Maupertuis, in a little volume of his letters, observes on the “Philosophical Stone,” that we can not prove the impossibility of obtaining it, but we can easily see the folly of those who employ their time and money in seeking for it. This price is too great to counterbalance the little probability of succeeding in it. However it is still a bantling of modern chemistry, who has nodded very affectionately on it. Of the “Perpetual Motion,” he shows the impossibility, at least in the sense in which it is generally received. On the “Quadrature of the Circle,” he says he can not decide if this problem be resolvable or not; but he observes, that it is very useless to search for it any more; since we have arrived by approximation to such a point of accuracy, that on a large circle, such as the orbit which the earth describes round the sun, the geometrician will not mistake by the thickness of a hair. The quadrature of the circle is still, however, a favorite game of some visionaries, and several are still imagining that they have discovered the perpetual motion; the Italians nick-name them _matto perpetuo_; and Bekker tells us of the fate of one Hartmann, of Leipsic, who was in such despair at having passed his life so vainly in studying the perpetual motion, that at length he hanged himself. THE CO-RELATED FORCES. By RICHARD BUDD PAINTER. I will give a short account of some forces which influence matter in a very powerful degree. These are _Heat_, _Light_, _Electricity_, _Magnetism_, _Chemical Affinity_ (or chemical change), and _Motion_. Of these forces, as of those of attraction and repulsion, we again can only judge by their effects. God alone knows their cause and real quality. Until a few years ago they were supposed to be quite different things essentially, but Grove, Joule, and others have now shown them to be so co-related as to be convertible the one into the other, and hence the brilliant theory of the “Correlation of the Physical Forces.” To show this co-relation and capacity for transformation I will give a few examples. Rub a piece of iron briskly, or repeatedly strike it with a hammer, and it will become warm. We know from this, therefore, that motion will produce heat. Or strike a lucifer match against the box, and the rapid motion of the match against the hard surface will produce sufficient heat to cause the sensitive chemical substance at the end of the match to inflame, and so to give out heat and light. Or watch a horse trotting on a hard road at night, and sparks will every now and then fly from his feet. This is because by the rapid forcible motion of his legs the iron of his shoes every now and then comes in contact with a stone, and a minute particle of steel being struck off with great force and rapidity it becomes red-hot, and thus presents another example of how motion can be converted into heat.