34 
THE FAIRY-LAND OF SCIENCE. 
boards of the floor. Again, if I speak to you, how 
does the sound reach your ear? Not by anything 
being thrown from my mouth to your ear, but by 
the motion of the air. When I speak I agitate the 
air near my mouth, and that makes a wave in the air 
beyond, and that one, another, and another (as we 
shall see more fully in Lecture VI), till the last wave 
hits the drum of your ear. 
Thus we see there are two ways of touching any- 
thing at a distance: ist, by throwing some thing at it 
and hitting it ; 2nd, by sending a movement or wave 
across to it, as in the case of the quivering boards and 
the air. 
Now the great natural philosopher Newton thought 
that the sun touched us in the first of these ways, and 
that sunbeams were made of very minute atoms of 
matter thrown out by the sun, and making a perpetual 
cannonade on our eyes. It is easy to understand 
that this would make us see light and feel heat, just as 
a blow in the eye makes us see stars, or on the body 
makes us feel hot : and for a long time this explanation 
was supposed to be the true one. But we know now 
that there are many facts which cannot be explained 
on this theory, though we cannot go into them here. 
What we will do, is to try and understand what 
now seems to be the true explanation of a sun- 
beam. 
About the same time that Newton wrote, a Dutch- 
man, named Huyghens, suggested that light comes 
from the sun in tiny waves, travelling across space 
much in the same way as ripples travel across a pond. 
The only difficulty was to explain in what substance 
