Show DARK IX IN Elihu Thomson explains the perplexing phenomenon ot of the dark flashes ot of lightning seen In some lome photographs photograph In lIuch pictures a black line similar to n a streak of lightning Is apparent This has ha glen given rIse to the theory that there WM n a adark dark os aa well as a light flash In such atmospheric disturbances Thomson says sas that dark Is 11 Isa n a myth mth due to contrast elI Cu when shen seen by the eye ee and to peculiarities of plato sensitIveness when The effect ct Is due simp simply to actions ot of a photographic plate during exposure and It |