66 
THE FAIRY-LAND OF SCIENCE. 
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, in- 
deed, 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 
outward 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 outward 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 dis- 
turbed. 
I hope we realize how heavily the air presses down 
upon our earth, but it is equally necessary to under- 
stand how, being elastic, it also presses upward; and 
we can prove this by a simple experiment. I fill 
this tumbler with water, and keeping a piece of card 
firmly pressed against it, I turn the whole upside- 
down. When I now take my hand away you would 
naturally expect the card to fall, and the water to be 
spilt. But no! the card remains as if glued to the 
FIG. 14. Soaked leather lifting a 
stone paper-weight. 
