Chapter XIII.

Of Our Sight, and by what Means We See.

Democritus and Epicurus suppose that sight is caused by the insertion of little images into the visive organ, and by the reception of certain rays which return to the eye after meeting the object. Empedocles supposes that images are mixed with the rays of the eye; these he styles the rays of images. Hipparchus, that the visual rays extend from both the eyes to the superficies of bodies, and give to the sight the apprehension¹ of those same bodies, after the same manner in which the hand touching² the extremity³ of bodies gives the sense of feeling. Plato, that the sight is the splendor⁴ of united rays; there is a light which reaches some distance from the eyes into a cognate⁵ air, and there is likewise a light shed from bodies, which meets and joins with the fiery⁶ visual light in the intermediate air (which is liquid and mutable); and the union of these rays gives the sense of seeing. This is Plato’s corradiancy, or splendor of united rays.

1 apprehension   

n.理解，领悟；逮捕，拘捕；忧虑

参考例句：

• There were still areas of doubt and her apprehension grew.有些地方仍然存疑，于是她越来越担心。
• She is a girl of weak apprehension.她是一个理解力很差的女孩。

2 touching   

adj.动人的，使人感伤的

参考例句：

• It was a touching sight.这是一幅动人的景象。
• His letter was touching.他的信很感人。

3 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？

4 splendor   

n.光彩；壮丽，华丽；显赫，辉煌

参考例句：

• Never in his life had he gazed on such splendor.他生平从没有见过如此辉煌壮丽的场面。
• All the splendor in the world is not worth a good friend.人世间所有的荣华富贵不如一个好朋友。

5 cognate   

adj.同类的，同源的，同族的；n.同家族的人，同源词

参考例句：

• Mathematics and astronomy are cognate sciences.数学和天文学是互相关联的科学。
• English,Dutch and German are cognate languages. 英语、荷兰语、德语是同语族的语言。

6 fiery   

adj.燃烧着的，火红的；暴躁的；激烈的

参考例句：

• She has fiery red hair.她有一头火红的头发。
• His fiery speech agitated the crowd.他热情洋溢的讲话激动了群众。