there is always some air under it. If, however, I could get the
air quite away from one side of the paper, then the pressure on
the other side would show itself. I can do this by simply
wetting the paper and letting it fall on the table, and the water
will prevent any air from getting under it. Now see! if I try to
lift it by the thread in the middle, I have great difficulty,
because the whole 15 pounds' weight of the atmosphere is pressing
it down. A still better way of making the experiment is with a
piece of leather, such as the boys often amuse themselves with in
the streets. This piece of leather has been well soaked. I drop
it on the floor and see! it requires all my strength to pull it
up. (In fastening the string to the leather the hole must be
very small and the know as flat as possible, and it is even well
to put a small piece of kid under the knot. When I first made
this experiment, not having taken these precautions, it did not
succeed well, owing to air getting in through the hole.) I now
drop it on this stone weight, and so heavily is it pressed down
upon it by the atmosphere that I can lift the weight without its
breaking away from it.

Have you ever tried to pick limpets off a rock? If so, you know
how tight they cling. the limpet clings to the rock just in the
same way as this leather does to the stone; the little animal
exhausts the air inside it's shell, and then it is pressed
against the rock by the whole weight of the air above.

Perhaps you will wonder how it is that if we have a weight of 15
lbs. pressing on every square inch of our bodies, it does not
crush us. And, indeed, it amounts on the whole to a weight of
about 15 tons upon the body of a grown man. It would crush us if