A barometer measures the rising and lowering of pressure of the atmosphere. High pressure indicates clear weather; low pressure indicates less favorable weather.

Materials:

• A clear bottle with a neck (catsup or vinegar bottles work well)
• A clear, narrow glass jar (to hold about 2 cups or 480 ml of water)
• Water
• Food coloring
• Permanent marker

Procedure:

1. Remove all labels from the jar and bottle. Clean thoroughly.
2. Invert the bottle into the jar, making sure the bottle does not touch the bottom of the jar.
3. Fill the jar with enough water to reach just over the mouth of the Inverted bottle by an inch (2.5 cm) or so.
4. Add a few drops of food coloring to the water.
5. Release air bubbles from the bottle by tipping it gently.
6. Using a permanent marker, mark the water level on the jar.
7. Place the barometer in a shaded area.
8. Throughout the week, observe the level of the colored water.

The water level in the bottle should be high during good weather and low in bad weather.