Altimeter

What a beautiful instrument. Based solely on atmospheric pressure--which is lower, the higher one moves through the atmosphere and approaches space--this instrument indicates one's altitude. Inside the cylindrical instrument (the cylinder, extending a few inches behind the indicator, is not visible in this photo) is a very sensitive capsule of air in a thin-walled tank; as the tank expands (as pressure is lowered with increasing altitude) or contracts (as pressure increases with decreasing altitude), its motions are translated into the turning of a series of toothed gears that in turn rotate the hands on the dial, indicating altitude. The instrument requires no power, a big point in the design of my flying machine.

Like all instruments, this machine points, generally, at reality; but things other than sheer altitude can effect atmospheric pressure, leading to an erroneous altitude reading...these are things I need to know about, and which I am learning about as I research the variables of the exploration of the stratosphere.