THE FAIRY-LAND OF SCIENCE. 
has been shining brightly on the cut-glass pendants 
of the chandelier, and you may see them still more 
distinctly if you let a ray of light into a darkened 
room, and pass 
it through the 
prism as in the 
diagram (Fig. 7). 
What are these 
colours? Do they 
come from the 
glass ? No ; for 
FIG. 7. Coloured spectrum thrown by a you will remem- 
prism on the wall. D E, window-shut- fogr to have seen 
ter ; F, round hole in it ; A B C, glass- them in the rain _ 
prism ; M N, wall. , . 
bow, and in the 
soap-bubble, and even in a drop of dew or the scum 
on the top of a pond. This beautiful coloured line is 
only our sunbeam again, which has been split up into 
many colours by passing through the glass, as it is in 
the rain-drops of the rainbow and the bubbles of the 
scum of the pond. 
Till now we have talked of the sunbeam as if it were 
made of only one set of waves, but in truth it is made 
of many sets of waves of different sizes, all travelling 
along together from the sun. These various waves 
have been measured, and we know that the waves 
which make up red light are larger and more lazy than 
those which make violet light, so that there are only 
thirty-nine thousand red waves in an. inch, while there 
are fifty-seven thousand violet waves in the same space. 
How is it then, that if all these different waves, 
making different colours, hit on our eye, they do not 
