The employment of a cement which is not soluble in methyl alcohol renders it useable for dust examination. As the chamber is not of open moat construction, it cam be hermetically sealed and employed in the study of the growth of microorganisms. The Whipple eyepiece micrometer, 21.0mm diameter, is recommended for use with the instrument for most operations. The cover glass, 60 x 25mm, is optically plane on both sides and is 0.5mm thick.