The London, Edinburgh and Dublin philosophical magazine and journal of science . (Upper diagram.) Two alternating dove-tailed stimuli A0 and a colour of the photometric field is An and at /3 it is B0. (Lower diagram.) The impression as recorded by a transmittingmedium. The amplitudes of fluctuation are reduced. At x the colouris a mixture of A0 and B0 with A0 predominating; at /3 a mixture withB0 predominating. the two would be continuously uniformly illuminated. Fig. .Sshows, in the upper diagram, the manner in which the poweris supplied to the two lamp filaments, and in the lower 712 M
The London, Edinburgh and Dublin philosophical magazine and journal of science . (Upper diagram.) Two alternating dove-tailed stimuli A0 and a colour of the photometric field is An and at /3 it is B0. (Lower diagram.) The impression as recorded by a transmittingmedium. The amplitudes of fluctuation are reduced. At x the colouris a mixture of A0 and B0 with A0 predominating; at /3 a mixture withB0 predominating. the two would be continuously uniformly illuminated. Fig. .Sshows, in the upper diagram, the manner in which the poweris supplied to the two lamp filaments, and in the lower 712 Messrs. H. E. Ives and E. F. Kingsbury on the diagram the light from each—the fluctuations in the lightbeing of much smaller amplitude than in the power supply,because of the thermal capacity of the filaments. Supposethe two lamps to have equal candle-power, but as above, adifferent character of filament. The illumination conditionson the test-surface at various times due to the two lamps are shown in fig. 4, where the line C refers to the thick Fig. Fluctuation in intensity of two incandescent lamp filaments of samemean candle power, but different thickness. C, thick fiiament; A, thinfilament; S, summation. Their fluctuating sum exhibits also the resultof alternating the two equally bright lights represented by a and c infig. 1. filament and the line A to the thin filament. The re-sultant of the two (the summation) is obviously a flickeringillumination, although the mean value of each componentillumination is the same. Before carrying this physical case any further let us referto fig. 1. Here any point on one of the straight lines indi-cates the illumination at which, for that particular colour, acertain speed of alternation causes flicker to disappear. Nowthe disappearance of visible flicker may be taken as occurringwhen in the physiological transmitting apparatus the per-centage range of the fluctuation (which has been very muchsmoothed out, as compared with the origina
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
