THE FAIRY-LAND OF SCIENCE. 
away from the vacuum tube, it will still glow brightly. 
And if you then put your hand between the tube and 
the screen you will see the bones of your hand on the 
glowing paint, exactly as shown in Fig. 10. The X-rays 
will have passed almost entirely through the flesh of 
your hand and through the wood or cardboard, throw- 
ing only a very faint shadow upon the screen, while 
the bones will have stopped 
them altogether, and so cast a 
deep black shadow. You will 
see that the ring on the finger 
also casts a deep shadow, 
showing that the X-rays could 
not pass through the gold. 
I have done this myself 
and seen the bones of my own 
hand, and I have made an 
equally strange experiment. 
I held a stout leather bag be- 
tween the tube and the screen, 
and lo! the leather of the bag 
became only a very faint shad- 
ow, like the flesh of my hand 
had done, and I saw upon the screen the metal frame- 
work of the bag, and within it a bunch of keys, an 
opera glass, and several coins which were shut up in- 
side the bag. 
The reason of all these marvels is that the X-rays 
will pass through flesh, wood, leather, paper, card- 
board, even through a pack of cards, and through sev- 
eral other substances which entirely stop the ordinary 
rays of light and heat. But they will not pass through 
FIG. 10. Shadow of the 
human hand as thrown 
on the fluorescent 
screen by the X-rays. 
Also as shown when 
photographed by the 
same rays. 
