On the Magnet/III-2
verticity): what it is, how it exists in the loadstone;
and in what way it is acquired when innate.
* weight, dug up and cut out of its vein, after we had first observed and marked its ends; then after it was dug out, we placed it in a boat on water, so that it could turn freely; then immediately the face which had looked toward the north in the quarry began to turn to the north on the waves and at length settled toward that point. For that face which looked toward the north in the quarry is the southern, and is attracted by the northern parts of the earth,  under change of verticity. But there is a different rotation of the internal parts of the earth, which are perfectly united to the earth and which are not separated from the true substance of the earth by the interposition of bodies as are loadstones in the upper portion of the earth, which is maimed, corrupt, and variable. Let A B be a piece of magnetick ore; between which and the uniform globe of the earth lie various soils or mixtures which separate the ore to a certain extent from the globe of the true earth. It is therefore influenced by the forces of the earth just in the same way as C D, a piece of iron, in the air. So the face B of some ore or of that piece of it is moved toward the Boreal pole G, just as the extremity C of the iron, not A or D. But the condition of the piece E F is different, which piece is produced in one connected mass with the whole, and is not separated from it by any earthy mixture. For if the part E F were taken out and floated freely in a boat by itself, it is not E that would be directed toward the Boreal pole, but F. So in those substances which acquire their verticity in the air, C is the southern part and is seen to be attracted by the Boreal pole G. In the case of others which are found in the upper unstable portion of the earth, B is the south, and in like manner inclines toward the Boreal pole. But if those pieces deep down which are produced along with the earth are dug up, they turn about on a different plan. For F turns toward the Boreal parts of the earth, because * is the southern part; E toward the south, because it is the northern. So of a magnetick body, C D, placed close to the earth, the end C turns toward the Boreal pole; of one that is adnate to it B A, B inclines to the North; of one that is innate in it, E F, E turns toward the southern pole; which is confirmed by the * the terrella were moved toward the earth's south, the end E of the piece cut out by itself, if not brought too near to the stone, would also move of itself toward the south. But the end C of the piece of iron, placed beyond its orbe of virtue, will turn toward the north. The part E F of the terrella, whilst in the mass, produced the same direction as the whole; but when it is separated and suspended by a thread, E turns to B, and F to A. * solicited by the opposite pole. But if the small piece F E is placed back again in its bed or brought close to, without any substances intervening, it acquires its former combination, and, as a part of the whole once more united, accords with the whole and sticks readily in its former position; and E remains toward A, and F toward B, and they settle steadily in their mother's lap. The reasoning is the same when the stone is divided into equal parts through the poles. * whether therefore the surface A B is in the one part facing upward (as in the former diagram) or lying on its face in both parts (as in * the latter), the end A tends toward B. But it must also be understood that the point A is not carried with a definite aim always toward the point B, because in consequence of the division the verticity proceeds to other points, as to F G, as appears in the fourteenth chapter of this book. And L M are now the axes in each, and A B is no longer the axis; for magnetick bodies, as soon as they are divided, become single magnetick wholes; and they have vertices in accordance with their mass, new poles arising at each end in consequence of the division. Yet the axis and the poles always follow the leading of a meridian; because that force passes along the meridians of the stone from the æquator to the poles, by an everlasting rule, the inborn virtue of the substance agreeing thereto from the long and lasting position and the facing of a suitable substance toward the poles of the earth; by whose strength continued through many centuries it has been fashioned; toward fixed and determined parts of which it has remained since its origin firmly and constantly turned.
The page and line references given in these notes are in all cases first to the Latin edition of 1600, and secondly to the English edition of 1900.
202 ^ Page 120, line 8. Page 120, line 5. dicturi sumus.—Change of verticity is treated of in book iii., chap. x., pp. 137 to 140.