When the glass runs out, prepare to hit it. When the cup rises, fly the kite. Vintage illustration of a weather barometer. This is a simple adage about observing and reading barometric pressure. In the early days of this meteorometer, it was called "glass" (due to the presence of mercury in the glass tube). When the "glass" is low (ie, when mercury is low, ie, low pressure), rain and bad weather can usually be expected. If the mercury is high, there will or will be a high pressure system and you can enjoy bad weather.
When the glass runs out, prepare to hit it. When the cup rises, fly the kite. Vintage illustration of a weather barometer. This is a simple adage about observing and reading barometric pressure. In the early days of this meteorometer, it was called "glass" (due to the presence of mercury in the glass tube). When the "glass" is low (ie, when mercury is low, ie, low pressure), rain and bad weather can usually be expected. If the mercury is high, there will or will be a high pressure system and you can enjoy bad weather.