THE author has previously published several detached notices and papers showing the utility of rotatory dispersion in producing radiant energy of some desired spectral distribution. 2 It is possible to obtain by this artifice spectral distributions corresponding to a complete radiator (black body) at temperatures far above anything possible in the actual operation of a furnace, or any artificial incandescent source. In certain studies in colorimetry and physiologic optics 3 it is desirable to

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... able to produce at will such high temperature energy distributions in the visible spectrum. In the previous papers this matter was not treated in a sufficiently unified manner, and data now at hand were not available when they were published. The purpose of the present notice is to state the precise specifications for producing radiant energy of the visible spectral distribution of a theoretical complete radiator (by Planck's formula, 2 = 4350) at any temperature between 3000 K and 70000 K, by means of an apparatus which permits of the convenient adjustment of the distribution to correspond to any temperature within this range. 4 The detailed treatment of the theory of this method and the computations leading to these results are reserved for a subsequent paper. 5 The source of radiant energy is a gas-filled tungsten lamp 6 ' Published by permission of the Director, Bureau of Standards.