Abstract.The practice of coating glass surfaces in order to reduce the reflected and increase the transmitted light is now well known, but little attention has so far been given to the particular problems presented by the microscope objective. It will be shown that much can be done to improve observing conditions when a cover‐glass illuminator is used, and in this connection the requirements of the metallurgist will receive special consideration. It will be shown that the coating of glass surfaces may result in a marked diminution of fogging light and to enhanced contrast in the image, and also in the more efficient operation of tbe cover‐glass illumina