically made of ivory, used on mercury barometers to establish a precise zero point for pressure measurements. The mercury column is adjusted until its surface just touches this point, allowing for accurate reading of the atmospheric pressure against a calibrated scale. This method accounts for variations in the mercury level within the cistern.",
  "url": "https://mlchart.com/terminology/meteorology/ivory-point/"
}