66 The Microscope. 



can another circumstance, believed to be very import- 

 int to the optical perfection of the eye, namely, that 

 its lens, composed all through of a substance princi- 

 pally consisting of albumen (like white of egg), 

 gradually increases in density from its surface to its 

 centre. And now let us see these curious peelings, 

 which are no other than collections of the fibres above 

 described. 



One of these layers, which extend from top to 

 bottom of the lens, like the meridians on a globe, and 

 in the cod-fish, haddock, and many others, meet at 

 points to which the name of ' ' poles " has been given. 

 Magnified six diameters, as you will see, nothing 

 remarkable appears. There are some indications of 

 its being covered with fine lines, so we will there- 

 fore examine them, magnifying them 130 dia- 

 meters. 



They now appear on every part of the layer, and 

 are beautifully regular. Look at the real size of the 

 fragment, and think how delicate these lines must 

 be! 



We can just distinguish that they are waved lines 

 with a magnifying power of 100 diameters; but we 

 see the real form of the lines very distinctly on mag- 

 nifying them 670 diameters. Every line is toothed in 

 this way, and every fibre which your pen-knife strips 

 off the lens, could be divided into as many narrow 

 pieces as it contains lines. I have frequently torn 

 them into minute threads, which proved to be single 

 fibres, or two or three together. The little teeth lock 

 into each other, very much in the manner in which 



