. . ., for it will help us to explain how these glasses show us many things we could never see without them. Here are two pictures of the human eyeball (Figs. 10 and 11), one as it appears from the front, and the other as we should see the parts if we cut an eyeball across from the front to [Pg 30] the back. From these drawings we see that the eyeball is round; it only looks oval, because it is seen through the oval slit of the eyelids. It is really a hard, shining, white ball with a thick nerve cord (on, Fig. 11) passing out at the back, and a dark glassy mound c, c in the centre of the white in front. In this mound we can easily distinguish two parts—first, the coloured iris or elastic curtain (i, Fig. 10); and secondly, the dark spot or pupil p in the centre. The iris is the part which gives the eye its colour; it is composed of a number of fibres, the outer ones radiating towards the centre, the inner ones forming a ring round the pupil; and behind thes. . . Read More