In the one instance, the centre of gravity is near the ground, and falls well within the base, as at No. 1, fig. 57. In the other, the centre of gravity is considerably elevated above the ground, and having met with an obstruction which has raised one side higher than the other, the line of direction has fallen outside the wheels, and the waggon is overturning as at No. 2. The various postures of the human body may be regarded as so many experiments upon the position of the centre of gravity which we are every moment unconsciously performing. To maintain an erect position, a man must so place his body as to cause the line of direction of his weight to fall within the base formed by his feet. [Illustration: Fig. 58.] The more the toes are turned outwards, the more contracted will be the base, and the body will be more liable to fall backwards or forwards; and the closer the feet are drawn together, the more likely is the body to fall on either side. The acrobats, and so-called "India-Rubber Brothers", dancing dogs, &c., unconsciously acquire the habit of accurately balancing themselves in all kinds of strange positions; but as these accomplishments are not to be recommended to young people, some other marvels (such as balancing a pail of water on a stick laid upon a table) may be adduced, as illustrated in fig. 59. Let A B represent an ordinary table, upon which place a broomstick, C D, so that one-half shall lay upon the table and the other extend from [Page 44] it; place over the stick the handle of an empty pail (which may possibly require to be elongated for the experiment) so that the handle touches or falls into a notch at H; and in order to bring the pail well under the table, another stick is placed in the notch E, and is arranged in the line G F E, one end resting at G and the other at E. Having made these preparations, the pail may now be filled with water; and although it appears to be a most marvellous result, to see the pail apparently balanced on the end of a stick which may easily tilt up, the principles already explained will enable the observer to understand that the centre of gravity of the pail falls within the line of direction shown by the dotted line; and it amounts in effect to nothing more than carrying a pail on the centre of a stick, one end of which is supported at E, and the other through the medium of the table, A B. [Illustration: Fig. 59.] This illustration may be modified by using a heavy weight, rope, and stick, as shown in our sketch below. [Illustration: Fig. 60.]