_B._ Dr. Gilbert, that was the first that wrote anything of this subject rationally, inclines to that opinion. Descartes thought the earth, excepting this upper crust of a few miles depth, to be of the same nature with all other stars, and bright. For my part, I am content to be ignorant; but I believe the loadstone hath been given its virtue by a long habitude in the mine, the vein of it lying in the plane of some of the meridians, or rather of some of the great circles that pass through the poles of the ecliptic, which are the same with the poles of the like motion supposed in the earth. _A._ If that be true, I need not ask why the filings of iron laid on a loadstone equally distant from its poles will lie parallel to the axis, but on each side will incline to the pole that is next. Nor why by drawing a loadstone all along a needle of iron, the needle will receive the same poles. Nor why when the loadstone and iron, or two loadstones, are put together floating upon water, will fall one of them astern of the other, that their like parts may look the same way, and their unlike touch, in which action they are commonly said to repel one another. For all this may be derived from the union of their motions. One thing more I desire to know, and that is; what are those things they call spirits? I mean ghosts, fairies, hobgoblins, and the like apparitions. _B._ They are no part of the subject of natural philosophy. _A._ That which in all ages, and all places is commonly seen (as those have been, unless a great part of mankind be liars) cannot, I think, be supernatural. _B._ All this that I have hitherto said, though upon better ground than can be had for a discourse of ghosts, you ought to take but for a dream. _A._ I do so. But there be some dreams more like sense then others. And that which is like sense pleases me as well in natural philosophy, as if it were the very truth. _B._ I was dreaming also once of these things; but was wakened by their noise. And they never came into any dream of mine since, unless apparitions in dreams and ghost be all one. ========== CHAPTER VIII. THE DELPHIC PROBLEM, OR DUPLICATION OF THE CUBE. _A._ Have you seen a printed paper sent from Paris, containing the duplication of the cube, written in French? _B._ Yes. It was I that writ it, and sent it thither to be printed, on purpose to see what objections would be made to it by our professors of algebra here. _A._ Then you have also seen the confutations of it by algebra. _B._ I have seen some of them; and have one by me. For there was but one that was rightly calculated, and that is it which I have kept. _A._ Your demonstration then is confuted though but by one. _B._ That does not follow. For though an arithmetical calculation be true in numbers, yet the same may be, or rather must be false, if the units be not constantly the same.