If you are able to find a piece of coal, you can prove this for yourself by doing the following simple experiment.

     First wrap the coal lump in a sturdy rag and hammer it into a fine powder. With a wad of soft paper, plug the narrow end of the funnel and pour the coal powder into the other end. Holding the funnel upright, invert the coffee can over it. Then pressing the funnel against the bottom of the can, return the can to its original position. Remove the paper wad.

     Now gently pour water into the can until the water is about an inch above the funnel (if it’s a plastic funnel, you’ll have to hold it down to keep it from floating). The water, of course, will enter the funnel. Next, take the small bottle and submerge it, open end up, in the water. After it fills completely, turn the bottle upside down, keeping it under water so that no air gets into it. Then carefully maneuver it over the funnel – again, staying under water. Finally, lower the bottle and let it rest on the funnel. That’s all you have to do.

     Put the can aside, and in a day or so you will see a large bubble at the upper part of the bottle.