History of the British Thermal Unit

  title={History of the British Thermal Unit},
  author={G. Woledge},
THE date of the phrase “British thermal unit” can be pushed back by fifteen years; it occurs in W. J. M. Rankine, “Manual of the Steam Engine” (1859), p. 300; but here, as in the 1875 quotation given by Dr. Powell1, it is a descriptive phrase and not a technical term; Rankine is in fact contrasting the British thermal unit and the French thermal unit.