Letter from J W [John William] Nicholson, Trinity College, Cambridge, to J [Joseph] Larmor As Larmor suggests, the change in phase is negligible, but this does not matter so much in the case he is considering. He gives explanatory equations, writing that although his variable medium changes slowly, the final change is not necessarily small. He discusses the size of the final absorption coefficient. The broadness of stratum is the essential. If Larmor agrees with his reasoning, Nicholson should insert more of it into the paper to prevent confusion. 25 October 1907