62 
THE FAIRY-LAND OF SCIENCE. 
Fig- 13- 
the little animal ex- 
hausts the air inside 
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 with- 
out 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 lea- 
ther does to the stone ; 
Soaked leather lifting a stone paper- 
weight. 
its 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 Ibs. 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 
it were not that there are gases and fluids inside our 
bodies which press outwards and balance the weight so 
that we do not feel it at all. 
This is why Mr. Glaisher's veins swelled and he grew 
giddy in thin air. The gases and fluids inside his 
body were pressing outwards as much as when he was 
below, but the air outside did not press so heavily, and 
so all the natural condition of his body was disturbed. 
I hope we now realize how heavily the air presses 
down upon our earth, but it is equally necessary to 
