TO SHOW THAT RAYS OF LIGHT DO NOT OBSTRUCT EACH OTHER.
Make a small hole in a sheet of pasteboard, and placing it upright before three candles, placed closely together, it will be found that the images of all the candle flames will be formed separately on a piece of paper, laid on the table to receive them. This proves that the rays of light do not obstruct each other in their progress, although all cross in passing through the hole.