Soaked leather lifting a stone paper- 
weight 
62 THE FAIRY-LAND OF SCIENCE. 
I now drop it on this stone weight, and so heavily is 
it pressed down upon it by the atmosphere that I can 
f 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 ; 
the little animal ex- 
hausts the air inside 
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 1 5 tons 
upon the body of a grown man. It would crush us ii 
it were not that there are gases and fluids inside oui 
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 hi 
body were pressing outwards as much as when he was 
below, but the air outside did not press so heavily, anc 
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 t( 
