(p. 101) Nothing is more common in the history of science than independent discovery of the same phenomenon, unless it is a fight over priority. To this day, historians debate how much prior awareness of the theory of latent heat was in Watt’s possession, but they miss Black’s real contribution, which anyone can see by examining the columns of neat script that attest to Watt’s careful recording of experimental results. Watt didn’t discover the existence of latent heat from Black, at least not directly; but he rediscovered it entirely through exposure to the diligent experimental habits of professors such as Black, John Robison, and Robert Dick.
Source:
Rosen, William. The Most Powerful Idea in the World: A Story of Steam, Industry, and Invention. New York: Random House, 2010.