SUNBEAMS AND THEIR WORK. 35 
these waves could be travelling: not through water, 
for we know that there is no water in space nor 
through air, for the air ceases at a comparatively short 
distance from our earth. There must then be some- 
thing filling all space between us and the sun, finer 
than either water or air. 
And now I must ask you to use all your imagina- 
tion, for I want you to picture to yourselves something 
quite as invisible as the Emperor's new clothes in 
Andersen's fairy-tale, only with this difference, that 
our invisible something is very active ; and though we 
can neither see it nor touch it we know it by its 
effects. You must imagine a fine substance filling all 
space between us and the sun and the stars; a sub- 
stance so very delicate and subtle, that not only is 
it invisible, but it can pass through solid bodies such 
as glass, ice, or even wood or brick walls. This sub- 
stance we call " ether." I cannot give you here the 
reasons why we must assume that it is throughout 
all space ; you must take this on the word of such men 
as Sir John Herschel or Professor Clerk-Maxwell, 
until you can study the question for yourselves. 
Now if you can imagine this ether filling every 
corner of space, so that it is everywhere and passes 
through everything, ask yourselves, what must happen 
when a great commotion is going on in one of the 
large bodies which float in it? When the atoms of 
the gases round the sun are clashing violently together 
to make all its light and heat, do you not think they 
must shake this ether all around them? And then, 
since the ether stretches on all sides from the sun to 
our earth and all other planets, must not this quiver- 
