SUNBEAMS AND THEIR WORK. 51 
bone nor through heavy metals. Therefore the frame- 
work of the bag, the brass tubes of the opera glass, 
the coins, and the bunch of keys stopped them alto- 
gether and threw deep shadows. It is not necessary 
to make these rays visible in order to enable them to 
do work. If you take the fluorescent screen away and 
put in its place a properly prepared photographic 
plate, wrapped in black paper to keep out the light- 
rays, or in a wooden box, and place your hand again 
in front of the tube, the X-rays will pass through your 
flesh and through the black paper, or the wood, and 
cast the shadow of your bones and ring upon the plate, 
altering the chemicals everywhere except where this 
shadow lies. Then when the plate is taken out, prop- 
erly developed, and printed on paper you will have the 
image shown in Fig. 10 just as we had the impres- 
sion of the lace just now. 
Is not this like a magician's story ! And it has the 
advantage of being useful to mankind, for surgeons 
now use these X-rays to see the exact spot where bul- 
lets or other solid objects are buried in the flesh of 
people's bodies, so that they can cut them out. These 
rays have several other curious properties, and we do 
not yet know half the wonders they may reveal to us, 
but they teach us how much more we have still to learn 
about sunbeams and their work. 
And now, tell me, may we not honestly say, that 
the invisible waves which make our sunbeams, are 
wonderful fairy messengers as they travel eternally 
and unceasingly across space, never resting, never 
tiring in doing the work of our world? Little as we 
have been able to learn about them in one short hour, 
