22 
THE YOUNG SCIENTIST. 
stout nails, but see that one piece of twine 
does not have the advantage of the other, 
owing to one of them being placed against 
a sharp edge or corner. If you now give a 
sudden jerk to the lower cord, you will 
find that it will break, while the upper 
cord, which apparently supports not only 
the force of the jerk, but the weight of the 
block, is not at all affected. Any person 
to whom the arrangement is shown before 
the cord is pulled, upon being asked 
"Which cord will break?" will almost 
I pull, but the weight of the block of wood. 
This is merely another illustration of a 
law which we may see in action around 
us constantly, and which is frequently 
taken advantage of to produce very 
strange results. Thus we would hardly 
suppose that a man lying flat on his back 
could bear the blows of a sledge hammer 
delivered by a strong man on his chest. 
But if we place a good heavy anvil on his 
chest, he will be able to bear the weight 
of the anvil and the blows too, if the latter 
CURIOUS EXPEEIMENT IN INEETIA. 
certainly answer, " The upper one ! " And 
great will be his astonishment when he 
sees that the block does not fall. 
The explanation of this singular experi- 
ment is very simple ; if the jerk be sudden 
and strong, the under string gives way 
before there is time to transmit the motion 
to the ball, and consequently the force to 
the upper string. The inertia of the ball, 
therefore, saves the upper string from 
breaking. If, however, we pull the lower 
string slowly, the upper string will break, 
l)ecause it has to support not only the 
are struck on the anvil. For the blow, 
which by its velocity would crush in the* 
chest, is taken up by the anvil and ren- 
dered slow and harmless. 
So, too, a leaden ball thrown from the 
hand will, if it strike a window, communi- 
cate its motion to the glass and shiver it 
to fragments. But if it be shot from a 
gun, so that its velocity is very great, it 
will not have time to transfer its motion 
to any more of the glass than just a space 
equal to its own size; this it will carry 
away, leaving a round hole. 
