O n referring to the earlier books it will be found shown that a loadstone has its poles, and that a piece of iron has also poles, and rotation1, and a certain verticity; finally, that the loadstone and the iron direct their poles toward the poles of the earth. Now, however, we must make clear the causes of these things and their admirable workings, pointed2 out indeed before, but not proven. All those who have written before us about these rotations3 have left us their opinions so briefly4, so meagrely, and with such hesitating judgment5 that they seem hardly likely ever to persuade anyone, or even to be able to satisfy themselves; and all their petty reasons are rejected by the more prudent6 as useless, uncertain, and absurd, being supported by no proofs or arguments; whence also magnetick science, being all the more neglected and not understood, has been in exile. The true austral pole of a loadstone, not the boreal (as all before us used to think), if the loadstone is placed in its boat on the surface of water, turns to the North; in the case of a piece of iron also, whether it has been excited by a loadstone or not, the southern end moves toward the North. An oblong piece of iron of three or four digits7' length196, when skilfully8 rubbed with a loadstone, quickly turns north and south. Wherefore mechanicians, taking a piece of iron prepared in this way, balance it on a pin in a box, and fit it up with the requisites9 of a sun-dial; or they prepare the versorium out of two curved pieces of iron with their ends touching10 one another, so that the motion may be more constant. In this way the mariners11' versorium is arranged, which is an instrument beneficial, useful, and auspicious12 to sailors for indicating, like a good genius, safety and the right way. But it must be understood on the threshold of this argument (before we proceed further) that these pointings of the loadstone or of iron are not perpetually made toward the true poles of the world, do not always seek those fixed13 and definite points, or remain on the line of the true meridian14; but usually diverge15 some distance to the East or to the West. Sometimes also at certain places on land or sea they do indicate exactly the true poles. This discrepancy16 is called the Variation of the iron or of the loadstone; and since this is brought about by other causes, and is merely a certain disturbance17 and perversion18 of the true direction, we are directing our attention in this place to the true direction of the compass and of the magnetick iron (which would be equally toward the true poles and on the true meridian everywhere on the earth, unless other obstacles and an untoward19 pervertency hindered it). Of its variation and the cause of the perversion we shall treat in the next book. Those who wrote about the world and about natural philosophy a century ago, especially those remarkable20 elementary philosophers, and all those who trace their knowledge and training to them down to our own times, those men, I say, who represented the earth as always at rest and, as it were, a useless weight, placed in the centre of the universe at an equal distance from the sky on every side, and its nature to be simple, imbued21 only with the qualities of dryness and cold, sought diligently22 for the causes of all things and of all effects in the heavens, the stars, the planets, in fire, air, waters and substances of mixed natures. Never indeed did they recognize that the terrestrial globe had, besides dryness and cold, some special, effective, and predominant properties, strengthening, directing, and moving the globe itself through its whole mass and its very deepest vitals; nor did they ever inquire whether there were any such. For this reason the crowd of philosophizers, in order to discover the reasons of the magnetical motions, called up causes lying remote and far away. And one man seems to me beyond all others worthy23 of censure24, Martin Cortes, who, since there was no cause which could satisfy him in the whole of nature, dreamed that there was a point of magnetical attraction beyond the heavens, which attracted iron. Peter Peregrinus thinks that the direction arises from the poles of the sky. Cardan thought that the turning of iron was caused by a star in the tail of the Great Bear; Bessard, the Frenchman, opines that a magnetick turns toward the pole of the zodiack. Marsilius Ficinus will have it that the loadstone follows its own Arctick pole; but that iron follows the loadstone, straws amber25; whilst this perhaps follows the Antarctick pole — a most foolish dream. Others have recourse to I know not what magnetick rocks and mountains. Thus it is always customary with mortals, that they despise things near home, whilst foreign and distant things are dear and prized. But we study the earth itself and observe in it the cause of so great an effect. The earth, as the common mother, has these causes inclosed in her innermost parts; in accordance with her rule, position, condition, verticity, poles, æquator, horizons, meridians26, centre, circumference27, diameter, and the nature of the whole interior of her substance, must all magnetical motions be discussed. The earth has been ordered by the highest Artificer and by nature in such a way that it should have parts dissimilar in position, bounds of the whole and complete body, ennobled by certain functions, by which it might itself remain in a definite direction. For just as a loadstone, when it is floated on water in a suitable vessel28, or is hung by slender threads in the air, by its implanted verticity conforms its poles to the poles of the common mother in accordance with magnetick laws; so if the earth were to deviate29 from its natural direction and its true position in the universe, or if its poles were to be drawn30 aside (if this were possible) toward the sun-rising or the sun-setting or toward any other points whatsoever31 in the visible firmament32, they would return again to the north and south by magnetical motion, and would settle at the same points at which they are now fixed. The reason why the terrestrial globe seems to remain more steadily33 with the one pole toward those parts and directed toward the Cynosure34, and why its pole diverges35 by 23 degrees 29 minutes, with a certain variation not sufficiently36 investigated as yet by Astronomers37, from the poles of the ecliptick, depends on its virtue38 magnetical. The causes of the precession of the æquinoxes and the progression of the fixed stars, and of the change, moreover, in the declinations of the sun and of the tropicks, must be sought from magnetick influences; so that neither that absurd motion of trepidation39 of Thebit Bencora197, which is at great variance40 with observations, nor the monstrous41 superstructures of other heavens, are any longer needed. A versatory iron turns to the position of the earth, and if disturbed ever so often returns always to the same points. For in the far regions of the north, in a latitude42 of 70 or 80 degrees (to which at the milder seasons of the year our sailors are accustomed to penetrate43 without injury from the cold); in the regions halfway44 between the poles; on the æquator in the torrid zone; and again in all the maritime45 places and lands of the south, in the highest latitude which has thus far been reached, always the iron magnetick finds its way, and points to the poles in the same manner (excepting for the difference of variation); on this side of the æquator (where we live), and on the other side to the south, less well known, but yet in some measure explored by sailors: and always the lily of the compass points toward the North. This we have had confirmed by the most eminent46 captains, and also by very many of the more intelligent sailors. These facts have been pointed out to me and confirmed by our most illustrious Sea-god, Francis Drake, and by another circumnavigator of the globe, Thomas Candish; our terrella also indicates the same thing. This is demonstrated in the case of the .
orbicular stone, whose poles are A and B; an iron wire CD, which is placed upon the stone, always points directly along the meridian toward the poles AB, whether the centre of the wire is on the central line or æquator of the stone, or on any other part situated47 between the æquator and the poles, as at H, G, F, E. So the cusp of a versorium on this side of the æquator points toward the north; on the other side the cross is always directed toward the south; but the cusp or lily198 does not, as some one has thought, turn toward the south beyond the æquator. Some inexperienced people indeed, who in distant parts beyond the æquator have seen the versorium sometimes become more sluggish48 and less prompt, thought that the distance from the arctick pole or from the magnetick rocks was the cause of this. But they are very much mistaken; for it is as powerful199, and adjusts itself as quickly to the meridian or to the point of variation in the southern as in the northern parts of the earth. Yet sometimes the motion appears slower, namely, when the supporting pin by lapse49 of time and long voyaging has become somewhat blunt, or the magnetick iron parts have lost, by age or rust50, some of their acquired vigour51. This may also be shown experimentally by the versatory iron of a small sun-dial placed on a very short pin set perpendicular52 to the surface of the stone, for the iron when touched by a loadstone points toward the poles of the stone and leaves the poles of the earth; for the general and remoter cause is overcome by the particular and powerful cause which is so near at hand. Magnetick bodies have of themselves an inclination53 toward the position of the earth and are influenced by a terrella. Two equal stones of equal strength adjust themselves to a terrella in accordance with magnetick laws. The iron conceives vigour from the loadstone and is influenced by the magnetical motions. Wherefore true direction is the motion of a magnetick body in regard to the verticity of the earth, the natures of both agreeing and working together toward a natural position and unity54. For indeed we have found out at length, by many experiments and in many ways, that there is a disposing nature, moving them together by reason of their various positions by one form that is common to both, and that in all magnetick substances there is attraction and repulsion. For both the stone200 and the magnetick iron arrange themselves by inclination and declination, according to the common position of their nature and the earth. And the force of the earth by the virtue of the whole, by attracting toward the poles, and repelling55, arranges all magneticks which are unfixed and loose. For in all cases all magneticks conform themselves to the globe of the earth in the same ways and by the same laws by which another loadstone or any magneticks do to a terrella.
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1
rotation
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| n.旋转；循环，轮流 | |
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pointed
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| adj.尖的，直截了当的 | |
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rotations
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| 旋转( rotation的名词复数 )； 转动； 轮流； 轮换 | |
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4
briefly
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| adv.简单地，简短地 | |
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judgment
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| n.审判；判断力，识别力，看法，意见 | |
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prudent
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| adj.谨慎的，有远见的，精打细算的 | |
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7
digits
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| n.数字( digit的名词复数 )；手指，足趾 | |
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skilfully
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| adv. (美skillfully)熟练地 | |
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requisites
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| n.必要的事物( requisite的名词复数 ) | |
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10
touching
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| adj.动人的，使人感伤的 | |
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mariners
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| 海员，水手（mariner的复数形式） | |
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auspicious
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| adj.吉利的；幸运的，吉兆的 | |
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13
fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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14
meridian
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| adj.子午线的；全盛期的 | |
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15
diverge
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| v.分叉，分歧，离题，使...岔开，使转向 | |
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discrepancy
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| n.不同；不符；差异；矛盾 | |
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disturbance
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| n.动乱，骚动；打扰，干扰；(身心)失调 | |
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perversion
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| n.曲解；堕落；反常 | |
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19
untoward
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| adj.不利的，不幸的，困难重重的 | |
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20
remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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imbued
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| v.使（某人/某事）充满或激起（感情等）( imbue的过去式和过去分词 )；使充满；灌输；激发（强烈感情或品质等） | |
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22
diligently
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| ad.industriously;carefully | |
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worthy
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| adj.(of)值得的，配得上的；有价值的 | |
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24
censure
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| v./n.责备；非难；责难 | |
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25
amber
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| n.琥珀；琥珀色；adj.琥珀制的 | |
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meridians
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| n.子午圈( meridian的名词复数 )；子午线；顶点；（权力，成就等的）全盛时期 | |
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circumference
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| n.圆周，周长，圆周线 | |
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28
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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deviate
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| v.(from)背离，偏离 | |
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30
drawn
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| v.拖，拉，拔出；adj.憔悴的，紧张的 | |
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whatsoever
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| adv.（用于否定句中以加强语气）任何；pron.无论什么 | |
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32
firmament
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| n.苍穹；最高层 | |
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33
steadily
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| adv.稳定地；不变地；持续地 | |
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cynosure
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| n.焦点 | |
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diverges
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| 分开( diverge的第三人称单数 )； 偏离； 分歧； 分道扬镳 | |
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sufficiently
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| adv.足够地，充分地 | |
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astronomers
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| n.天文学者，天文学家( astronomer的名词复数 ) | |
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38
virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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39
trepidation
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| n.惊恐，惶恐 | |
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40
variance
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| n.矛盾，不同 | |
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41
monstrous
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| adj.巨大的；恐怖的；可耻的，丢脸的 | |
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42
latitude
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| n.纬度，行动或言论的自由(范围)，(pl.)地区 | |
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43
penetrate
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| v.透(渗)入；刺入，刺穿；洞察，了解 | |
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44
halfway
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| adj.中途的，不彻底的，部分的；adv.半路地，在中途，在半途 | |
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45
maritime
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| adj.海的，海事的，航海的，近海的，沿海的 | |
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46
eminent
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| adj.显赫的，杰出的，有名的，优良的 | |
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47
situated
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| adj.坐落在...的，处于某种境地的 | |
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48
sluggish
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| adj.懒惰的，迟钝的，无精打采的 | |
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49
lapse
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| n.过失，流逝，失效，抛弃信仰，间隔；vi.堕落，停止，失效，流逝；vt.使失效 | |
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50
rust
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| n.锈；v.生锈；(脑子)衰退 | |
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51
vigour
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| （=vigor）n.智力，体力，精力 | |
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52
perpendicular
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| adj.垂直的，直立的；n.垂直线，垂直的位置 | |
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53
inclination
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| n.倾斜；点头；弯腰；斜坡；倾度；倾向；爱好 | |
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54
unity
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| n.团结，联合，统一；和睦，协调 | |
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55
repelling
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| v.击退( repel的现在分词 )；使厌恶；排斥；推开 | |
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