Book IV chapter 5

An island in Ocean does not change the variation223, as neither do mines of loadstone.

Islands, although they be more magnetick than the sea, yet do not change the magnetick directions or variations. For since direction is a motion derived¹ from the power of the whole earth, not from the attraction of any hill but from the disposing and turning power of the whole; so variation (which is a perturbation of the direction) is an aberration² of the real turning power arising from the great inequalities of the earth, in consequence of which it, of itself, slightly diverts movable magneticks toward those which are the largest and the more powerful. The cause now shown may suffice to explain that which some so wonder at about the Island of Elba (and although this is productive of loadstone, yet the versorium (or mariners³' compass) makes no special inclination⁴ toward it whenever vessels⁵ approach it in the Tyrrhenian sea); and the following causes are also to be considered, viz.: that the virtue⁶ of smaller magnetick bodies extends scarcely or not at all of itself beyond their own mines: for variation does not occur because of attraction, as they would have it who have imagined magnetick poles. Besides, magnetick mines are only agnate to the true earth, not innate⁷: hence the whole globe does not regard them, and magneticks are not borne to them, as is demonstrated by the diagram of eminences⁸.

1 derived   

vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取

参考例句：

• Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
• He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》

2 aberration   

n.离开正路，脱离常规，色差

参考例句：

• The removal of the chromatic aberration is then of primary importance.这时消除色差具有头等重要性。
• Owing to a strange mental aberration he forgot his own name.由于一种莫名的精神错乱，他把自己的名字忘了。

3 mariners   

海员，水手（mariner的复数形式）

参考例句：

• Mariners were also able to fix their latitude by using an instrument called astrolabe. 海员们还可使用星盘这种仪器确定纬度。
• The ancient mariners traversed the sea. 古代的海员漂洋过海。

4 inclination   

n.倾斜；点头；弯腰；斜坡；倾度；倾向；爱好

参考例句：

• She greeted us with a slight inclination of the head.她微微点头向我们致意。
• I did not feel the slightest inclination to hurry.我没有丝毫着急的意思。

5 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

6 virtue   

n.德行，美德；贞操；优点；功效，效力

参考例句：

• He was considered to be a paragon of virtue.他被认为是品德尽善尽美的典范。
• You need to decorate your mind with virtue.你应该用德行美化心灵。

7 innate   

adj.天生的，固有的，天赋的

参考例句：

• You obviously have an innate talent for music.你显然有天生的音乐才能。
• Correct ideas are not innate in the mind.人的正确思想不是自己头脑中固有的。

8 eminences   

卓越( eminence的名词复数 )； 著名； 高地； 山丘

参考例句：

• Both are truly grey eminences who have become accustomed to the exercise of influence. 两个人都是真正的幕后操纵者，他们已习惯于用其影响进行幕后操纵。