Bulletin of the Museum of Comparative Zoology at Harvard College (Volume 53) - Tapa blanda

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1908. Not illustrated. Excerpt: ... neglected or else unsuccessfully coped with. This error consists in ascribing the effect of colored light solely to its wave-length and of ignoring the factor of intensity. In order to separate the effects of color from those of intensity in monochromatic light it was necessary to have recourse to some special device for measuring the intensities of lights of known but different wave-length. The instrument with which this was finally accomplished was the thermo-electric apparatus of Boys, known as a radiomicrometer, to be briefly described later. With the aid of this instrument a fact was discovered which prohibited the use of mono-chromatic light obtained through colored solutions. Since the infra-red waves, so potent in thermal energy, penetrated all solutions tested, it was impossible to get a measure of the intensity of the colors uncombined with that of the infra-red, and it was therefore necessary to resort to spectral light. When the physical obstacle of intensity had been overcome, attention was turned to biological considerations. The subject of the migration of pigment in the retina was suggested to me for study, and since it was still an unsettled question whether the quality of light did in reality have any influence upon this phenomenon, the field seemed to be one full of promise. The problem was accordingly formulated as follows:--to determine whether different regions of the spectrum, when reduced to equal intensity, were equipollent in eliciting the migration of pigment; and if they were not, to seek, as a corollary to the problem, some quantitative expression for the difference in efficiency between the red and blue ends of the spectrum. The research was carried on in the Zoological Laboratory of Harvard University under the supervision of Prof....