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Businessman standing and pointing to blank presentation board for your copy space or design.
Operating at typical atmospheric pressures at two different tube heights, works because gravity pulling down on the tube with the liquid at higher level, leaves reduced pressure at the top of the siphon, vintage line drawing or engraving illustration
Cartoon man with pointer. Blue coat, glasses. Smiling
For strategy explaination, with movement marks.
Silhouettes of teachers and students are in a classroom setting, isolated on white background.