LIST OF ILLUSTRATIONS. 
FIG. PAGE 
1. Section through the Human Eye....... aibieseaters ia sete eid 2 
2. Illustration of Refraction... ..cceecca cece en cece s con eeeneee 4 
3. Refraction by Prisms....... shila Wao s Fe $26 Melarsehene attain 5 
4. Refractions in Prisms of Different Angles............4. reas 5 
5. Plano-convex Lens and its Principal Focus........ avciebbtaace ees 6 
6. Course of Rays according to the Relation of a Luminous Point 
tothe Rrincipal Hocus: 0000 sa 024i: ss Sade ers eea 7 
7. Formation of Image by Object outside Principal Focus...... . 8 
8. oc “ac “cc es “ inside a3 BOS od 9 
g. Leeuwenhoek’s Microscope...........5- RAS Sega aeparaiaien Rees II 
10. Hooke’s Compound Microscope.......-ceeeeeeerece aveiey stevie 12 
11. Course of Rays in Compound Microscope............0+.000- 13 
12, Chromatic Aberration.......cccceecseeesceererace oo Sekar 14 
13. Achromatic Objective... ... cece. e cee eee b sasaceuexstencases 15 
14. Effect of Homogeneous Immersion,............006 aallaseusccbeie 16 
15. The Microscope. vi.iccc oe essa sineng ssosagag aes eevee sgahare eins 18 
16, Relation of Distance from Principal Focus to Size and Position 
Of Images. 3.05 soa anda oe os plauguniayeeuagiad dss ga setae O84 5 21 
17, Proper Position for Observer... ....ceee eee e eee eee a eeneene 24 
18, Method of"Inserting Objectives.........00000. hg asbeaiesciaciaiows . 26 
19. Abbé Condenser.......... .. eee eee eee Siaioungeerattens aides tude 28 
20. Refraction by Air-bubbles and Oil- saloons breeds oer Hewsese s, 30 
21. Disturbing Effect of the Cover-glass......... scares Biase <0 32 
22. Micrometer Calipers........ {ASWES FNS Cee SRN Oe 33 
23. Curvaturevof the: Field wis cose waives ven wena aw doo 8 6 aie 35 
24. Turntable...............065 sh cid 2 heath tere. aos 42 
25. Thoma Microtome..... yak aie se a avis ueecead dust Dvendl euch dale a) seacoushekeslona 48 
26. Camera Lucida........... PeoGudy arabada pudadd SSpcramenertianer teen 55 
27. Course of Rays in the Camera Lucida.........seeeeeeeeeeee 56 
