Bryn Mawr College monographs . Its cost, however, is prohibitive for the greaternumber of laboratories. The same thing might well be said ofthe best of the filter units. The ones most familiar to us all andthe most available from the standpoint of cost are the bluebulb lamps. With regard to these lamps, however, only arough approximation to daylight is claimed. We have thoughtthat it may be of interest to show here a spectrophotometriccomparison of one of them, the type C-2 Mazda lamp, and ofsome of the closer approximations to daylight, with the blackbody at 5000 degrees absolute which is som
Bryn Mawr College monographs . Its cost, however, is prohibitive for the greaternumber of laboratories. The same thing might well be said ofthe best of the filter units. The ones most familiar to us all andthe most available from the standpoint of cost are the bluebulb lamps. With regard to these lamps, however, only arough approximation to daylight is claimed. We have thoughtthat it may be of interest to show here a spectrophotometriccomparison of one of them, the type C-2 Mazda lamp, and ofsome of the closer approximations to daylight, with the blackbody at 5000 degrees absolute which is sometimes taken asthe standard of average daylight. (See Fig. L) For the( iiii) irative curves given in this figure we are indebted to theElectrical Testing Laboratories, 80th street and East Endavenue, New York City. The comparison here, it will be re-membered, is photometric, not colorimetric. 86 FERREE, RAND, AND HAUPT ri CDLDR CHARACTERBTICS (SPECTROPHOTONETRIC CURVES) NATURAL LIEMT ARTIFICIAL DAVLIEHT CPUIPMENTS MA70A LAMPS. .41 .43 .45 .47 .49Violet I Blue LAMPCOMniTTEE REPOTrr 1916 Wavp Lrn^+h^ .51 .53 .55 .57 .59 Green | Yellow .61 .63 .65 ,67 .69 Orange I Red Fig. I A—Black body at 5000 degrees absolute (Average Daylight) B—Blue sky (Ives) I. E. S. Transactions, 1910, p. 208. C—Daylight glass with Mazda C lamp (Brady) I. E. S. Transactions. 1914, p. 952. D—Bluish glass with Mazda C lamp (Sharp) I. E. S. Transactions, 1915, p. —Mazda C2 lamp. F—Mazda B lamp ( lumens per watt).G—Mazda C lamp (20 lumens per watt). H—Moore tube (Paper read before I. E. S. November 11, 1915).I—Trutint glass, (Luckiesh) I. E. S. Transactions, 1914, p. —Trutint glass, (Luckiesh) I. E. S. Transactions, 1914, p. 839. {Reprinted from Journal of Exf^krimental Psychology. Vol. Ill, No. i. Feb., iq2().I AN APPARATUS FOR DETERMINING ACUITY ATLOW ILLUMINATIONS, FOR TESTING THELIGHT AND COLOR SENSE AND FOR DETECT-ING SMALL ERRORS IN REFRACTION AND INTHEIR CORRECT
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