That the rays of light flow in all directions from different bodies, without interrupting one another, is plain from the following experiment:—Make a little hole in a thin plate of metal, and set the plate upright on a table, facing a row of lighted candles standing near together; then place a sheet of paper or pasteboard at a little distance from the other side of the plate; and the rays of all the candles, flowing through the hole, will form as many specks of light on the paper as there are candles before the plate; each speck as distinct and large as if there were only one candle to cast one speck; which shows that the rays do not obstruct each other in their motions, although they all cross in the same hole.
The Power of Water.
Let a strong small iron tube of twenty feet in height be inserted into the bung-hole of a cask, and the aperture round so strongly closed, that it shall be water-tight; pour water into the cask till it is full, through the pipe; also continue filling the pipe till the cask bursts, which will be when the water is within a foot of the top of the tube. In this experiment the water, on bursting the vessel, will fly about with considerable violence.
The Pressure of Water.
The pressure of water may be known to every one who will only take the trouble to look at the cock of a water-butt when turned: if the tub or cistern be full, the water runs with much greater velocity through the cock, and a vessel will be filled from it in a shorter time than when it is only half-full, although the cock, in both cases, is equally replete with the fluid during the time the vessel is filling. From this also is understood, how a hole or leak, near the keel of a ship, admits the water much quicker, and with greater violence, than one of the same size near what the mariners call the water's edge.
Refraction of Light.
In the middle of an empty basin put a piece of money, and then retire from it till the edge of the basin hides the piece from your sight: then keep your head steady, let another person fill the basin gently with water; as the water rises in the basin the money will come in view; and when of a sufficient height in the basin, the whole of the piece will be in sight.
Wonderful Nature of Lightning.
If two persons, standing in a room, looking different ways, and a loud clap of thunder, accompanied with zigzag lightning, happen, they will both distinctly see the flash at the same time; not only the illumination, but the very form of the lightning itself, and every angle it makes in its course will be as distinctly perceptible, as though they had both looked directly at the cloud from whence it proceeded. If a person happened at that time to be looking on a book, or other object, which he held in his hand, he would distinctly see the form of the lightning between him and the object at which he looked. This property seems peculiar to lightning, as it does not apply to any other kind of fire whatever.