Optical essays, [electronic resource] : Containing, I. A practical description of the several sorts of single, solar, and compound microscops; with their apparatus, and latest improvments. II. The nature of vision in insects demonstrated by microscopic observations. III. A catalogue of all principal microscopic objects. IV. The use of the reflecting telescope as an universal perspective for viewing every sort of object in the greatest perfection. V. The manner of computing the magnifying power in single and double microscopes. VI. A new method of applying a micrometer to take the dimension: of small objects. VII. An illustration of the whole in a great variety of figures on a large copper-plate. By B. Martin.