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
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 understand how, being
elastic, it also presses upwards; and we can prove this by a
simple experiment.
Pages:
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92