A NEW MICRO-REFLECTOMETER

In this instrument the use of modulated light signals created by a rotating polaroid permits amplification after detection by a photomultiplier. Matching is against a comparison beam and is performed optically, mineral and glass standards being used. The instrument is very stable and is capable of high sensitivity especially at low light intensities. TaIS paper describes an instrument that has been developed for use in investigations into the optical properties of the coal macerals. The low reflectivity of the material together with the small field areas available have necessitated the construction of an apparatus of high sensitivity and stability. The photoelectric portion of the apparatus is identical with that of an instrument designed by Mr. I. A. Marshall of the National Coal Board, Coal Survey Laboratory at Sheffield and constructed by Messrs. Cooke, Troughton and Simms (1), and although the optical systems are similar in principle it has been found desirable to perform certain modifications, which, it is felt, increase the accuracy of matching and avoid difficulties from elliptica