This experiment is not a case of pure balancing, but depends principally upon the nice adjustment of the two pieces of stick by means of which the position of the two glasses is maintained. A couple of slender pen-holders may be used, and must be trimmed down at the ends until the right length is obtained. The position of the sticks and the manner in which the glasses are supported can best be gathered by a study of the illustration below.
17.—BALANCING CUPS.
Simple methods of balancing a milk-jug and tea-cup respectively are shown in Figs. 17, A and B. In the first illustration the cork is placed inside the handle of the vessel, in which position it should fit with moderate firmness, so as not to slip, and then two knives are thrust in, one from each side of the handle, between the cork and the cup itself, when the cup may be balanced upon any fixed point. In the second a cork is fixed into the handle, as before, and into the cork the prongs of a fork are fastened, holding the fork in such a position as to bring the centre of gravity below the point of suspension. The cup may then be balanced as before.
18.—THE BALANCED PLATE.
This is a rather more elaborate experiment and one of the most effective of the whole series. The requirements are: a plate, the basting-ladle used in previous experiments, and, in addition, a "skimmer." The handle of the ladle is hooked over the edge of the plate and made secure by a wedge cut from a bottle cork. The opposite edge of the plate is then rested upon the edge of a bottle in the position shown in Fig. 18, and the handle of the skimmer is finally hooked into the bowl of the ladle, making the structure shown.