The variables are noticeable but the level in the ruler underneath the bottle should be controlled (there is a hint for one more impartial variable). If you are seriously keen you could potentially do the two bottle experiment as revealed beneath. There is a superior paper on this experiment by http://compositecladdingtannumsa12098.ampblogs.com/Considerations-To-Know-About-Composite-Cladding-Tannum-Sands-23717637