How Iron acquires Verticity through a Loadstone, and how that verticity is lost and changed.
riction between an oblong piece of iron and a loadstone imparts to the former magnetick virtues1, which are not corporeal3 nor inherent and persistent4 in any body, as we showed in the discussion on coition. It is plain that the iron, when it has been rubbed hard with one end and applied5 to the stone for a pretty long time, receives no stony6 nature, acquires no weight; for if, before the iron is touched by the stone, you weigh it in a small and very exact goldsmith's balance, you will see after the rubbing that it has exactly the same weight, neither diminished nor increased. But if you wipe the iron with cloths after it has been touched, or wash it in water, or scour7 it with sand or on a grindstone, still it in nowise lays aside its acquired strength. For the force is spread through the whole body and conceived in the inmost parts, and cannot in any way be washed or wiped away. Let an experiment then be made in fire, that untamed tyrant8 of nature. Take a piece of iron of the length of a palm and the thickness of a goosequill pen; let this iron be passed through a suitable round cork9 and placed on the surface of water, and observe the end which turns to the north; rub this particular end with the true southern end of a loadstone; the iron so rubbed turns toward the south. Remove the cork, and place the end which was excited in the fire until the iron is just red-hot; when it is cooled, it will retain the strength of the loadstone and the verticity, though it will not be so prompt, whether because the force of the fire had not yet continued long enough to overcome all its strength, or because the whole iron was not heated to redness, for the virtue2 is diffused10 through the whole. Remove the cork a second time, and putting the whole iron in the fire, blow the fire with the bellows11, so that it may be all aglow12, and let it remain a little longer time red-hot; when cooled (so, however, that, whilst it is cooling, it does not rest in one position), place it again on the water with the cork, and you will see that it has lost the verticity which it had acquired from the stone. From these experiments it is clear how difficult it is for the property of polarity implanted by the loadstone to be destroyed. But if a small loadstone had remained as long in the same fire, it would have lost its strength. Iron, because it does not so easily perish, and is not so easily burnt up as very many loadstones, retains its strength more stably, and when it is lost can recover it again from a loadstone; but a loadstone when burnt does not revive. But now that iron, which has been deprived of its magnetick form, moves in a different way from any other piece of iron, for it has lost its polar nature; and whereas before the touch of the loadstone it may have had a motion toward the north, and after contact toward the south; now it turns to no definite and particular point; but afterwards, very slowly and after a long time, it begins to turn in a doubtful fashion toward the poles of the earth (having acquired some power from the earth). I have said that the cause of direction was twofold, one implanted in the stone and iron, but the other in the earth, implanted by the disponent virtue; and for that reason (the distinction of poles and the verticity in the iron having now been destroyed) a slow and weak directive power is acquired anew from the verticity of the earth. We may see, therefore, with what difficulty and only by the application of hot fires and by long ignition of the iron heated to softness, the imparted magnetick virtue is eradicated14. When this ignition has overcome the acquired polarity, and it has been now completely subdued15 and not awakened16 again, that iron is left unsettled and utterly17 incapable18 of direction. But we must further inquire how iron remains19 affected20 by verticity. It is manifest that it strongly affects and changes the nature of the iron, because the presence of a loadstone attracts the iron to itself with an altogether wonderful readiness. Nor is it only the part that is rubbed, but on account of the rubbing (on one end only) the whole iron is affected together, and gains by it a permanent though an unequal power. This is demonstrated as follows. Rub an iron wire on the end so that it is excited, and it will turn towards the north; afterward13 cut off some portion of it; you will see that it still turns toward the north (as before), but more feebly. For it must be understood that the loadstone excites a steady verticity in the whole iron (if the rod be not too long) more vigorous throughout the whole mass in a shorter bar, and as long as the iron remains touching21 the loadstone a little stronger. But when the iron is separated from contact with it, then it becomes much weaker, especially in the end that was not touched. Just as a long rod, one end of which is placed in the fire and heated, grows exceedingly hot at that end, less so in the parts adjoining and in the middle, whilst at the other end it can be held in the hand, and that end is only warm; so the magnetical vigour22 diminishes from the excited end to the other end; but it is present there instantly, and does not enter after an interval23 of time nor successively, as the heat in the iron; for as soon as a piece of iron has been touched by a loadstone it is excited throughout its whole length. For the sake of experiment, let there be a rod of iron 4 or 5 digits24 long, untouched by a loadstone; as soon as you touch one end only with a loadstone, the opposite end immediately, or in the twinkling of an eye, by the power that it has conceived, repels25 or attracts a versorium, if it be applied to it ever so quickly.
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virtues
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| 美德( virtue的名词复数 )； 德行； 优点； 长处 | |
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virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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corporeal
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| adj.肉体的，身体的；物质的 | |
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4
persistent
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| adj.坚持不懈的，执意的；持续的 | |
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applied
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| adj.应用的；v.应用，适用 | |
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stony
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| adj.石头的，多石头的，冷酷的，无情的 | |
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7
scour
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| v.搜索；擦，洗，腹泻，冲刷 | |
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8
tyrant
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| n.暴君，专制的君主，残暴的人 | |
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cork
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| n.软木，软木塞 | |
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diffused
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| 散布的，普及的，扩散的 | |
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bellows
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| n.风箱；发出吼叫声，咆哮（尤指因痛苦）( bellow的名词复数 )；（愤怒地）说出（某事），大叫v.发出吼叫声，咆哮（尤指因痛苦）( bellow的第三人称单数 )；（愤怒地）说出（某事），大叫 | |
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aglow
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| adj.发亮的；发红的；adv.发亮地 | |
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afterward
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| adv.后来；以后 | |
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eradicated
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| 画着根的 | |
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subdued
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| adj. 屈服的，柔和的，减弱的 动词subdue的过去式和过去分词 | |
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awakened
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| v.（使）醒( awaken的过去式和过去分词 )；（使）觉醒；弄醒；（使）意识到 | |
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utterly
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| adv.完全地，绝对地 | |
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incapable
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| adj.无能力的，不能做某事的 | |
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remains
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| n.剩余物，残留物；遗体，遗迹 | |
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affected
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| adj.不自然的，假装的 | |
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touching
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| adj.动人的，使人感伤的 | |
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22
vigour
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| （=vigor）n.智力，体力，精力 | |
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23
interval
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| n.间隔，间距；幕间休息，中场休息 | |
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24
digits
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| n.数字( digit的名词复数 )；手指，足趾 | |
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repels
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| v.击退( repel的第三人称单数 )；使厌恶；排斥；推开 | |
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