Heat is nothing other than motive power, or perhaps motive power that has had a change of form.
Julius Robert Mayer , German, ship's doctor, Jakarta 1840, noticed that veinous blood was redder in the tropics than in cooler climates. Explored the relation between heat and work following this observation. Discovered the first law of thermodynamics, but wrote so unintelligibly nobody noticed. On the Caloric Effect of Magneto-Electricity, and on the Mechanical Value of Heat .