Chronometer, a timepiece that is exceptionally accurate. Traditionally, the term refers to the marine chronometer, a rugged mechanical instrument used at sea to keep time for navigational purposes. By measuring the position of a celestial body (with a device called a sextant), and by knowing the exact time of the measurement, a navigator can determine a ship's longitude from published tables. The typical marine chronometer is mounted on suspension devices called gimbals to keep it in a horizontal position and to reduce the effect of vibrations from the ship.
Climate, the average condition of the weather in an area for a period of years.
Folks in Montana usually expect snow or rain to fall from the sky, not ash. But the 1980 eruption of Mount St. Helens in Washington flung ash across state lines. What is this gritty, gray stuff?