This little book is intended for the teacher, and the beginner with the microscope, not for the specialist. It contains very few original data and treats no single subject with completeness.<br><br>Almost all the branches of technical microscopy have been already made the basis for monographs with which the present volume can in no way compete. On the other hand, there are many entertaining popular books on the microscope which treat it as a mere adjunct to the study of natural history. Neither type of work was suited for the use of a class in Industrial Microscopy which is offered to second-year Chemists and Biologists at the Massachusetts Institute of Technology. The object of this course is twofold - first, to give facility in the manipulation of the microscope; and second, to furnish an acquaintance with the scope of its practical application.