This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
To use a discarded electric bulb as a fairly reliable barometer the point is broken off with a pair of pliers while holding the bulb under water. As the bulb is a vacuum, it completely fills with water. If the bulb is now suspended from a wire or thread fastened at the socket end, the water will not run out of it in fair weather when the atmospheric pressure is normal or high, but if the pressure falls, as happens when bad weather is approaching, the water will begin to bulge out of the small opening and sometimes a small drop may even fall off. When, with returning fair weather, the atmospheric pressure increases, the water can no longer bulge or drop out of the bulb.