PHILOSOPHICAL EXPERIMENTS.

An empty bottle being corked, and by means of a weight let down a certain depth into the sea, it will be broken, or the cork will be driven into it by the perpendicular pressure. But a bottle filled with water, wine, &c. may be let down to any depth, without damage, because in this case the internal pressure is equal to the external.

Cover a wine glass completely filled with water, or wine, with a piece of writing paper: then place the palm of the hand over the paper, so as to hold it tight and accurately even. The glass may then be turned upside down, and the hand removed, without the water running out. The pressure of the air upon the paper sustains the weight of water.

Take a glass tumbler half full of water and put a silver half dollar into it, then put a saucer or plate upon it, and holding it tight on, turn plate and glass together; a byestander unacquainted with the laws of refraction, will suppose that he sees a dollar and a half: the one is seen by refraction through the water, the other by the rays after refraction at the surface.