My first question: Why spirit? and not water, oil, acetone, mercury or maple
I have a hunch it has something to do with the effects of surface tension
near the ends of a short vial. But I can not explain it rigorously.
Viscosity should affect speed but not sensitivity.
Second: What impacts the sensitivity in terms of linear motion/angle?
Specific Gravity and Surface tension?
Some vials are shape in an arc convex on top. Why? To me this seems to
reduce sensitivity. At the extreme, a toroidal vial should be useless, you
could turn it 180 and see the bubble on top.
Again I have a hunch that the surface tension at the ends is of fundamental
Can somebody shed some light on this ancient technology?