It also became a standard ship's instrument to predict approaching storms. No chemical solutions, no complicated gimmicks and wizardry. Simple basic applied science. The level of the water in the spout is influenced by the surrounding air pressure. We all know from countless times watching the weather report that high air pressure means good weather.
High pressure pushes the water down into the spout and creates a low spout level.
Low pressure systems come with storms and rain, and create a high water level in the spout. Fast approaching storms may even make the water overflow, which is why a drop catcher comes in handy at times. For best results, keep the glass out of the sun's reach. Place it in surroundings with a stable temperature, and enjoy the accurate forecast. Unless otherwise protected, Copyright 1998-2001, Sandcastle Publishing Company .