Chapter XVIII.

Of the Aurea, or a Circle About a Star.

The aurea or circle is thus formed. A thick and dark air intervening between the moon or any other star and our eye, by which means our sight is dilated¹ and reflected, when now our sight falls upon the outward circumference² of the orb³ of that star, there presently seems a circle to appear. This circle thus appearing is called the [Greek omitted] or halo; and there is constantly such a circle seen by us, when such a density⁴ of sight happens.

1 dilated   

adj.加宽的，扩大的v.（使某物）扩大，膨胀，张大( dilate的过去式和过去分词 )

参考例句：

• Her eyes dilated with fear. 她吓得瞪大了眼睛。
• The cat dilated its eyes. 猫瞪大了双眼。 来自《简明英汉词典》

2 circumference   

n.圆周，周长，圆周线

参考例句：

• It's a mile round the circumference of the field.运动场周长一英里。
• The diameter and the circumference of a circle correlate.圆的直径与圆周有相互关系。

3 orb   

n.太阳；星球；v.弄圆；成球形

参考例句：

• The blue heaven,holding its one golden orb,poured down a crystal wash of warm light.蓝蓝的天空托着金色的太阳，洒下一片水晶般明亮温暖的光辉。
• It is an emanation from the distant orb of immortal light.它是从远处那个发出不灭之光的天体上放射出来的。

4 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。