Bryn Mawr College monographs . airly representative of theDlors that show a relative change in luminosity with changef mtensity. And (2) the yellow, green, and blue filters each•ansmits components that undergo opposite luminositylanges with a change of intensity of the source. That is,le best yellow of the series transmits also a green com-onent; the best green, a yellow component; and the bestue transmits some of the violet. The photometric apparatus employed was for the sake ofymparison made to conform very closely in its essentialMatures to that described by Dr. The general plan<
Bryn Mawr College monographs . airly representative of theDlors that show a relative change in luminosity with changef mtensity. And (2) the yellow, green, and blue filters each•ansmits components that undergo opposite luminositylanges with a change of intensity of the source. That is,le best yellow of the series transmits also a green com-onent; the best green, a yellow component; and the bestue transmits some of the violet. The photometric apparatus employed was for the sake ofymparison made to conform very closely in its essentialMatures to that described by Dr. The general plan< our apparatus is indicated in Fig. 5. It consists of a photo-leter bar carrying the standard white light {A), a second barcrrying the colored light {B), a sectored disc (C), and a ^ Ives, H. E., op. ciu, p. 161. 134 C. E. FERREE AND GERTRUDE RAND m screen (Z)) provided with a small aperture {0) through which [the light comes to the eye. The standard white light was enclosed in a black light-proof box (£), which was provided. Fig. s in front with a circular opening 4 cm. in diameter for the trans-mission of the light. In passing to the sectored disc, thelight was screened both from the observers eye and from thecolored source by black screens properly placed. The lightwhich was passed through the colored filters was placed in asimilar light-proof box {F) provided with an opening 4 for the transmission of the light. Above and belowthis opening were grooves into which the color filters wereslid. The sectored discs were made of aluminum. The edgesof these discs were carefully bevelled and the surface was keptfreshly covered with magnesium oxide deposited from theburning metal. The aperture in the screen through whichthe light passed to the observers eye was 3 mm. visual angle subtended by this aperture at the observerseye at 20 cm. distance was very small. A small angle wasneeded to guard against the unequal sensitivity of the centraland paracentral portions
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Keywords: ., bookauthorbrynmawr, bookcentury1900, bookdecade1900, bookyear1901
