[Illustration: Fig. 45. Fig. 46.] [Illustration: Fig. 47.] 102. =Curious Experiments.=--You can not hang a pail of water on a stick laid upon a table, as represented in Fig. 44, for the centre of gravity is not supported. But if you place another stick a as a brace, in the manner represented in Fig. 45 (p. 73), so as to push the pail under the table, it will hang securely, because the centre of gravity is now under the point of suspension. The explanation of the following experiment is the same: Run a large needle through a cork; fasten to the cork a fork, and you can suspend the whole on the edge of a table, as seen in Fig. 46. Here the centre of gravity is directly under the point of suspension, which is at the point of the needle. The same can be said of the very common toy represented in Fig. 47. The horse, made of very light material, stands securely, because the centre of gravity of the whole is in the heavy ball, which is under the point of suspension. If the horse be made to rock back and forth, the centre of gravity in the ball moves in a curved line, as in the case of a ball suspended by a string (Fig. 39). It is at its lowest place only when the horse is at rest. The hanging of a cane with a hook-shaped handle on the edge of a table is to be explained in the same way. [Illustration: Fig. 48. Fig. 49. Fig. 50.] [Illustration: Fig. 51.] [Illustration: Fig. 52.] 103. =Stability of Bodies.=--The firmness with which a body stands depends upon two circumstances--the height of its centre of gravity, and the extent of its base. The lower the centre of gravity, and the broader the base, the firmer does the body stand. A cube, represented in Fig. 48, is more stable, that is, less easily turned over, than a body shaped as Fig. 49, because it has a larger base. The contrast is still greater between Figs. 48 and 50. The reason of the stability of a body with a broad base is found in the fact, that in turning it over the centre of gravity must be raised more than in turning over one of a narrower base. The curved lines indicate the paths of the centres of gravity as the bodies are turned over. In the case of a perfectly round ball, the base is a mere point, and therefore the least touch turns it over. Its centre of gravity does not rise at all, but moves in a horizontal line, as shown in Fig. 51. The pyramid is the firmest structure in the world, because it possesses in the highest degree the two elements--a broad base, and a low position of the centre of gravity. On both these accounts the centre of gravity must ascend considerably when the body is turned over, as seen in Fig. 52. [Illustration: Fig. 53.] [Illustration: Fig. 54.]