The branch of the physical sciences which relates to the air and its
various phenomena is called Pneumatics. By it we learn many curious
particulars. By it we find that the air has weight and pressure,
color, density, elasticity, compressibility, and some other properties
with which we shall endeavor to make the young reader acquainted by
many pleasing experiments, earnestly impressing upon him to lose no
opportunity of making physical science his study.
The common leather sucker by which boys raise stones will show the
pressure of the atmosphere. It consists of a piece of soft but firm
leather having a piece of string drawn through its center. The leather
is made quite wet and pliable, and then its under part is placed on the
stone and stamped down by the foot. This pressing excludes the air from
between the leather and the stone, and by pulling the string a vacuum
is left underneath its center; consequently the leather is firmly
attached to the stone, which enables you to lift it.