The water barometer, or "Goethe glass", shows the air pressure and therefore the coming weather. Fill the barometer as shown with distilled water, which can also be dyed, and hang it somewhere indoors. If the water climbs up the spout, the weather is bad, if it comes back down again, it will be fine. Note: If the water overflows you need to add some more water straight away. Very few glass blowers have mastered the art of blowing this object to perfection.