Book IV chapter 21

How the deviation¹ of the versorium is augmented² and diminished by reason of the distance of places.

I n the middle of great and continent lands there is no variation. Nor, generally, in the middle of very great seas. On the margin³ of those lands and seas the variation is often ample, yet not so great as at a little further distance on the sea. As, for example, near Cape⁴ St. Augustine the compass varies; but at 50 miles from land toward the East it varies more; and 80 miles off it varies still more; and yet still more at a distance of 100 miles. But from a distance of 100 miles the diminutions of deviation are slower, when they are navigating⁵ toward the mainland, than at a distance of 80 miles, and at a distance of 80 miles than at 50: for the deviations⁶ change and are diminished rather more swiftly the more they approach and draw near land than when at a great distance off. As, for instance, navigating toward Newfoundland the change of variation is more rapid (that is, it decreases a degree in a smaller arc of the course on the parallel) when they are not far from land than when they are a hundred miles distant: but when travelling on land toward the interiors of regions the changes are slower in the first parts of the journey than when they come more into the interior.

The ratio of the arcs on a parallel circle, when a versorium is moved toward continents which extend to the pole, corresponds with the degrees of variation. Let A be the pole; B the eminences⁷ of the dominant⁸ lands; at C there is no variation caused by B, for it is too far away; at D the variation is very great because the versorium is allured⁹ or turned by the whole earth toward the eminent¹⁰ land B; and moreover it is not hindered, or restrained or brought back to the pole by the verticity of the earth; but, tending of its own nature to the pole, it is nevertheless deflected¹¹ from it by reason of the

site, or position, and convenient distance of the dominant and high lands.

Now from C toward D the variation increases; the versorium, however, does not deviate¹² so rapidly in the first spaces as near D: for more miles are traversed on the parallel circle C D, near C, in order that the versorium may deviate by one degree from the pole A, than near D. So also in order that the variation may be diminished from D toward E more miles are required near D than near E. Thus the deviations become equal in unequal courses, whether the variation be increasing or decreasing; and yet the variation decreases by lesser¹³ intervals¹⁴ than it increases. There intervene, however, many other causes which perturb¹⁵ this proportion.

1 deviation   

n.背离，偏离；偏差，偏向；离题

参考例句：

• Deviation from this rule are very rare.很少有违反这条规则的。
• Any deviation from the party's faith is seen as betrayal.任何对党的信仰的偏离被视作背叛。

2 Augmented   

adj.增音的 动词augment的过去式和过去分词形式

参考例句：

• 'scientists won't be replaced," he claims, "but they will be augmented." 他宣称：“科学家不会被取代；相反，他们会被拓展。” 来自英汉非文学 - 科学史
• The impact of the report was augmented by its timing. 由于发表的时间选得好，这篇报导的影响更大了。

3 margin   

n.页边空白；差额；余地，余裕；边，边缘

参考例句：

• We allowed a margin of 20 minutes in catching the train.我们有20分钟的余地赶火车。
• The village is situated at the margin of a forest.村子位于森林的边缘。

4 cape   

n.海角，岬；披肩，短披风

参考例句：

• I long for a trip to the Cape of Good Hope.我渴望到好望角去旅行。
• She was wearing a cape over her dress.她在外套上披着一件披肩。

5 navigating   

v.给（船舶、飞机等）引航，导航( navigate的现在分词 )；（从海上、空中等）横越；横渡；飞跃

参考例句：

• These can also be very useful when navigating time-based documents, such as video and audio. 它对于和时间有关的文档非常有用，比如视频和音频文档。 来自About Face 3交互设计精髓
• Vehicles slowed to a crawl on city roads, navigating slushy snow. 汽车在市区路上行驶缓慢，穿越泥泞的雪地。 来自互联网

6 deviations   

背离，偏离( deviation的名词复数 )； 离经叛道的行为

参考例句：

• Local deviations depend strongly on the local geometry of the solid matrix. 局部偏离严格地依赖于固体矩阵的局部几何形状。
• They were a series of tactical day-to-day deviations from White House policy. 它们是一系列策略上一天天摆脱白宫政策的偏向。

7 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。

8 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。

9 allured   

诱引，吸引( allure的过去式和过去分词 )

参考例句：

• They allured her into a snare. 他们诱她落入圈套。
• Many settlers were allured by promises of easy wealth. 很多安家落户的人都是受了诱惑，以为转眼就能发财而来的。

10 eminent   

adj.显赫的，杰出的，有名的，优良的

参考例句：

• We are expecting the arrival of an eminent scientist.我们正期待一位著名科学家的来访。
• He is an eminent citizen of China.他是一个杰出的中国公民。

11 deflected   

偏离的

参考例句：

• The ball deflected off Reid's body into the goal. 球打在里德身上反弹进球门。
• Most of its particles are deflected. 此物质的料子大多是偏斜的。

12 deviate   

v.(from)背离，偏离

参考例句：

• Don't deviate from major issues.不要偏离主要问题。
• I will never deviate from what I believe to be right.我绝不背离我自信正确的道路。

13 lesser   

adj.次要的，较小的；adv.较小地，较少地

参考例句：

• Kept some of the lesser players out.不让那些次要的球员参加联赛。
• She has also been affected,but to a lesser degree.她也受到波及，但程度较轻。

14 intervals   

n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息

参考例句：

• The forecast said there would be sunny intervals and showers. 预报间晴，有阵雨。
• Meetings take place at fortnightly intervals. 每两周开一次会。

15 perturb   

v.使不安，烦扰，扰乱，使紊乱

参考例句：

• Stellar passings can perturb the orbits of comets.行星的运行会使彗星的轨道发生扰动。
• They perturb good social order with their lie and propaganda.他们以谎言和宣传扰乱良好的社会秩序。