“I suppose,” observed Louisa, “that this is the reason why carriages, when too much loaded, are so apt to upset.” “Say, when too much loaded on their _tops_, and you will be right. As you now, I trust, understand this part of the subject, let us proceed a step farther: if you take any body, with a view to suspend it, is it not evident, that if it be suspended by that point in which the centre of gravity is situated, it must remain at rest in _any_ position indifferently?” “I thought,” said Tom, “we had already settled that question.” “True, my dear boy; but there is another question of great importance arising out of it, and which you have not yet considered: tell me, should the body be suspended on any other point, in what position it can rest?” “I do not exactly understand the question.” “There are,” replied his father, “only two positions in which it could rest, either where the centre of gravity is exactly _above_, or exactly _below_, the point of suspension; so that, in short, this point shall be in the _line of direction_. Where the point of suspension is _below_ the centre of gravity, it is extremely difficult to balance or support a tall body by such a method, because the centre of gravity is always endeavouring to get under the point of support. Look at this diagram, and you will readily comprehend my meaning. K is the centre of gravity of the diamond-shaped figure, which may be supported, or balanced, on a pin passing through it at M, as long as the centre of gravity K is immediately over the point of suspension M: but if that centre is removed in the slightest degree, either to the right or left of its place K, the body will no longer retain its erect position I K L, but it will revolve upon M, and place itself in the situation indicated by the dotted lines beneath the point M: and its centre of gravity will now be removed to N, directly _under_ M, and in the line K L, which, as you well know, is the line of direction. Have I rendered myself intelligible?” [Illustration: Fig. 12. Diagram of a kite’s center of gravity.] “I understand it perfectly,” answered Tom. “And do you also, my dear Louisa?” Louisa’s answer was equally satisfactory, and Mr. Seymour went on to state that the information they had now acquired would enable them to ascertain the situation of the centre of gravity of any plane surface which was portable, notwithstanding it might possess the utmost irregularity of shape. “You shall, for example,” continued he, “find the centre of gravity in your kite.” “I cannot say,” observed Tom, “how I should set about it.” “Well, fetch your kite, and I will explain the method.” Tom soon produced it, and the tail having been removed, Mr. Seymour proceeded as follows:-- [Illustration: Fig. 13. Kite viewed right side up.]