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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...91-155. reach their maximum brightness only two colors were used. These colors were obtained by means of gelatine filters. The experimental procedure was the same as was employed for the determination of the time required for the colors to reach their maximum saturation, with the exception that the closed sectors of the episkotister used to vary the brightness of the standard stimulus were made black instead of the gray of the brightness of the color. The maximum brightness of each of these two colors was attained in approximately 0.130 seconds. Berliner also mentions the irregularities in the rates of development of the color sensations. This was especially true of their rise in saturation. (4) Charpentier. Charpentier16 determined the effect of difference of intensity on the time required for white light to produce its maximum effect in sensation. Working with four intensities of light, he derived the law that the time required for the sensation to reach its maximum value varies inversely as the fourth root of the intensity of the light. He does not fully describe his method of working; but, so far as can be determined from the description given, it is considerably cruder than that employed by Broca and Sulzer, Buchner, or Berliner. (5) Lough." Lough, 1896, worked also with white lights of different intensities. With regard to the effect of intensity on the rate of rise of sensation he came to the following conclusions. (1) The time required for the sensation to reach its maximum varies with the intensity of light. An increase in the intensity of light decreases the time required for the sensation to come to its full value. (2) For intervals of exposure less than is needed to bring the sensation to its maximum value, the intensity of sensation varies...