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Julius von Mayer (1814-1878). Century engraving of the German physicist and physician Julius Robert von Mayer. Mayer was a pioneer of the theory of the conservation of energy. He noted that blood retained more oxygen in hot weather and deduced that this was because the body required less oxygen to maintain body heat, and concluded that there was a fixed relationship be-tween heat and work. He studied the specific heat of gases, & argued that a gas cools as it expands because the heat is used up in expanding against atmospheric pressure. He later applied his theory of the conservation of energy more widely. From Weltall und Menscheit (Universe and Humanity), by Hans Kraemer (ca.
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