

UJ LI 



'LIST OF ILLUSTRATIONS. ^^3'<A>> 



A 



All of the Figures, except when otherwise indicated, are original, and were drawn 



by Mrs. Gage. 



PLATES. 



PLATE I. 



Fig. 



i. Double convex lens showing the principal plane, the principal focus, and the 

 focal distance. 



2. Converging lens showing formation of a virtual image. 



3. Converging lens showing formation of a real image. 



4. Simple microscope with retinal image, and its projection as a virtual image. 



5. Compound microscope, tracing the rays from the object to the final, virtual 



image. 



6. Huygenian ocular or eye-piece, showing action of field-lens (Ross). 



7. Huygenian ocular showing the eye-point. 



PLATE II. 

 9. Tripod magnifier. 



10. Stand of a compound microscope with names of parts. 



11. Section of stage of compound microscope showing proper position of dia- 



phragms. 



12. Section of a low, dry objective and reflected light. 



13. Section of an adjustable, immersion objective, transmitted axial and oblique 



light. 



14. Diagram showing how to put on a cover-glass. 



15. Slides showing how to enclose the lines of a micrometer or of some part of a 



preparation by a small ring. 



16. Double eye-shade. 



PLATE III. 



20-22. Sectional views of the Abbe illuminator showing various methods of illu- 

 mination, — with parallel rays of central light, with oblique light, with con- 

 verging rays, and for dark-ground illumination. 



23. Letters mounted in stairs to show order of coming into focus. 



24. Glass rod in air and in glycerin. 



25. Glass rod coated with collodion to show double contour. 



26. Blood corpuscles on edge, to show surface and optical sections. 



27. Wollaston's camera lucida in section, showing the overlapping fields. 



28. Position of the microscope for determining magnification with Wollaston's 



camera lucida ; also the necessity of a standard distance at which to measure 

 the image. 



29. Figures of the image of the stage and ocular micrometers, showing correct mu- 



tual arrangement of lines in determining the ocidar micrometer valuation. 



