The Dry version of this program shows a volume of air with generic
'dry air' molecules present. Students then change the pressure of
the parcel, thereby changing its altitude (unmeasured), temperature,
and pressure, and density percentage. The density percentage is used
because the volume size is supposed to be small, but abstract. Therefore,
the program is initialized with a preset density, and then changes
to the volume of the parcel cause relative (hence percentage) changes
to the density.
The theory behind the parcel in Lifting Air (Dry) program can be
found in the parcel controlling class ParcelSet*