Book II chapter 31

On Long and Round Stones.

P ieces of iron join more firmly with a long stone than with a round one, provided that the pole of the stone is at the extremity¹ and end of its length; because, forsooth, in the case of a long stone, a magnetick is directed at the end straight towards the body in which the virtue² proceeds in straighter lines and through the longer diameter. But a somewhat long stone has but little power on the side, much less indeed than a round one. .

It is demonstrable180, indeed, that at A and B the coition is stronger in a round stone than at C and D, at like distances from the pole.

1 extremity   

n.末端，尽头；尽力；终极；极度

参考例句：

• I hope you will help them in their extremity.我希望你能帮助在穷途末路的他们。
• What shall we do in this extremity?在这种极其困难的情况下我们该怎么办呢？

2 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。