Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 572
methods employed i> for theobserver to gaze Bteadily at a card uponwhich certain letters are printed, and tonotice the period of time before which the letters l.ecnllie slightly UllITed. It appear- that this method is Sensitive both itigue of the eye and to abnormalconditions due to headache,…
Lighting
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