Journal - Franklin Institute of the State of Pennsylvania (1826)
Franklin Institute, Philadelphia, Franklin Institute (Philadelphia, Pa.) · [Philadelphia : Franklin Institute] · leaf 560
as two rough-ground flashedopal glass disks at opposite ends of a brass tube 4.5 cms. in diame-ter and white inside. The first disk is flush with the inner wall of Oct., 1922.] Notes from Nela Research Laboratories. 545 the sphere, and the second disk is imaged in the photometer tul)e.Just behind… … Door removed. In operation a perfect color-match may be obtained betweenthe two lights compared without the use of any color-filters. Thephotometric scales are made to read correctly by means of theadjustable horizontal bars shown in Fig. 3. As compared with any type of bar photometer this…
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