A Simple Portable Instrument for the Abso - Lute Measurement of Reflection and Transmission Factors

Early this year the author presented at the convention of the Optical Society of America a paper giving a brief review of the methods which had previously been used in measuring reflection factors, and describing a new type of absolute reflectometer. The complete description of that instrument, with the derivation of the theory, is now available in a scientific paper of this Biureau.* The instrument described at that time was very thoroughly tested and was found to give correct results. However, certain precautions are necessary in its use and the mathematical equations are somewhat complex. These factors might tend to limit its use in the hands of inexperienced observers, though not necessarily so, as a calibration curve can be calculated ofid drav/n for use in routine measurements. One of the extremely interesting and important developments